Klearchos K Papas

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Chapters

• Papas, K. K. (2022). Oxygenation of the pancreas. In Pancreas and Beta Cell Replacement(pp 113-124). Academic Press. doi:https://doi.org/10.1016/C2020-0-00260-4
• Papas, K. K., & DeLeon, H. (2019). Transplantation, Bioengineering, and Regeneration of the Endrocrine Pancreas. In Transplantation, Bioengineering, and Regeneration of the Endocrine Pancreas(pp 503-519). Preservation of Pancreatic Islets.
• Papas, K. K. (2020). Pancreas and islet preservation. In Transplantation, Bioengineering, and Regeneration of the Endocrine Pancreas(pp 503-527). doi:https://doi.org/10.1016/B978-0-12-814833-4.00042-3
• Gruessner, A. C., Gruessner, A. C., Jie, T., Jie, T., Papas, K. K., Papas, K. K., Porubsky, M., Porubsky, M., Gruessner, A. C., Jie, T., Papas, K. K., & Porubsky, M. (2015). Transplantation. In Schwartz's Principles of Surgery(pp 321-363). McGraw-Hill Companies Inc.
• Papas, K. K. (2012). In Schwartz's Principle of surgery 10th Edition. New York, NY: The McGraw-Hill Companies, Inc.
• Papas, K. K. (2006). Characterization of Islet Preparations. In Cell transplantation from laboratory to clinical(pp 85-133). New York: Elsevier Inc.

Journals/Publications

• Einstein, S. A., Einstein, S. A., Steyn, L. V., Steyn, L. V., Weegman, B. P., Weegman, B. P., Suszynski, T. S., Suszynski, T. S., Sambanis, A., Sambanis, A., O'Brien, T. D., O'Brien, T. D., Avgoustiniatos, E. S., Avgoustiniatos, E. S., Firpo, M. T., Firpo, M. T., Graham, M. L., Graham, M. L., Janecek, J., , Janecek, J., et al. (2023). Hypoxia within subcutaneously implanted macroencapsulation devices limits the viability and functionality of densely loaded islets. Frontiers in Transplantation, 2. doi:10.3389/frta.2023.1257029
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  Introduction: Subcutaneous macroencapsulation devices circumvent disadvantages of intraportal islet therapy. However, a curative dose of islets within reasonably sized devices requires dense cell packing. We measured internal PO2 of implanted devices, mathematically modeled oxygen availability within devices and tested the predictions with implanted devices containing densely packed human islets.Methods: Partial pressure of oxygen (PO2) within implanted empty devices was measured by noninvasive 19F-MRS. A mathematical model was constructed, predicting internal PO2, viability and functionality of densely packed islets as a function of external PO2. Finally, viability was measured by oxygen consumption rate (OCR) in day 7 explants loaded at various islet densities.Results: In empty devices, PO2 was 12 mmHg or lower, despite successful external vascularization. Devices loaded with human islets implanted for 7 days, then explanted and assessed by OCR confirmed trends proffered by the model but viability was substantially lower than predicted. Co-localization of insulin and caspase-3 immunostaining suggested that apoptosis contributed to loss of beta cells.Discussion: Measured PO2 within empty devices declined during the first few days post-transplant then modestly increased with neovascularization around the device. Viability of islets is inversely related to islet density within devices.1. IntroductionIslet replacement therapy remains a potential cure for type 1 diabetes (1–9). Despite recent improvements in islet transplantation, only about half of patients treated at the most experienced centers are insulin independent five years after transplantation (2–5, 10–19). The current standard for islet transplantation—the intraportal delivery of islets—is admittedly imperfect due to significant islet graft dysfunction and loss over time. Factors contributing to suboptimal engraftment in the liver include: blood-mediated reactions, resulting in inflammation and thrombus formation (20–23); recurrent autoimmunity (24); immunosuppressive drug-related cytotoxicity (25–33); and poor oxygenation (34–44). Importantly, cells transplanted into the liver are difficult to monitor for survival and function and are irretrievable (45–49). Because of the challenges and limitations imposed by intrahepatic transplantation of islets, there has been persistent interest in and a resurgence of investigational studies focused on developing extrahepatic tissue-engineered islet grafts, a “bioartificial pancreas” (50–55).Although extrahepatic islet transplantation using tissue-engineered grafts (TEGs) obviates many of the limitations imposed by intraportal islet transplantation, the bioengineering, experimental, and clinical implementation of a TEG-based approach introduces its own challenges, including: (1) To avoid the necessity for systemic immunosuppression to protect allografted islets, the encapsulation strategy may incorporate an immunoisolation membrane; this prevents host immunomodulatory cells from gaining access to the islets. However, the unintended but unavoidable consequence of immunoisolation is to prevent host vascular penetration into the graft; biophysically, this distances the vasculature from the encapsulated islets, creating an additional hindrance to the rapid diffusion of gases and small molecules. The consequence is that delivery of oxygen and nutrients to the islets and the efflux of insulin and other effectors from the graft is to a degree impeded (50, 56–63). (2) Because transplantation of large numbers of islet equivalents (IE) based on body weight (>5,000 IE/kg) are needed to achieve insulin independence (64–66), grafts must be seeded at high densities in order to use devices of a reasonable size for patients (43, 57, 67–70). (3) The implantation site for the device is no less important; the optimal site would ensure proper access to nutrients and allow for efficient insulin secretion (59, 60). Many extrahepatic sites have been considered and investigated (38, 39, 47, 71–78) but the local partial pressures of oxygen (PO2) at these proposed sites is seldom reported, especially within TEGs. Adequate oxygenation is critical: the survival and especially the functionality of islets are highly sensitive to hypoxic or anoxic conditions (79–83). Accurate and precise monitoring of oxygenation status is therefore a critical parameter in the design and implementation of therapeutic TEGs.This study investigated the effects of increasing islet density on the viability and function of TEGs implanted in either the subcutaneous space or the intraperitoneal cavity of inbred rats. Internal PO2 of sham (acellular) TEGs was measured using fluorine-19 magnetic resonance spectroscopy (19F-MRS); this technique has been validated for the measurement of TEG PO2 in vitro and in vivo (84, 85). These measurements, at intervals over 29 days post implantation, were employed to inform a mathematical model constructed to predict the effects of PO2 external to a device loaded with high islet densities, on graft viability and function. The model was then challenged by loading TEGs with islets at various densities, then implanting them in athymic nude rats (to minimize immunological reactivity) for one week. The devices were then explanted and the viability of their cellular contents measured by oxygen consumption rate (OCR); the data obtained were compared to predictions from the mathematical model.2. Methods 2.1. Ethics statement and experimental schemaAll animal research was performed with the approval of and in accordance with guidelines of the University of Minnesota and the University of Arizona Institutional Animal Care and Use Committees (IACUC). Procurement of human islets was approved and overseen by the University of California Institutional Review Board and informed consent was obtained for all donors.The experimental schema is described and illustrated in Figure 1.Figure 1FIGURE 1. Schema for the experiments reported herein. Rats implanted with sham TEGs containing perfluoro-15-crown-5-ether (PFCE) and hydrogel, but without islets, were submitted to non-invasive fluorine-19 magnetic resonance spectroscopy (19F-MRS) to measure the partial pressure of oxygen within the in vivo devices. The data obtained informed the mathematical model constructed to estimate graft viability and function for various islet graft densities. The model results were challenged by implanting islet-loaded TEGs at different densities and measuring their viabilities by OCR after explantation. The OCR values obtained were used to calculate fractional viability and functionality, the final outputs. All implanted TEGs were examined histologically after their removal.2.2. Sham (acellular) tissue-engineered graft (TEG) constructionThe contents of TEG constructs for 19F-MRS were constituted as a matrix and protected within a clinically-established macroencapsulating immunoisolation device (TheraCyte Inc., Laguna Hills, CA, USA) (59, 86–92), a device chosen for its flexibility, biocompatibility, and published record of successful pre-clinical (86, 93–98) and clinical implementation (91). All implantation procedures were performed using sterile techniques, materials, and reagents.Sham implants (without islets, n = 9) were loaded with equal volumes of porcine plasma (Sigma Aldrich, St. Louis, MO, USA) and perfluoro-15-crown-5-ether (PFCE) (Exfluor Research Corporation, Round Rock, TX, USA), a type of perfluorocarbon with high oxygen solubility. The emulsion was injected into a 40 μl immunoisolation device using a 250 µl precision syringe (Hamilton Company, Reno, NV, USA), then cross-linked with 5% v/v bovine thrombin solution. The latter was prepared by diluting concentrated topical thrombin solution (GenTrac Inc., Middleton, WI, USA) in phosphate-buffered saline with calcium and magnesium. After loading the TEG, the cell access port was trimmed and sealed with adhesive (Dermabond, Ethicon Inc., Somerville, NJ, USA).2.3. Surgical implantation of sham TEGsTo measure the oxygenation status of TEGs in vivo, individual sham TEGs containing PFCE (see 2.2) were implanted in the subcutaneous space (n = 6) or the peritoneal cavity (n = 3) of non-diabetic Lewis rats (RT1I, Charles River Laboratories International, Inc., Wilmington, MA, USA). Anesthesia was induced with isoflurane by inhalation and maintained by spontaneous ventilation of isoflurane (1%–3%). The surgical site was clipped of hair and the skin prepped with chlorhexidine or an equivalent antiseptic. For subcutaneous implants, a 1.5 cm dorsal incision was made just inferior to the scapulae and perpendicular to and symmetrical about the mid-line. Using gentle blunt dissection, a small pocket sufficient to accommodate the device was created. After rinsing the pocket with saline, the device was placed in the pocket. For peritoneal implants, a 1.5 cm incision was made through the anterior abdominal wall to expose the peritoneum. The TEG implant was gently introduced into the abdominal cavity and tacked to the peritoneum using non-absorbable sutures, taking care not to place the TEG directly beneath the incision. The abdominal fascia and skin were closed with absorbable suture and the incision sealed with surgical glue (Dermabond). For postoperative analgesia, a nonsteroidal anti-inflammatory drug (NSAID) (meloxicam 1 mg/kg) was administered by subcutaneous injection once daily for at least 3 days. Animals were monitored daily until the incision was fully healed. After completion of the study, anesthetized animals were euthanized by inhalation of 100% carbon dioxide.2.4. 19F-MRS oximetryOxygen measurements from implanted (see 2.3) TEGs containing PFCE (see 2.2) were acquired with a 16.4 tesla, horizontal-bore MRI system (Agilent Technologies, Santa Clara, CA, USA), Figure 1. Anesthesia was induced and maintained with inhaled isoflurane (1%–3%) in 47%–49% oxygen; the slight variations in oxygen content occurred as isoflurane flow was adjusted to maintain appropriate sedation. The rat was immobilized using a holder which centered the TEG over a 1.5 cm radius, custom-built, single-loop surface coil tuned to the 19F resonance frequency (656.8 MHz). The holder was inserted into the MRI system for scanning, during which the body temperature of the rat was carefully stabilized at 37 ± 0.2°C, as measured with a rectal thermocouple and regulated with a forced-air heater. The spin-lattice relaxation rate constant (R1) was measured using an inversion-recovery pulse sequence with adiabatic pulses. The inversion-recovery curve was fitted to the Bloch equation solution for longitudinal magnetization, using 3-parameter non-linear regression, with Graphpad-Prism software (Graphpad Software Inc., La Jolla, CA, USA). Each R1 was measured in six replicates separated by 6 s intervals, to ensure complete relaxation between repetitions. The R1 of each measurement was converted to PO2 using the previously determined multiparametric calibration (84). In vivo PO2 was measured on days 1, 4, 8, 15, 22, and 29 postimplantation (Figure 2). It is important to note that in vivo PO2 values determined by 19F-MRS oximetry represent average measurements across each device (84).Figure 2FIGURE 2. Oxygen partial pressure (PO2) measurements in subcutaneously implanted sham TEGs, as measured with non-invasive fluorine-19 magnetic resonance spectroscopy (19F-MRS). Average PO2 of subcutaneously implanted sham TEGs (N = 6) were measured on days 1, 4, 8, 15, 22, and 29 post-implantation. The mean PO2 was significantly higher (p  0.1 mmHg) and functionality (decreasing below 8 mmHg) are plotted against ambient PO2.2.7. Explant OCR measurementsTo test the effects of islet density on viability in vivo within TEGs, implants containing various quantities of human islets were implanted in rats for 7 days and then explanted for OCR measurements (Figure 1). TEGs (n = 19) were of the same construction as the sham devices described above (see 2.2), except that they were loaded with islets. Human islets were isolated at the University of California, San Francisco, cultured at 22°C in supplemented CMRL culture medium for up to 14 days, and shipped to the University of Arizona in 10 cm2 G-Rex devices (Wilson Wolf Manufacturing, New Brighton, MN, USA) (112, 113). Islets were quantified by DNA content (114–116) and aliquoted into tubes in various doses ranging from 500 to 8,000 IE per device. Each aliquot was then allowed to settle by gravity in its tube, the supernatant was removed, and the islets were re-suspended in 5 or 20 µl of sterile 1% sodium alginate solution. The islet suspension was then injected into the cell compartment of a 4.5 or 20 µl immunoisolation device, respectively, using a 100 µl precision syringe (Hamilton Company). The TEG was submerged in a 1.2 mM calcium chloride solution (PBS++) for 20–30 min to cross-link the alginate, then placed in PBS++ solution in preparation for implantation.TEGs prepared with various doses of human islets were implanted in the subcutaneous space of 7 non-diabetic nude rats (athymic nude mutant, Hsd:RH-Foxn1rnu, Harlan Laboratories, Inc, Indianapolis, IN, USA). Each rat received two to four devices, each separately placed in its own subcutaneous pocket. Seven days later, the TEGs were surgically removed for measurements of OCR to assess islet viability and for immunohistochemical staining. The surgical implantation and explantation procedures were identical to those described for sham TEGs (see 2.3).The OCR of each explanted TEG was measured by a method similar to that described for the assessment of free islet viability (117). The surgically recovered TEGs were stripped of adherent surrounding tissue, placed in a modified OCR chamber, and filled with air-saturated cell culture medium. In the sealed chamber, the PO2 of the medium was continuously monitored until the values achieved a linear slope; the OCR was calculated from the slope. By normalizing the OCR to the number of IE originally loaded into each device, individual islet graft viability (OCR/IE) was calculated. Previous OCR data obtained in vitro of human islets in devices under ideal conditions were used to calculate the “predicted OCR” at different densities (Figure 4A).Figure 4FIGURE 4. (A) Viability, measured by OCR of islets in explanted TEGs (n is given above the 'Measured OCR' columns), originally loaded with various densities and implanted in the SC space seven days previously; a dramatic decline in measured OCR in comparison to OCR predicted from the loading densities is observed with increasing islet density, far greater than that predicted by the mathematical model. (B) Fractional survival declined precipitously with increasing IE loading. (C) The absolute numbers of IE surviving number about 400 per device, regardless of the loading density. (D,E) Representative sections of the human islet cells within the same TEGs explanted after 7 days’ residence in the subcutaneous space of nude rats. The tissues are stained with the nuclear stain DAPI (blue) or by immunohistochemistry for either the insulin (red) or caspase-3 (green) proteins (see 2.8 and 3.5). Two densities of human islets within TEGs are illustrated: (D) low density, 500 IE/cm2, and (E) high density, 4,000 IE/cm2. At the greater density, there are fewer viable cells (DAPI), less production of insulin, and prominent caspase-3 protein. The composite image at low density demonstrates viable islet cells producing insulin and devoid of caspase-3 whereas at the higher density caspase-3 co-localizes with the remaining insulin-producing cells, suggesting that apoptosis and necrosis of the islet cells have occurred. Labeled are the walls of the TEG, the islet cell graft within it, and the surrounding tissue.2.8. Immunohistochemistry of human islets in seven-day TEGsTEGs containing various densities of human islets were explanted from nude rats after seven days, fixed in 4% paraformaldehyde and embedded in paraffin. Sections of 6 µm thickness were stained with DAPI (1 µg/ml, Roche, Indianapolis, IN, USA) or for insulin (guinea pig anti-porcine insulin 1:500, Dako, Carpinteria, CA, USA), and for cleaved caspase-3 (rabbit anti-human caspase-3, 1:250, Cell Signaling Technology, Danvers, MA, USA); detection was with affinity-purified secondary antiserum conjugated to donkey anti-rabbit IgG and donkey anti-guinea pig IgG (Alexa Fluor 488 and Alex Fluor 594, Jackson ImmunoResearch Laboratories, West Grove, PA, USA), as previously described (118). Independent images for each fluorophore were acquired using a Leica DM5500 microscope system, and the images were processed using Image Pro Plus 6.3 software (Media Cybernetics, Silver Spring, MD, USA); composite images were colored and assembled (blue = DAPI; red = insulin; green = caspase-3).2.9. Statistical analysisAverage values are reported as the mean value and the standard error of the mean (SEM). Least squares-weighted-means and error values are reported for PO2 measurements due to large variabilities observed with some of the PO2 measurements. Statistical comparisons were performed with Graphpad-Prism software or SAS analysis package (version 9.2; SAS Institute, Cary, NC, USA).3. Results 3.1. In vivo PO2 in empty subcutaneous and intraperitoneal TEGsAn important first step in modeling islet function and viability in TEGs was to obtain accurate measurements of oxygen concentrations within devices devoid of cells (see Figure 1). For this purpose, sham (acellular) TEGs loaded only with PFCE (2.2) were implanted in the subcutaneous space (n = 6) or peritoneal cavity (n = 3) of nine rats (2.3), monitored for 29 days using 19F-MRS oximetry (2.4), then explanted for histologic examination (2.5). Internal PO2 measurements were successfully acquired in all animals at six time points (1, 4, 8, 15, 22, and 29 days) following implantation.The average internal PO2 of subcutaneously implanted sham TEGs one day following implantation was 39 (SEM 9) mmHg (Figure 2), about that of venous blood (40 mmHg). The day 1 value however was the highest obtained; it was significantly greater (p 2,000 IE/cm2) than predicted (Figures 3E,F). Histologic examination was confirmatory; at a density of 4,000 IE/cm2 (Figure 4E) compared to 500 IE/cm2 (Figure 4D), far fewer cells stained positive for insulin; importantly, staining for caspase-3 indicated that many of the remaining islet cells were undergoing apoptosis. Although the images documented apoptosis, it must be assumed that necrosis had also occurred; several reports have noted that the two processes are often coincident, perhaps sequential (137–139). However, whether both apoptosis and necrosis are both primarily the consequence of hypoxia alone remains to be determined.Our data and conclusions should not be taken as a blanket condemnation of this technology. Transplanting cells inside a TEG offers essential advantages (68, 70, 140, 141): it localizes the graft within the device, the cells are therefore more amenable to in vivo assessments and, if need be, can be retrieved. Previous efforts (142) to develop a tissue-engineered islet graft (or bioartificial pancreas) have struggled to achieve clinical translation (58, 61, 63, 143–145), but with recent developments in stem cell and xenogeneic islet technologies (87, 146–155) and the promise of scalable alternative β-cell sources (142, 151, 156, 157), there is a renewed interest in—and progress toward—developing a functional insulin-producing, cell-containing TEG for diabetes treatment (87, 158–161).Previously published reports described the challenges of oxygenation for TEGs, especially in scenarios which require high cell-densities to achieve the therapeutic objective with a device of practical size (50, 55, 75, 162). The sham TEG measurements of available oxygen in vivo suggest that the subcutaneous space is profoundly hypoxic, with an average available PO2 of 12 (SEM 5) mmHg [and only 6.8 (SEM 10) mmHg in the peritoneal space].These trends in oxygen levels are not statistically significant, but they are consistent with the pathophysiologic processes that follow a surgical insult and the implantation of foreign materials. TEGs implanted in the peritoneum had a similar PO2 trend and a similar hypoxic environment as subcutaneous TEGs during the 29-day period of observation (Supplementary Information Figure S1). The histological findings from explanted sham TEGs support this interpretation of the dynamic PO2 changes in vivo (Supplemental Information Figure S2). By 29 days, the surrounding tissue had developed a moderate amount of neovascularization; in comparison, only mild fibrosis and foreign body reaction were identified. These findings are consistent with previous reports using similar TEGs (75, 99, 103); fibrosis and foreign body reactions are not unexpected with these materials but can be effectively mitigated with induction of neovascularization aided by the proper selection of materials and membrane microarchitecture (125, 163–165). It should be emphasized that neovascularization of TEGs having vascularizing external membranes is – in fact – a rapid process. Padera and Colton (164) have carefully documented the time course of vascularization of a suitable membrane: vascularity at the interface “increased up to 10 days and remained at this level even at 329 days post-implantation”. Similar observations have been reported by others (88, 165, 166). Investigations of pro-angiogenic factors and other approaches to accelerate vascularization have recently been reviewed (167).In summary, these results suggest that without oxygen supplementation, thin devices with high oxygen permeability are required to maintain viability of encapsulated tissues; even then, to ensure adequate islet function, only low islet densities can be loaded. To accommodate TEGs with low islet densities (≤500 IE/cm2), very large implants would be required to achieve the surface area needed for oxygenation; a device of the required size would be impractical for implantation in humans (57). In addition to the hypoxic stress that encapsulated islets face within these TEGs, there are other in vivo considerations that may further decrease or limit the viability and function of such grafts. Although these considerations are beyond the scope of this work, they may help explain the greater viability loss observed in our experimental measurements using OCR in comparison to the model results. Oxygenation is especially challenging when using high cell densities, which create significant oxygen transport limitations within the graft (50). These challenges are recognized in recent reviews (50, 55, 128). Our results confirm a critical need for improved oxygenation in macroencapsulated TEGs to support the high-cell densities needed for therapeutic applications. Many engineered tissues for the treatment of human disease will require developing complex tissues with high (near native) cell densities to provide therapeutic benefit. Oxygenation is a critical challenge facing the field of tissue engineering and especially for encapsulation approaches that do not allow complete re-vascularization of tissues.Data availability statementThe original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding author.Ethics statementAll animal research was performed with the approval of and in accordance with guidelines of the University of Minnesota and the University of Arizona Institutional Animal Care and Use Committees (IACUC). Procurement of human islets was approved and overseen by the University of California Institutional Review Board and informed consent was obtained for all donors. Ethical approval was not required for the studies on humans in accordance with the local legislation and institutional requirements because only commercially available established cell lines were used. The animal study was approved by University of Minnesota and the University of Arizona Institutional Animal Care and Use Committees (IACUC). The study was conducted in accordance with the local legislation and institutional requirements.Author contributionsSE: Conceptualization, Data curation, Investigation, Writing – original draft, Writing – review & editing. LS: Conceptualization, Data curation, Investigation, Writing – original draft. BW: Writing – review & editing, Conceptualization, Data curation, Formal Analysis, Investigation, Methodology, Supervision, Visualization, Writing – original draft. TS: Conceptualization, Investigation, Writing – original draft. AS: Conceptualization, Methodology, Formal Analysis, Visualization, Writing – review & editing. TO: Conceptualization, Writing – original draft, Investigation. EA: Conceptualization, Data curation, Investigation, Writing – original draft. MF: Conceptualization, Writing – original draft. MLG: Conceptualization, Writing – original draft, Investigation. JJ: Investigation, Writing – original draft. LE: Writing – original draft, Data curation. MG: Data curation, Investigation, Writing – original draft, Writing – review & editing. CP: Writing – review & editing. KP: Conceptualization, Writing – original draft, Writing – review & editing.FundingThe author(s) declare financial support was received for the research, authorship, and/or publication of this article.JDRF Grants: JDRF 5-2013-141, 3-SRA-2015-40-Q-R. NIH Grants: P41 EB015894, S10 RR025031, P30 DK063720, P30 CA023074, 1DP3DK106933-01. Additional funding was provided by the Minnesota Lions Diabetes Foundation, the Schott Foundation, The Carol Olson Memorial Fund, and the Richard M. Schulze Family Foundation.AcknowledgmentsThe authors dedicate this report to our co-author, Meri T. Firpo, who tragically passed prematurely before submission of the manuscript. Human islets were provided by the University of California, San Francisco, Islet and Cellular Production Facility which is supported by the Diabetes Endocrinology Research Center grant (NIH P30 DK063720). Histological samples for sham devices were processed by the Comparative Pathology Shared Resource (CPC) at the University of Minnesota. Immunohistochemical images of devices containing human islets were generated by the Tissue Acquisition and Cellular/Molecular Analysis Shared Service (TACMASR Core) which is supported by the University of Arizona Cancer Center Support grant (NIH P30 CA023074). The authors wish to acknowledge Chan A. Ion and Jennifer Kitzmann-Miner for their work in preparing graphic materials.Conflict of interestKP is the co-founder and CEO of Procyon Technologies, LLC, a startup company focused on the development of oxygenated cell encapsulation devices. BW, who was a graduate student at the time of this study, is now employed by Sylvatica Biotech Inc.The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.The author MG declared that he was an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.Publisher's noteAll claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.Supplementary materialThe Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/frtra.2023.1257029/full#supplementary-materialReferences1. Basile G, Qadir MMF, Mauvais-Jarvis F, Vetere A, Shoba V, Modell AE, et al. Emerging diabetes therapies: bringing back the β-cells. Mol Metab. (2022) 60:101477. doi: 10.1016/j.molmet.2022.101477PubMed Abstract | CrossRef Full Text | Google Scholar2. Hatipoglu BA, Blanchette J. Islet cell therapy and stem cell therapy for type 1 diabetes: there will always be a hope. Endocrinol Metab Clin North Am. (2023) 52(1):187–93. doi: 10.1016/j.ecl.2022.07.001PubMed Abstract | CrossRef Full Text | Google Scholar3. Rickels MR, Robertson RP. Pancreatic islet transplantation in humans: recent progress and future directions. Endocr Rev. 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• Papas, K. K. (2023).

  116.2: Dynamic insulin/glucagon measurements from human islet perifusion

  . Transplantation, 107(10S2), 21-21. doi:10.1097/01.tp.0000993832.82292.21
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  Introduction: The islets of Langerhans of the pancreas (multicellular spheroidal organoids constituting 1-3% of the pancreas volume) are the primary endocrine cells regulating glucose homeostasis via two primary hormones, insulin, and glucagon. Insulin is secreted from beta cells and glucagon from alpha cells. The two hormones have opposing effects on glucose homeostasis: insulin promotes glucose uptake into several cell types and thus lowers blood glucose levels; glucagon drives glucose production in the liver, thus raising glucose levels. Secretion of both hormones is a highly dynamic process, involving complex mechanisms including crosstalk within islets, which are not fully understood. Most of these dynamic processes have been studied primarily with rodent islets, whereas human islets studies are limited. Methods: For our study, we used a Biorep perifusion system to collect samples for the concurrent measurements of insulin and glucagon secreted from human islets exposed to two glucose concentrations, as well as KCl or arginine stimulation. Human islets were isolated at the Institute for Cellular Transplantation at the University of Arizona. Perifusions were performed on 25 individual islet isolations in which insulin and glucagon were simultaneously measured using a multiplex assay. Results: Glucose stimulation (16.7mM) caused a biphasic insulin response with the 1st phase peaking ~ 2 minutes and lasting 6-8 minutes, followed by a sustained 2nd phase. As predicted, glucagon levels decreased during glucose stimulation and remained repressed until islets were again exposed to low glucose (2.8mM). KCL (30mM) was used to mimic depolarization, which induced a monophasic peak for both glucagon and insulin secretion. Arginine stimulation (10mM) under low glucose conditions initiated a biphasic glucagon response and a modest monophasic increase in insulin. Conclusions: Our data provides a physiological template to assess islet function for clinical and research use, as well as a method to test novel drugs to potentiate/inhibit secretion of these hormones. We would like to thank the members of the Institute for Cellular Transplantation at the University of Arizona for their technical support and contributions to this research. Partial funding from NIH/NIDDK (1DP3DK106933-01, 1R43DK113537-01) and JDRF (1-PNF-2018-520-SB, 1-PNF-2018-519-SB).
• Papas, K. K. (2023).

  401.2: Effects of hyperoxia on human and rat islets

  . Transplantation, 107(10S2), 159-159. doi:10.1097/01.tp.0000994636.20851.f5
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  Background: Islet transplantation of encapsulated cells within an immunoprotective device is a promising approach to cure Type 1 diabetes without the need for lifelong immunosuppression. Unfortunately, in order to use a device of a reasonable size, the large number of cells required for diabetes reversal dictates high-cell packing density, which results in oxygen limitations affecting the viability and functionality of the encapsulated cells. Oxygen at a high concentration delivered to encapsulated cells can help reduce the hypoxia induced reduction of encapsulated cell viability and function. However, hyperoxia can also be detrimental to cells, so the toxicity of high oxygen exposure needs to be investigated so as to establish safe levels of oxygen exposure. In this study, we investigated rat and human islets exposed to different concentrations of oxygen and evaluated the viability and function of the cells at various time points. Methods: Human and rat islets were exposed to normoxic and hyperoxic conditions (40, 60, and 95%) for up to 7 days. Islet viability was assessed by oxygen consumption rate (OCR) and membrane integrity staining with fluorescein diacetate and propidium iodide. Islet function was assessed by dynamic glucose stimulated insulin secretion (GSIS) via perifusion (Biorep). Results: In hyperoxic 40% culture, neither OCR nor GSIS were changed in human or rat islets for as long as 7 days of exposure relative to normoxic control. In hypoxic 60% culture, neither OCR nor GSIS were changed in rat islets relative to normoxic control; however, OCR was reduced by ~15% after 1 day of exposure and by ~30% after 7 days of exposure in human islets. GSIS was also significantly reduced as early as 1 day of exposure. Hyperoxic 95% culture significantly reduced both OCR and GSIS in both rat and human islets after 1 day of exposure and with a very small fraction of surviving cells after 7 days of exposure. Conclusions: Supplemental oxygen, particularly in the peri-transplant period, will be essential to support enough insulin secreting cells within a reasonably sized encapsulation device for the treatment of Type 1 diabetes in a research animal model or human patients. Our data indicates that up to 40% oxygen can be supplied to rat and human islets and it is not detrimental to viability or function. However, hyperoxia of >60% can be toxic to human islets with as little as 24 hours of exposure. Future work will be aimed at further defining the “safe” oxygen exposure limits at which islet viability and function are maintained for primary and stem cell derived islets. We would like to thank all of the members of the Papas Laboratory at ICT including Jose Cano and Barry Huey. Work was performed with funding from NIH/NIDDK (1DP3DK106933-01, 1R43DK113537-01), JDRF (3-SRA-2015-40-Q-R, 1-PNF-2018-520-SB, 1-PNF-2018-519-SB), and Procyon Technologies LLC.
• Papas, K. K. (2023).

  401.3: The development of a sheep model for encapsulated cell therapies

  . Transplantation, 107(10S2), 159-159. doi:10.1097/01.tp.0000994640.18377.bb
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  Introduction: Cell therapy has become increasingly studied for therapeutic use in drug delivery and regenerative medicine. Immunoisolating devices intended for implantation of cells require construction of membranes that can safely contain transplanted cells, provide a barrier to the host immune system, and induce close vessel formation. Sheep make an excellent model for translational research because of their nearly comparable size, physiology, and disease profile with humans, as well as their docility, capacity for repeated blood draws, ability to tolerate numerous implants during a single operation, and affordability. In this study, sheep were implanted with devices containing allogeneic primary fetal sheep or xenogeneic Rat-2 fibroblasts, to determine cell survival in immunoisolating devices and immune response. Methods: Primary fetal sheep fibroblasts were isolated from a healthy fetus and cultured in RPMI. Rat-2 fibroblasts (ATCC) were cultured in DMEM. On the day of transplant, cells were aliquoted and loaded into devices at different densities. Sheep underwent allogeneic or xenogeneic transplantation with cell-loaded devices, as well as empty control and perforated devices. Devices were implanted subcutaneously through small incisions along the flank within individual pockets made by blunt dissection. Devices remained in vivo until explant at days 3, 7, 21 and 38 to evaluate host responses, vascularization, and cell survival. Explanted devices were fixed, embedded, and sectioned for histological evaluation. Results: Primary fetal sheep cells survived at different densities as assessed by histology, confirming alloprotection with good vascularization and absence of a major foreign body response or extensive inflammation around the device host interface. Devices at the highest densities were overloaded and exhibited some host immune responses. Perforated devices exhibited a greater immune response that infiltrated the device. A robust inflammatory response was seen around devices loaded with xenogeneic Rat-2 fibroblasts with no encapsulated cells surviving. Conclusion: Sheep make a valuable large animal model in cell therapy research. The results of this study concluded alloprotection in immunoisolating devices, allorejection in purposely perforated devices, as well as host immune response to xenogeneic transplantation, representing a feasible model for translational development of cell therapies. Future work with this accessible and relevant platform will include not only allogeneic studies but also avoiding xenogeneic rejection by incorporating immunomodulatory technologies using genetically edited cells or factors. We would like to thank all of the members of the Papas Laboratory at ICT and the Limesand Laboratory at the William J. Parker Agricultural Research Center. Partial funding from JDRF (2-SRA-2020-870-S-B and 2-SRA-2018-685-S-B) and Procyon Technologies LLC.
• Papas, K. K. (2023).

  401.4: Sustained hyperoxic exposure decreases cell viability and reduces cell growth in pancreatic beta cell lines

  . Transplantation, 107(10S2), 160-160. doi:10.1097/01.tp.0000994644.91754.36
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  Background. Immunoprotective encapsulation devices hold promise for enabling cell-based insulin replacement therapies without immunosuppression, for example with human islets or stem cell–derived β cells. However, for the encapsulation device to be of reasonable size, cell densities within the device must be high; this contributes to a hypoxic environment within the device. Supplemental oxygen to an encapsulation device would reduce the highly detrimental effects of low oxygen on the cells residing within it. However, hyperoxia can also be toxic; this study investigates the effects of various oxygen concentrations on pancreatic β-cell lines in order to identify a safe oxygen exposure level. Methods. Pancreatic β-cell lines were exposed to normoxic or hyperoxic culture conditions (40, 60, and 95%) for 7 days, after which viability was assessed by oxygen consumption rate (OCR) and with acridine orange staining. Cell counts were performed after nuclear DNA staining with DAPI. Results. In hyperoxia of only 40% O2, MIN6 cells showed reduced OCR (P
• Papas, K. K. (2023).

  Accelerated absorption of regular insulin administered via a vascularizing permeable microchamber implanted subcutaneously in diabetic Rattus norvegicus

  . PLoS One, 18(Issue 6). doi:10.1371/journal.pone.0278794
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  http://dx.doi.org.ezproxy3.library.arizona.edu/10.1371/journal.pone.0278794
• Papas, K. K. (2023).

  Development of a Compact NMR System to Measure pO2 in a Tissue-Engineered Graft

  . Journal of Magnetic Resonance. doi:10.1016/j.jmr.2023.107578
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  Cellular macroencapsulation devices, known as tissue engineered grafts (TEGs), enable the transplantation of allogeneic cells without the need for life-long systemic immunosurpression. Islet containing TEGs offer promise as a potential functional cure for type 1 diabetes. Previous research has indicated sustained functionality of implanted islets at high density in a TEG requires external supplementary oxygen delivery and an effective tool to monitor TEG oxygen levels. A proven oxygen-measurement approach employs a 19F oxygen probe molecule (a perfluorocarbon) implanted alongside therapeutic cells to enable oxygen- and temperature- dependent NMR relaxometry. Although the approach has proved effective, the clinical translation of 19F oxygen relaxometry for TEG monitoring will be limited by the current inaccessibility and high cost of MRI. Here, we report the development of an affordable, compact, and tabletop 19F NMR relaxometry system for monitoring TEG oxygenation. The system uses a 0.5 T Halbach magnet with a bore diameter (19 cm) capable of accommodating the human arm, a potential site of future TEG implantation. 19F NMR relaxometry was performed while controlling the temperature and oxygenation levels of a TEG using a custom-built perfusion setup. Despite the magnet’s nonuniform field, a pulse sequence of broadband adiabatic full-passage pulses enabled accurate 19F longitudinal relaxation rate (R1) measurements in times as short as 2 min (R1 vs oxygen partial pressure and temperature (R2 > 0.98)). The estimated sensitivity of R1 to oxygen changes at 0.5 T was 1.62-fold larger than the sensitivity previously reported for 16.4 T. We conclude that TEG oxygenation monitoring with a compact, tabletop 19F NMR relaxometry system appears feasible.
• Papas, K. K. (2023).

  Encapsulated Cells for the Treatment of Diabetes: Danger of Acute Hypoglycemia Following Injury?

  . Cell Transplantation, 32, 096368972311632. doi:10.1177/09636897231163233
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  Transplants comprised of encapsulated islets have shown promise in treating insulin-dependent diabetes. A question raised in the scientific and clinical communities is whether the insulin released from an implanted encapsulation device damaged in an accident could cause a serious hypoglycemic event. In this commentary, we consider the different types of damage that a device can sustain, including the encapsulation membrane and the islets within, and the amount of insulin released in each case. We conclude that the probability that device damage would cause an adverse hypoglycemic event is indeed very low.
• Papas, K. K. (2023).

  Kisspeptin Modulates Mitochondrial Metabolic State and Potentiates Glucose Stimulated Insulin Secretion in INS 832/3 Cells and Pseudo-Islets

  . Physiology, 38(S1). doi:10.1152/physiol.2023.38.s1.5733735
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  Glucagon Like Peptide-1 (GLP-1) and Kisspeptin (KP) receptors are co-expressed on pancreatic β-cells, and activation of both receptors potentiates glucose-stimulated insulin secretion (GSIS). Due to their roles in enhancing GSIS, GLP-1 and KP represent targets for controlling blood glucose in patients with diabetes. Unlike GLP-1, KP has a low affinity for receptor activation (EC50 GLP-1 ~20 nM vs KP ~1 μM) making it difficult to use as a therapeutic agent. GLP-1 has been shown to potentiate insulin secretion via cAMP dependent pathways. Conversely, previous studies in isolated rat islets of Langerhans indicated that KP potentiation of GSIS was not dependent on cAMP and may be related to changes in beta cell metabolism (Schwetz TA, et al., Differential Stimulation of Insulin Secretion by GLP-1 and Kisspeptin-10. PLoS ONE 9: e113020, 2014). In the current studies, we evaluated KP signaling in comparison to GLP-1, in order to determine if there are unique components to target in the KP signaling pathway. The effects of GLP-1 and a 10 amino acid analog of KP (KP10) on insulin secretion and cell signaling were compared in insulinoma INS 832/3 cells. As previously described, KP had no effect on insulin secretion in the absence of glucose. In the presence of stimulatory glucose (15.5 mM), KP10 (10 μM) doubled insulin secretion (GSIS without KP10= 471.3 +/- 83.8, GSIS with KP10 = 865.0 +/- 23.8 pgm/min; +/- SEM) with an EC50 of ~5-10 μM. At saturating doses, KP10 (100 μm) and GLP-1 (100 nM) had similar effects on GSIS. Importantly, in combination, they had an additive effect (GLP-1 = 612.5 +/- 25.0, GLP-1 + KP-10 = 739.8 +/- 70.0 pgm/min) consistent with activation of independent downstream signaling pathways. GLP-1 increased cAMP production (165.0 +/- 17.4% over control), whereas KP-10 had no effect. Neither GLP-1 nor KP-10 altered intracellular Ca2+ levels at basal or activating glucose concentrations. Conversely, the addition of KP-10 enhanced glucose-stimulated oxygen consumption (% change over baseline O_2 consumption= 221.2 +/- 44.2%) from INS 832/3 pseudo-islets (Hart et al. Insulinoma-derived pseudo-islets for diabetes research. Am. J. Physio. 321, C247-C256, 2021) which was correlated with a sustained increase in mitochondrial NADH fluorescence. Our findings indicate that KP modulation of mitochondrial metabolic state is related to its ability to potentiate GSIS. Moreover, the KP induced potentiation is synergistic with that promoted by GLP-1 indicating the potential for targeting the KP activated metabolic pathway to further enhance GLP-1 therapeutic effectiveness. Funded by the Juvenile Diabetes Research Foundation (2-SRA-2018-685-S-B), and Procyon Technologies LLC This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
• Papas, K. K. (2023).

  Short‐term function and immune‐protection of microencapsulated adult porcine islets with alginate incorporating CXCL12 in healthy and diabetic non‐human primates without systemic immune suppression: A pilot study

  . Xenotransplantation. doi:10.1111/xen.12826
• Papas, K. K. (2021). Insulinoma-derived pseudo-islets for diabetes research. American Journal of Physiology-Cell Physiology, 321(2), 247-256. doi:https://doi.org/10.1152/ajpcell.00466.2020
• Papas, K. K. (2022). Clinical Islet Transplantation Consortium. Long-term outcomes with islet-alone and islet-after-kidney transplantation for type 1 diabetes in the clinical islet transplantation consortium: The CIT-08 study.. Diabetes care, 45, 2967-2975. doi:https://doi.org/10.2337/dc21-2688
• Papas, K. K. (2022). A predictive computational platform for optimizing the design of bioartificial pancreas devices. Nature Communications, 13, 1-8. doi:https://doi.org/10.1038/s41467-022-33760-5
• Papas, K. K. (2022). Clinically available immunosuppression averts rejection but not systemic inflammation after porcine islet xenotransplant in cynomolgus macaques. American Journal of Transplantation, 22(3). doi:https://doi.org/10.1111/ajt.16876
• Papas, K. K. (2020). Insulinoma derived pseudo-islets for diabetes research. American Journal of Physiology-Cell Physiology, 247-256.
• Papas, K. K. (2021). An inverse-breathing encapsulation system for cell delivery. . Science Advances, 7(20).
• Papas, K. K. (2021). Long-term outcomes with islet-alone and islet-after-kidney transplantation for type 1 diabetes in the clinical islet transplantation consortium: The CIT-08 study. Diabetes Care, 45, 2967-2975. doi:https://doi.org/10.2337/dc21-2688
• Papas, K. K. (2021). An inverse-breathing encapsulation system for cell delivery. Science Advances.
• Papas, K. K. (2021). An inverse-breathing encapsulation system for cell delivery. ScienceAdvances, 7(20). doi:https://www.science.org/doi/10.1126/sciadv.abd5835
• Papas, K. K. (2020). Mathematical predictions of oxygen availability in micro‐ and macro‐encapsulated human and porcine pancreatic islets. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 108(2), 343-352. doi:https://doi.org/10.1002/jbm.b.34393
• Papas, K. K. (2020). Noninvasive Fluorine-19 Magnetic Resonance Relaxometry Measurement of the Partial Pressure of Oxygen in Acellular Perfluorochemical-loaded Alginate Microcapsules Implanted in the Peritoneal Cavity of Nonhuman Primates. Transplantation, 104(2), 259-269. doi:10.1097/TP.0000000000002896
• Cao, R., Avgoustiniatos, E., Papas, K., de Vos, P., & Lakey, J. R. (2019). Mathematical predictions of oxygen availability in micro- and macro-encapsulated human and porcine pancreatic islets. Journal of biomedical materials research. Part B, Applied biomaterials.
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  Optimal function of immunoisolated islets requires adequate supply of oxygen to metabolically active insulin producing beta-cells. Using mathematical modeling, we investigated the influence of the pO on islet insulin secretory capacity and evaluated conditions that could lead to the development of tissue anoxia, modeled for a 300 μm islet in a 500 μm microcapsule or a 500 μm planar, slab-shaped macrocapsule. The pO was used to assess the part of islets that contributed to insulin secretion. Assuming a 500 μm macrocapsule with a 300 μm islet, with oxygen consumption rate (OCR) of 100-300 nmol min mg DNA, islets did not develop any necrotic core. The nonfunctional zone (with no insulin secretion if pO  
• Kelly, A. C., Smith, K. E., Purvis, W. G., Min, C. G., Weber, C. S., Cooksey, A. M., Hasilo, C., Paraskevas, S., Suszynski, T. M., Weegman, B. P., Anderson, M. J., Camacho, L. E., Harland, R. C., Loudovaris, T., Jandova, J., Molano, D. S., Price, N. D., Georgiev, I. G., Scott, W. E., , Manas, D. M., et al. (2019). Oxygen Perfusion (Persufflation) of Human Pancreata Enhances Insulin Secretion and Attenuates Islet Proinflammatory Signaling. Transplantation, 103(1), 160-167.
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  All human islets used in research and for the clinical treatment of diabetes are subject to ischemic damage during pancreas procurement, preservation, and islet isolation. A major factor influencing islet function is exposure of pancreata to cold ischemia during unavoidable windows of preservation by static cold storage (SCS). Improved preservation methods may prevent this functional deterioration. In the present study, we investigated whether pancreas preservation by gaseous oxygen perfusion (persufflation) better preserved islet function versus SCS.
• Lavery, L. A., Niederauer, M. Q., Papas, K. K., & Armstrong, D. G. (2019). Does Debridement Improve Clinical Outcomes in People With Diabetic Foot Ulcers Treated With Continuous Diffusion of Oxygen?. Wounds : a compendium of clinical research and practice, 31(10), 246-251.
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  This post hoc analysis evaluates the association between the frequency of diabetic foot ulcer (DFU) debridement and the proportion of ulcers treated with active continuous diffusion of oxygen (CDO) that heal in a 12-week evaluation period.
• Moshref, M., Tangey, B., Gilor, C., Papas, K. K., Williamson, P., Loomba-Albrecht, L., Sheehy, P., & Kol, A. (2019). Concise Review: Canine Diabetes Mellitus as a Translational Model for Innovative Regenerative Medicine Approaches. Stem cells translational medicine, 8(5), 450-455.
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  Diabetes mellitus (DM) is a common spontaneous endocrine disorder in dogs, which is defined by persistent hyperglycemia and insulin deficiency. Like type 1 diabetes (T1D) in people, canine DM is a complex and multifactorial disease in which genomic and epigenomic factors interact with environmental cues to induce pancreatic β-cell loss and insulin deficiency, although the pathogenesis of canine DM is poorly defined and the role of autoimmunity is further controversial. Both diseases are incurable and require life-long exogenous insulin therapy to maintain glucose homeostasis. Human pancreatic islet physiology, size, and cellular composition is further mirrored by canine islets. Although pancreatic or isolated islets transplantation are the only clinically validated methods to achieve long-term normoglycemia and insulin independence, their availability does not meet the clinical need; they target a small portion of patients and have significant potential adverse effects. Therefore, providing a new source for β-cell replacement is an unmet need. Naturally occurring DM in pet dogs, as a translational platform, is an untapped resource for various regenerative medicine applications that may offer some unique advantages given dogs' large size, longevity, heterogenic genetic background, similarity to human physiology and pathology, and long-term clinical management. In this review, we outline different strategies for curative approaches, animal models used, and consider the value of canine DM as a translational animal/disease model for T1D in people. Stem Cells Translational Medicine 2019;8:450-455.
• Papas, K. K., De Leon, H., Suszynski, T. M., & Johnson, R. C. (2019). Oxygenation strategies for encapsulated islet and beta cell transplants. Advanced drug delivery reviews, 139, 139-156.
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  Human allogeneic islet transplantation (ITx) is emerging as a promising treatment option for qualified patients with type 1 diabetes. However, widespread clinical application of allogeneic ITx is hindered by two critical barriers: the need for systemic immunosuppression and the limited supply of human islet tissue. Biocompatible, retrievable immunoisolation devices containing glucose-responsive insulin-secreting tissue may address both critical barriers by enabling the more effective and efficient use of allogeneic islets without immunosuppression in the near-term, and ultimately the use of a cell source with a virtually unlimited supply, such as human stem cell-derived β-cells or xenogeneic (porcine) islets with minimal or no immunosuppression. However, even though encapsulation methods have been developed and immunoprotection has been successfully tested in small and large animal models and to a limited extent in proof-of-concept clinical studies, the effective use of encapsulation approaches to convincingly and consistently treat diabetes in humans has yet to be demonstrated. There is increasing consensus that inadequate oxygen supply is a major factor limiting their clinical translation and routine implementation. Poor oxygenation negatively affects cell viability and β-cell function, and the problem is exacerbated with the high-density seeding required for reasonably-sized clinical encapsulation devices. Approaches for enhanced oxygen delivery to encapsulated tissues in implantable devices are therefore being actively developed and tested. This review summarizes fundamental aspects of islet microarchitecture and β-cell physiology as well as encapsulation approaches highlighting the need for adequate oxygenation; it also evaluates existing and emerging approaches for enhanced oxygen delivery to encapsulation devices, particularly with the advent of β-cell sources from stem cells that may enable the large-scale application of this approach.
• Papas, K. K., DeLeon, H., Suszynski, T. M., & Johnson, R. C. (2019). Oxygenation Strategies for Encapsulated Islet and Beta Cell Transplants. Advanced Drug Delivery Reviews.
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  Papas K.K., De Leon, H, Suszynski, TM, Johnson RC,. “Oxygenation Strategies for Encapsulated Islet and Beta Cell Transplants” Advanced Drug Delivery Reviews. 2019
• Safley, S. A., Graham, M. L., Weegman, B. P., Einstein, S. A., Barber, G. F., Janecek, J. J., Mutch, L. A., Singh, A., Ramachandran, S., Garwood, M., Sambanis, A., Papas, K. K., Hering, B. J., & Weber, C. J. (2019). Noninvasive Fluorine-19 Magnetic Resonance Relaxometry Measurement of the Partial Pressure of Oxygen in Acellular Perfluorochemical-loaded Alginate Microcapsules Implanted in the Peritoneal Cavity of Nonhuman Primates. Transplantation.
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  We have utilized a noninvasive technique for measuring the partial pressure of oxygen (pO2) in alginate microcapsules implanted intraperitoneally (i.p,) in healthy non-human primates (NHPs). Average pO2 is important for determining if a transplant site and capsules with certain passive diffusion characteristics can support the islet viability, metabolic activity, and dose necessary to reverse diabetes.
• Sremac, M., Lei, J., Penson, M. F., Schuetz, C., Lakey, J. R., Papas, K. K., Varde, P. S., Hering, B., de Vos, P., Brauns, T., Markmann, J., & Poznansky, M. C. (2019). Preliminary Studies of the Impact of CXCL12 on the Foreign Body Reaction to Pancreatic Islets Microencapsulated in Alginate in Nonhuman Primates. Transplantation direct, 5(5), e447.
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  We previously demonstrated that the incorporation of the chemokine CXCL12 into alginate microbeads supported long-term survival of microencapsulated auto-, allo-, and xenogeneic islets in murine models of diabetes without systemic immune suppression. The purpose of this study was to test whether CXCL12 could abrogate foreign body responses (FBRs) against alginate microbeads which were empty or contained autologous islets in healthy nonhuman primates (NHPs; n = 4).
• Yates, D. T., Camacho, L. E., Kelly, A. C., Steyn, L. V., Davis, M. A., Antolic, A. T., Anderson, M. J., Goyal, R., Allen, R. E., Papas, K. K., Hay, W. W., & Limesand, S. W. (2019). Postnatal β2 adrenergic treatment improves insulin sensitivity in lambs with IUGR but not persistent defects in pancreatic islets or skeletal muscle. The Journal of physiology, 597(24), 5835-5858.
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  Previous studies in fetuses with intrauterine growth restriction (IUGR) have shown that adrenergic dysregulation was associated with low insulin concentrations and greater insulin sensitivity. Although whole-body glucose clearance is normal, 1-month-old lambs with IUGR at birth have higher rates of hindlimb glucose uptake, which may compensate for myocyte deficiencies in glucose oxidation. Impaired glucose-stimulated insulin secretion in IUGR lambs is due to lower intra-islet insulin availability and not from glucose sensing. We investigated adrenergic receptor (ADR) β2 desensitization by administering oral ADRβ modifiers for the first month after birth to activate ADRβ2 and antagonize ADRβ1/3. In IUGR lambs ADRβ2 activation increased whole-body glucose utilization rates and insulin sensitivity but had no effect on isolated islet or myocyte deficiencies. IUGR establishes risk for developing diabetes. In IUGR lambs we identified disparities in key aspects of glucose-stimulated insulin secretion and insulin-stimulated glucose oxidation, providing new insights into potential mechanisms for this risk.
• Kelly, A. C., Camacho, L. E., Pendarvis, K., Davenport, H. M., Steffens, N. R., Smith, K. E., Weber, C. S., Lynch, R. M., Papas, K. K., & Limesand, S. W. (2018). Adrenergic receptor stimulation suppresses oxidative metabolism in isolated rat islets and Min6 cells. Molecular and cellular endocrinology.
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  Insulin secretion is stimulated by glucose metabolism and inhibited by catecholamines through adrenergic receptor stimulation. We determined whether catecholamines suppress oxidative metabolism in β-cells through adrenergic receptors. In Min6 cells and isolated rat islets, epinephrine decreased oxygen consumption rates compared to vehicle control or co-administration of epinephrine with α2-adrenergic receptor antagonist yohimbine. Epinephrine also decreased forskolin-stimulated oxygen consumption rates, indicating cAMP dependent and independent actions. Furthermore, glucose oxidation rates were decreased with epinephrine, independent of the exocytosis of insulin, which was blocked with yohimbine. We evaluated metabolic targets through proteomic analysis after 4 h epinephrine exposure that revealed 466 differentially expressed proteins that were significantly enriched for processes including oxidative metabolism, protein turnover, exocytosis, and cell proliferation. These results demonstrate that acute α2-adrenergic stimulation suppresses glucose oxidation in β-cells independent of nutrient availability and insulin exocytosis, while cAMP concentrations are elevated. Proteomics and immunoblots revealed changes in electron transport chain proteins that were correlated with lower metabolic reducing equivalents, intracellular ATP concentrations, and altered mitochondrial membrane potential implicating a new role for adrenergic control of mitochondrial function and ultimately insulin secretion.
• Kelly, A. C., Smith, K. E., Purvis, W. G., Min, C. G., & Papas, K. K. (2018). Oxygen Perfusion (Persufflation) of Human Pancreata Enhances Insulin Secretion and Attenuates Islet Proinflammatory Signaling. Transplantation. doi:10.1097
• Min, C. G., & Papas, K. K. (2018). Recent Developments of Persufflation for Organ Preservation. Current Opinion in Organ Transplantation, 23(3), 330-335. doi:10.1097
• Min, C. G., & Papas, K. K. (2018). Recent developments in persufflation for organ preservation. Current opinion in organ transplantation, 23(3), 330-335.
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  To summarize current literature and recent findings on the potential of humidified oxygenated gas perfusion (persufflation) as an alternative method for improved organ preservation.
• Niederauer, M., Michalek, J., Liu, Q., Papas, K. K., Lavery, L., & Armstrong, D. (2018). Continuous diffusion of oxygen improves diabetic foot ulcer healing when compared with a placebo control: a randomised, double-blind, multicentre study. Journal of Wound Care, 27(Sup9), S30-S45. doi:10.12968
• Osum, K., Burrack, A., Martinov, T., Sahli, N., Mitchell, J., Tucker, C., Pauken, K., Papas, K. K., Appakalai, B., Spanier, J., & Fife, B. (2018). Interferon-gamma drives programmed death-ligand 1 expression on islet β cells to limit T cell function during autoimmune diabetes.. Scientific Reports, 8(1), 8295.
• Smith, K. E., Johnson, R. C., & Papas, K. K. (2018). Update on cellular encapsulation. Xenotransplantation, 25(5), e12399.
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  There is currently a significant disparity between the number of patients who need lifesaving transplants and the number of donated human organs. Xenotransplantation is a way to address this disparity and attempts to enable the use of xenogeneic tissues have persisted for centuries. While immunologic incompatibilities have presented a persistent impediment to their use, encapsulation may represent a way forward for the use of cell-based xenogeneic therapeutics without the need for immunosuppression. In conjunction with modern innovations such as the use of bioprinting, incorporation of immune modulating molecules into capsule membranes, and genetic engineering, the application of xenogeneic cells to treat disorders ranging from pain to liver failure is becoming increasingly realistic. The present review discusses encapsulation in the context of xenotransplantation, focusing on the current status of clinical trials, persistent issues such as antigen shedding, oxygen availability, and donor selection, and recent developments that may address these limitations.
• Smith, K. E., Purvis, W. G., Davis, M. A., Min, C. G., Cooksey, A. C., Weber, C. C., Jandova, J., Price, N., Molano, D., Stanton, J. B., Kelly, A. C., Steyn, L. V., & Papas, K. K. (2018). In vitro characterization of neonatal, juvenile, and adult porcine islet oxygen demand, β-cell function, and transcriptomes.. Xenotransplantation.
• Min, C., Pandey, A., Steyn, L., Taylor, M., Harland, R., Galons, J., & Papas, K. K. (2017). Quality Assessments of Persufflated and Cold Storage Preservation in Subnormothermic Isolated Porcine Kidneys. Transplantation.
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  Abstract
• Papas, K. K., Smith, K. E., Kelly, A. C., Min, C. G., Weber, S. C., McCartney, F. M., Steyn, L. V., Badarinarayana, V., Kitzmann, J. P., Strop, P., Gruessner, A. C., Lynch, R. M., & Limesand, S. W. (2017). Acute Ischemia induced b high density culture increases cytokine expression and diminishes the function and viability of highly purified human islets of Langerhans. Transplantation.
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  Abstract
• Smith, K. E., Kelly, A. C., Min, C. G., Weber, C. S., McCarthy, F. M., Steyn, L. V., Badarinarayana, V., Stanton, J. B., Kitzmann, J. P., Strop, P., Gruessner, A. C., Lynch, R. M., Limesand, S. W., & Papas, K. K. (2017). Acute Ischemia Induced by High-Density Culture Increases Cytokine Expression and Diminishes the Function and Viability of Highly Purified Human Islets of Langerhans. Transplantation, 101(11), 2705-2712.
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  Encapsulation devices have the potential to enable cell-based insulin replacement therapies (such as human islet or stem cell-derived β cell transplantation) without immunosuppression. However, reasonably sized encapsulation devices promote ischemia due to high β cell densities creating prohibitively large diffusional distances for nutrients. It is hypothesized that even acute ischemic exposure will compromise the therapeutic potential of cell-based insulin replacement. In this study, the acute effects of high-density ischemia were investigated in human islets to develop a detailed profile of early ischemia induced changes and targets for intervention.
• Smith, K., Kelly, A., Min, C., Weber, C., McCarthy, F., Steyn, L., Badarinarayana, V., Kitzmann, J., Strop, P., Gruessner, A., Lynch, R., Limesand, S., & Papas, K. K. (2017). Acute ischemia induced by high density culture increases cytokine expression and diminishes the function and viability of highly purified human islets of Langerhans. Transplantation. doi:10.1097
• Einstein, S. A., Weegman, B. P., Firpo, M. T., Papas, K. K., & Garwood, M. (2016). Development and Validation of Noninvasive Magnetic Resonance Relaxometry for the In Vivo Assessment of Tissue-Engineered Graft Oxygenation. TISSUE ENGINEERING PART C-METHODS, 22(11), 1009-1017.
• Einstein, S. A., Weegman, B. P., Kitzmann, J. P., Papas, K. K., & Garwood, M. (2016). Noninvasive assessment of tissue-engineered graft viability by oxygen-17 magnetic resonance spectroscopy. Biotechnology and bioengineering. doi:10.1002/bit.26227
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  Transplantation of macroencapsulated tissue-engineered grafts (TEGs) is being investigated as a treatment for type 1 diabetes, but there is a critical need to measure TEG viability both in vitro and in vivo. Oxygen deficiency is the most critical issue preventing widespread implementation of TEG transplantation and delivery of supplemental oxygen (DSO) has been shown to enhance TEG survival and function in vivo. In this study, we demonstrate the first use of oxygen-17 magnetic resonance spectroscopy ((17) O-MRS) to measure the oxygen consumption rate (OCR) of TEGs and show that in addition to providing therapeutic benefits to TEGs, DSO with (17) O2 can also enable measurements of TEG viability. Macroencapsulated TEGs containing βTC3 murine insulinoma cells were prepared with three fractional viabilities and provided with (17) O2 . Cellular metabolism of (17) O2 into nascent mitochondrial water (H2(17) O) was monitored by (17) O-MRS and, from the measured data, OCR was calculated. For comparison, OCR was simultaneously measured on a separate, but equivalent sample of cells with a well-established stirred microchamber technique. OCR measured by (17) O-MRS agreed well with measurements made in the stirred microchamber device. These studies confirm that (17) O-MRS can quantify TEG viability noninvasively. Biotechnol. Bioeng. 2016;9999: 1-4. © 2016 Wiley Periodicals, Inc.
• Kelly, A. C., Steyn, L. V., Kitzmann, J. P., Anderson, M. J., Mueller, K. R., Hart, N. J., Lynch, R. M., Papas, K. K., & Limesand, S. W. (2016). Function and expression of sulfonylurea, adrenergic, and glucagon-like peptide 1 receptors in isolated porcine islets. Xenotransplantation, 21(4), 385-91.
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  The scarcity of human cadaveric pancreata limits large-scale application of islet transplantation for patients with diabetes. Islets isolated from pathogen-free pigs provide an economical and abundant alternative source assuming immunologic barriers are appropriate. Membrane receptors involved in insulin secretion that also have potential as imaging targets were investigated in isolated porcine islets. Quantitative (q)PCR revealed that porcine islets express mRNA transcripts for sulfonylurea receptor 1 (Sur1), inward rectifying potassium channel (Kir6.2, associated with Sur1), glucagon-like peptide 1 receptor (GLP1R), and adrenergic receptor alpha 2A (ADRα2A). Receptor function was assessed in static incubations with stimulatory glucose concentrations, and in the presence of receptor agonists. Glibenclamide, an anti-diabetic sulfonylurea, and exendin-4, a GLP-1 mimetic, potentiated glucose-stimulated insulin secretion >2-fold. Conversely, epinephrine maximally reduced insulin secretion 72 ± 9% (P < 0.05) and had a half maximal inhibitory concentration of 60 nm in porcine islets (95% confidence interval of 45-830 nm). The epinephrine action was inhibited by the ADRα2A antagonist yohimbine. Our findings demonstrate that porcine islets express and are responsive to both stimulatory and inhibitory membrane localized receptors, which can be used as imaging targets after transplantation or to modify insulin secretion.
• Min, C., Steyn, L., Weegman, B., Hoeger, A., Kirkeide, L., Aly, F., Harland, R., Galons, J., & Papas, K. (2016). Persufflation Improves Viability and Function of Porcine Kidneys Relative to Static Cold Storage. AMERICAN JOURNAL OF TRANSPLANTATION, 16, 68-68.
• Papas, K. K., & Scott, III, W. E. (2016). Persufflation Improves Porcine Pancreas Preservation for Islet Isolation when Compared with the Two-Layer Method (TLM).. Transplantation Proceedings, 42.
• Papas, K. K., Avgoustiniatos, E. S., & Suszynski, T. M. (2016). Effect of oxygen supply on the size of implantable islet-containing encapsulation devices. PANMINERVA MEDICA, 58(1), 72-77.
• Papas, K. K., Avgoustiniatos, E. S., & Suszynski, T. M. (2016). Effect of oxygen supply on the size of implantable islet-containing encapsulation devices. Panminerva medica, 58(1), 72-7.
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  Beta-cell replacement therapy is a promising approach for the treatment of diabetes but is currently limited by the human islet availability and by the need for systemic immunosuppression. Tissue engineering approaches that will enable the utilization of islets or β-cells from alternative sources (such as porcine islets or human stem cell derived beta cells) and minimize or eliminate the need for immunosuppression have the potential to address these critical limitations. However, tissue engineering approaches are critically hindered by the device size (similar to the size of a large flat screen television) required for efficacy in humans. The primary factor dictating the device size is the oxygen availability to islets to support their viability and function (glucose-stimulated insulin secretion [GSIS]). GSIS is affected (inhibited) at a much higher oxygen partial pressure [pO2] than that of viability (e.g. 10 mmHg as opposed to 0.1 mmHg). Enhanced oxygen supply (higher pO2) than what is available in vivo at transplant sites can have a profound effect on the required device size (potentially reduce it to the size of a postage stamp). This paper summarizes key information on the effect of oxygen on islet viability and function within immunoisolation devices and describes the potential impact of enhanced oxygen supply to devices in vivo on device size reduction.
• Papas, K. K., Einstein, S. A., Weegman, B. P., Firpo, M. T., & Garwood, M. (2016). Development and validation of noninvasive magnetic resonance relaxometry for the in vivo assessment of tissue-engineered graft oxygenation.. Tissue Eng. Part C Methods. doi:10.1089/ten.TEC.2016.0106
• Papas, K. K., Einstein, S. A., Weegman, B. P., Kitzmann, J. P., & Garwood, M. (2016). Noninvasive Assessment of Tissue-Engineered Graft Viability with Oxygen-17 Magnetic Resonance Spectroscopy.. Biotechnology and Bioengineering. doi:10.1002/bit.26227
• Papas, K. K., Weegman, B. P., Nash, P., Essawy, A., Carlson, A. L., Volzke, K. J., Geng, Z., Becker, B., & Firpo, M. T. (2016). Nutrient Regulation by Continuous Feeding for Large-scale Expansion of Mammalian Cells in Spheroids. Jove. doi:10.3791/52224
• Papas, K. K., Weegman, B. P., Taylor, M. J., Baicu, S. C., Mueller, K., O'Brien, T. D., & Wilson, J. (2016). Plasticity and Aggregation of Juvenile Porcine Islets in Modified Culture: Preliminary Observations.. Cell Transplantation, 25(10). doi:10.3727/096368916X691475
• Suszynski, T. M., Avgoustiniatos, E. S., & Papas, K. K. (2016). Oxygenation of the Intraportally Transplanted Pancreatic Islet. JOURNAL OF DIABETES RESEARCH.
• Suszynski, T. M., Avgoustiniatos, E. S., & Papas, K. K. (2016). Oxygenation of the Intraportally Transplanted Pancreatic Islet. Journal of diabetes research, 2016, 7625947.
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  Intraportal islet transplantation (IT) is not widely utilized as a treatment for type 1 diabetes. Oxygenation of the intraportally transplanted islet has not been studied extensively. We present a diffusion-reaction model that predicts the presence of an anoxic core and a larger partly functional core within intraportally transplanted islets. Four variables were studied: islet diameter, islet fractional viability, external oxygen partial pressure (P) (in surrounding portal blood), and presence or absence of a thrombus on the islet surface. Results indicate that an islet with average size and fractional viability exhibits an anoxic volume fraction (AVF) of 14% and a function loss of 72% at a low external P. Thrombus formation increased AVF to 30% and function loss to 92%, suggesting that the effect of thrombosis may be substantial. External P and islet diameter accounted for the greatest overall impact on AVF and loss of function. At our institutions, large human alloislets (>200 μm diameter) account for ~20% of total islet number but ~70% of total islet volume; since most of the total transplanted islet volume is accounted for by large islets, most of the intraportal islet cells are likely to be anoxic and not fully functional.
• Weegman, B. P., Essawy, A., Nash, P., Carlson, A. L., Voltzke, K. J., Geng, Z., Jahani, M., Becker, B. B., Papas, K. K., & Firpo, M. T. (2016). Nutrient Regulation by Continuous Feeding for Large-scale Expansion of Mammalian Cells in Spheroids. Journal of visualized experiments : JoVE.
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  In this demonstration, spheroids formed from the β-TC6 insulinoma cell line were cultured as a model of manufacturing a mammalian islet cell product to demonstrate how regulating nutrient levels can improve cell yields. In previous studies, bioreactors facilitated increased culture volumes over static cultures, but no increase in cell yields were observed. Limitations in key nutrients such as glucose, which were consumed between batch feedings, can lead to limitations in cell expansion. Large fluctuations in glucose levels were observed, despite the increase in glucose concentrations in the media. The use of continuous feeding systems eliminated fluctuations in glucose levels, and improved cell growth rates when compared with batch fed static and SSB culture methods. Additional increases in growth rates were observed by adjusting the feed rate based on calculated nutrient consumption, which allowed the maintenance of physiological glucose over three weeks in culture. This method can also be adapted for other cell types.
• Weegman, B. P., Kumar Sajja, V. S., Suszynski, T. M., Rizzari, M. D., Scott Iii, W. E., Kitzmann, J. P., Mueller, K. R., Hanley, T. R., Kennedy, D. J., Todd, P. W., Balamurugan, A. N., Hering, B. J., & Papas, K. K. (2016). Continuous Quadrupole Magnetic Separation of Islets during Digestion Improves Purified Porcine Islet Viability. Journal of diabetes research, 2016, 6162970.
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  Islet transplantation (ITx) is an emerging and promising therapy for patients with uncontrolled type 1 diabetes. The islet isolation and purification processes require exposure to extended cold ischemia, warm-enzymatic digestion, mechanical agitation, and use of damaging chemicals for density gradient separation (DG), all of which reduce viable islet yield. In this paper, we describe initial proof-of-concept studies exploring quadrupole magnetic separation (QMS) of islets as an alternative to DG to reduce exposure to these harsh conditions. Three porcine pancreata were split into two parts, the splenic lobe (SPL) and the combined connecting/duodenal lobes (CDL), for paired digestions and purifications. Islets in the SPL were preferentially labeled using magnetic microparticles (MMPs) that lodge within the islet microvasculature when infused into the pancreas and were continuously separated from the exocrine tissue by QMS during the collection phase of the digestion process. Unlabeled islets from the CDL were purified by conventional DG. Islets purified by QMS exhibited significantly improved viability (measured by oxygen consumption rate per DNA, p < 0.03) and better morphology relative to control islets. Islet purification by QMS can reduce the detrimental effects of prolonged exposure to toxic enzymes and density gradient solutions and substantially improve islet viability after isolation.
• Weegman, B. P., Sajja, V., Suszynski, T. M., Rizzari, M. D., Scott, W., Kitzmann, J. P., Mueller, K. R., Hanley, T. R., Kennedy, D. J., Todd, P. W., Balamurugan, A. N., Hering, B. J., & Papas, K. K. (2016). Continuous Quadrupole Magnetic Separation of Islets during Digestion Improves Purified Porcine Islet Viability. JOURNAL OF DIABETES RESEARCH.
• Weegman, B. P., Taylor, M. J., Baicu, S. C., Mueller, K., O'Brien, T. D., Wilson, J., & Papas, K. K. (2016). Plasticity and Aggregation of Juvenile Porcine Islets in Modified Culture: Preliminary Observations. CELL TRANSPLANTATION, 25(10), 1763-1775.
• Hart, N. J., Weber, C., Papas, K. K., Limesand, S. W., Vagner, J., & Lynch, R. M. (2019). Multivalent activation of GLP-1 and Sulfonylurea receptors modulates β-cell Second Messenger Signaling and Insulin Secretion. American journal of physiology. Cell physiology.
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  Linking two pharmacophores that bind different cell surface receptors into a single molecule can enhance cell-targeting specificity to cells that express the complementary receptor pair. In this report, we developed and tested a synthetic multivalent ligand consisting of glucagon-like peptide-1 (GLP-1) linked to glibenclamide (Glb) for signaling efficacy in β-cells. Expression of receptors for these ligands, as a combination, are relatively specific to the β-cell in the pancreas. The multivalent GLP-1/Glb increased both intracellular cAMP and Ca, although Ca responses were significantly depressed compared to the monomeric Glb. Moreover, GLP-1/Glb increased glucose-stimulated insulin secretion in a dose-dependent manner. However, unlike the combined monomers, GLP-1/Glb did not augment insulin secretion at non-stimulatory glucose concentrations in INS 832/13 β-cells or human islets of Langerhans. These data suggest that linking two binding elements into a single bivalent ligand, such as GLP-1 and Glb, can provide a unique functional agent targeted to β-cells.
• Kitzmann, J. P., Law, L., Shome, A., Muzina, M., Elliott, R. B., Mueller, K. R., Schuurman, H. J., & Papas, K. K. (2015). Real-time assessment of encapsulated neonatal porcine islets prior to clinical xenotransplantation. Xenotransplantation, 19(6), 333-6.
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  Porcine islet transplantation is emerging as an attractive option for the treatment of patients with type 1 diabetes, with the possibility of providing islets of higher and more consistent quality and in larger volumes than available from human pancreata. The use of encapsulated neonatal porcine islets (ENPI) is appealing because it can address islet supply limitations while reducing the need for anti-rejection therapy. Pre-transplant characterization of ENPI viability and potency is an essential component of the production process. We applied the validated assay for oxygen consumption rate normalized for DNA content (OCR/DNA) to characterize ENPI viability.
• Papas, K. K. (2015). VIABLE ISLET DOSE BASED ON OXYGEN CONSUMPTION RATE PREDICTS CLINICAL ISLET AUTOTRANSPLANT OUTCOME. PLoS One. doi:10.1371/journal.pone.0134428
• Papas, K. K., Bellin, M. D., Sutherland, D. E., Suszynski, T. M., Kitzmann, J. P., Avgoustiniatos, E. S., Gruessner, A. C., Mueller, K. R., Beilman, G. J., Balamurugan, A. N., Loganathan, G., Colton, C. K., Koulmanda, M., Weir, G. C., Wilhelm, J. J., Qian, D., Niland, J. C., & Hering, B. J. (2015). Islet Oxygen Consumption Rate (OCR) Dose Predicts Insulin Independence in Clinical Islet Autotransplantation. PloS one, 10(8), e0134428.
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  Reliable in vitro islet quality assessment assays that can be performed routinely, prospectively, and are able to predict clinical transplant outcomes are needed. In this paper we present data on the utility of an assay based on cellular oxygen consumption rate (OCR) in predicting clinical islet autotransplant (IAT) insulin independence (II). IAT is an attractive model for evaluating characterization assays regarding their utility in predicting II due to an absence of confounding factors such as immune rejection and immunosuppressant toxicity.
• Papas, K. K., Bellin, M. D., Sutherland, D., Suszynski, T. M., Kitzmann, J. P., Avgoustiniatos, E. S., Gruessner, A. C., Mueller, K. R., Beilman, G. J., Balamurugan, A. N., Loganathan, G., Colton, C. K., Koulmanda, M., Weir, G. C., Wilhelm, J. J., Qian, D., Niland, J. C., & Hering, B. J. (2015). Islet Oxygen Consumption Rate (OCR) Dose Predicts Insulin Independence in Clinical Islet Autotransplantation. PLOS ONE, 10(8).
• Scott, W. E., Weegman, B. P., Balamurugan, A. N., Ferrer-Fabrega, J., Anazawa, T., Karatzas, T., Jie, T., Hammer, B. E., Matsumoto, S., Avgoustiniatos, E. S., Maynard, K. S., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2015). Magnetic resonance imaging: a tool to monitor and optimize enzyme distribution during porcine pancreas distention for islet isolation. XENOTRANSPLANTATION, 21(5), 473-479.
• Suszynski, T. M., Rizzari, M. D., Kidder, L. S., Mueller, K., Chapman, C. S., Kitzmann, J. P., Pongratz, R. L., Cline, G. W., Todd, P. W., Kennedy, D. J., O'Brien, T. D., Avgoustiniatos, E. S., Schuurman, H., & Papas, K. K. (2015). Paramagnetic microparticles do not elicit islet cytotoxicity with co-culture or host immune reactivity after implantation. XENOTRANSPLANTATION, 18(4), 239-244.
• Weegman, B. P., Suszynski, T. M., Scott, W. E., Ferrer Fábrega, J., Avgoustiniatos, E. S., Anazawa, T., O'Brien, T. D., Rizzari, M. D., Karatzas, T., Jie, T., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2015). Temperature profiles of different cooling methods in porcine pancreas procurement. Xenotransplantation, 21(6), 574-81.
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  Porcine islet xenotransplantation is a promising alternative to human islet allotransplantation. Porcine pancreas cooling needs to be optimized to reduce the warm ischemia time (WIT) following donation after cardiac death, which is associated with poorer islet isolation outcomes. This study examines the effect of four different cooling Methods on core porcine pancreas temperature (n = 24) and histopathology (n = 16). All Methods involved surface cooling with crushed ice and chilled irrigation. Method A, which is the standard for porcine pancreas procurement, used only surface cooling. Method B involved an intravascular flush with cold solution through the pancreas arterial system. Method C involved an intraductal infusion with cold solution through the major pancreatic duct, and Method D combined all three cooling Methods. Surface cooling alone (Method A) gradually decreased core pancreas temperature to
• Abdelli, S., Papas, K. K., Mueller, K. R., Murtaugh, M. P., Hering, B. J., & Bonny, C. (2014). Regulation of the JNK3 signaling pathway during islet isolation: JNK3 and c-fos as new markers of islet quality for transplantation. PloS one, 9(7), e99796. doi:10.1371/journal.pone.0099796
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  Stress conditions generated throughout pancreatic islet processing initiate the activation of pro-inflammatory pathways and beta-cell destruction. Our goal is to identify relevant and preferably beta-specific markers to assess the activation of beta-cell stress and apoptotic mechanisms, and therefore the general quality of the islet preparation prior to transplantation. Protein expression and activation were analyzed by Western blotting and kinase assays. ATP measurements were performed by a luminescence-based assay. Oxygen consumption rate (OCR) was measured based on standard protocols using fiber optic sensors. Total RNA was used for gene expression analyzes. Our results indicate that pancreas digestion initiates a potent stress response in the islets by activating two stress kinases, c-Jun N-terminal Kinase (JNK) and p38. JNK1 protein levels remained unchanged between different islet preparations and following culture. In contrast, levels of JNK3 increased after islet culture, but varied markedly, with a subset of preparations bearing low JNK3 expression. The observed changes in JNK3 protein content strongly correlated with OCR measurements as determined by the Spearman's rank correlation coefficient rho [Formula: see text] in the matching islet samples, while inversely correlating with c-fos mRNA expression [Formula: see text]. In conclusion, pancreas digestion recruits JNK and p38 kinases that are known to participate to beta-cell apoptosis. Concomitantly, the islet isolation alters JNK3 and c-fos expression, both strongly correlating with OCR. Thus, a comparative analysis of JNK3 and c-fos expression before and after culture may provide for novel markers to assess islet quality prior to transplantation. JNK3 has the advantage over all other proposed markers to be islet-specific, and thus to provide for a marker independent of non-beta cell contamination.
• Atchison, N., Swindlehurst, G., Papas, K. K., Tsapatsis, M., & Kokkoli, E. (2014). Maintenance of ischemic β cell viability through delivery of lipids and ATP by targeted liposomes. Biomaterials science, 2(4), 548-559.
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  Islet transplantation is a promising treatment for type 1 diabetes, but despite the successes, existing challenges prevent widespread application. Ischemia, occurring during pancreas preservation and isolation, as well as after islet transplantation, decreases islet viability and function. We hypothesized that the liposomal delivery of adenosine triphosphate (ATP) could prevent the loss of cell viability during an ischemic insult. In this work we use a model β cell line, INS-1 to probe the liposome/cell interactions and examined the ability of liposomes functionalized with the fibronectin-mimetic peptide PR_b to facilitate the delivery of ATP to ischemic β cells. We demonstrate that PR_b increases the binding and internalization of liposomes to the β cells. Unexpectedly, when comparing the ability of PR_b liposomes with and without ATP to protect INS-1 cells from ischemia we found that both formulations increased cell survival. By probing the functional activity of ischemic cells treated with PR_b functionalized liposomes with and without ATP we find that both lipids and ATP play a role in maintaining cell metabolic activity after an ischemic insult and preventing cell necrosis. This approach may be beneficial for preventing ischemia related damage to islet cells, especially in the organ preservation stage.
• Balamurugan, A. N., Breite, A. G., Anazawa, T., Loganathan, G., Wilhelm, J. J., Papas, K. K., Dwulet, F. E., McCarthy, R. C., & Hering, B. J. (2014). Successful Human Islet Isolation and Transplantation Indicating the Importance of Class 1 Collagenase and Collagen Degradation Activity Assay. TRANSPLANTATION, 89(8), 954-961. doi:10.1097/TP.0b013e3181d21e9a.
• Papas, K. K., Balamurugan, A. N., Naziruddin, B., Lockridge, A., Tiwari, M., Loganathan, G., Takita, M., Matsumoto, M., Trieger, M., Rainis, H., Kin, T., Kay, T. H., Wease, S., Ricordi, C., Alejandro, R., Markmann, J., Kerr-Conti, J., Rickels, M. R., Liu, C., , Zhang, X., et al. (2014). Islet product characteristics and factors related to successful human islet transplantation from the Collaborative Islet Transplant Registry (CITR) 1999-2010. American Journal of transplantation, 14(11), 2595-606. doi:10.1111/ajt.12872
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  The Collaborative Islet Transplant Registry (CITR) collects data on clinical islet isolations and transplants. This retrospective report analyzed 1017 islet isolation procedures performed for 537 recipients of allogeneic clinical islet transplantation in 1999-2010. This study describes changes in donor and islet isolation variables by era and factors associated with quantity and quality of final islet products. Donor body weight and BMI increased significantly over the period (p
• Papas, K. K., Kitzmann, J. P., Karatzas, T., Avgoustiniatos, E. S., Mueller, K. R., Gruessner, A. C., Balamurugan, A. N., Bellin, M. D., & Hering, B. J. (2014). Islet preparation purity is overestimated and less pure fractions have lower post-culture viability prior to clinical allo-transplantation. Transplantation Proceedings, 46(6), 1953-5. doi:10.1016/j.transproceed.2014.06.011.
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  Replacement of β-cells with the use of isolated islet allotransplantation (IT) is an emerging therapy for type 1 diabetics with hypoglycemia unawareness. The current standard protocol calls for a 36-72-hour culture period before IT. We examined 13 clinical islet preparations with ≥2 purity fractions to determine the effect of culture on viability.
• Papas, K. K., Suszynski, T. M., Mueller, K. R., & Gruessner, A. C. (2014). Metabolic Profile of porcine pancreatic acinar and islet tissue in culture. Transplantation Proceedings, 46(6), 1960-2. doi:10.1016/j.transproceed.2014.06.003
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  The amount and condition of exocrine impurities may affect the quality of islet preparations, especially during culture. In this study, the objective was to determine the oxygen demand and viability of islet and acinar tissue post-isolation and whether they change disproportionately while in culture.We compared the oxygen consumption rate (OCR) normalized to DNA (OCR/DNA, a measure of fractional viability in units of nmol/min/mg DNA), and the percent change in OCR and DNA recoveries between adult porcine islet and acinar tissue from the same preparation (paired) over 6-9 days of standard culture. Paired comparisons were done to quantify differences in OCR/DNA between islet and acinar tissue from the same preparation, at specified time points during culture.The mean (±SE) OCR/DNA was 74.0 ± 11.7 units higher for acinar (vs islet) tissue on the day of isolation (n = 16, P
• Suszynski, T. M., Avgoustiniatos, E. S., & Papas, K. K. (2014). Intraportal islet oxygenation. Journal of diabetes science and technology, 8(3), 575-80. doi:10.1177/1932296814525827
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  Islet transplantation (IT) is a promising therapy for the treatment of diabetes. The large number of islets required to achieve insulin independence limit its cost-effectiveness and the number of patients who can be treated. It is believed that >50% of islets are lost in the immediate post-IT period. Poor oxygenation in the early post-IT period is recognized as a possible reason for islet loss and dysfunction but has not been extensively studied. Several key variables affect oxygenation in this setting, including (1) local oxygen partial pressure (pO(2)), (2) islet oxygen consumption, (3) islet size (diameter, D), and (4) presence or absence of thrombosis on the islet surface. We discuss implications of oxygen-limiting conditions on intraportal islet viability and function. Of the 4 key variables, the islet size appears to be the most important determinant of the anoxic and nonfunctional islet volume fractions. Similarly, the effect of thrombus formation on the islet surface may be substantial. At the University of Minnesota, average size distribution data from clinical alloislet preparations (n = 10) indicate that >150-µm D islets account for only ~30% of the total islet number, but >85% of the total islet volume. This suggests that improved oxygen supply to the islets may have a profound impact on islet survivability and function since most of the β-cell volume is within large islets which are most susceptible to oxygen-limiting conditions. The assumption that the liver is a suitable islet transplant site from the standpoint of oxygenation should be reconsidered.
• Suszynski, T. M., Wilhelm, J. J., Radosevich, D. M., Balamurugan, A. N., Sutherland, D. E., Beilman, G. J., Dunn, T. B., Chinnakotla, S., Pruett, T. L., Vickers, S. M., Hering, B. J., Papas, K. K., & Bellin, M. D. (2014). Islet size index as a predictor of outcomes in clinical islet autotransplantation. Transplantation, 97(12), 1286-91.
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  The islet size distribution in a preparation may contribute to islet transplant outcomes. At the same islet equivalent (IE) dose, larger islets may exhibit poorer therapeutic value and this may be because of oxygen diffusion limitations that worsen in proportion to islet size.
• Weegman, B. P., Suszynski, T. M., Scott, W. E., Fabrega, J. F., Avgoustiniatos, E. S., Anazawa, T., O'Brien, T. D., Rizzari, M. D., Karatzas, T., Jie, T., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2014). Temperature profiles of different cooling methods in porcine pancreas procurement. XENOTRANSPLANTATION, 21(6), 574-581. doi:10.1111/xen.12114
• Kaddis, J. S., Hanson, M. S., Cravens, J., Qian, D., Olack, B., Antler, M., Papas, K. K., Iglesias, I., Barbaro, B., Fernandez, L., Powers, A. C., & Niland, J. C. (2013). Standardized Transportation of Human Islets: An Islet Cell Resource Center Study of More Than 2,000 Shipments. CELL TRANSPLANTATION, 22(7), 1101-1111.
• Kaddis, J. S., Hanson, M. S., Cravens, J., Qian, D., Olack, B., Antler, M., Papas, K. K., Iglesias, I., Barbaro, B., Fernandez, L., Powers, A. C., & Niland, J. C. (2013). Standardized transportation of human islets: an islet cell resource center study of more than 2,000 shipments. Cell transplantation, 22(7), 1101-11. doi:10.3727/096368912X653219.
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  Preservation of cell quality during shipment of human pancreatic islets for use in laboratory research is a crucial, but neglected, topic. Mammalian cells, including islets, have been shown to be adversely affected by temperature changes in vitro and in vivo, yet protocols that control for thermal fluctuations during cell transport are lacking. To evaluate an optimal method of shipping human islets, an initial assessment of transportation conditions was conducted using standardized materials and operating procedures in 48 shipments sent to a central location by eight pancreas-processing laboratories using a single commercial airline transporter. Optimization of preliminary conditions was conducted, and human islet quality was then evaluated in 2,338 shipments pre- and postimplementation of a finalized transportation container and standard operating procedures. The initial assessment revealed that the outside temperature ranged from a mean of -4.6 ± 10.3°C to 20.9 ± 4.8°C. Within-container temperature drops to or below 15°C occurred in 16 shipments (36%), while the temperature was found to be stabilized between 15°C and 29°C in 29 shipments (64%). Implementation of an optimized transportation container and operating procedure reduced the number of within-container temperature drops (≤ 15°C) to 13% (n = 37 of 289 winter shipments), improved the number desirably maintained between 15°C and 29°C to 86% (n = 250), but also increased the number reaching or exceeding 29°C to 1% (n = 2; overall p < 0.0001). Additionally, postreceipt quality ratings of excellent to good improved pre- versus postimplantation of the standardized protocol, adjusting for preshipment purity/viability levels (p < 0.0001). Our results show that extreme temperature fluctuations during transport of human islets, occurring when using a commercial airline transporter for long distance shipping, can be controlled using standardized containers, materials, and operating procedures. This cost-effective and pragmatic standardized protocol for the transportation of human islets can potentially be adapted for use with other mammalian cell systems and is available online at http://iidp.coh.org/sops.aspx.
• Loganathan, G., Graham, M. L., Radosevich, D. M., Soltani, S. M., Tiwari, M., Anazawa, T., Papas, K. K., Sutherland, D. E., Hering, B. J., & Balamurugan, A. N. (2013). Factors affecting transplant outcomes in diabetic nude mice receiving human, porcine, and nonhuman primate islets: analysis of 335 transplantations. Transplantation, 95(12), 1439-47.
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  In the absence of a reliable islet potency assay, nude mice (NM) transplantation is the criterion standard to assess islet quality for clinical transplantation. There are factors other than islet quality that affect the transplant outcome.
• Loganathan, G., Graham, M. L., Radosevich, D. M., Soltani, S. M., Tiwari, M., Anazawa, T., Papas, K. K., Sutherland, D., Hering, B. J., & Balamurugan, A. N. (2013). Factors Affecting Transplant Outcomes in Diabetic Nude Mice Receiving Human, Porcine, and Nonhuman Primate Islets: Analysis of 335 Transplantations. TRANSPLANTATION, 95(12), 1439-1447.
• Mueller, K. R., Balamurugan, A. N., Cline, G. W., Pongratz, R. L., Hooper, R. L., Weegman, B. P., Kitzmann, J. P., Taylor, M. J., Graham, M. L., Schuurman, H., & Papas, K. K. (2013). Differences in glucose-stimulated insulin secretion in vitro of islets from human, nonhuman primate, and porcine origin. XENOTRANSPLANTATION, 20(2), 75-81.
• Mueller, K. R., Balamurugan, A. N., Cline, G. W., Pongratz, R. L., Hooper, R. L., Weegman, B. P., Kitzmann, J. P., Taylor, M. J., Graham, M. L., Schuurman, H., & Papas, K. K. (2013). Differences in glucose-stimulated insulin secretion in vitro of islets from human, nonhuman primate, and porcine origin. Xenotransplantation, 20(2), 75-81.
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  Porcine islet xenotransplantation is considered a potential cell-based therapy for type 1 diabetes. It is currently being evaluated in diabetic nonhuman primates (NHP) to assess safety and efficacy of the islet product. However, due to a variety of distinct differences between the respective species, including the insulin secretory characteristics of islets, the suitability and predictive value of the preclinical model in the extrapolation to the clinical setting remain a critical issue. Islets isolated from human (n = 3), NHP (n = 2), adult pig (AP, n = 3), and juvenile pig (JP, n = 4) pancreata were perifused with medium at basal glucose (2.5 mm) followed by high glucose (16.7 mm) concentrations. The total glucose-stimulated insulin secretion (GSIS) was calculated from generated insulin secretion profiles. Nonhuman primate islets exhibited GSIS 3-fold higher than AP islets, while AP and JP islets exhibited GSIS 1/3 and 1/30 of human islets, respectively. The insulin content of NHP and AP islets was similar to that of human islets, whereas that of JP islets was 1/5 of human islets. Despite the fact that human, NHP, and AP islets contain similar amounts of insulin, the much higher GSIS for NHP islets than for AP and JP islets suggests the need for increased dosing of islets from JP and AP in pig-to-NHP transplantation. Porcine islet xenotransplantation to humans may require significantly higher dosing given the lower GSIS of AP islets compared to human islets.
• Mueller, K. R., Martins, K. V., Murtaugh, M. P., Schuurman, H., & Papas, K. K. (2013). Manufacturing porcine islets: culture at 22 °C has no advantage above culture at 37 °C: a gene expression evaluation. Xenotransplantation, 20(6), 418-28. doi:10.1111/xen.12048
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  The manufacturing process of islets includes a culture step which was originally introduced to ease the logistics of procedures in preparing the graft and transplant recipient. It has been suggested that culture at room temperature has an advantage over culture at 37 °C, in part by reducing immunogenicity via preferential elimination of contaminating cells (such as passenger leukocytes) within islets. We investigated this using islets isolated from pancreata of adult pigs.
• Papas, K. K., Balamurugan, A. N., O'Brien, T. D., Loganathan, G., Soltani, S., Bellin, M. D., Anazawa, T., Tiwari, M., Vickers, S. M., Hering, B. J., & Sutherland, D. E. (2013). Severely Fibrotic Pancreases from Young Patients with Chronic Pancreatitis: Evidence for a Ductal Origin of Islet Neogenesis. Acta Diabetologica, 50(5), 807-14. doi:10.1007/s00592-011-0306-9
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  While it is known that islet cell mass increases considerably after birth, general uncertainty surrounds the source of new beta cells in humans. Chronic pancreatitis (CP) presents a natural injury model for studying postnatal beta-cell regeneration in the human pancreas. In this report, we present histological evidence from human CP pancreases to support the theory that islet neogenesis can occur from ductal precursor cells after birth. Three young patients (ages 16, 12, and 28 years) underwent total pancreatectomy for the management of CP followed by islet isolation and autologous transplantation to prevent or minimize postsurgical diabetes. In all cases, the pancreases had extensive fibrosis, a rock-like consistency, and calcifications in the ducts. During islet isolations, we observed the unusual release of islets with many ductal fragments. In histopathological evaluation of these pancreases, solid cords of cells sometimes formed islet like structures intraductally or extending from ductal structures. Immunofluorescence staining for chromogranin, insulin, proinsulin, PDX1, glucagon, and cytokeratins confirmed these structures to be composed of chromogranin-positive endocrine cells which included both β-cells and α-cells. Labeling for Ki67 to demonstrate mitotic activity showed frequent labeling of duct epithelial cells and of some periductal cells. Using insulin and wide-spectrum cytokeratin double immunofluorescent labeling, we found insulin-positive cells to be present within the ductal lumens, among the cytokeratin-positive ductal epithelium, and extending from the ductal epithelium into surrounding connective tissues, providing evidence for a ductal origin of islet neogenesis.
• Papas, K. K., Brandhorst, H., Iken, M., Scott III, W. E., Theisinger, B., Johnson, P. R., Korsgren, O., & Brandhorst, D. (2013). Quality of isolated pig islets is improved using perfluorohexyloctane for pancreas storage in a split lobe model. Cell Transplantation, 22(8), 1477-1483. doi:10.3727/096368912X657639
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  Pancreas transportation between donor center and islet production facility is frequently associated with prolonged ischemia impairing islet isolation and transplantation outcomes. It is foreseeable that shipment of pig pancreases from distant centralized biosecure breeding facilities to institutes that have a long-term experience in porcine islet isolation is essentially required in future clinical islet xenotransplantation. Previously, we demonstrated that perfluorohexyloctan (F6H8) is significantly more efficient to protect rat and human pancreata from ischemically induced damage compared to perfluorodecalin (PFD). To evaluate the effect of F6H8 on long-term stored pig pancreases in a prospective study, we utilized the split lobe model to minimize donor variability. Retrieved pancreases were dissected into the connecting and splenic lobe, intraductally flushed with UW solution and immersed alternately in either preoxygenated F6H8 or PFD for 8-10 h. Prior to pancreas digestion, the intrapancreatic pO2 and the ratio of ATP-to-inorganic phosphate was compared utilizing 31P-NMR spectroscopy. Isolated islets were cultured for 2-3 days at 37°C and subjected to quality assessment. Pancreatic lobes stored in preoxygenated F6H8 had a significantly higher intrapancreatic pO2 compared to pancreata in oxygen-precharged PFD (10.11 ± 3.87 vs. 1.64 ± 1.13 mmHg, p < 0.05). This correlated with a higher ATP-to-inorganic phosphate ratio (0.30 ± 0.04 vs. 0.14 ± 0.01). No effect was observed concerning yield and purity of freshly isolated islets. Nevertheless, a significantly improved glucose-stimulated insulin response, increased viability and postculture survival (57.2 ± 5.7 vs. 39.3 ± 6.4%, p < 0.01) was measured in islets isolated from F6H8-preserved pancreata. The present data suggest that F6H8 does not increase islet yield but improves quality of pig islets isolated after prolonged cold ischemia.
• Papas, K. K., Karatzas, T., Berney, T., Minor, T., Pappas, P., Pattou, F., Shaw, J., Toso, C., & Schuurman, H. (2013). International workshop: islet transplantation without borders enabling islet transplantation in Greece with international collaboration and innovative technology. Clinical transplantation. doi:10.1111/ctr.12066
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  Recently, initiatives have been undertaken to establish an islet transplantation program in Athens, Greece. A major hurdle is the high cost associated with the establishment and maintenance of a clinical-grade islet manufacturing center. A collaboration was established with the University Hospitals of Geneva, Switzerland, to enable remote islet cell manufacturing with an established and validated fully operational team. However, remote islet manufacturing requires shipment of the pancreas from the procurement to the islet manufacturing site (in this case from anywhere in Greece to Geneva) and then shipment of the islets from the manufacturing site to the transplant site (from Geneva to Athens). To address challenges related to cold ischemia time of the pancreas and shipment time of islets, a collaboration was initiated with the University of Arizona, Tucson, USA. An international workshop was held in Athens, December 2011, to mark the start of this collaborative project. Experts in the field presented in three main sessions: (i) islet transplantation: state-of-the-art and the "network approach"; (ii) technical aspects of clinical islet transplantation and outcomes; and (iii) islet manufacturing - from the donated pancreas to the islet product. This manuscript presents a summary of the workshop.
• Suszynski, T. M., Rizzari, M. D., Scott, W. E., Eckman, P. M., Fonger, J. D., John, R., Chronos, N., Tempelman, L. A., Sutherland, D. E., & Papas, K. K. (2013). Persufflation (gaseous oxygen perfusion) as a method of heart preservation. Journal of cardiothoracic surgery, 8, 105. doi:1186/1749-8090-8-105.
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  Persufflation (PSF; gaseous oxygen perfusion) is an organ preservation technique with a potential for use in donor heart preservation. Improved heart preservation with PSF may improve outcomes by maintaining cardiac tissue quality in the setting of longer cold ischemia times and possibly increasing the number of donor hearts available for allotransplant. Published data suggests that PSF is able to extend the cold storage times for porcine hearts up to 14 hours without compromising viability and function, and has been shown to resuscitate porcine hearts following donation after cardiac death. This review summarizes key published work on heart PSF, including prospective implications and future directions for PSF in heart transplantation. We emphasize the potential impact of extending preservation times and expanding donor selection criteria in heart allotransplant. Additionally, the key issues that need to be addressed before PSF were to become a widely utilized preservation strategy prior to clinical heart transplantation are summarized and discussed.
• Weegman, B. P., Nash, P., Carlson, A. L., Voltzke, K. J., Geng, Z., Jahani, M., Becker, B. B., Papas, K. K., & Firpo, M. T. (2013). Nutrient regulation by continuous feeding removes limitations on cell yield in the large-scale expansion of Mammalian cell spheroids. PloS one, 8(10), e76611. doi:http://dx.doi.org/10.1371/journal.pone.0076611
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  Cellular therapies are emerging as a standard approach for the treatment of several diseases. However, realizing the promise of cellular therapies across the full range of treatable disorders will require large-scale, controlled, reproducible culture methods. Bioreactor systems offer the scale-up and monitoring needed, but standard stirred bioreactor cultures do not allow for the real-time regulation of key nutrients in the medium. In this study, β-TC6 insulinoma cells were aggregated and cultured for 3 weeks as a model of manufacturing a mammalian cell product. Cell expansion rates and medium nutrient levels were compared in static, stirred suspension bioreactors (SSB), and continuously fed (CF) SSB. While SSB cultures facilitated increased culture volumes, no increase in cell yields were observed, partly due to limitations in key nutrients, which were consumed by the cultures between feedings, such as glucose. Even when glucose levels were increased to prevent depletion between feedings, dramatic fluctuations in glucose levels were observed. Continuous feeding eliminated fluctuations and improved cell expansion when compared with both static and SSB culture methods. Further improvements in growth rates were observed after adjusting the feed rate based on calculated nutrient depletion, which maintained physiological glucose levels for the duration of the expansion. Adjusting the feed rate in a continuous medium replacement system can maintain the consistent nutrient levels required for the large-scale application of many cell products. Continuously fed bioreactor systems combined with nutrient regulation can be used to improve the yield and reproducibility of mammalian cells for biological products and cellular therapies and will facilitate the translation of cell culture from the research lab to clinical applications.
• Avgoustiniatos, E. S., Scott, W. E., Suszynski, T. M., Schuurman, H., Nelson, R. A., Rozak, P. R., Mueller, K. R., Balamurugan, A. N., Ansite, J. D., Fraga, D. W., Friberg, A. S., Wildey, G. M., Tanaka, T., Lyons, C. A., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2012). Supplements in human islet culture: human serum albumin is inferior to fetal bovine serum. Cell transplantation, 21(12), 2805-14. doi:10.3727/096368912X653138
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  Culture of human islets before clinical transplantation or distribution for research purposes is standard practice. At the time the Edmonton protocol was introduced, clinical islet manufacturing did not include culture, and human serum albumin (HSA), instead of fetal bovine serum (FBS), was used during other steps of the process to avoid the introduction of xenogeneic material. When culture was subsequently introduced, HSA was also used for medium supplementation instead of FBS, which was typically used for research islet culture. The use of HSA as culture supplement was not evaluated before this implementation. We performed a retrospective analysis of 103 high-purity islet preparations (76 research preparations, all with FBS culture supplementation, and 27 clinical preparations, all with HSA supplementation) for oxygen consumption rate per DNA content (OCR/DNA; a measure of viability) and diabetes reversal rate in diabetic nude mice (a measure of potency). After 2-day culture, research preparations exhibited an average OCR/DNA 51% higher (p < 0.001) and an average diabetes reversal rate 54% higher (p < 0.05) than clinical preparations, despite 87% of the research islet preparations having been derived from research-grade pancreata that are considered of lower quality. In a prospective paired study on islets from eight research preparations, OCR/DNA was, on average, 27% higher with FBS supplementation than that with HSA supplementation (p < 0.05). We conclude that the quality of clinical islet preparations can be improved when culture is performed in media supplemented with serum instead of albumin.
• Avgoustiniatos, E. S., Scott, W., Suszynski, T. M., Schuurman, H., Nelson, R. A., Rozak, P. R., Mueller, K. R., Balamurugan, A. N., Ansite, J. D., Fraga, D. W., Friberg, A. S., Wildey, G. M., Tanaka, T., Lyons, C. A., Sutherland, D., Hering, B. J., & Papas, K. K. (2012). Supplements in Human Islet Culture: Human Serum Albumin Is Inferior to Fetal Bovine Serum. CELL TRANSPLANTATION, 21(12), 2805-2814.
• Balamurugan, A. N., Loganathan, G., Bellin, M. D., Wilhelm, J. J., Harmon, J., Anazawa, T., Soltani, S. M., Radosevich, D. M., Yuasa, T., Tiwari, M., Papas, K. K., McCarthy, R., Sutherland, D. E., & Hering, B. J. (2012). A New Enzyme Mixture to Increase the Yield and Transplant Rate of Autologous and Allogeneic Human Islet Products. TRANSPLANTATION, 93(7), 693-702.
• Balamurugan, A. N., Loganathan, G., Bellin, M. D., Wilhelm, J. J., Harmon, J., Anazawa, T., Soltani, S. M., Radosevich, D. M., Yuasa, T., Tiwari, M., Papas, K. K., McCarthy, R., Sutherland, D. E., & Hering, B. J. (2012). A new enzyme mixture to increase the yield and transplant rate of autologous and allogeneic human islet products. Transplantation, 93(7), 693-702.
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  The optimal enzyme blend that maximizes human islet yield for transplantation remains to be determined. In this study, we evaluated eight different enzyme combinations (ECs) in an attempt to improve islet yield. The ECs consisted of purified, intact or truncated class 1 (C1) and class 2 (C2) collagenases from Clostridium histolyticum (Ch), and neutral protease (NP) from Bacillus thermoproteolyticus rokko (thermolysin) or Ch (ChNP).
• Minor, T., Scott, W. E., Rizzari, M. D., Suszynski, T. M., Luer, B., Efferz, P., Papas, K. K., & Paul, A. (2012). Energetic recovery in porcine grafts by minimally invasive liver oxygenation. The Journal of surgical research, 178(2), e59-63.
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  Gaseous insufflation of oxygen via the venous vascular system has proven to be an effective tool for preventing anoxic tissue injury after extended time periods of ischemic liver preservation. Most experimental studies so far have been undertaken in rat models and include a series of pinpricks into postsinusoidal venules as an outlet for the insufflated gas. Here, we describe a simplified technique for minimally invasive liver oxygenation in porcine grafts, representing a hassle-free access to organ oxygenation without vascular lesions.
• Papas, K. K., Karatzas, T., Berney, T., Minor, T., Pappas, P., Pattou, F., Shaw, J., Toso, C., & Schuurman, H. (2012). International workshop: islet transplantation without borders enabling islet transplantation in Greece with international collaboration and innovative technology. CLINICAL TRANSPLANTATION, 27(2), E116-E125. doi:10.1111/ctr.12066
• Papas, K. K., Minor, T., Scott III, W. E., Rizzari, M. D., Suszynski, T. M., Luer, B., Efferz, P., & Paul, A. (2012). Improvement of energetic homeostasis prior to reperfusion by minimally invasive liver oxygenation in porcine grafts. Journal of Surgical Research, 178(2), 59-63.
• Papas, K. K., Scott, III, W. E., & Suszyynski, T. M. (2012). Anoxia in the Intraportally Transplantation Islet and the Effect of Thrombosis. American Journal of Transplantation.
• Papas, K. K., Scott, W. E., Razzari, M. D., Weegman, B. P., Avgoustiniatos, E. S., Balamurugan, A. N., Gruessner, A. C., Kitzmann, J. P., Templeman, L. A., Stein, S. A., & Hammer, B. E. (2012). Oxygen Persufflation Extends Human Pancreas Preservation from 10 to 24 Hr without Loss i Viable Islet Yield and Quality. American Journal of Transplantation.
• Papas, K. K., Suszynski, T. M., Scott, W. E., Li, J., Lam, A. S., Fonger, J. D., Ritter, J. M., Rizzari, M. D., Eckman, P. M., Templeman, L. A., John, R., & Chrones, N. (2012). persufflation (gas perfusion) may enable extended cold ischemia time (CIT) during donor heart preservation, American Journal of transplantation Volume 12. American Journal of Transplatation, 12, 392.
• Papas, K. K., Suszynski, T. M., Scott, W. E., Weegman, B. P., Lin, J., Lam, A. S., Fonger, J. D., Ritter, J. M., Rizzari, M. D., Eckman, P. M., Templeman, L. A., John, R., & Chrones, N. (2012). Persufflation (i.e., Gas Perfusion) May Extend Allowable Ischemia Time during Donor Heart Preservation. Journal of heart and lung Transplantation, 31, 150. doi:http://dx.doi.org/10.1016/j.healun.2012.01.433
• Papas, K. K., Weegman, B. P., Taylor, M. J., Baicu, S. C., Scott III, W. E., Mueller, K. R., Kitzmann, J. D., & Rizzari, M. D. (2012). Hypothermic Perfusion Preservation of Pancreas for Islet Grafts: Validation using a Split Lobe Porcine Model. Cell Medicine, 2(3), 105-110. doi:10.3727/215517911X617897
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  The demand for high-quality islets for transplantation in type I diabetics will increase as the current clinical trials transition into standard of care. The mode of preservation of donor pancreata is critical to this mission since islets are very sensitive to ischemic injury. Hypothermic perfusion preservation (HPP) is being investigated for extended pancreas preservation in light of the beneficial effects reported for other organs. The present pilot study aimed to establish the potency of porcine islets isolated from pancreata after 24 h of HPP at 4–8°C. The study design included a split-lobe pancreas model that permitted paired comparisons of islets isolated from 24-h HPP splenic lobes with nonperfused, fresh control duodenal/connecting lobes stored at 4°C for
• Suszynski, T. M., Rizzari, M. D., Scott, W. E., Tempelman, L. A., Taylor, M. J., & Papas, K. K. (2012). Persufflation (or gaseous oxygen perfusion) as a method of organ preservation. Cryobiology, 64(3), 125-43. doi:10.1016/j.cryobiol.2012.01.007.
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  Improved preservation techniques have the potential to improve transplant outcomes by better maintaining donor organ quality and by making more organs available for allotransplantation. Persufflation, (PSF, gaseous oxygen perfusion) is potentially one such technique that has been studied for over a century in a variety of tissues, but has yet to gain wide acceptance for a number of reasons. A principal barrier is the perception that ex vivo PSF will cause in vivo embolization post-transplant. This review summarizes the extensive published work on heart, liver, kidney, small intestine and pancreas PSF, discusses the differences between anterograde and retrograde PSF, and between PSF and other conventional methods of organ preservation (static cold storage, hypothermic machine perfusion). Prospective implications of PSF within the broader field of organ transplantation, and in the specific application with pancreatic islet isolation and transplant are also discussed. Finally, key issues that need to be addressed before PSF becomes a more widely utilized preservation strategy are summarized and discussed.
• Suszynski, T. M., Rizzari, M. D., Scott, W., Tempelman, L. A., Taylor, M. J., & Papas, K. K. (2012). Persufflation (or gaseous oxygen perfusion) as a method of organ preservation. CRYOBIOLOGY, 64(3), 125-143.
• Abouaish, J., Graham, M., Bansal-Pakala, P., Loganathan, G., Soltani, S. M., Tiwari, M., Yuasa, T., Papas, K. K., Sutherland, D. E., McCarthy, R. C., Hering, B. J., & Balamurugan, A. N. (2011). Successful isolation and transplantation of nonhuman primate islets using a novel purified enzyme blend. Transplantation, 92(8), e40-2.
• Abrahante, J. E., Martins, K., Papas, K. K., Hering, B. J., Schuurman, H., & Murtaugh, M. P. (2011). Microbiological safety of porcine islets: comparison with source pig. Xenotransplantation, 18(2), 88-93. doi:10.1111/j.1399-3089.2011.00632.x.
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  Pig islet donors intended for clinical xenotransplantation for the treatment of diabetes must meet stringent conditions. Among others, viruses with the potential to cross the species barrier should be excluded from the herd: this list includes encephalomyocarditis virus (EMCV), hepatitis E virus (HEV), porcine cytomegalovirus (PCMV) and porcine γ-lymphotropic herpesvirus (PLHV). As an islet product is isolated from the pancreas and then subjected to culture before implantation, the question is raised whether islets could be negative even if the animal itself is positive for a distinct pathogen.
• Anazawa, T., Matsumoto, S., Yonekawa, Y., Loganathan, G., Wilhelm, J. J., Soltani, S. M., Papas, K. K., Sutherland, D. E., Hering, B. J., & Balamurugan, A. N. (2011). Prediction of pancreatic tissue densities by an analytical test gradient system before purification maximizes human islet recovery for islet autotransplantation/allotransplantation. Transplantation, 91(5), 508-14.
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  Using standard density gradient (SDG) ranges for human islet purification frequently results in islet loss and transplantation of lower islet mass. Measuring the densities of islet and acinar tissue beforehand to customize the gradient range for the actual COBE 2991 cell processor (COBE) purification is likely to maximize the recovery of islets. We developed an analytical test gradient system (ATGS) for predicting pancreatic tissue densities before COBE purification to minimize islet loss during purification.
• Atchison, N., Fan, W., Brewer, D. D., Arunagirinathan, M. A., Hering, B. J., Kumar, S., Papas, K. K., Kokkoli, E., & Tsapatsis, M. (2011). Silica-Nanoparticle Coatings by Adsorption from Lysine-Silica-Nanoparticle Sols on Inorganic and Biological Surfaces. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 50(7), 1617-1621.
• Atchison, N., Fan, W., Brewer, D. D., Arunagirinathan, M. A., Hering, B. J., Kumar, S., Papas, K. K., Kokkoli, E., & Tsapatsis, M. (2011). Silica-nanoparticle coatings by adsorption from lysine-silica-nanoparticle Sols on inorganic and biological surfaces. Angewandte Chemie (International ed. in English), 50(7), 1617-21. doi:10.1002/anie.201006231
• Cline, G. W., Pongratz, R. L., Zhao, X., & Papas, K. K. (2011). Rates of insulin secretion in INS-1 cells are enhanced by coupling to anaplerosis and Kreb's cycle flux independent of ATP synthesis. BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 415(1), 30-35.
• Cline, G. W., Pongratz, R. L., Zhao, X., & Papas, K. K. (2011). Rates of insulin secretion in INS-1 cells are enhanced by coupling to anaplerosis and Kreb's cycle flux independent of ATP synthesis. Biochemical and biophysical research communications, 415(1), 30-5.
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  Mechanistic models of glucose stimulated insulin secretion (GSIS) established in minimal media in vitro, may not accurately describe the complexity of coupling metabolism with insulin secretion that occurs in vivo. As a first approximation, we have evaluated metabolic pathways in a typical growth media, DMEM as a surrogate in vivo medium, for comparison to metabolic fluxes observed under the typical experimental conditions using the simple salt-buffer of KRB. Changes in metabolism in response to glucose and amino acids and coupling to insulin secretion were measured in INS-1 832/13 cells. Media effects on mitochondrial function and the coupling efficiency of oxidative phosphorylation were determined by fluorometrically measured oxygen consumption rates (OCRs) combined with (31)P NMR measured rates of ATP synthesis. Substrate preferences and pathways into the TCA cycle, and the synthesis of mitochondrial 2nd messengers by anaplerosis were determined by (13)C NMR isotopomer analysis of the fate of [U-(13)C] glucose metabolism. Despite similar incremental increases in insulin secretion, the changes of OCR in response to increasing glucose from 2.5 to 15mM were blunted in DMEM relative to KRB. Basal and stimulated rates of insulin secretion rates were consistently higher in DMEM, while ATP synthesis rates were identical in both DMEM and KRB, suggesting greater mitochondrial uncoupling in DMEM. The relative rates of anaplerosis, and hence synthesis and export of 2nd messengers from the mitochondria were found to be similar in DMEM to those in KRB. And, the correlation of total PC flux with insulin secretion rates in DMEM was found to be congruous with the correlation in KRB. Together, these results suggest that signaling mechanisms associated with both TCA cycle flux and with anaplerotic flux, but not ATP production, may be responsible for the enhanced rates of insulin secretion in more complex, and physiologically-relevant media.
• Graham, M. L., Bellin, M. D., Papas, K. K., Hering, B. J., & Schuurman, H. (2011). Species incompatibilities in the pig-to-macaque islet xenotransplant model affect transplant outcome: a comparison with allotransplantation. Xenotransplantation, 18(6), 328-42.
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  Porcine islet transplantation into diabetic non-human primates is considered most relevant in translational research supporting a clinical application. Most studies have focused on immunosuppressive protocols, while metabolic aspects have mainly been utilized in graft monitoring. We evaluated data from our group regarding human and non-human primate (NHP) allotransplantation and pig-to-NHP xenotransplantation to identify incompatibilities in metabolic factors and their consequences for transplant outcomes.
• Kennedy, D. J., Todd, P., Logan, S., Becker, M., Papas, K. K., & Moore, L. R. (2011). Engineering quadrupole magnetic flow sorting for the isolation of pancreatic islets. JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 311(1), 388-395.
• Loganathan, G., Dawra, R. K., Pugazhenthi, S., Guo, Z., Soltani, S. M., Wiseman, A., Sanders, M. A., Papas, K. K., Velayutham, K., Saluja, A. K., Sutherland, D. E., Hering, B. J., & Balamurugan, A. N. (2011). Insulin degradation by acinar cell proteases creates a dysfunctional environment for human islets before/after transplantation: benefits of α-1 antitrypsin treatment. Transplantation, 92(11), 1222-30.
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  Pancreatic acinar cells are commonly cotransplanted along with islets during auto- and allotransplantations. The aims of this study were to identify how acinar cell proteases cause human islet cell loss before and after transplantation of impure islet preparations and to prevent islet loss and improve function with supplementation of α-1 antitrypsin (A1AT).
• Loganathan, G., Dawra, R. K., Pugazhenthi, S., Guo, Z., Soltani, S. M., Wiseman, A., Sanders, M. A., Papas, K. K., Velayutham, K., Saluja, A. K., Sutherland, D., Hering, B. J., & Balamurugan, A. N. (2011). Insulin Degradation by Acinar Cell Proteases Creates a Dysfunctional Environment for Human Islets Before/After Transplantation: Benefits of alpha-1 Antitrypsin Treatment. TRANSPLANTATION, 92(11), 1222-1230.
• Papas, K. K., Suszynski, T. M., Avgoustiniatos, E. S., Stein, S. A., Falde, E. J., & Hammer, B. E. (2011). Assessment of tissue-engineered islet graft viability by fluorine magnetic resonance spectroscopy. Transplantation Proceedings, 43(9), 3221-5. doi:10.1016/j.transproceed.2011.09.009
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  Despite significant progress in the last decade, islet transplantation remains an experimental therapy for a limited number of patients with type 1 diabetes. Tissue-engineered approaches may provide promising alternatives to the current clinical protocol and would benefit greatly from concurrent development of graft quality assessment techniques. This study was designed to evaluate whether viability of tissue-engineered islet grafts can be assessed using fluorine magnetic resonance spectroscopy ((19)F-MRS), by the noninvasive measurement of oxygen partial pressure (pO(2)) and the subsequent calculation of islet oxygen consumption rate (OCR).
• Sajja, V. S., Hanley, T. R., Gapsis, H., Guernsey, B., Kennedy, D. J., Taylor, M. J., Papas, K. K., & Todd, P. W. (2011). Application of magnetic particle tracking velocimetry to quadrupole magnetic sorting of porcine pancreatic islets. Biotechnology and bioengineering, 108(9), 2107-17. doi:10.1002/bit.23157
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  Magnetic isolation is a promising method for separating and concentrating pancreatic islets of Langerhans for transplantation in Type 1 diabetes patients. We are developing a continuous magnetic islet sorter to overcome the restrictions of current purification methods that result in limited yield and viability. In Quadrupole Magnetic Sorting (QMS) islets are magnetized by infusing superparamagnetic microbeads into islets' vasculature via arteries that serve the pancreas. The performance of the islet sorter depends on the resulting speed of the islets in an applied magnetic field, a property known as magnetophoretic mobility. Essential to the design and successful operation of the QMS is a method to measure the magnetophoretic mobilities of magnetically infused islets. We have adapted a Magnetic Particle Tracking Velocimeter (MPTV) to measure the magnetophoretic mobility of particles up to 1,000 µm in diameter. Velocity measurements are performed in a well-characterized uniform magnetic energy gradient using video imaging followed by analysis of the video images with a computer algorithm that produces a histogram of absolute mobilities. MPTV was validated using magnetic agarose beads serving as islet surrogates and subjecting them to QMS. Mobility distributions of labeled porcine islets indicated that magnetized islets have sufficient mobility to be captured by the proposed sorting method, with this result confirmed in test isolations of magnetized islets.
• Abrahante, J. E., Martins, K., Papas, K. K., Hering, B. J., Schuurman, H., & Murtaugh, M. P. (2010). Microbiological safety of porcine islets: comparison with source pig. XENOTRANSPLANTATION, 18(2), 88-93.
• Atchison, N. A., Fan, W., Papas, K. K., Hering, B. J., Tsapatsis, M., & Kokkoli, E. (2010). Binding of the fibronectin-mimetic peptide, PR_b, to alpha5beta1 on pig islet cells increases fibronectin production and facilitates internalization of PR_b functionalized liposomes. Langmuir : the ACS journal of surfaces and colloids, 26(17), 14081-8.
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  Islet transplantation is a promising treatment for type 1 diabetes. Recent studies have demonstrated that human islet allografts can restore insulin independence to patients with this disease. As islet isolation and immunotherapeutic techniques improve, the demand for this cell-based therapy will dictate the need for other sources of islets. Pig islets could provide an unlimited supply for xenotransplantation and have shown promise as an alternative to human islet allografts. However, stresses imposed during islet isolation and transplantation decrease islet viability, leading to loss of graft function. In this study, we investigated the ability of a fibronectin-mimetic peptide, PR_b, which specifically binds to the alpha(5)beta(1) integrin, to re-establish lost extracellular matrix (ECM) around isolated pig islets and increase internalization of liposomes. Confocal microscopy and Western blotting were used to show the presence of the integrin alpha(5)beta(1) on the pig islets on day 0 (day of isolation) as well as on different days of islet culture. Islets cultured in medium supplemented with free PR_b for 48 h were found to have increased levels of ECM fibronectin secretion compared to islets in normal culture conditions. Using confocal microscopy and flow cytometry, we found that PR_b peptide-amphiphile functionalized liposomes delivered to the pig islets internalized into the cells in a PR_b concentration dependent manner and nonfunctionalized liposomes showed minimal internalization. These studies proved that the fibronectin-mimetic peptide, PR_b, is an appropriate peptide bullet for applications involving alpha(5)beta(1) expressing pig islet cells. Fibronectin production stimulated through alpha(5)beta(1) PR_b binding may decrease apoptosis and therefore increase islet viability in culture. In addition, PR_b peptide-amphiphile functionalized liposomes may be used for targeted delivery of different agents to pig islet cells.
• Papas, K. K. (2010). Successful Human Islet Isolation and Transplantation Indicating the Importance of Class 1 Collagenase ad Collagen Degradation Activity Assay. Transplantation. doi:10.1097/TP.0b013e3181d21e9a
• Papas, K. K., Colton, C. K., Qipo, A., Wu, H., Nelson, R. A., Hering, B. J., Weir, G. C., & Koulmanda, M. (2010). Prediction of marginal mass required for successful islet transplantation. Journal of investigative surgery : the official journal of the Academy of Surgical Research, 23(1), 28-34.
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  Islet quality assessment methods for predicting diabetes reversal (DR) following transplantation are needed. We investigated two islet parameters, oxygen consumption rate (OCR) and OCR per DNA content, to predict transplantation outcome and explored the impact of islet quality on marginal islet mass for DR. Outcomes in immunosuppressed diabetic mice were evaluated by transplanting mixtures of healthy and purposely damaged rat islets for systematic variation of OCR/DNA over a wide range. The probability of DR increased with increasing transplanted OCR and OCR/DNA. On coordinates of OCR versus OCR/DNA, data fell into regions in which DR occurred in all, some, or none of the animals with a sharp threshold of around 150-nmol/min mg DNA. A model incorporating both parameters predicted transplantation outcome with sensitivity and specificity of 93% and 94%, respectively. Marginal mass was not constant, depended on OCR/DNA, and increased from 2,800 to over 100,000 islet equivalents/kg body weight as OCR/DNA decreased. We conclude that measurements of OCR and OCR/DNA are useful for predicting transplantation outcome in this model system, and OCR/DNA can be used to estimate the marginal mass required for reversing diabetes. Because human clinical islet preparations in a previous study had OCR/DNA.
• Papas, K. K., Murtaugh, M., Hammer, B. E., Scott III, W. E., Ferrer-Fabrega, J., Avgoustiniatos, E. S., Anazawa, T., Weegman, B. P., Matsumoto, S., O'Brien, T. D., Yu, I., Kidder, L. S., Maynard, K. S., Stone, S. G., Tempelman, L., Sutherland, D. R., & Hering, B. J. (2010). Persufflation improves pancreas preservation when compared with the two-layer method. Transplant Proc., 42(6), 2016-19. doi:10.1016/j.transproceed.2010.05.092
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  Islet transplantation is emerging as a promising treatment for patients with type 1 diabetes. It is important to maximize viable islet yield for each organ due to scarcity of suitable human donor pancreata, high cost, and the large dose of islets required for insulin independence. However, organ transport for 8 hours using the two-layer method (TLM) frequently results in low islet yields. Since efficient oxygenation of the core of larger organs (eg, pig, human) in TLM has recently come under question, we investigated oxygen persufflation as an alternative way to supply the pancreas with oxygen during preservation. Porcine pancreata were procured from donors after cardiac death and preserved by either TLM or persufflation for 24 hours and subsequently fixed. Biopsies collected from several regions of the pancreas were sectioned, stained with hematoxylin and eosin, and evaluated by a histologist. Persufflated tissues exhibited distended capillaries and significantly less autolysis/cell death relative to regions not exposed to persufflation or to tissues preserved with TLM. The histology presented here suggests that after 24 hours of preservation, persufflation dramatically improves tissue health when compared with TLM. These results indicate the potential for persufflation to improve viable islet yields and extend the duration of preservation, allowing more donor organs to be utilized.
• Papas, K. K., Rizzari, M. D., Suszynski, T. M., Kidder, L. S., Stein, S. A., O'Brien, T. D., Scott III, W. E., Kirchner, V. A., Weegman, B. P., Avgoustiniatos, E. S., Todd, P. W., Kennedy, D. J., Hammer, B. E., Sutherland, D. R., & Hering, B. J. (2010). Surgical Protocol Involving the Infusion of Paramagnetic Microparticles for Preferential Incorporation within Porcine Islets. Transplant Proc., 42(10), 4209-12. doi:10.1016/j.transproceed.2010.09.138
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  Despite significant advances, widespread applicability of islet cell transplantation remains elusive. Refinement of current islet isolation protocols may improve transplant outcomes. Islet purification by magnetic separation has shown early promise. However, surgical protocols must be optimized to maximize the incorporation of paramagnetic microparticles (MP) within a greater number of islets. This study explores the impact of MP concentration and infusion method on optimizing MP incorporation within islets.
• Papas, K. K., Scott, W. E., Avgoustiniatos, E. S., Ferrer-Fabrega, J., Anazawa, T., Weegman, B. P., Kidder, L. S., Stein, S., Matsumoto, S., Hammer, B. E., Balamurugan, A. N., O'brien, T. D., Murtaugh, M., Templeman, L., Sutherland, D. E., & Hering, B. J. (2010). Pancreas oxygen persufflation increases ATP levels as shown by nuclear magnetic resonance (NMR). Transplant Proc. doi:10.1016/j.transproceed.2010.05.091.
• Pisania, A., Papas, K. K., Powers, D. E., Rappel, M. J., Omer, A., Bonner-Weir, S., Weir, G. C., & Colton, C. K. (2010). Enumeration of islets by nuclei counting and light microscopic analysis. Laboratory investigation; a journal of technical methods and pathology, 90(11), 1676-86.
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  Islet enumeration in impure preparations by conventional dithizone staining and visual counting is inaccurate and operator dependent. We examined nuclei counting for measuring the total number of cells in islet preparations, and we combined it with morphological analysis by light microscopy (LM) for estimating the volume fraction of islets in impure preparations. Cells and islets were disrupted with lysis solution and shear, and accuracy of counting successively diluted nuclei suspensions was verified with (1) visual counting in a hemocytometer after staining with crystal violet, and automatic counting by (2) aperture electrical resistance measurement and (3) flow cytometer measurement after staining with 7-aminoactinomycin-D. DNA content averaged 6.5 and 6.9 pg of DNA per cell for rat and human islets, respectively, in agreement with literature estimates. With pure rat islet preparations, precision improved with increasing counts, and samples with about ≥160 islets provided a coefficient of variation of about 6%. Aliquots of human islet preparations were processed for LM analysis by stereological point counting. Total nuclei counts and islet volume fraction from LM analysis were combined to obtain the number of islet equivalents (IEs). Total number of IE by the standard method of dithizone staining/manual counting was overestimated by about 90% compared with LM/nuclei counting for 12 freshly isolated human islet research preparations. Nuclei counting combined with islet volume fraction measurements from LM is a novel method for achieving accurate islet enumeration.
• Papas, K. K. (2009). Devices and methods for maintenance of temperature and pressure during islet shipment. Transplant Proc, 40(2), 407-410. doi:10.1016/j.transproceed.2008.01.060
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  Exposure to extreme temperatures and pressure fluctuations during shipment by air may have a detrimental impact on islet quality. In this study, we sought to assess the ability of methods and devices to provide better control of the internal environment of islet shipping containers in terms of temperature and pressure.
• Papas, K. K. (2009). Human islet isolation for autologous transplantation: comparison of yield and function using SERVA/Nordmark versus Roche enzymes. American Journal of Transplantation. doi:10.1111/j.1600-6143.2009.02765.x
• Papas, K. K. (2009). lessons learned from continuous temperature monitoring during 83 human islet shipments. Organ Biology.
• Papas, K. K., Suszynski, T. M., & Colton, C. K. (2009). Islet assessment for transplantation. Current opinion in organ transplantation, 14(6), 674-82.
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  There is a critical need for meaningful viability and potency assays that characterize islet preparations for release prior to clinical islet cell transplantation. Development, testing, and validation of such assays have been the subject of intense investigation for the last decade. These efforts are reviewed, highlighting the most recent results while focusing on the most promising assays.
• Shenkman, R. M., Chalmers, J. J., Hering, B. J., Kirchhof, N., & Papas, K. K. (2009). Quadrupole magnetic sorting of porcine islets of Langerhans. Tissue engineering. Part C, Methods, 15(2), 147-56.
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  Islet transplantation is emerging as a treatment option for selected patients with type 1 diabetes. Inconsistent isolation, purification, and recovery of large numbers of high-quality islets remain substantial impediments to progress in the field. Removing islets as soon as they are liberated from the pancreas during digestion and circumventing the need for density gradient purification is likely to result in substantially increased viable islet yields by minimizing exposure to proteolytic enzymes, reactive oxygen intermediates, and mechanical stress associated with centrifugation. This study capitalized on the hypervascularity of islets compared with acinar tissue to explore their preferential enrichment with magnetic beads to enable immediate separation in a magnetic field utilizing a quadrupole magnetic sorting. The results demonstrate that (1) preferential enrichment of porcine islets is achievable, but homogeneous bead distribution within the pancreas is difficult to achieve with current protocols; (2) greater than 70% of islets in the dissociated pancreatic tissue were recovered by quadrupole magnetic sorting, but their purity was low; and (3) infused islets purified by density gradients and subsequently passed through quadrupole magnetic sorting had similar potency as uninfused islets. These results demonstrate proof of concept and define the steps for implementation of this technology in pig and human islet isolation.
• Shenkman, R. M., Godoy-Silva, R., Papas, K. K., & Chalmers, J. J. (2009). Effects of energy dissipation rate on islets of Langerhans: implications for isolation and transplantation. Biotechnology and bioengineering, 103(2), 413-23.
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  Acute physical stresses can occur in the procurement and isolation process and potentially can contribute to islet death or malfunction upon transplantation. A contractional flow device, previously used to subject suspended cells to well-defined hydrodynamic forces, has been modified and used to assess the vulnerability of porcine islets of Langerhans to hydrodynamic forces. The flow profiles and velocity gradients in this modified device were modeled using commercial CFD software and characterized, as in previous studies, with the scalar parameter, energy dissipation rate (EDR). Porcine islets were stressed in a single pass at various stress levels (i.e., values of EDR). Membrane integrity, oxygen uptake rate, caspase 3/7 activity, and insulin release were not affected by the levels of fluid stress tested up to an EDR of 2 x 10(3) W/m(3). Visual observation of the stressed islets suggested that cells at the islet exterior were peeled away at EDR greater than 10,000 W/m(3), however, this observation could not be confirmed using image analysis software, which determined the ratio of surface perimeter to total area. The result of this study suggests an upper limit in fluid stress to which islets can be subjected. Such upper limits assist in the design and operation of future islet processing equipment and processes.
• Anazawa, T., Matsumoto, S., Yonekawa, Y., Loganathan, G., Wilhelm, J. J., Soltani, S. M., Papas, K. K., Sutherland, D. E., Hering, B. J., & Balamurugan, A. N. (2008). Prediction of Pancreatic Tissue Densities by an Analytical Test Gradient System Before Purification Maximizes Human Islet Recovery for Islet Autotransplantation/Allotransplantation. TRANSPLANTATION, 91(5), 508-514.
• Boyd, V., Cholewa, O. M., & Papas, K. K. (2008). Limitations in the Use of Fluorescein Diacetate/Propidium Iodide (FDA/PI) and Cell Permeable Nucleic Acid Stains for Viability Measurements of Isolated Islets of Langerhans. Current trends in biotechnology and pharmacy, 2(2), 66-84.
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  BACKGROUND: A review of current literature shows that the combined use of the cell permeable esterase-substrate fluorescein diacetate (FDA) and the cell impermeant nucleic acid stain propidium iodide (PI) to be one of the most common fluorescence-based methods to assess the viability of isolated islets of Langerhans, and it is currently used for islet product release prior to transplantation in humans. However, results from this assay do not correlate with islet viability and function or islet transplantation success in animals or humans (Eckhard et al. 2004; Ricordi et al. 2001). This may be in part attributed to considerable differences as well as discrepancies in the use of these reagents on islets. We critically surveyed the literature and evaluated the impact of a number of variables associated with the use of FDA/PI to determine their reliability in assessing islet cell viability. In addition, we evaluated other fluorescent stains, such as SYTO(R)13, SYTO(R)24 and SYBR(R)14 as possible alternatives to FDA. RESULTS: We found that the stability of stains in storage and stock solutions, the number of islets stained, concentration of stains, staining incubation time, the buffer/media used, and the method of examining islets were significant in the final scoring of viability. For archival file photos, the exposure time and camera/software settings can also impact interpretation of viability. Although our results show that FDA does detect intracellular esterase activity and staining with PI does assess cell membrane integrity, the results obtained from using these stains did not correlate directly with expected islet function and viability per transplantation into diabetic athymic nude mice (Papas et al. 2007). In addition, the use of two nucleic acid stains, such as SYTO(R)13 and PI, for live/dead scoring exhibited staining anomalies which limit their accuracy in assessing islet viability. CONCLUSIONS: From a review of the literature and from our observations on the impact of reagent handling and various staining and imaging parameters used to visually evaluate islets, consistent interpretation of islet cell membrane integrity and viability is dependent upon a number of factors. We discuss the utility and limitations of these reagents in evaluating islet cell membrane integrity and viability.
• Ferrer, J., Scott, W. E., Weegman, B. P., Suszynski, T. M., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2008). Pig Pancreas Anatomy: Implications for Pancreas Procurement, Preservation, and Islet Isolation. TRANSPLANTATION, 86(11), 1503-1510.
• Iwanaga, Y., Sutherland, D. E., Harmon, J. V., & Papas, K. K. (2008). Pancreas preservation for pancreas and islet transplantation. Current opinion in organ transplantation, 13(4), 445-51.
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  To summarize advances and limitations in pancreas procurement and preservation for pancreas and islet transplantation, and review advances in islet protection and preservation.
• Papas, K. K. (2008). Devices and methods for maintenance of temperature and pressure during islet shipment. Transplant Proc, 407-410. doi:doi:10.1016/j.transproceed.2008.01.060
• Papas, K. K. (2008). Porcine Pancreas Anatomy: Implication in pancreas procurement, presentation and islet isolation. Transplantation, 1503-1510. doi:10.1097/TP.0b013e31818bfda1
• Papas, K. K., Avgoustiniatos, E. S., Hering, B. J., Wilson, P. R., Wilson, J. R., Tempelman, L. A., Balamurugan, A. N., Welch, D. P., Weegman, B. P., & Suszynski, T. M. (2008). Commercially available gas-permeable cell culture bags may not prevent anoxia in cultured or shipped islets. Transplant Proc., 40(2), 396-400. doi:10.1016/j.transproceed.2008.01.059.
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  Prolonged anoxia has deleterious effects on islets. Gas-permeable cell culture devices can be used to minimize anoxia during islet culture and especially during shipment when elimination of gas-liquid interfaces is required to prevent the formation of damaging gas bubbles. Gas-permeable bags may have several drawbacks, such as propensity for puncture and contamination, difficult islet retrieval, and significantly lower oxygen permeability than silicone rubber membranes (SRM). We hypothesized that oxygen permeability of bags may be insufficient for islet oxygenation. We measured oxygen transmission rates through the membrane walls of three different types of commercially available bags and through SRM currently used for islet shipment. We found that the bag membranes have oxygen transmission rates per unit area about 100-fold lower than SRM. We solved the oxygen diffusion-reaction equation for 150-microm diameter islets seeded at 3000 islet equivalents per cm2, a density adequate to culture and ship an entire human or porcine islet preparation in a single gas-permeable device, predicting that about 40% of the islet volume would be anoxic at 22 degrees C and about 70% would be anoxic at 37 degrees C. Islets of larger size or islets accumulated during shipment would be even more anoxic. The model predicted no anoxia in islets similarly seeded in devices with SRM bottoms. We concluded that commercially available bags may not prevent anoxia during islet culture or shipment; devices with SRM bottoms are more suitable alternatives.
• Papas, K. K., Bellin, M., Kandaswamy, R., Parkey, J., Zhang, H., Liu, B., Ihm, S., Ansite, J., Witson, J., Bansala-Pakala, P., Moran, A., Sutherland, D., & Hering, B. J. (2008). Prolonged Insulin Independence after Islet Allotransplants in Patients with Type 1 Diabetes. American Journal of Transplantation, 8(11), 2463-2470. doi:10.1111/j.1600-6143.2008.02404.x.
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  We sought to determine the long-term outcomes in type 1 diabetic recipients of intraportal alloislet transplants on a modified immunosuppressive protocol. Six recipients with hypoglycemia unawareness received one to two islet infusions. Induction therapy was with antithymocyte globulin (ATG) plus etanercept for tumor necrosis factor-alpha blockade. Recipients received cyclosporine and everolimus for maintenance immunosuppression for the first year posttransplant, with mycophenolic acid or mycophenolate mofetil subsequently substituted for everolimus. Recipients have been followed for 1173 +/- 270 days since their last infusion for islet graft function (insulin independence, hemoglobin A(1c) levels and C-peptide production) and for adverse events associated with the study protocol. Of the six recipients, five were insulin-independent at 1 year, and four continue to be insulin-independent at a mean of 3.4 +/- 0.4 years posttransplant. None of the six recipients experienced recurrence of severe hypoglycemia. Measured glomerular filtration rate decreased from 110.5 +/- 21.2 mL/min/1.73 m(2) pretransplant to 82.6 +/-19.1 mL/min/1.73 m(2) at 1 year posttransplant. In conclusion, islet transplants restored insulin independence for a mean of >3 years in four of six recipients treated with ATG and etanercept induction therapy and with cyclosporine and, initially, everolimus for maintenance. Our results suggest this immunosuppressive protocol may allow long-term graft survival.
• Papas, K. K., Scott III, W. E., Matsumoto, S., Tanaka, T., Avgoustiniatos, E. S., Graham, M. L., Williams, P. C., Tempelman, L. A., Sutherland, D. E., Hering, B. J., & Hammer, B. E. (2008). Real-time non-invasive assessment of pancreatic ATP levels during cold preservation. Transplant Proc, 40(2), 403-406. doi:10.1016/j.transproceed.2008.01.042.
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  31P-NMR spectroscopy was utilized to investigate rat and porcine pancreatic ATP:P(i) ratios to assess the efficacy of existing protocols for cold preservation (CP) in maintaining organ quality. Following sacrifice, rat pancreata were immediately excised or left enclosed in the body for 15 minutes of warm ischemia (WI). After excision, rat pancreata were stored at 6 degrees C to 8 degrees C using histidine-tryptophan-ketoglutarate solution (HTK) presaturated with air (S1), HTK presaturated with O2 (S2), or the HTK/perfluorodecalin two-layer method (TLM) with both liquids presaturated with O2 (S3). 31P-NMR spectra were sequentially collected at 3, 6, 9, 12, and 24 hours of CP from pancreata stored with each of the three protocols examined. The ATP:Pi ratio for rat pancreata exposed to 15 minutes of WI and stored with S3 increased during the first 9 hours of CP, approaching values observed for organs procured with no WI. A marked reduction in the ATP:Pi ratio was observed beyond 12 hours of CP with S3. After 6 hours of CP, the ATP:Pi ratio was highest for S3, substantially decreased for S2, and below detection for S1. In sharp contrast to the rat model, ATP was barely detectable in porcine pancreata exposed to minimal warm ischemia (
• Papas, K. K., Suszynski, T. M., Wildey, G. M., Falde, E. J., Cline, G. W., Maynard, K. S., Ko, N., Sotiris, J., Naji, A., & Hering, B. J. (2008). The ATP/DNA Ratio is a Better Indicator of Islet Cell Viability than the ADP/ATP Ratio. Transplant Proc, 40(2), 346-350. doi:10.1016/j.transproceed.2008.01.061
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  Real-time, accurate assessment of islet viability is critical for avoiding transplantation of nontherapeutic preparations. Measurements of the intracellular ADP/ATP ratio have been recently proposed as useful prospective estimates of islet cell viability and potency. However, dead cells may be rapidly depleted of both ATP and ADP, which would render the ratio incapable of accounting for dead cells. Since the DNA of dead cells is expected to remain stable over prolonged periods of time (days), we hypothesized that use of the ATP/DNA ratio would take into account dead cells and may be a better indicator of islet cell viability than the ADP/ATP ratio. We tested this hypothesis using mixtures of healthy and lethally heat-treated (HT) rat insulinoma cells and human islets. Measurements of ATP/DNA and ADP/ATP from the known mixtures of healthy and HT cells and islets were used to evaluate how well these parameters correlated with viability. The results indicated that ATP and ADP were rapidly (within 1 hour) depleted in HT cells. The fraction of HT cells in a mixture correlated linearly with the ATP/DNA ratio, whereas the ADP/ADP ratio was highly scattered, remaining effectively unchanged. Despite similar limitations in both ADP/ADP and ATP/DNA ratios, in that ATP levels may fluctuate significantly and reversibly with metabolic stress, the results indicated that ATP/DNA was a better measure of islet viability than the ADP/ATP ratio.
• Graham, M. L., Bellin, M. D., Papas, K. K., Hering, B. J., & Schuurman, H. (2011). Species incompatibilities in the pig-to-macaque islet xenotransplant model affect transplant outcome: a comparison with allotransplantation. XENOTRANSPLANTATION, 18(6), 328-342.
• Papas, K. K. (2007). Engineering Quadrupole magnetic flow sorting for the isolation of pancreatic islets. Journal of Magnetism and Magnetic Materials, 311, 388-395. doi:10.1016/j.jmmm.2006.10.1160
• Papas, K. K., Colton, C. K., Nelson, R. A., Rozak, P. R., Scott III, W. E., Avgoustiniatos, E. S., Pisania, A., Weir, G. C., & Hering, B. J. (2007). Human islet oxygen consumption rate and DNA measurements predict diabetes reversal in nude mice. American Journal of Transplantation, 7(3), 707-13.
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  There is a need for simple, quantitative and prospective assays for islet quality assessment that are predictive of islet transplantation outcome. The current state-of-the-art athymic nude mouse bioassay is costly, technically challenging and retrospective. In this study, we report on the ability of 2 parameters characterizing human islet quality: (1) oxygen consumption rate (OCR), a measure of viable volume; and (2) OCR/DNA, a measure of fractional viability, to predict diabetes reversal in nude mice. Results demonstrate that the probability for diabetes reversal increases as the graft's OCR/DNA and total OCR increase. For a given transplanted OCR dose, diabetes reversal is strongly dependent on OCR/DNA. The OCR and OCR/DNA (the 'OCR test') data exhibit 89% sensitivity and 77% specificity in predicting diabetes reversal in nude mice (n = 86). We conclude that the prospective OCR test can effectively replace the retrospective athymic nude mouse bioassay in assessing human islet quality prior to islet transplantation.
• Papas, K. K., Dvorak, C. M., Hårdstedt, M., Xie, H., Wang, M., Hering, B. J., Murtaugh, M. P., & Fahrenkrug, S. C. (2007). Transcriptional profiling of stress-response in cultured porcine islets. Biochem Biophys Res Commun., 357(1), 118-125.
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  Cell-based diabetes therapy may be achieved through xenotransplantation of adult porcine islets, but tissue quality and immunoreactivity barriers need to be overcome. Early identification and exclusion of irreversibly stressed and dying islets may improve transplant outcomes. We used oligonucleotide microarray and quantitative RT-PCR to identify molecular markers of physiological and immunological stress in porcine islets cultured under stress conditions of elevated glucose (16.7 mM), inflammatory cytokine addition (IL-1beta, TNF-alpha, and IFN-gamma), or both, for 48 h. Hyperglycemic conditions were associated with increased thioredoxin interacting protein and metabolic process mRNAs, as observed in rodent and primate species. Cytokine treatment increased expression of JAK-STAT pathway components, oxidative stress (transglutaminase 2), and beta cell dysfunction genes. Transglutaminase 2 induction is unique to porcine islets. Biomarkers involved in hyperglycemia and islet inflammation may serve as novel targets for improving and monitoring isolated porcine islet function and viability.
• Papas, K. K., Pisania, A., Wu, H., Weir, G. C., & Colton, C. K. (2007). A stirred microchamber for oxygen consumption rate measurements with pancreatic islets. Biotechnology and bioengineering, 98(5), 1071-82.
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  Improvements in pancreatic islet transplantation for treatment of diabetes are hindered by the absence of meaningful islet quality assessment methods. Oxygen consumption rate (OCR) has previously been used to assess the quality of organs and primary tissue for transplantation. In this study, we describe and characterize a stirred microchamber for measuring OCR with small quantities of islets. The device has a titanium body with a chamber volume of about 200 microL and is magnetically stirred and water jacketed for temperature control. Oxygen partial pressure (pO(2)) is measured by fluorescence quenching with a fiber optic probe, and OCR is determined from the linear decrease of pO(2) with time. We demonstrate that measurements can be made rapidly and with high precision. Measurements with betaTC3 cells and islets show that OCR is directly proportional to the number of viable cells in mixtures of live and dead cells and correlate linearly with membrane integrity measurements made with cells that have been cultured for 24 h under various stressful conditions.
• Avgoustiniatos, E. S., Hering, B. J., & Papas, K. K. (2006). The rat pancreas is not an appropriate model for testing the preservation of the human pancreas with the two-layer method. Transplantation, 81(10), 1471-2; author reply 1472.
• Kitzmann, J. P., Law, L., Shome, A., Muzina, M., Elliott, R. B., Mueller, K. R., Schuurman, H., & Papas, K. K. (2012). Real-time assessment of encapsulated neonatal porcine islets prior to clinical xenotransplantation. XENOTRANSPLANTATION, 19(6), 333-336.
• Papas, K. K., Avgoustiniatos, E. S., Tempelman, L. A., Weir, G. C., Colton, C. K., Pisania, A., Rappel, M. J., Friberg, A. S., Bauer, A. C., & Hering, B. J. (2005). High-density culture of human islets on top of silicone rubber membranes. Transplant Proc, 37(8), 3412-3414.
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  Islet culture has emerged as a standard practice prior to clinical transplantation. However, culturing large numbers of islets requires low islet density (number of islets per unit surface area) and, consequently, 20 to 30 flasks per pancreas in order to avoid hypoxia-induced death (HID). There is a need for a simple, practical, small-footprint culture vessel that will accommodate aseptic maintenance of entire human islet isolations while avoiding HID. In this communication, we examine the hypothesis that by improving oxygen transfer through culture of islets on silicone rubber membranes (SRM), we may increase islet surface coverage and reduce the number of flasks required while avoiding HID. Our results demonstrate that islets cultured for up to 48 hours in vessels with SRM bottoms at 2000 to 4000 islet equivalents (IE)/cm(2), a surface coverage 10- to 20-fold higher than the standard culture protocol, displayed no significant loss of viability. In contrast, islets cultured for 48 hours at 4000 IE/cm(2) in flasks with gas-impermeable bottoms suffered a 60% to 70% reduction in viability. The data suggest that it is possible to culture all islets isolated from a human pancreas on SRM in a single, standard-sized vessel while maintaining the same viability as with the current, standard culture protocols that require 20 to 30 flasks. This approach may lead to substantial improvements in islet culture for research and clinical transplantation.
• Papas, K. K., Hering, B. J., Gunther, L., Rappel, M. J., Colton, C. K., & Avgoustiniatos, E. S. (2005). Pancreas oxygenation is limited during preservation with the two-layer method. Transplant Proc, 37(8), 3501-3504.
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  Islet culture has emerged as a standard practice prior to clinical transplantation. However, culturing large numbers of islets requires low islet density (number of islets per unit surface area) and, consequently, 20 to 30 flasks per pancreas in order to avoid hypoxia-induced death (HID). There is a need for a simple, practical, small-footprint culture vessel that will accommodate aseptic maintenance of entire human islet isolations while avoiding HID. In this communication, we examine the hypothesis that by improving oxygen transfer through culture of islets on silicone rubber membranes (SRM), we may increase islet surface coverage and reduce the number of flasks required while avoiding HID. Our results demonstrate that islets cultured for up to 48 hours in vessels with SRM bottoms at 2000 to 4000 islet equivalents (IE)/cm(2), a surface coverage 10- to 20-fold higher than the standard culture protocol, displayed no significant loss of viability. In contrast, islets cultured for 48 hours at 4000 IE/cm(2) in flasks with gas-impermeable bottoms suffered a 60% to 70% reduction in viability. The data suggest that it is possible to culture all islets isolated from a human pancreas on SRM in a single, standard-sized vessel while maintaining the same viability as with the current, standard culture protocols that require 20 to 30 flasks. This approach may lead to substantial improvements in islet culture for research and clinical transplantation.
• Cline, G. W., Lepine, R. L., Papas, K. K., Kibbey, R. G., & Shulman, G. I. (2004). 13C NMR isotopomer analysis of anaplerotic pathways in INS-1 cells. The Journal of biological chemistry, 279(43), 44370-5.
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  Anaplerotic flux into the Kreb's cycle is crucial for glucose-stimulated insulin secretion from pancreatic beta-cells. However, the regulation of flux through various anaplerotic pathways in response to combinations of physiologically relevant substrates and its impact on glucose-stimulated insulin secretion is unclear. Because different pathways of anaplerosis generate distinct products, they may differentially modulate the insulin secretory response. To examine this question, we applied 13C-isotopomer analysis to quantify flux through three anaplerotic pathways: 1) pyruvate carboxylase of pyruvate derived from glycolytic sources; 2) pyruvate carboxylase of pyruvate derived from nonglycolytic sources; and 3) glutamate dehydrogenase (GDH). At substimulatory glucose, anaplerotic flux rate in the clonal INS-1 832/13 cells was approximately 40% of Kreb's cycle flux, with similar contributions from each pathway. Increasing glucose to 15 mm stimulated insulin secretion approximately 4-fold, and was associated with a approximately 4-fold increase in anaplerotic flux that could mostly be attributed to an increase in PC flux. In contrast, the addition of glutamine to the perfusion media stimulated GDH flux approximately 6-fold at both glucose concentrations without affecting insulin secretion rates. In conclusion, these data support the hypothesis that a signal generated by anaplerosis from increased pyruvate carboxylase flux is essential for glucose-stimulated insulin secretion in beta-cells and that anaplerosis through GDH does not play a major role in this process.
• Papas, K. K. (2003). Islet oxygen consumption rate as a predictor of in vivo efficacy post-transplantation. Xenotransplanation.
• Papas, K. K. (2002). P-31 NMR assessment of uncoupling activity during glucose stimulated insulin secretion (GSIS) in INS-1 and beta HC9 Cells. Diabetes.
• Papas, K. K. (2001). Rapid islet quality assessment prior to transplantation. Cell Transplantation.
• Papas, K. K., Colton, C. K., Gounarides, J. S., Roos, E. S., Jarema, M. A., Shapiro, M. J., Cheng, L. L., Cline, G. W., Shulman, G. I., Wu, H., Bonner-Weir, S., & Weir, G. C. (2001). NMR Spectroscopy in β-cell Engineering and Islet Transplantation. Annals of NY Academy of Sciences, 96-119.
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  Islet transplantation is a promising method for restoring normoglycemia and alleviating the long term complications of diabetes. Widespread application of islet transplantation is hindered by the limited supply of human islets and requires a large increase in the availability of suitable insulin secreting tissue as well as robust quality assessment methodologies that can ensure safety and in vivo efficacy. We explore the application of nuclear magnetic resonance (NMR) spectroscopy in two areas relevant to beta cell engineering and islet transplantation: (1) the effect of genetic alterations on glucose metabolism, and (2) quality assessment of islet preparations prior to transplantation. Results obtained utilizing a variety of NMR techniques demonstrate the following: (1) Transfection of Rat1 cells with the c-myc oncogene (which may be involved in cell proliferation and cell cycle regulation) and overexpression of Bcl-2 (which may protect cells from stresses such as hypoxia and exposure to cytokines) introduce a wide array of alterations in cellular biochemistry, including changes in anaerobic and oxidative glucose metabolism, as assessed by 13C and 31P NMR spectroscopy. (2) Overnight incubation of islets and beta cells in the bottom of centrifuge tubes filled with medium at room temperature, as is sometimes done in islet transportation, exposes them to severe oxygen limitations that may cause cell damage. Such exposure, leading to reversible or irreversible damage, can be observed with NMR-detectable markers using conventional 13C and 31P NMR spectroscopy of extracts. In addition, markers of irreversible damage (as well as markers of hypoxia) can be detected and quantified without cell extraction using high-resolution magic angle spinning 1H NMR spectroscopy. Finally, acute ischemia in a bed of perfused beta cells leads to completely reversible changes that can be followed in real time with 31P NMR spectroscopy.
• Papas, K. K. (2000). Effects of Short-term Hypoxia on the Bioenergetic and insulin secretion of Alginate-Entrapped Muse Insulinoma βTC3 Cells. Cell Transplantation.
• Papas, K. K., Long, R. C., Constantinidis, I., & Sambanis, A. (2000). In vitro monitoring of Total Choline Levels in a Bioartificial Pancreas: 1H NMR studies of the Effects of Oxygen Level. Journal of Magnetic Resonance, 146(1), 49-57.
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  This investigation implements specifically designed solvent-suppressed adiabatic pulses whose properties make possible the long-term monitoring of (1)H NMR detectable metabolites from alginate/poly-l-lysine/alginate (APA)-encapsulated betaTC3 cells. Our encapsulated preparations were maintained in a perfusion bioreactor for periods exceeding 30 days. During this prolonged cultivation period, the cells were exposed to repetitive hypoxic episodes of 4 and 24 h. The ratio of the total choline signal (3.20 ppm) to the reference signal (observed at 0.94 ppm assigned to isoleucine, leucine, and valine) decreased by 8-10% for the 4-h and by 20-32% for the 24-h episodes and returned to its prehypoxic level upon reoxygenation. The decrease in the mean value of total choline to reference signal ratio for three 4-h and two 24-h episodes in two different cultures was highly significant (P
• Papas, K. K. (1999). Toward the Development of Bio artificial Pancreas: I. Effect of Glucose on Long-Term Entrapped βTC3 Cell Cultures. Biotechnology and Bio-engineering. doi:10.1002/(SICI)1097-0290(1999)66:4<231::AID-BIT4>3.0.CO;2-U
• Papas, K. K., Long, R. C., Sambanis, A., & Constantinidis, I. (1999). Towards the Development of a Bioartificial Pancreas: II. Effects of Oxygen on Long-term Entrapped βTC3 Cell Cultures. Biotechnology and Bioengineering, 66(4), 231-237. doi:10.1002/(SICI)1097-0290(1999)66:4<231::AID-BIT4>3.0.CO;2-U
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  Tissue-engineered pancreatic constructs based on immunoisolated, insulin-secreting cells are promising in providing an effective, relatively inexpensive, long-term treatment for type I (insulin-dependent) diabetes. An in vitro characterization of construct function under conditions mimicking the in vivo environment is essential prior to any extensive animal experimentation. Encapsulated cells may experience hypoxic conditions postimplantation as a result of one or more of the following: the design of the construct; the environment at the implantation site; or the development of fibrosis around the construct. In this work, we studied the effects of 3- and 4-day-long hypoxic episodes on the metabolic and secretory activities and on the levels of intracellular metabolites detectable by phosphorus-31 nuclear magnetic resonance (31P NMR) of alginate/poly-L-lysine/alginate entrapped βTC3 mouse insulinomas continuously perfused with culture medium. Results show that, upon decreasing the oxygen concentration in the surrounding medium, the encapsulated cell system reached a new, lower metabolic and secretory state. Hypoxia drove the cells to a more anaerobic glycolytic metabolism, increased the rates of glucose consumption (GCR) and lactate production (LPR), and reduced the rates of oxygen consumption (OCR) and insulin secretion (ISR). Furthermore, hypoxia reduced the levels of intracellular nucleotide triphosphates (NTP) and phosphorylcholine (PC) and caused a rapid transient increase in inorganic phosphate (Pi). Upon restoration of the oxygen concentration in the perfusion medium, all parameters returned to their prehypoxic levels within 2 to 3 days following either gradual unidirectional changes (ISR, NTP, PC) or more complicated dynamic patterns (OCR, GCR, LPR). A further increase in oxygen concentration in the perfusion medium drove OCR, ISR, NTP, PC, and Pi to new, higher levels. It is concluded that 31P NMR spectroscopy can be used for the prolonged noninvasive monitoring of the bioenergetic changes of encapsulated βTC3 cells occurring with changes in oxygen tension. The data also indicate that the oxygen-dependent states might be related to the total number of viable, metabolically active cells supported by the particular oxygen level to which the system is exposed. These findings have significant implications in developing and non-invasively monitoring a tissue-engineered bioartificial pancreas based on transformed β cells, as well as in understanding the biochemical events pertaining to insulin secretion from βTC3 insulinomas. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 66: 231–237, 1999.
• Papas, K. K., Sun, L., Roos, S. E., Gounarides, J., Shapiro, M., & Nalin, C. (1999). Change In Lactate Production In Myc-Transfected Cells Precedes Apoptosis and Can Be Inhibited by Bcl-2 Overexpression. FEBS Lett., 446(2-3), 338-342.
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  As a result of Myc-dependent transcription of the LDH-A gene, Myc-transformed cells (Rat1-Myc) exhibit increased lactate production rates (LPR) even under aerobic conditions (the Warburg effect). Recently, the increased susceptibility to stress-induced apoptosis associated with Myc transfection has been linked to the overexpression of the LDH-A gene. In this report we demonstrate that the overexpression of the anti-apoptotic protein Bcl-2 in Rat1-Myc cells (Rat1-Myc-Bcl-2) reduces the molar ratio of lactate production to glucose consumption (Y(L/G)). The Bcl-2 induced reduction in Y(L/G) may be associated with reduced expression of the LDH-A gene, or a decrease in LDH-A activity. Stimulation of apoptosis by staurosporine, a protein kinase C inhibitor, reduces the LPR in Rat1-Myc cells in a dose-dependent manner. The staurosporine effect on the LPR is rapid and precedes the execution phase of apoptosis as defined by caspase activation and PARP cleavage. This effect on LPR is completely blocked by Bcl-2 overexpression. Serum starvation alone does not affect the LPR of Rat1-Myc or Rat1-Myc-Bcl-2 cells; however, the effect of staurosporine on the LPR of Rat1-Myc cells is potentiated by serum starvation. These data demonstrate that Bcl-2 overexpression reduces the Y(L/G) in Rat1-Myc cells, perhaps via a reduction in the activity or expression of the LDH-A gene, and this reduction may desensitize cells to some pro-apoptotic stimuli. The reduction in LPR in response to staurosporine may be an early step in the induction of apoptosis in Rat1-Myc cells. By abolishing the reduction in LPR, Bcl-2 may protect Rat1-Myc cells from staurosporine-induced apoptosis. Moreover, the lack of effect by serum starvation on the LPR supports a model in which serum starvation induces apoptosis through a pathway distinct from that of the staurosporine and glucose-dependent apoptotic pathway(s) in Myc-transformed cells.
• Papas, K. K., & Jarema, M. A. (1998). Glucose-stimulated Insulin Secretion is not Obligatorily Linked to an Increase in O2 Consumption in βHC9 Cells. The American Journal of Physiology, 38, E1100-E1106.
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  We investigated the effects of glucose on the rates of oxygen consumption (OCR) and insulin secretion (ISR) by betaHC9 cells derived from mouse pancreatic islets with beta-cell hyperplasia. Our results demonstrate that the OCR by betaHC9 cells incubated in nutrient-rich DMEM is unaffected by glucose (0-25 mM), is dissociated from the ISR (which increases with the addition of glucose), and is always higher than that measured in PBS. Glucose (25 mM) increases both the OCR and ISR when added to nutrient-free PBS. On the basis of results presented here, we suggest that, contrary to the current consensus, the observed increases in the OCR by beta-cells upon addition of glucose to nutrient-free buffers may be unrelated to the process of glucose-stimulated insulin secretion (GSIS) and, instead, related to nutrient starvation. We believe that a reevaluation of the implication of changes in OCR upon glucose stimulation in the process of GSIS is warranted and that OCR and ISR measurements should be performed in more physiological media to avoid nutrient starvation artifacts. Glucose-stimulated insulin secretion is not obligatorily linked to an increase in O2 consumption in HC9 cells (PDF Download Available). Available from: https://www.researchgate.net/publication/13443489_Glucose-stimulated_insulin_secretion_is_not_obligatorily_linked_to_an_increase_in_O2_consumption_in_HC9_cells [accessed Feb 11, 2016].
• Papas, K. K., Long, R. C., Constantinidis, I., & Sambanis, A. (1997). The Role of ATP and Pi on the Mechanism of Insulin Secretion in the Mouse Insulinoma βTC3 Cell Line. Biochemical Journal, 326(3), 807-814. doi:10.1042/bj3260807
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  Understanding the biochemical events associated with glucose-stimulated insulin secretion by pancreatic β cells is of importance in gaining insight into both the pathophysiology of diabetes and the development of tissue-engineered bioartificial pancreatic substitutes. We have investigated the effects of glucose concentration on the bioenergetic status and on the metabolic and secretory functions exhibited by mouse insulinoma βTC3 cells entrapped in calcium alginate/poly-L-lysine/alginate (APA) beads. Cells entrapped in APA beads constitute a possible implantable bioartificial pancreas for the long-term treatment of insulin-dependent diabetes mellitus. Our results show that, in entrapped βTC3 cells, the oxygen consumption rate and the intracellular nucleotide triphosphate levels are unaffected by a step change in glucose concentration from 16 mM to 0 mM for 4.5 h and then back to 16 mM. The intracellular Pi level and the ammonia production rate were doubled, while insulin secretion was decreased 10-fold, upon switching from 16 mM to 0 mM glucose. The implications of these findings in the context of pancreatic β cell biochemistry and the mechanism of the ‘Fuel Hypothesis’ are discussed.
• Papas, K. K. (1995). The effects of glucose on the oxygen consumption ad insulin Secretion from Free and Alginate-Entrappped betaTC3 Cells. Biochem,Biophys. Res. Comm..
• Papas, K. K., Long, R. C., Constantinidis, I., & Sambanis, A. (1996). Effects of Oxygen on Metabolic and Secretory Activities of βTC3 Cells. Biochimica et Biophysica Acta, 1291, 163-166. doi:10.1016/0304-4165(96)00062-1
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  We have investigated the rates of glucose consumption, lactate production and insulin secretion by mouse insulinoma βTC3 cells exposed to high glucose and oxygen concentrations in the range of 132 mmHg (normoxia) to 0 mmHg (anoxia). The rates of glucose consumption and lactate production, and the yield of lactate on glucose were 6.4 ± 0.2 nmol/h − 105 cells, 7.7 ± 0.5 nmol/h − 105 cells, and 1.2 ± 0.1 respectively, at oxygen concentrations between 132-25 mmHg. These values increased gradually as the oxygen concentration was reduced below 25 mmHg, reaching a maximum value of 12.8 ± 0.4, 23.8 ± 1.1, 1.9 ± 0.1 respectively, at complete anoxia. Insulin secretion remained constant at 360 ± 24 pmol/h − 108 cells at oxygen concentrations between 132-7 mmHg, but was inhibited at lower oxygen concentrations, dropping to 96 ± 24 pmol/h − 108 cells at 0 mmHg. The rate of insulin secretion in the presence of high glucose under anoxia was significantly higher than the rate of basal secretion (28.2 ± 3.0 pmol/h − 108 cells) at normoxia. The secretory properties of βTC3 cells at low oxygen concentrations may have implications in the development of a diffusion-based bioartificial tissue constructs for the long-term treatment of Insulin Dependent Diabetes Mellitus.
• Papas, K. K., Sambanis, A., Flanders, P. C., Long, R. C., Kang, H., & Constantinidis, I. (1994). Towards The Development of a Bioartificial Pancreas: Immunoisolation and NMR Monitoring of Mouse Insulinomas. Cytotechnology., 15(1-3), 351-363.
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  A promising method for diabetes treatment is the implantation of immunoisolated cells secreting insulin in response to glucose. Cell availability limits the application of this approach at a medically-relevant scale. We explore the use of transformed cells that can be grown to large homogeneous populations in developing artificial pancreatic tissues. We also investigate the use of NMR in evaluating, non-invasively, cellular bioenergetics in the tissue environment. The system employed in this study consisted of mouse insulinoma beta TC3 cells entrapped in calcium alginate/poly-L-lysine (PPL)/alginate beads. The PPL layer imposed a molecular weight cutoff of approximately 60 kDa, allowing nutrients and insulin to diffuse through but excluding high molecular weight antibodies and cytotoxic cells of the host. We fabricated a radiofrequency coil that can be double-tuned to 1H and 31P, and an NMR-compatible perfusion bioreactor and support circuit that can maintain cells viable during prolonged studies. The bioreactor operated differentially, was macroscopically homogeneous and allowed the acquisitions of 1H images and 31P NMR spectra in reasonable time intervals. Results indicated that entrapment had little effect on cell viability; that insulin secretion from beads was responsive to glucose; and that the bioenergetics of perfused, entrapped cells were not grossly different from those of cells never subjected to the immobilization procedure. These findings offer promise for developing an artificial pancreatic tissue for diabetes treatment based on continuous cell lines.
• Papas, K. K., Constantinidis, I., & Sambanis, A. (1993). Cultivation of Recombinant Insulin-Secreting AtT-20 cells as free and entrapped spheroids. Cytotechnology, 13(1), 1-12.
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  Animal cells from endocrine glands have potential applications in bioprocessing, for the production of hormones, enzymes, possibly also recombinant proteins, and in tissue engineering, for the development of immunoisolated, implantable devices for long-term treatment of endocrine disorders. Immunoisolation can be achieved by surrounding cells with a biocompatible polymer which allows diffusion of nutrients and metabolites, including hormones, but excludes higher molecular weight antibodies and cytotoxic cells. Primary hormone-secreting cells cannot be effectively amplified in culture, so the large-scale application of implantable systems based on such cells is limited by cell availability. In this study, we conducted an initial assessment of the feasibility of using transformed, continuous cell lines in immunoisolated devices. The model system employed consisted of mouse pituitary tumor AtT-20 cells which secrete recombinant proinsulin and an insulin-like peptide and exhibit a high growth potential. Cells were cultivated as spheroids in spinner flasks and entrapped as such in alginate/polylysine/alginate beads. Free and entrapped spheroids were propagated in fed-batch, suspension cultures. Entrapment did not significantly affect spheroid metabolism or basal secretion. Entrapped spheroids did not increase in size or number and maintained roughly constant metabolic and basal secretory activities over a 15-day period. Free spheroids in suspension increased in size during the same period, but also maintained constant metabolism and basal secretion, apparently because of a concomitant increase in hypoxic and/or necrotic cells. The potential of using continuous cell lines in the development of bioartificial endocrine organs is discussed.

Presentations

• Papas, K. K. (2020, April). JDRF Beta Cell Replacement (BCR) Consortium Virtual Meeting.
• Papas, K. K. (2020, Fall). Towards Clinical Translation of High Cell-Density Oxygen Enabled Encapsulation Devices in an Allo- and Xeno-Porcine Model. Fall JDRF Beta Cell Replacement (BCR) Consortium Virtual Meeting.
• Papas, K. K. (2019, Fall). Current progress in enzymatic tissue digestion for cell isolation and purification. CTRMS Congress 2019Nordmark.
• Papas, K. K. (2019, Fall). Immunoisolation devices vs. non-immunoisolating scaffolds: pros and cons. CTRMS Congress 2019.
• Papas, K. K. (2019, Fall). Retrievable high-capacity scaffolds for ß-cell replacement therapy: Vascularization & Oxygen Supply. Fall JDRF Beta Cell Replacement (BCR) Consortium Meeting.
• Papas, K. K. (2019, Fall). The Time Capsule. Fall JDRF Beta Cell Replacement (BCR) Consortium.
• Papas, K. K. (2019, May). Porcine islet and Human Stem Cell derived ß-Cell Source: Practical Considerations for Clinical Translation. Spring JDRF Beta Cell Replacement (BCR) Consortium. New York, NY: JDRF.
• Papas, K. K. (2019, Summer). Oxygen Preservation Out of the Box. 17th Congress IPITA.
• Min, C. G., & Papas, K. K. (2017, September). Quality Assessments of Persufflated and Cold Storage Preservation in Subnormothermic Isolated Porcine Kidneys. 14th Congress of the International Society for Organ Donation & Procurement. Geneva, Switzerland: Organ Donation Congress.
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  Student Oral Presentation at an international conferenceSession Title: Allocation and Preservation
• Papas, K. K. (2017, April). Cell-macroencapsulation for the treatment of diabetes without immunosuppression. Regenerative Medicine Track 2nd Molecular, Cell and Tissue Bio-engineering Symposium. Arizona State University, Tempe Pheonix: Arizona State University.
• Papas, K. K. (2017, April). Persufflation in Solid Organ Transplantation: Back to the Future. Newcastle Upon Tyne. Newcastle University, United Kingdom.
• Papas, K. K. (2017, August). Translation of high density encapsulation devices with enhanced oxygen supply. FDA Educational Symposium. Silver Spring, MD: JDRF and FDA.
• Papas, K. K. (2017, August). Unlocking A New World of Transplant Capabilities Through Organ Perfusion Platforms. The Summit on Organ Banking through Converging Technologies. Boston, MA.
• Papas, K. K. (2017, December). Session III - Endocrinology. Regenerative Medicine Innovative Workshop: Focus on Adult Stem Cells. Bethesda, MD: NIH.
• Papas, K. K. (2017, February). Cell-based insulin replacement therapies for the treatment of diabetes. Endocrinology grand rounds. University of Arizona.
• Papas, K. K. (2017, January). Persufflation: a Novel Approach to Pancreas Preservation Prior to Islet Isolation. Pharmacology Grand Rounds. University of Arizona.
• Papas, K. K. (2017, June). Challenges and Strategies for improving Hypoxia during Pancreas Transport. IPITA 16th congress. Oxford, UK: IPITA.
• Papas, K. K. (2017, June). Novel Devices for Oxygenation and Beta Cell Delivery. American Diabetes Association 77th Scientific sessionAmerican Diabetes Association.
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  Technical Innovations in Islet transplantation - Novel Approaches Session, American Diabetes Association 77th scientific session.
• Papas, K. K. (2017, March). Oxygen in Wounds – Real or Hot Air?. Lunch Symposium, Diabetic Foot Global Conference. Houston, Texas.
• Papas, K. K. (2017, November). Pairing of human stem cell derived beta-like cells with a high capacity, oxygen-enabled immunoisolation device. Fall JDRF Encapsulation Consortium Meeting. Long Beach, CA: JDRF.
• Papas, K. K. (2017, November). Retrievable high-capacity scaffolds for ß-cell replacement therapy in humans. Fall JDRF Encapsulation Consortium Meeting. Long Beach, CA: JDRF.
• Papas, K. K. (2017, November). Towards Clinical Translation of High Density Encapsulation Devices with Enhanced Oxygen Supply. Fall JDRF Encapsulation Consortium Meeting. Long Beach, CA: JDRF.
• Papas, K. K. (2017, September). Novel Devices for Cell Encapsulation. CST-CTRMS Congress. Halifax, Canada.
• Papas, K. K. (2016, April). Towards Clinical Translation of High Density Encapsulation Devices with Enhanced Oxygen Supply. JDRF Encapsulation Consortium Meeting. New York , NY.
• Papas, K. K. (2016, Fall). Oxygen Demand and Effects of Oxygenation on Neonatal, Juvenile, and Adult Porcine Islets in vitro and in vivo. The Fall JDRF Encapsulation Consortium Meeting.
• Papas, K. K. (2016, January). Cell Therapies for the Treatment of Diabetes. Cell Therapy and Regenerative Medicine Inaugural Symposium/New Tools and Device for Cell-based Therapy. University of Arizona, Tucson, Arizona.
• Papas, K. K. (2016, July). Cell-Based Therapies for Diabetes. Grifols. Barcelona, Spain: Grifols.
• Papas, K. K. (2016, March). “Diabetes”, Challenges in Biomedical Engineering. University of Arizona.
• Papas, K. K. (2016, May). Cell-based Therapies for the Treatment of Diabetes. Department of Surgery Research Symposium and Grand Rounds. Tucson, Az.
• Papas, K. K. (2016, September). Towards Clinical Translation of High Density Encapsulation Devices with Enhanced Oxygen Supply. Fall JDRF Encapsulation Consortium Meeting.
• Papas, K. K., & Min, C. (2016, February). Comparison of persufflated and static cold storage of ex vivo porcine kidneys viability and function. Cutting Edge of Transplantation Meeting. Phoenix, AZ: American Society of Transplantation.
• Papas, K. K., Min, C., Steyn, L. V., Pandley, A., Harland, R. C., & Galons, J. P. (2016, June). Persufflation improves viability and function of porcine kidneys relative to static cold storage. ATC Meeting. Boston, Massachusetts.
• Papas, K. K., Min, C., Steyn, L. V., Weegman, B. P., Kirkeide, L., Hoeger, A., Aly, F. Z., Harland, R. C., & Galons, J. P. (2016, January). Ex vivo porcine kidney assessments for viability and function. 16th ASTS State of the Art Winter Symposium. Miami, Florida.
• Papas, K. K., Smith, K. E., Cookset, A. M., Kelly, A. C., Purvis, W. G., Price, N. D., Weber, C. S., Georgiev, I., Min, C., Steyn, L. V., McCarthy, F. M., Lynch, R., & Limesand, S. W. (2016, April). Enabling the Use of Alternative Donor Sources for Pancreatic Islet Transplantation. Arizona Physiological Society Annual Meeting.
• Papas, K. K., Weegman, B., Taylor, M., Baicu, S., Mueller, K., O’brien, T., & Wilson, J. (2016, July). Oxygen Considerations for the Preservation of Pancreata and Culture of Pancreatic Islets. CRYO2016: The 53rd Annual Meeting of the Society for Cryobiology. Ottawa, Canada.
• Papas, K. K. (2015, April). Cell-based Insulin Replacement Therapies: Engineering Contributions. University of California Irvine, Department of Biomedical Engineering. California.
• Papas, K. K. (2015, February). Persufflation in organ preservation and conditioning prior to cryopreservation and during rewarming. Organ preservation alliance 1st World Organ Banking Summit. California.
• Papas, K. K. (2015, January). Oxygen Demand and Effects of Oxygenation on Neonatal, Juvenile, and Adult Porcine Islets in vitro and in vivo. JDRF, Encapsulation Consortium Meeting. New York.
• Papas, K. K. (2015, January). Oxygen Supply to Encapsulated Cell Implants. SEMMA Therapeutics. Massachusetts.
• Papas, K. K. (2015, June). Cell-based Insulin Replacement Therapies: The Promise of Encapsulation. JDRF DSW Board of Directors Meeting. Arizona.
• Papas, K. K. (2015, November). Non-invasive Fluorine-19 Magnetic Resonance Spectroscopy Measurements of Oxygen within Tissue-Engineered Islet Grafts In Vivo: Effects of in situ Delivery of Supplemental Oxygen. Diabetes Imaging Symposium. Stockholm, Sweden.
• Papas, K. K. (2015, November). Oxygen limitations – engineering solutions for different scenarios. Islet Encapsulation meeting at the IPITA Lunch Symposium. Australia.
• Papas, K. K., Davis, M. A., Smith, K. E., Salama, B. F., Korbutt, G. S., & Limesand, S. W. (2015, November). Stimulation of porcine beta-cell proliferation is inhibited with hypoxic culture conditions. joint IPITA-IXA-CTS Meeting. Melbourne, Australia.
• Papas, K. K., Einstein, S. A., Weegman, B. P., Kitzmann, J. P., & Kirkeide, L. R. (2015, November). Non-invasive assessment of tissue-engineered graft viability with oxygen-17 magnetic resonance spectroscopy. joint IPITA-IXA-CTS Meeting. Melbourne, Australia.
• Papas, K. K., Einstein, S. A., Weegman, B. P., Suszynski, T. M., Firpo, M. T., Graham, M. L., Eberly, L. E., & Garwood, M. (2015, April). Non-Invasive Assessment of Tissue-Engineered Graft Oxygenation in Vivo by Fluorine-19 Magnetic Resonance Spectroscopy. 56th Experimental Nuclear Magnetic Resonance Conference. Pacific Grove, California.
• Papas, K. K., Irvin, A., Kos, C., Mariana, L., Kay, T., & Loudovaris, T. (2015, November). Oxygenation of cell encapsulating devices allows for greater survival of cells in vitro. joint IPITA-IXA-CTS meeting. Melbourne, Australia.
• Papas, K. K., Karatzas, T., Purvis, W., Kitzmann, J., Gruessner, A., O'Gorman, D., Kin, T., Shapiro, J., & Tempelman, L. (2015, November). Pancreas Oxygen Gas Perfusion (Persufflation) During Preservation Improves Clinical Islet Isolation Yields and Success Rates. joint IPITA-IXA-CTS Meeting. Melbourne, Australia.
• Papas, K. K., Min, C., Smith, K. E., Steyn, L. V., Weber, C., Purvis, W. G., Stanton, J. B., Burachek, A. M., Limesand, S. W., & Lynch, R. M. (2015, November). Comparison of adult, juvenile, and neonatal porcine islets demonstrates age dependant beta-cell fraction, insulin content and insulin secretion. Joint IPITA-IXA-CTS Meeting. Melbourne, Australia.
• Papas, K. K., Min, C., Steyn, L. V., Purvis, W. G., & Galons, J. P. (2015, November). Ex vivo assessments for porcine kidney viability and function. 14th Transplantation Science Symmposium. Lourne, Australia.
• Papas, K. K., Smith, K. E., Kelly, A. C., Weber, C., Min, C., Smith, B., McCarthy, F., Steyn, L. V., Badarinarayana, V., Strop, P., Lynch, R. M., & Limesand, S. W. (2015, November). Acute ischemic exposure leads to functional deficits and a transcriptome enriched in inflammatory and hypoxic pathways in human islets. joint IPITA-IXA-CTS Meeting. Melbourne, Australia.
• Papas, K. K., Smith, K. E., Steyn, L. V., Weber, C., Min, C., Purvis, W. G., Stanton, J. B., Burachek, A., Salama, B. F., Korbutt, G. S., Lynch, R. M., & Limesand, S. W. (2015, November). Direct comparison of adult, juvenile, and neonatal porcine islets in vitro reveals age dependent viability and function. joint IPITA-IXA-CTS. Melbourne, Australia.
• Papas, K. K., Smith, K. E., Steyn, L. V., Weber, C., Min, C., Purvis, W. G., Stanton, J. B., Burachek, A., Salama, B. F., Korbutt, G. S., Lynch, R. M., & Limesand, S. W. (2015, November). In vitro comparison of adult, juvenile, and neonatal porcine islets reveals age dependent resistance to ischemia. joint IPITA-IXA-CTS Meeting. Melbourne, Australia.
• Papas, K. K., Steyn, L. V., Davis, M. A., Min, C., Smith, K., Purvis, W. G., Stanton, J. B., Loudovaris, T., Weegman, B. P., Mueller, K. R., Kitzmann, J. P., Avgoustiniatos, E. S., Tempelman, L., & Limesand, S. W. (2015, November). In Situ Oxygen Delivery to Islets within an Implantable Immunoisolating Device In Vivo Enhances Viability and Function. joint IPITA-IXA-CTS Meeting. Melbourne, Australia.
• Papas, K. K., Steyn, L. V., Smith, K., Min, C., Purvis, W. G., Stanton, J. B., Davis, M. A., Mueller, K. R., Kitzmann, J. P., Weegman, B. P., Avgoustiniatos, E. S., Tempelman, L., & Limesand, S. W. (2015, November). Increasing Islet Density within an Immunoisolation Device has a Detrimental Impact on Viability In Vivo. joint IPITA-IXA-CTS Meeting. Melbourne, Australia.
• Papas, K. K., Steyn, L. V., Smith, K., Purvis, W. B., Min, C., Davis, M. A., Weegman, B. P., Mueller, K. R., Kitzmann, J. P., Avgoustiniatos, E. S., Tempelman, L., & Limesand, S. W. (2015, September). High Islet Density within a Tissue Engineered Device has a Negative Impact on Viability and Function In Vivo. Tissue Engineering and Regenerative Medicine International Society (TERMIS) World Congress. Boston, MA.
• Papas, K. K., Weegman, B. P., Einstein, S. A., Purvis, W., Steyn, L. V., Stanton, J. B., Kitzmann, J. P., Mueller, K. R., Limesand, S. W., Suszynski, T. M., Firpo, M. T., Graham, M. L., Janecek, J., Eberly, L. E., & Garwood, M. (2015, May). Non-Invasive Monitoring of Hypoxia and Viability Assessment of Implanted High-Cell-Density Tissue-Engineered Grafts. The Nineteenth Annual Hilton Head Regenerative Medicine Workshop. South Carolina.
• Papas, K. K., Weegman, B. P., Einstein, S. A., Steyn, L. V., & Garwood, M. (2015, September). Delivery of Supplemental Oxygen Improves Oxygenation of Tissue-Engineered Grafts in Vitro and in Vivo as measured with Fluorine-19 Magnetic Resonance Spectroscopy. Tissue Engineering and Regenerative Medicine International Society (TERMIS) World Congress. Boston, MA.
• Papas, K. K., Weegman, B. P., Einstein, S. A., Steyn, L. V., & Garwood, M. (2015, September). Non-invasive Fluorine-19 Magnetic Resonance Spectroscopy Measurements of Oxygen within Tissue-Engineered Islet Grafts In Vivo: Effects of in situ Delivery of Supplemental Oxygen. Diabetes Imaging Symposium. Stockholm, Sweden.
• Papas, K. K., Weegman, B. P., Einstein, S. A., Steyn, L. V., Firpo, M. T., Graham, M. L., & Garwood, M. (2015, May). Delivery of Oxygen-Enriched Gas Enhances Implanted Tissue-Engineered Graft Oxygenation Status as Measured with Fluorine-19 Magnetic Resonance Spectroscopy. The Nineteenth Annual Hilton Head Regenerative Medicine Workshop.
• Papas, K. K., Weegman, B. P., Einstein, S. A., Steyn, L. V., Suszynski, T. M., Firpo, M. T., Graham, M. L., Janecek, J., Eberly, L. E., & Garwood, M. (2015, November). Continuous oxygen delivery improves oxygenation of tissue-engineered grafts implanted in rats as measured with fluorine-19 magnetic resonance spectroscopy. joint IPITA-IXA-CTS Meeting. Melbourne, Australia.
• Papas, K. K., Weegman, B. P., Einstein, S. E., Steyn, L. V., & Garwood, M. (2015, June). Delivery of Supplemental Oxygen Improves Oxygenation of Tissue-Engineered Grafts in Vitro and in Vivo as measured with Fluorine-19 Magnetic Resonance Spectroscopy. TERMIS. Boston, MA.
• Papas, K. K. (2014, February). Persufflation for Pancreas Preservation Prior to Islet Isolation. CYBAN. Cyprus.
• Papas, K. K. (2014, July). Cell Therapies for Diabetes. Sanofi. Tucson, AZ.
• Papas, K. K. (2014, July). Novel Approaches to Pancreas Preservation Prior to Islet Isolation. Moscone West Convention Center.
• Papas, K. K. (2014, June). Enhanced O2 Supply to a Bioartificial Pancreas. JDRF. New York.
• Papas, K. K. (2014, September). Cell-based Therapies for Diabetes. Grifols. Spain.
• Papas, K. K. (2014, September). Engineering Approaches to Cell Therapies for the Treatment of Diabetes. University of Athens, Department of Physiology. Greece.
• Papas, K. K. (2014, September). High Density Bioartificial Pancreas enabled by Implantable Oxygen Generator. Johnson and Johnson (Betalogics). New Jersey.
• Papas, K. K., Stein, S. A., Weegman, B. P., Suszynski, T. M., Firpo, M. T., Graham, M. L., & Garwood, M. (2014, May). Monitoring Tissue-Engineered Graft Oxygenation In Vivo by Fluorine-19 Magnetic Resonance Spectroscopy. Joint Annual Meeting ISMRM-ESMRMB. Milan, Italy.
• Papas, K. K., Steyn, L. V., Davis, M., Loudovaris, T., Limesand, S., Tempelman, L., & Avgoustiniatos, E. S. (2014, November). Enhanced Oxygen Supply to Immunoisolated Islets In vivo Enables their Viability and Function at Tissue Like Densities. TERMIS Americas 2014 Annual Conference and Exposition. Washington, DC.
• Papas, K. K., Steyn, L. V., Davis, M., Smith, K., Purvis, W., Kitzmann, J., Mueller, K., Weegman, B., & Limesand, S. W. (2014, October). Enhanced function and viability of islets supplemented with oxygen within an implantable bioartificial pancreas device. 7th Annual Arizona Physiology Society Meeting.
• Papas, K. K. (2013, August). Cell Based Therapies for the Treatment of Diabetes. UA School of Animal & Comparative Biomedical Sciences.
• Papas, K. K. (2013, February). Engineering Solutions to Problems in Cell-based Insulin Replacement Therapies for the Treatment of Diabetes. UA Department of Chemical & Environmental Engineering Spring Seminar.
• Papas, K. K. (2013, January). Supplemented oxygenation during hypothermic storage: friend or foe. Special Symposium on “Hypothermic Medicine” joint conference of the American College of Cryosurgery and Society for Cryobiology.
• Papas, K. K. (2013, October). Enhanced Oxygen Supply to a Bioartificial Pancreas. JDRF encapsulation Consortium meeting. New York.
• Papas, K. K. (2013, October). Oxygen persufflation of the pancreas - Current International Status. Newcastle University Institute of Cellular Medicine. UK.
• Papas, K. K. (2013, October). Tissue Engineering for Cell Based Insulin Replacement Therapies. Frontiers in Medical Research Seminar. Tucson, AZ.
• Papas, K. K. (2013, September). Oxygen persufflation of the pancreas. European Society of Organ Transplantation (ESOT) and the European Pancreas and Islet transplant Association (EPITA). Vienna, Austria.
• Papas, K. K., Bellin, M. D., Sutherland, D. E., Kitzmann, J. P., Avgoustiniatos, E. S., Gruessner, A. C., Mueller, K. R., Balamurugan, A. N., Rozak, P. R., Loganathan, G., Suszynski, T., Wilhelm, J., Qian, D., Nilan, J. C., & Hering, B. J. (2013, July). Clinical islet auto-transplant outcome is highly correlated with viable islet dose as measured by oxygen consumption rate. 12th Congress of the Cell Transplantation Society. Milan, Italy.
• Papas, K. K., Bellin, M. D., Sutherland, D. E., Kitzmann, J. P., Avgoustiniatos, E. S., Gruessner, A. C., Mueller, K. R., Balamurugan, A. N., Rozak, P. R., Loganathan, G., Suszynski, T., Wilhelm, J., Qian, D., Nilan, J. C., & Hering, B. J. (2013, September). Viable islet dose based on oxygen consumption rate is highly predictive of clinical islet auto-transplant outcome. 14th World Congress of IPITA. Monterey, CA.
• Papas, K. K., Kelly, A. C., Macko, A. R., Penrod, L. V., Kitzmann, J. P., & Mueller, K. R. (2013, September). Epinephrine culture creates metabolic quiescence that leads to enhanced insulin secretion in isolated porcine islets and Min6. 14th World Congress of IPITA. Monterey.
• Papas, K. K., Kelly, A. C., Penrod, L. V., Anderson, M. J., Hart, N. J., Kitzmann, J. P., Mueller, K. R., Lynch, R. M., & Limesand, S. W. (2013, April). Sulfonylurea Receptor 1, Glucagon-Like Peptide Receptor 1 And Adrenergic Receptor α2ᴀ Are Expressed And Functional In Adult Porcine Islets. NIDDK- Imaging Pancreatic Beta Cell 5thWorkshop. Bethesda, MD.
• Papas, K. K., Kelly, A. C., Penrod, L. V., Anderson, M. J., Kitzmann, J. P., Hart, N. J., Mueller, K. R., Lynch, R. M., & Limesand, S. W. (2013, September). Sulfonylurea receptor 1, glucagon-like peptide receptor 1, and adrenergic receptor α2A are expressed and functional in adult porcine islets. 14th World Congress of IPITA. Monterey.
• Papas, K. K., Kitzmann, J. P., Mueller, K. R., Avgoustiniatos, E. S., Gruessner, A. C., Balamurugan, A. N., Bellin, M. D., & Hering, B. J. (2013, September). Islet preparation purity is overestimated and less pure fractions have lower post-culture viability prior to clinical allo-transplantation. 14th World Congress of IPITA. Monterey, CA.
• Papas, K. K., Kitzmann, J. P., O'Gorman, D., Kin, T., Gruessner, A. C., Senior, P., Imes, S., Gruessner, R. W., & Shapiro, A. M. (2013, July). Islet oxygen consumption rate predicts clinical islet allo-transplant insulin independence for first transplants. 12th Congress of the Cell Transplantation Society. Milan, Italy.
• Papas, K. K., Kitzmann, J. P., O'Gorman, D., Kin, T., Gruessner, A. C., Senior, P., Imes, S., Gruessner, R. W., & Shapiro, A. M. (2013, September). Islet oxygen consumption rate predicts clinical islet allo-transplant insulin independence for first transplants. 14th World Congress of IPITA. Monterey, CA.
• Papas, K. K., Kitzmann, J. P., Pepper, A. R., Lopez, B. G., Pawlick, R., Kin, T., O'Gorman, D., Mueller, K. R., Gruessner, A. C., Szot, G. L., Posselt, A. M., Stock, P. G., Wilson, J. R., & Shapiro, A. M. (2013, September). Human islet viability and function is maintained during high density shipment on silicon rubber membrane vessels. 14th World Congress of IPITA. Monterey, CA.
• Papas, K. K., Marshall, H. L., Mueller, K. R., & Shaw, J. A. (2013, March). Rapid detection of hypoxic islet stress by oxygen consumption rate using standardized beta cell model. Diabetes UK Professional Conference. Manchester, UK.
• Papas, K. K., Mueller, K. R., Penrod, L., Davis, M., Kitzmann, J. P., Gruessner, S. G., Suszynski, T., Jie, T., Tempelman, L., Limesand, S., & Avgoustiniatos, E. S. (2013, September). Macroencapsulated human islet viability is drastically reduced in vivo as the number of islets per device is increased. 14th World Congress of IPITA. Monterey.
• Papas, K. K., Mueller, K. R., Scott III, W. E., Jie, T., Weegman, B. P., Balamurugan, A. N., Kitzmann, J. P., Marshall, H., Shaw, J., Manas, D., Persaud, S., Huang, G. C., Khorsandi, S. E., Tempelman, L., Pongratz, R. L., Cline, G. W., Gruessner, A. C., & Gruessner, R. W. (2013, September). Human pancreas persufflation ameliorates hypoxia-induced impairment of islet function post-isolation. 14th World Congress of IPITA. Monterey, CA.
• Papas, K. K., Suszynski, T. M., Mueller, K. R., & Gruessner, A. C. (2013, May). Oxygen Consumption Rate (or Respiratory) Profiles of Pancreatic Acinar and Islet Tissue in Culture. 13th Annual American Transplant Congress (ATC). Seattle, Washington.
• Papas, K. K., Suszynski, T. M., Mueller, K. R., & Gruessner, A. C. (2013, September). Oxygen consumption rate of porcine pancreatic acinar and islet tissue in culture. 14th World Congress of IPITA. Monterey, CA.
• Papas, K. K., Suszynski, T. M., Wilhelm, J. J., Radosevich, D. M., Balamurugan, A. N., Sutherland, D. E., Beilman, G. J., Dunn, T. B., Chinnakotla, S., Pruett, T. L., Vickers, S. M., Hering, B. J., & Bellin, M. D. (2013, September). Islet Size Index as a Predictor of Outcomes in Clinical Islet Autotransplantation. 14th World Congress of IPITA. Monterey, CA.
• Papas, K. K., Weegman, B. P., Kumar Sajja, V. S., Rizzari, M. D., Suszynski, T. M., Scott III, W. E., Kitzmann, J. P., Mueller, K. P., Hanley, T. R., Kennedy, D. J., & Todd, P. W. (2013, March). Continuous Magnetic Separation Improves Viability of Isolated Islets of Langerhans. 17th Annual Hilton Head Workshop entitled "Regenerative Medicine: Technologies Enabling Novel Therapies". South Carolina.
• Papas, K. K., Weegman, B. P., Sajja, V. S., Rizzari, M. D., Suszynski, T. M., Scott III, W. E., Kitzmann, J. P., Mueller, K. R., Hanley, T. R., Kennedy, D. J., Todd, P. W., Balamurugan, A. N., & Hering, B. J. (2013, September). Improving purified porcine islet viability by continuous quadrupole magnetic sorting (QMS). 14th World Congress of IPITA. Monterey, CA.
• Papas, K. K. (2012, April). NMR in Cell based Therapies for the Treatment of Diabetes. University the Center for Magnetic Resonance Research Seminar. University of Minnesota.
• Papas, K. K. (2012, April). NMR in Islet Transplantation. ARIBI Research Seminar Series.
• Papas, K. K. (2012, April). Novel methods for pancreas and islet preservation and quality assessment: Implications for clinical islet transplantation. Oxford Centre for Diabetes Endocrinology and Metabolism. Oxford University.
• Papas, K. K. (2012, April). Overcoming Critical Barriers for Large-Scale Clinical Application of Islet Transplantation: A Roadmap with a Focus on the Islet. Newcastle University. United Kingdom.
• Papas, K. K. (2012, June). Distribution of Human Islets for Diabetes Research. American Diabetes Association.
• Papas, K. K. (2012, March). The Application of NMR to Cell Therapies for the Treatment of Diabetes. ARIBI Spring Workshop. University of Arizona.
• Papas, K. K. (2012, September). Cell-based Insulin Replacement Therapies: Engineering Contributions. Department of Biomedical Engineering. University of Arizona.
• Papas, K. K. (2012, September). Pancreatic Islets: From Isolation to Transplantation. Indo US Science and Technology Forum (IUSSTF). India.
• Papas, K. K., Graham, M., Avgoustiniatos, E., Mueller, K., Flanagan, B., Schuurman, H., & Hering, B. (2012, January). Oxygen consumption rate measurements correlate with graft function in the pig-to-monkey islet transplantation model. 2nd Joint AIDPIT and EPITA Winter Symposium.
• Papas, K. K., Scott, W. E., Rizzari, M. D., Weegman, B. P., Suszynski, T. M., Avgoustiniatos, E. S., Balamurugan, A. N., Gruessner, A. C., Kitzmann, J. P., Tempelman, L. A., Stein, S. A., & Hammer, B. E. (2012, January). Oxygen persufflation can extend human pancreas preservation time from 10 to 24 hours while maintaining viable islet yield and quality. 2nd Joint AIDPIT and EPITA Winter Symposium.
• Papas, K. K. (2011, December). Enabling Technologies for Shipment and Assessment of Pancreas and Islet Products. Islet Transplantation without borders. Athens, Greece.
• Papas, K. K. (2011, December). The Athens-Geneva-Tucson Project. International Workshop: Islet Transplantation without borders. Athens, Greece.
• Papas, K. K. (2011, June). Beta-cell replacement: An engineer’s view through the lens of an isletologist. Brussels Free University. Brussels, Belgium.
• Papas, K. K. (2011, June). Oxygen Persufflation. World Congress of the International Pancreas and Islet Transplant Association. Prague, Czech Republic.
• Papas, K. K., Abouaish, J., Graham, M., Pakala, P., Loganathan, G., Tiwari, M., Yuasa, T., Sutherland, D. E., McCarthy, R. C., Hering, B. J., & Balamurugan, A. N. (2011, June). A new purified enzyme blend for non-human primate islet isolation. 13th World Congress of IPITA. Prague, the Czech Republic.
• Papas, K. K., Atchison, N., Tsapatsis, M., & Kokkoli, E. (2011, October). ATP Delivery to Insulin Producing β Cells Using Peptide Targeted Liposomes. 2011 AIChE Annual Meeting. Minneapolis, MN.
• Papas, K. K., Avgoustiniatos, E. S., Rozak, P. R., Mueller, K. R., Lyons, C. A., Scott III, W. E., Falde, E. J., Kitzmann, J. P., Wilson, J. R., & Hering, B. J. (2011, October). Silicone rubber membrane devices allow islet culture at 20 times the standard surface density with no adverse effects on islet viability, recovery, or potency. joint CTS-IXA. Miami.
• Papas, K. K., Balamurugan, A. N., Loganathan, G., Bellin, M. D., Dunn, T., Vickers, S. M., Beilman, G. J., Hering, B. J., & Sutherland, D. E. (2011, June). High islet yield from pre-teenage pediatric patients undergoing total pancreatectomy and islet autotransplantation for chronic pancreatitis compared to teen-age and adult patients. 71st ADA Scientific Sessions. San Diego, CA.
• Papas, K. K., Balamurugan, A. N., Loganathan, G., Bellin, M. D., Wilhelm, J. J., Yuasa, T., Tiwari, M., Vickers, S., Beilman, G. J., Hering, B. J., & Sutherland, D. E. (2011, April-May). Islet isolation outcome from minimal change chronic pancreatitis is comparable with clinical grade allograft pancreases. American Transplant Congress. Philadelphia, PA.
• Papas, K. K., Graham, M. L., Avgoustiniatos, E. S., Mueller, K. R., Flanagan, B., Schuurman, H., & Hering, B. J. (2011, October). Quality assessment as a predictor for graft function in the pig-to-nonhuman primate islet transplantation model. joint CTS-IXA meeting. Miami.
• Papas, K. K., Kitzmann, J. P., Law, L., Shome, A., Muzina, M., Elliott, R. B., Mueller, K. R., & Schuurman, H. J. (2011, October). Real-time assessment of encapsulated neonatal porcine islets prior to clinical xenotransplantation. joint CTS-IXA meeting. Miami.
• Papas, K. K., Loganathan, G., Dawra, R. K., Pugazhenthi, S., Guo, Z., Soltani, S. M., Wiseman, A., Sanders, M. A., Saluja, A. K., Sutherland, D. E., Hering, B. J., & Balamurugan, A. N. (2011, June). Acinar cell proteases reduce insulin granules of human islets in vitro and degrade insulin after transplantation: Preventive effect of Alpha-1 antitrypsin. 13th World Congress of IPITA. Prague, the Czech Republic.
• Papas, K. K., Mueller, K. R., Appakalai, B., Cline, G., Pongratz, R., Hooper, R. L., Weegman, B. P., Taylor, M. J., Graham, M. L., & Schuurman, H. (2011, October). Comparison of glucose-stimulated insulin secretion between isolated human, nonhuman primate and porcine islets. joint CTS-IXA meeting. Miami.
• Papas, K. K., Mueller, K. R., Martins, K. V., Murtaugh, M. P., & Schuurman, H. (2011, October). Manufacturing porcine islets: culture at 22°C has no advantage of culture at 37°C. joint CTS-IXA meeting. Miami.
• Papas, K. K., Rizzari, M. D., Suszynski, T. M., Scott, W. E., Weegman, B. P., Finger, E. B., O'Brien, T. D., Kidder, L. S., Kandaswamy, R., Sutherland, D. E., & Avgoustiniatos, E. S. (2011, June). Preservation via Anterograde Persufflation May Decrease Renal Arterial Damage in a Porcine Kidney Transplant Model. XII TTS Basic Science Symposium. Boston.
• Papas, K. K., Scott III, W. E., Rizzari, M. D., Stein, S. A., Avgoustiniatos, E. S., Suszynski, T. M., Weegman, B. P., Tempelman, L. A., & Hammer, B. E. (2011, June). Oxygen persufflation of the human pancreas increases ATP levels and improves viable islet yields compared with the two-layer method. 13th World Congress of IPITA. Prague, the Czech Republic.
• Papas, K. K., Scott III, W. E., Weegman, B. P., Rizzari, M. D., Suszynski, T. M., Falde, E. J., Ferrer-Fabregra, J., & Avgoustiniatos, E. S. (2011, October). Warm ischemia during porcine pancreas procurement is significantly reduced by arterial and ductal flushing. joint CTS-IXA meeting. Miami.
• Papas, K. K., Soltani, S. M., Loganathan, G., Bellin, M. D., Dunn, T. B., Vickers, S. M., Beilman, G. J., Hering, B. J., Sutherland, D. E., & Balamurugan, A. N. (2011, June). Reducing the transplantable tissue volume for human islet auto-transplantation: A high density purification process different from islet allograft purification. 13th World Congress of IPITA. Prague, the Czech Republic.
• Papas, K. K., Suszynski, T. M., Avgoustiniatos, E. S., Stein, S. A., Falde, E. J., & Hammer, B. E. (2011, June). Assessment of tissue-engineered islet graft viability by fluorine magnetic resonance spectroscopy. 13th World Congress of IPITA. Prague, the Czech Republic.
• Papas, K. K., Suszynski, T. M., Scott III, W. E., & Avgoustiniatos, E. S. (2011, October). Implications of Thrombosis on the Oxygenation of the Intraportally Transplanted Islet. joint CTS-IXA meeting. Miami.
• Papas, K. K., Suszynski, T. M., Stein, S. A., Avgoustiniatos, E. S., Falde, E. J., Kitzmann, J. P., Wilson, J. R., & Hammer, B. E. (2011, October). Assessment of Pancreatic Tissue Oxygenation via Fluorine Magnetic Resonance Spectroscopy during Culture on Silicon Rubber Membrane. joint CTS- IXA meeting. Miami.
• Papas, K. K., Taylor, M. J., Baicu, S., & Weegman, B. (2011, March). Hypothermic Perfusion of Pancreas as an AideTowards Clinical Islet Transplantation. Hilton Head Regenerative Medicine Workshop.
• Papas, K. K., Weegman, B. P., Avgoustiniatos, E. S., Taylor, M. J., Baicu, S. C., Kitzmann, J. P., Mueller, K. R., Scott III, W. E., Appakalai, B., & Wilson, J. (2011, October). Shipping of Islets in Silicon Rubber Membrane (SRM) Vessels: Effects on Islet Recovery and Viability. joint CTS-IXA meeting. Miami.
• Papas, K. K., Weegman, B. P., Rizzari, M. D., Scott, W. E., Taylor, M. J., Baicu, S. C., Suszynski, T. M., Avgoustiniatos, E. S., & Loughnane, M. H. (2011, June). Whole Organ Oxygen Consumption Rate (WOOCR): A novel tool for organ assessment prior to transplant. XII TTS Basic Science Symposium. Cape Cod, Massachusetts.
• Papas, K. K., Weegman, B. P., Taylor, M. J., Baicu, S. C., Pongratz, R., Mueller, K., O'Brien, T. D., Cline, G., & Wilson, J. (2011, June). Biological characterization of isolated juvenile porcine islets as a potential source of tissue for xenotransplantation. 13th World Congress of IPITA. Prague, the Czech Republic.
• Papas, K. K., Weegman, B. P., Taylor, M. J., Baicu, S. C., Scott III, W. E., Mueller, K. R., Kitzmann, J. P., & Rizzari, M. D. (2011, June). Hypothermic perfusion preservation of pancreas for islet grafts: validation using a split lobe porcine model. 13th World Congress of IPITA. Prague, the Czech Republic.
• Papas, K. K., Weegman, B. P., Taylor, M. J., Baicu, S. C., Scott III, W. E., Mueller, K. R., Kitzmann, K. P., & Rizzari, M. D. (2011, July). Hypothermic perfusion preservation of pancreas for islet grafts: Validation using a split lobe porcine model. Cryobiology conference. Oregon State University.
• Papas, K. K. (2010, April). Cell Based Therapies for the Treatment of Diabetes. Design of Medical Devices Conference. University of Minnesota.
• Papas, K. K. (2010, July). Pancreas Persufflation Prior to Islet Isolation. Annual Meeting of the Society of Cryobiology. Bristol, UK.
• Papas, K. K. (2010, March). Engineering Solutions for Cell Based Insulin Replacement Therapies. Department of Chemical Engineering and Material Science. Minnesota.
• Papas, K. K. (2010, May). Novel Technologies for Cell Based Therapies for the Treatment of Diabetes. MGH East. Harvard Medical School.
• Papas, K. K. (2010, October). Islet Transplantation in 2010: Focus on the Islet. Islet Transplantation Group. University of Geneva.
• Papas, K. K. (2010, October). Novel Strategies for Increasing Viable Islet Yield Prior to Islet Transplantation. CHUV. Switzerland.
• Papas, K. K. (2010, Summer). Novel Tools for Pancreas Quality Assessment During Preservation. Organ Recovery Systems Inc. Chicago, IL.
• Papas, K. K., Atchison, N., Fan, W., Hering, B. J., Kokkoli, E., & Tsapatsis, M. (2010, November). Benign, Permselective Encapsulation of Porcine Islets: Active Nanomaterials Solutions for Xenotransplantation. 2010 AIChE Annual Meeting. Salt Lake City, Utah.
• Papas, K. K., Atchison, N., Fan, W., Hering, B. J., Tsapatsis, M., & Kokkoli, E. (2010, November). Targeting α5β1 On Pig Islets of Langerhans in Culture with PR_b, a Fibronectin-Mimetic Peptide, to Increase Islet Yield and Viability. 2010 AIChE Annual Meeting. Salt Lake City, Utah.
• Papas, K. K., Balamurugan, A. N., Loganathan, G., Bellin, M., Wilhelm, J. J., Harmon, J., Anazawa, T., Radosevich, D., Yuasa, T., Tiwari, M., McCarthy, R. C., Sutherland, D. E., & Hering, B. J. (2010, August). A New Enzyme Mixture to Consistently Achieve High Human Islet Yield and Improved Allogenic and Autograft Islet Transplantation Outcome. XXIII International Congress of The Transplantation Society. Vancouver, Canada.
• Papas, K. K., Bellin, M., Sutherland, D. E., Mueller, K., Avgoustiniatos, E. S., Balamurugan, A. N., Rozak, P. R., Loganathan, G. L., Qian, D., Niland, J. C., & Hering, B. J. (2010, August). Viable Islet Dose Based on Oxygen Consumption Rate Predicts Clinical Islet Autotransplant Outcome. XXIII International Congress of The Transplantation Society. Vancouver, Canada.
• Papas, K. K., Kirchner, V. A., Weegman, B. P., Scott III, W. E., Avgoustiniatos, E. S., Suszynski, T. M., Ferrer-Fabrega, J., Rizzari, M. D., Kidder, L. S., Kandaswamy, R., & Sutherland, D. E. (2010, May). Assessment of Kidney Viability Prior to Transplantation Based on Continuous Oxygen Consumption Measurement. Minnesota Surgical Society Annual Meeting. Minneapolis, MN.
• Papas, K. K., Patel, A., Hawthorne, W., & O'connell, P. (2010, June). Assessment of Human Islet Quality Using Oxygen Consumption Rate. Twenty-eighth Annual Scientific Meeting of the Transplantation Society of Australia and New Zealand. Canberra, Australia.
• Papas, K. K., Scott III, W. E., Avgoustiniatos, E. S., Ferrer-Fabrega, J., Weegman, B. P., Kirchner, V. A., Anazawa, T., Rizzari, M. D., Kidder, L. S., Stein, S. A., Matsumoto, S., Stone, J. J., Suszynski, T. M., Aasheim, T. C., Hammer, B. E., Balamurugan, A. N., O'brien, T. D., Murtaugh, M. P., Tempelman, L. A., , Sutherland, D. E., et al. (2010, August). Oxygen Persufflation Increases Pancreatic ATP Levels and Viable Islet Yield Following 24 Hours Preservation Compared with the Two-Layer Method (TLM). XXIII International Congress of The Transplantation Society. Vancouver, Canada.
• Papas, K. K. (2009, April). Towards Reduced Warm Ischemic Damage During Pig Pancreas Procurement. Joint Meeting of Cell Transplant Society.
• Papas, K. K. (2009, July). Cell Based Therapies for the Treatment of Diabetes. Innovations in Diabetes Symposium. Maryland.
• Papas, K. K. (2009, June). Oxygen Consumption Rate as a Potency Test for Human Islet Preparations Prior to Clinical Transplantation. NIH, Clinical Islet Transplant Consortium, Islet Potency Meeting.
• Papas, K. K. (2009, October). Cell Based Therapies for the Treatment of Diabetes - Current Status and Future Directions. Department of Biology, University of Cyprus.
• Papas, K. K. (2009, October). Cell Based Therapies for the Treatment of Diabetes. SJTRI. Georgia.
• Papas, K. K. (2009, October). Inhibition of JNK in Islet Transplantation. Xigen, Inc. Switzerland.
• Papas, K. K. (2009, October). Islet Preservation and Preconditioning Prior to Transplantation. IPITA, IXA meeting. Italy.
• Papas, K. K. (2009, October). MRI AS A novel tool to develop New Methods of pancreas distention to Enable homogeneous Enzyme Distribution for Successful Islet Isolation. Joint Meeting of the international Pancreas and Islet Transplant Association and the international Xenotrasplation Association. Venice, Italy.
• Papas, K. K. (2009, October). One-layer method with novel compound perfluorohexyloctane increases levels of ATP relative to perfluorodecalin as shown by 31P-NMR spectroscopy. 13th World Congress of the International Pancreas and Islet Transplantation Association. Venice, Italy.
• Papas, K. K., Anazawa, T., Balamurugan, A. N., Ferrer, J., Matsumoto, S., Avgoustiniatos, E. S., Sutherland, D. E., & Hering, B. J. (2009, October). Improved Method of Porcine Pancreas Procurement with Arterial Flush and Ductal Injection Enhances Islet Isolation Outcome. Joint Meeting of the International Pancreas and Islet Transplant Association and the International Xenotransplantation Association. Venice, Italy.
• Papas, K. K., Scott III, W. E., Ferrer-Fabrega, J., Avgoustiniatos, E. S., Anazawa, T., Weegman, B. P., Matsumoto, S., O'brien, T. D., Murtaugh, M., Hammer, B. E., Yu, I., Kidder, L. S., Maynard, K. S., Stone, S. G., Tempelman, L., Sutherland, D. E., & Hering, B. J. (2009, October). Pancreas Persufflation for 6HR and 24HR Improves Viable Islet Yields Compared With the Two-Layer Method. Joint Meeting of the International Pancreas and Islet Transplant Association and the International Xenotransplantation Association. Venice, Italy.
• Papas, K. K., Vance, C. J., Kubo, H., Maynard, K. S., & Oz, G. (2009, April). Phosphorous and Carbon Spectroscopy of Porcine Islet Extracts: Comparison of Effects of Normoxic and Hypoxic Culture Conditions. 17th Annual Meeting and Exhibition of the ISMRM. Honolulu, Hawaii.
• Papas, K. K., Weegman, B. P., Ferrer-Fabrega, J., Scott III, W. E., Anazawa, T., Avgoustiniatos, E. S., Yuasa, T., Loughnane, M. H., Hammer, B. E., & Hering, B. J. (2009, October). Whole Pancreas Oxygen Consumption Measurement: A Technique for Real-Time Viability Assessment. Joint Meeting of the International Pancreas and Islet Transplant Association and the International Xenotransplantation Association. Venice, Italy.
• Papas, K. K., Weegman, B. P., Scott III, W. E., Anazawa, T., Avgoustiniatos, E. S., Yuasa, T., Ferrer-Fabrega, J., Loughnane, M., Hammer, B. E., & Hering, B. J. (2009, October). Whole Kidney Oxygen Consumption Measurement: A Technique for Real-Time Viability Assessment. Joint Meeting of the International Pancreas and Islet Transplant Association and the International Xenotransplantation Association. Venice, Italy.
• Papas, K. K. (2008). Peritransplant therapy with thymoglobulin and Genzym 29155 delays rejection of intrahepatic porcine islets in nonhuman primates. Xenotransplantation 2007.
• Papas, K. K. (2008, November). MRI as a Novel tool to optimize Enzyme Distribution and Pancreas Distension for Successful Islet Isolation. 39th Annual Meeting of the American Pancreatic Association.
• Papas, K. K. (2008, November). Toward improved surgical techniques for pig pancreas procurement. Pancreas.
• Papas, K. K. (2008, October). Engineering Solutions for Improvements in Islet Isolation and TransplantationOutcomes. Department of Biomedical Engineering, UVA.
• Papas, K. K. (2008, October). Islet Transplantation: Current Status and Future Directions. Department of Surgery, UVA.
• Papas, K. K. (2008, October). Oxygen Consumption Rate and DNA Measurements - Assessing beta-cells in vitro. Annual Islet Cell Resource Center Islet Workshop. California.
• Papas, K. K., Kaddis, J., Dajun, Q., Olack, B., Cravens, J., Antler, M., Ruel, N., Hanson, M., Contreras, J., Fernandez, L., & Niland, J. (2008, January). Temperature and Pressure changes during islet transport using a standardized shipping container: A study by the National Islet Cell Resource Center Consortium. The 8th Annual Rachmiel Levine Diabetes and Obesity Symposium.
• Papas, K. K., Pongratz, R., Kibbey, R., & Cline, G. (2008, April). Media effects on mitochondrial pathways and energetics of glucose stimulated insulin secretion. Keystone Symposium on Islet and Beta Cell Biology. Snowbird, Utah.
• Papas, K. K. (2007). ATP/DNA ratio is a better indicator of islet cell viability than the ADP/ATP ratio. Xenotransplanation.
• Papas, K. K. (2007). Analysis of long term islet allograft function in recipients with type 1 diabetes given depleting T-cell antibodies for induction immunosuppression.
• Papas, K. K. (2007). Commercially Available Gas-Permeable Cell Culture Bags May Not Prevent Anoxia in Cultured or Shipped Islets. Xenotransplantation 2007.
• Papas, K. K. (2007). Improved islet culture on top of gas-permeable membranes. American Journal of transplantation.
• Papas, K. K. (2007). Phase change material maintains temperature control in an islet shipping container. Xenotransplanation 2007.
• Papas, K. K. (2007). Real-Time Noninvasive Assessment of Pancreatic ATP Levels During Preservation. Xenotransplanation 2007.
• Papas, K. K. (2007). Seven-day culture enhances potency and reduces immunogenicity of porcine islets. Xenotransplantation 2007.
• Papas, K. K. (2007). Vitamin E homologs improve bioenergetic of porcine islets and INS-1 cells under anoxia. Diabetologia 2007.
• Papas, K. K. (2007). islet culture at high surface densities on top of silicone rubber membranes compares favorably to standard culture. Xenotransplantation 2007.
• Papas, K. K. (2007). long-term survival of human islet allografts in type 1 diabetes.
• Papas, K. K. (2007, October). Shipping Human Islets. Annual Islet Cell Resource Center Islet Workshop.
• Papas, K. K. (2007, September). New approaches to pancreas preservation. Joint CTS, IPITA, IXA Conference. Minnesota.
• Papas, K. K. (2007, September). New equipment for islet culture and shipment. HIIT-NICE Satellite Workshop. Minnesota.
• Papas, K. K. (2007, September). survival of porcine islets transplanted into prefabricated omental pouches in rhesus macaques (RM). Joint ConfrenceXenotransplanation.
• Papas, K. K. (2006, November). Engineering Issues in Cell Based Insulin Replacement Therapies. AIChE National Meeting, Session #56. San Francisco, California.
• Papas, K. K. (2006, September). Islet Culture Devices. International Islet Isolation Workshop. France.
• Papas, K. K. (2006, September). Islet Oxygen Consumption. International Islet Isolation Workshop. France.
• Papas, K. K. (2006, September). Pancreas Preservation. International Islet Isolation Workshop. France.
• Papas, K. K., Kennedy, D. J., Todd, P. W., Logan, N. S., Becker, M., Chalmers, J. J., & Zborowski, M. (2006, May). Engineering Quadrupole Magnetic Flow Sorting for User Applications. 6th International Conference on the Scientific and Clinical Applications of Magnetic Carriers. Krems, Austria.
• Papas, K. K., Pisania, A., Bonner-Weir, S., Weir, G. C., & Colton, C. K. (2006, May). Temporal Behavior of Human Non-Islet Tissue after Isolation. 8th International Congress of the Cell Transplant Society. Milan.
• Papas, K. K., Pisania, A., Bonner-Weir, S., Weir, G. C., & Colton, C. K. (2006, November). Assessment of Islet Quality. AIChE National Meeting. San Francisco, California.
• Papas, K. K., Rappel, M. J., Avgoustiniatos, E. S., Tempelman, L. A., & Colton, C. K. (2006, May). Improving Culture of Islets of Langerhans: Removing Oxygen Limitations. 8th International Congress of the Cell Transplant Society. Milan.
• Papas, K. K., Rappel, M. J., Avgoustiniatos, E. S., Tempelman, L. A., & Colton, C. K. (2006, November). Transport Limitations in Islets of Langerhans Culture. AIChE National Meeting. San Francisco, California.
• Papas, K. K., Scott III, W. E., Avgoustiniatos, E. S., Nelson, R. A., Rozak, P. R., Ansite, J. D., Fraga, D. W., Wildey, G. M., Boyd, V., & Hering, B. J. (2006, May). Effect of Serum on Fractional Viability of Human Islets Cultured for 2 Days. 8th International Congress of the Cell Transplant Society. Milan.
• Papas, K. K., Shenkman, R., Choi, H. W., Moore, L. R., Chalmers, J. J., Hering, B. J., & Farson, D. (2006, November). Biocompatible and Biodegradable Nanoparticle Labels. AIChE National Meeting. San Francisco, California.
• Papas, K. K. (2005). Reversal of diabetes in nonhuman primates with pig islet transplantation. American Journal of transplantation.
• Papas, K. K. (2005). transplant islet oxygenation before revascularization: the critical role of blood vessel density and proximity. Diabetologia.
• Papas, K. K. (2005, January). Vitamin E homologs protect cultured islets from anoxia-induced death: implications in islet processing and engraftment. Diabetologia.
• Papas, K. K. (2005, July). Animal Model Correlations with Transplantation Outcome. Islet Cell Resource Centers Consortium. California.
• Papas, K. K. (2005, July). Islet Oxygen Consumption Rate. Islet Cell Resource Centers Consortium. California.
• Papas, K. K. (2005, October). Islet Quality Assessment and Improvement: Current Status and Future Directions. Larry L. Hillblom Islet Research Center Seminar Series. California.
• Papas, K. K. (2005, October). Islet Transplantation for the Treatment of Diabetes: Current Status and Future. ETSU. Tennessee.
• Papas, K. K. (2005, September). Islet Transplantation for the Treatment of Diabetes. CYU. Cyprus.
• Papas, K. K., Avgoustiniatos, E. S., Tempelman, L. A., Weir, G. C., Colton, C. K., Pisania, A., Rappel, M. J., Friberg, A. S., & Hering, B. J. (2005, May). High-density culture of human islets on top of silicone rubber membranes: One vessel per pancreas. IPITA 2005. Geneva, Switzerland.
• Papas, K. K., Hering, B. J., Gunther, L., Rappel, M. J., Colton, C. K., & Avgoustiniatos, E. S. (2005, May). Pancreas oxygenation is inadequate during preservation with the two-layer method. IPITA 2005. Geneva, Switzerland.
• Papas, K. K., Pisania, A., Powers, D. E., Rappel, M. J., Bonner-Weir, S., Weir, G. C., & Colton, C. K. (2005, May). Enumeration of Cells in Islet Preparations by Nuclei Counting. 10th World Congress of IPITA. Geneva.
• Papas, K. K., Pisania, A., Powers, D. E., Rappel, M. J., Weir, G. C., & Colton, C. K. (2005, May). A Quantitative Membrane Integrity Test for Islets of Langerhans. 10th World Congress of IPITA. Geneva.
• Papas, K. K., Rappel, M. J., Avgoustiniatos, E. S., Tempelman, L. A., & Colton, C. K. (2005, October-November). Improving culture of islets of Langerhans: removing oxygen limitations.. AIChE National Meeting. Cincinnati, OH.
• Papas, K. K., Shenkman, R., Chalmers, J., & Hering, B. (2005, November). Quadrupole Magnetic Separation (QMS) of Porcine Islets of Langerhans. Advances in Bioseparations session. Cincinnati, OH.
• Papas, K. K. (2004, July). Islet Transplantation - an update. N/A. Mexico.
• Papas, K. K. (2004, March). OCR in Islet Quality Assessment. University of Alberta. Canada.
• Papas, K. K. (2004, March). Role of Antioxidants in Alleviating and Managing Diabetic Complications. 3rd Cyprus Dietetic Association Conference and 26th American Overseas Dietetic Association. Cyprus.
• Papas, K. K., Avgoustiniatos, E. S., Gunther, L., Rappel, M. J., Colton, C. K., & Hering, B. J. (2004, November). Pancreas oxygenation during preservation: The two-layer method revisited. 7th International Cell Transplant Society Meeting. Boston.
• Papas, K. K., Bauer, A. C., Friberg, A., Avgoustiniatos, E. S., Rappel, M. J., Pisania, A., Colton, C. K., Tempelman, L. A., Weir, G. C., & Hering, B. J. (2004, November). High-density culture of an entire human islet preparation in a single silicone rubber membrane device. 7th International Cell Transplant Society Meeting. Boston.
• Papas, K. K., Bauer, A. C., Friberg, A., Papas, A., & Hering, B. J. (2004, November). Vitamin E homologs protect islets from death induced by anoxia. 7th International Cell Transplant Society Meeting. Boston.
• Papas, K. K., Pisania, A., Powers, D. E., Rappel, M. J., Lewis, A. S., Hardiman, M. T., Zhou, J., & Colton, C. K. (2004, November). Dynamics of cell death evaluated by mitochondrial function, apoptosis and membrane integrity assays. 7th International Cell Transplant Society Meeting. Boston.
• Papas, K. K., Rappel, M. J., Avgoustiniatos, E. S., Tempelman, L. A., & Colton, C. K. (2004, November). The effects of oxygen on islet quality in culture. 7th International Cell Transplant Society Meeting. Boston.
• Papas, K. K., Rappel, M. J., Pisania, A., Tempelman, L. A., & Colton, C. K. (2004, November). The effect of culture temperature on islet viability. 7th International Cell Transplant Society Meeting. Boston.
• Papas, K. K. (2003, January). Improved method for quantitating amount of islet tissue based on cellular nuclei counts. 6th International Congress of the Cell-Transplant-Society.
• Papas, K. K. (2003, January). Islet quality assessment and improvement. Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School,. Boston.
• Papas, K. K. (2003, January). Islet quality assay based on oxygen consumption rate and DNA measurements predicts graft function in mice. 6th International Congress of the Cell-Transplant-Society.
• Papas, K. K. (2003, November). Advances in Islet Product Testing. Rachmiel Levine Symposium. California.
• Papas, K. K. (2003, November). Predictive Islet Potency Assays. 4th Human Islet Isolation and Transplantation Techniques (HIIT). Florida.
• Papas, K. K. (2002). Iselet oxygen consumption rate as a predictor of in vivo efficacy post-transplanation.
• Papas, K. K. (2002, September). Rapid Islet Quality Assessment Prior to Transplantation. 2nd Human Islet Isolation Training Workshop. Canada.
• Papas, K. K., Koulmanda, M., Wu, H., Qipo, A., Auchincloss, H., & Colton, C. K. (2002, October). Viable Islet Equivalents (Oxygen Consumption Rate) and Fractional Viability Predict Graft Function. Symposium on: Advances in Islet Cell Biology: From Stem Cell Differentiation to Clinical Transplantation. California.
• Papas, K. K., Yalpani, M., Sotak, C. H., Henning, E. C., Silvan, M. D., Colton, C., & Cline, G. (2002, October). Novel biocompatible polymers: 19F NMR spectroscopy of soluble fluorinated alginates. Abstracts of Papers of the American Chemical Society.
• Papas, K. K. (2001, June). Glucose stimulation does not increase islet oxygen consumption rate in amino acid-rich media, diabetes.
• Papas, K. K. (2001, November). Rapid islet quality assessment prior to transplantation. Tissue Engineering Session at AlChE. Reno, Nevada.
• Papas, K. K., Avgoustiniatos, E. S., Wu, H., & Colton, C. K. (2001, November). Effect of Oxygen Diffusion Limitations on Viability and Function of Islets of Langerhans in Culture and in a Bioartificial Pancreas. Tissue Engineering Session at AIChE. Nevada.
• Papas, K. K., Colton, C. K., Wu, H., & Avgoustiniatos, S. (2000, October). Advances in Bioartificial Pancreasm Devices. United Engineering Foundation Conference. Switzerland.
• Papas, K. K., Jarema, M., Roos, E., Gounarides, J. S., Shapiro, M. J., Cheng, L. L., Cline, G. W., & Shulman, G. I. (2000, October). NMR in Cellular and Tissue Engineering. United Engineering Foundation Conference - Bioartificial Organs III. Switzerland.
• Papas, K. K. (1999, October). Non-invasive, NMR Monitoring of Immunoisolated Insulinomas: The Case of the Bioartificial Pancreas. Department of Chemistry, University of Cyprus, Nicosia, Cyprus. Cyprus.
• Papas, K. K., Hu, S., Wang, S., Roos, E. S., Gounarides, J. S., Shapiro, M. J., & de Souza, C. J. (1999, September). 2- Deoxyglucose Inhibits Glucose Metabolism But Not Insulin Secretion In HIT-T15 Cells In Nutrient- Rich DMEM Medium. Diabetologia.
• Papas, K. K., Hu, S., Wang, S., Roos, E. S., Gounarides, J. S., de Souza, C., & Shapiro, M. J. (1999, June). Disassociation of Insulin Secretion from Glucose Metabolism and KATP Channel Activity in HIT - T15 Cells in Nutrient-Rich Medium. Diabetes 48(S1).
• Papas, K. K., Jarema, M. A., Roos, E. S., Shapiro, M. J., & Gounarides, J. S. (1999, May). 31P and 13C-NMR Studies of Intact, Well-oxygenated, Perfused RINm5F Cells. 7th International Society of Magnetic Resonance Meeting. Pennsylvania.
• Papas, K. K., Jarema, M. A., Roos, E. S., Shapiro, M. J., & Gounarides, J. S. (1999, May). A Perfusion System for High Resolution, 31P and 13C-NMR Studies of Intact Perfused Insulin Secreting RINm5F Cells: Effects of Oxygenation. 7th International Society of Magnetic Resonance Meeting. Pennsylvania.
• Papas, K. K., Jarema, M. A., Roos, E. S., Shapiro, M. J., & Gounarides, J. S. (1999, May). NMR Studies of the Bioenergetics and Metabolism of RINm5F Monolayers Exposed to Hyperoxia, Normoxia, and Anoxia: Correlation to Insulin Secretion and Viability. 7th International Society of Magnetic Resonance Meeting. Pennsylvania.
• Papas, K. K., Roos, E. S., Wang, S., Gounarides, J. S., Shapiro, M. J., de Souza, C. J., & Hu, S. (1999, September). Effects Of Incubation Media On Stimulus-Secretion Coupling In HIT-T15 Cells: Buffered Salines Versus Nutrient-Rich DMEM. Diabetologia.
• Papas, K. K. (1996, February). 31P NMR Monitoring of Bioartificial Endocrine Tissue Constructs: Effects of Prolonged Cultivation, Glucose, and Oxygen Limitations. National Institute of Advanced Interdisciplinary Research (NAIR). Japan.
• Papas, K. K. (1998, June). Non-invasive, NMR Monitoring of Immunoisolated Insulinomas: Bioenergetics,. Department of Radiology, University of Pennsylvania Medical Center. Philadelphia.
• Papas, K. K. (1998, May). Non-invasive Monitoring of Immunoisolated Insulinomas by NMR: A Tool for. BetaGene Inc.. Dallas.
• Papas, K. K., Constantinidis, I., Long, R. C., & Sambanis, A. (1998, April). Towards the Development of a Bioartificial Pancreas: Effects of Long-term Hypoxia on Alginate-Entrapped Mouse Insulinoma βTC3 Cells. 6th International Society of Magnetic Resonance Meeting. Australia.
• Papas, K. K., Long, R. C., Sambanis, A., & Constantinidis, I. (1998, April). In vitro Monitoring of Total Choline Levels in a Bioartificial Pancreas: 1H NMR Spectroscopic Studies of the Effect of Oxygen Level on Immunoprotected βTC3 Insulinoma Cells. 6th International Society of Magnetic Resonance Meeting. Australia.
• Papas, K. K., Constantinidis, I., Long, R. C., & Sambanis, A. (1997, April). Towards the Development of a Bioartificial Pancreas: Bioenergetics and Insulin Secretion in Immunoprotected Mouse Insulinoma βTC3 Cells. 5th International Society of Magnetic Resonance Meeting. Canada.
• Papas, K. K., Constantinidis, I., Long, R. C., & Sambanis, A. (1997, April). Towards the Development of a Bioartificial Pancreas: Effects of Long-term Growth on the Relationship Between Bioenergetics and Insulin Secretion in Immunoprotected βTC3 Cells. 5th International Society of Magnetic Resonance Meeting. Canada.
• Papas, K. K., Long, R. C., Constantinidis, I., & Sambanis, A. (1996, November). Cellular Bioenergetics and Insulin Secretion in Mouse Insulinoma βTC3 Cells. 1996 Boston-Ithaca Islet Club Meeting, Joslin Diabetes Center. Boston.
• Papas, K. K., Sambanis, A., Constantinidis, I., & Long, R. C. (1996, November). Towards the Development of a Bioartificial Pancreas: Long-term in vitro Functions of Immunoisolated Mouse Insulinomas. ASME International Mechanical Engineering Congress and Exposition. Georgia.
• Papas, K. K., Sambanis, A., Tziampazis, E., Long, R. C., & Constantinidis, I. (1996, July). Towards the Development of a Bioartificial Pancreas: NMR Studies of Alginate Entrapped Mouse Insulinomas. 1996 Engineering Foundation Conference: Bioartificial Organs-Science and Technology. Tennessee.
• Papas, K. K. (1995, Fall). Towards the Development of a Bioartificial Pancreas: Fabrication, Characterization,. Sandoz Research Institute. New Jersey.
• Papas, K. K., Constantinidis, I., Long, R. C., & Sambanis, A. (1995, August). Towards the Development of a Bioartificial Pancreas: 31-P Studies of Immunoprotected βTC3 Insulinoma Cells. 1995 Society of Magnetic Resonance Annual Meeting. France.
• Papas, K. K., Sambanis, A., Constantinidis, I., & Long, R. C. (1995, April). Monitoring of Immunoisolated. Keystone Conference on Science and Engineering of Immunoprotected Cell Transplants. Colorado.
• Papas, K. K., Sambanis, A., Tziampazis, E., Long, R. C., & Constantinidis, I. (1995, June). Tissue Engineering a Bioartificial Pancreas Based on Transformed Endocrine Cells. 1995 ASME/AIChE/ASCE/BMES Summer Bioengineering Conference. Colorado.
• Papas, K. K., Constantinidis, I., Flanders, P. C., Kang, H., Long, R. C., & Sambanis, A. (1994, August). Correlations of NMR Data to Secretion of Insulin in Perfused Immunoprotected Cells. 1994 Society of Magnetic Resonance Annual Meeting. California.
• Papas, K. K., Sambanis, A., Constantinidis, I., & Long, R. C. (1994, November). Monitoring of Immunoisolated Insulinomas by NMR: Effect of Glucose and Oxygen Levels. 1994 AICheNational Meeting. California.
• Papas, K. K., Sambanis, A., & Constantinidis, I. (1993, September). Tissue Engineering of Endocrine Animal Cells. First International Conference on Cellular Engineering. England.
• Papas, K. K., Sambanis, A., Constantinidis, I., & Long, R. C. (1993, November). Towards the Development of a Bioartificial Pancreas: Fabrication and Non-Invasive Monitoring of Microbeads Containing Insulin- Secreting Transformed Cells. 1993 AIChE National Meeting. Missouri.
• Papas, K. K., Sambanis, A., Constantinidis, I., Long, R. C., & Dixon, T. W. (1993, July). Development and Characterization of a Prototype for NMR Studies of Mammalian Cells. Whitaker Foundation Biomedical Engineering Research Conference. Utah.
• Papas, K. K., & Sambanis, A. (1992, November). Characterization of the Metabolic and Secretory Behavior of Free and Immobilized Insulin-Producing AtT-20 Spheroids. 1992 AIChE National Meeting. Florida.
• Papas, K. K., Dyken, J. J., Vachtsevanos, J., & Sambanis, A. (1992, February). Endocrine Animal Cell Cultures in Bioprocessing and Tissue Engineering. Cell Culture Engineering III. Florida.
• Papas, K. K., Sambanis, A., Constantinidis, I., Long, R. C., & Dixon, T. W. (1992, August). Development and Characterization of a Prototype for NMR Studies of Mammalian Cells. Whitaker Foundation Biomedical Engineering Research Conference. Utah.
• Papas, K. K., & Sommerfeld, J. T. (1991, August). Comparisons of Tank Drainage Times: Orifice Drains Versus Piping. 1991 AIChE Summer National Meeting. Pennsylvania.

Poster Presentations

• Papas, K. K., Bellin, M. D., Sutherland, D. E., Kitzmann, J. P., Avgoustiniatos, E. S., Gruessner, A. C., Mueller, K. R., Balamurugan, A. N., Rozak, P. R., Loganathan, G., Suszynski, T., Wilhelm, J., Qian, D., Nilan, J. C., & Hering, B. J. (2013, May). Correlations of In Vitro Islet Potency Tests with Clinical Islet Auto-transplant Outcome. 13th annual meeting of the American Transplant Congress. Seattle, WA.
• Papas, K. K., Bellin, M. D., Sutherland, D. E., Kitzmann, J. P., Avgoustiniatos, E. S., Gruessner, A. C., Mueller, K. R., Balamurugan, A. N., Rozak, P. R., Loganathan, G., Suszynski, T., Wilhelm, J., Qian, D., Nilan, J. C., & Hering, B. J. (2013, May). Correlations of In Vivo Islet Potency Tests with Clinical Islet Auto-transplant Outcome. 13th annual meeting of the American Transplant Congress. Seattle, WA.
• Papas, K. K., Papas, K. K., Suszynski, T. M., Suszynski, T. M., Wilhelm, J. J., Wilhelm, J. J., Radosevich, D. M., Radosevich, D. M., Balamurugan, A. N., Balamurugan, A. N., Sutherland, D. E., Sutherland, D. E., Beilman, G. J., Beilman, G. J., Dunn, T. B., Dunn, T. B., Chinnakotla, S., Vickers, S. M., Pruett, T. L., , Hering, B. J., et al. (2013, May). Islet Size Index as a Predictor of Outcomes in Clinical Islet Autotransplantation. 13th annual meeting of the American Transplant Congress. Seattle, WA.
• Papas, K. K. (2010, January). Pancreas Oxygen Persufflation Increase ATP-Levels ad improves Islet Viability Compared with Two-Layer Methd (TLM). The American Society of Transplant Surgeons 10th Annual State of Art Winter Symposium. Lauderdale, FL.
• Papas, K. K., Balamurugan, A. N., Loganathan, G., Graham, M., Pakala, P., Yuasa, T., Sutherland, D. E., McCarthy, R. C., & Hering, B. J. (2010, October). Successful isolation and transplantation of non-human primate islets utilizing VitaCyte CIzyme™ collagenase MA and CIzyme thermolysin enzyme blends. ADA meeting. New Orleans.
• Papas, K. K., Balamurugan, A. N., Loganathan, G., Wilhelm, J. J., Yuasa, T., Radosevich, D. M., Bellin, M., Beilman, G. J., McCarthy, R. C., Sutherland, D. E., & Hering, B. J. (2010, March). Maximizing islet yield from deceased and pancreatitis human pancreata using a new enzyme mixture: Synergetic effect of Clostridium histolyticum high intact class 1 collagenase and neutral protease. 10th Annual Rachmiel Levine Diabetes and Obesity Symposium. Las Vegas, NV.
• Papas, K. K., Balamurugan, A. N., O'Brien, T. D., Loganathan, G., Bellin, M., Anazawa, T., Vickers, S., Hering, B. J., & Sutherland, D. E. (2010, August). Severely fibrotic pancreata from young patients with chronic pancreatitis: Evidence for ductal neogenesis of islets. XXIII International Congress of The Transplantation Society. Vancouver, Canada.
• Papas, K. K., Balamurugan, A. N., Wilhelm, J. J., Loganathan, G., Yuasa, T., Radosevich, D. M., Bellin, M., Beilman, G. J., Hering, B. J., & Sutherland, D. E. (2010, May). Improved Islet Yield from Diseased Pancreases for Autotransplantation Using a New Enzyme Mixture. 2010 American Transplant Congress. San Diego, CA.
• Papas, K. K., Cline, G., Pongratz, R., & Kibbey, R. (2010, April). Role for anaplerosis and pyruvate cycling in fuel- stimulated insulin secretion from human islets. Keystone Symposium on Islet Biology. Whistler, British Columbia.
• Papas, K. K., Kirchner, V. A., Weegman, B. P., Scott III, W. E., Avgoustiniatos, E. S., Suszynski, T. M., Ferrer-Fabrega, J., Rizzari, M. D., Kidder, L. S., Kandaswamy, R., & Sutherland, D. E. (2010, August). Viability Assessment of Donor Kidneys Prior to Transplantation Based on Continuous Oxygen Consumption Measurement. XXIII International Congress of The Transplantation Society. Vancouver, Canada.
• Papas, K. K., Loganathan, G., Radosevich, D., Anazawa, T., Graham, M., Sutherland, D. E., Hering, B. J., & Balamurugan, A. N. (2010, August). Factors affecting transplant outcome in diabetic nude mice receiving human, porcine, and non-human primate islets: Lessons from 328 transplantations. TTS International Congress (Vancouver).
• Papas, K. K., Rizzari, M. D., Suszynski, T. M., Kidder, L. S., Stein, S. A., O'Brien, T. D., Scott III, W. E., Kirchner, V. A., Weegman, B. P., Avgoustiniatos, E. S., Todd, P. W., Kennedy, D. J., Hammer, B. E., Sutherland, D. E., & Hering, B. J. (2010, August). Development of a Surgical Protocol for Infusion of Paramagnetic Microparticles for Preferential Incorporation Within Porcine Islets. XXIII International Congress of The Transplantation Society. Vancouver, Canada.
• Papas, K. K., Suszynski, T. M., Rizzari, M. D., Kidder, L. S., Mueller, K., Kitzmann, J. P., Chapman, C. S., Pongratz, R. L., Kirchner, V. A., Cline, G. W., & Avgoustiniatos, E. S. (2010, August). Co-culture of Porcine Pancreatic Islets with Paramagnetic Microparticles Does Not Result in Reduced Viability or Function. XXIII International Congress of The Transplantation Society. Vancouver, Canada.
• Papas, K. K., Fan, W., Atchison, N., Kidder, L. S., Maynard, K., Kokkoli, E., & Tsapatsis, M. (2009, November). Benign, 3D Encapsulation of Living Cells with Lys-Sil Nanoparticles. American Institute of Chemical Engineers (AIChE) Annual Meeting. Nashville, TN.
• Papas, K. K., Sajja, V. S., Kennedy, D. J., Todd, P. W., Green, M., McCarthy, R., & Hanley, T. R. (2009, November). Experimental Evaluation of Quadrupole Magnetic Flow Sorter for Pancreatic Islets. American Institute of Chemical Engineers (AIChE) Annual Meeting. Nashville, TN.
• Papas, K. K. (2007, May). Quality of research and Clinical Human Islet Preparations after culture. American Transplant Congress. San Francisco.

Reviews

• Smith, K., Johnson, R., & Papas, K. K. (2018. Update on Cellular Encapsulation.
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  Novel Technologies in Islet Transplantation
• Papas, K. K. (2011. paramagnetic Microparticles are neither Immunogenic in Mice nor Cytotoxic to Porcine Pancreatic Islets During Co-Culture.
• Papas, K. K. (2011. successful isolation and transplantation of non-human primates islets utilizing VitaCyte clyme collagenase MA and Clzym thermolysin purified enzymes.
• Papas, K. K. (2010. Continuous Real-time Viability Assessment of Kidneys Based on Oxygen Consumption.
• Papas, K. K., Suszynski, T. M., & Colton, C. K. (2010. Islet assessment for transplantation(pp 674-682).
• Suszynski, T. M., Rizzari, M. D., Scott, W. E., Eckman, P. M., Fonger, J. D., John, R., Chronos, N., Tempelman, L. A., Sutherland, D. E., & Papas, K. K. (2007. Persufflation (gaseous oxygen perfusion) as a method of heart preservation.

Others

• Papas, K. K. (2020, April). Characterization of Islet Health and Function Prior to Transplantation. The FASEB Journal.
• Papas, K. K. (2020, June). Composite Tissue Preservation. Annals of Plastic Surgery.
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  Abstract
• Papas, K. K. (2016, September). IPITA-JDRF/Helmsely-HSCI Key Opinion Leaders Meeting on Stem Cell Derived Beta Cells.
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  By Invitation onlyBoston, MA
• Papas, K. K., Hering, B. J., Rozak, P. R., Wilson, J., & Avgoustiniatos, E. S. (2015, MAY). Improved islet culture on top of gas-permeable membranes.. AMERICAN JOURNAL OF TRANSPLANTATION.
• Suszynski, T. M., Wilhelm, J. J., Radosevich, D. M., Balamurugan, A. N., Sutherland, D. E., Beilman, G. J., Dunn, T. B., Chinnakotla, S., Pruett, T. L., Vickers, S. M., Hering, B. J., Papas, K. K., & Bellin, M. D. (2015, SEP 27). Islet Size Index as a Predictor of Outcomes in Clinical Islet Autotransplantation. TRANSPLANTATION.
• Davis, M., Smith, K. E., Salama, B. F., Korbutt, G. S., Limesand, S. W., & Papas, K. K. (2014, NOV). Stimulation of porcine beta-cell proliferation is inhibited with hypoxic culture conditions. XENOTRANSPLANTATION.
• Papas, K. K. (2014, Jul-Aug). Function and expression of sulfonylurea, adrenergic, and glucagon-like peptide 1 receptors in isolated porcine islets.. Xenotransplantation.
• Papas, K. K. (2014, Jul-Aug). Human Islet Viability and Function is Maintained During High Density Shipment on Silicone Rubber Membrane Vessels. Transplantation Proceedings.
• Papas, K. K. (2014, Jul-Aug). Islet oxygen consumption rate dose predicts insulin independence for first clinical islet allotransplants.. Transplantation Proceeding.
• Papas, K. K. (2014, September). Magnetic resonance imaging: a tool to monitor and optimize enzyme distribution during porcine pancreas distention for islet isolation.. Xenotransplantion.
• Papas, K. K., Graham, M. L., Avgoustiniatos, E. S., Mueller, K. R., Flanagan, B., Schuurman, H., & Hering, B. J. (2014, SEP-OCT). Quality assessment as a predictor for graft function in the pig-to-nonhuman primate islet transplantation model. XENOTRANSPLANTATION.
• Scott, W. E., Theisenger, B., Weegman, B. P., Stein, S., Brandhorst, H., Hammer, B. E., Avgoustiniatos, E. S., Maynard, K. S., Korsgren, O., Papas, K. K., & Brandhorst, D. (2014, SEP-OCT). One-layer method with novel compound perfluorohexyloctane increases levels of ATP relative to perfluorodecalin as shown by 31P-NMR spectroscopy. XENOTRANSPLANTATION.
• Scott, W. E., Weegman, B. P., Balamurugan, A. N., Ferrer-Fabrega, J., Anazawa, T., Karatzas, T., Jie, T., Hammer, B. E., Matsumoto, S., Avgoustiniatos, E. S., Maynard, K. S., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2014, September). Magnetic resonance imaging: a tool to monitor and optimize enzyme distribution during porcine pancreas distention for islet isolation. Xenotransplantation.
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  Porcine islet xenotransplantation is emerging as a potential alternative for allogeneic clinical islet transplantation. Optimization of porcine islet isolation in terms of yield and quality is critical for the success and cost-effectiveness of this approach. Incomplete pancreas distention and inhomogeneous enzyme distribution have been identified as key factors for limiting viable islet yield per porcine pancreas. The aim of this study was to explore the utility of magnetic resonance imaging (MRI) as a tool to investigate the homogeneity of enzyme delivery in porcine pancreata. Traditional and novel methods for enzyme delivery aimed at optimizing enzyme distribution were examined. Pancreata were procured from Landrace pigs via en bloc viscerectomy. The main pancreatic duct was then cannulated with an 18-g winged catheter and MRI performed at 1.5-T. Images were collected before and after ductal infusion of chilled MRI contrast agent (gadolinium) in physiological saline. Regions of the distal aspect of the splenic lobe and portions of the connecting lobe and bridge exhibited reduced delivery of solution when traditional methods of distention were utilized. Use of alternative methods of delivery (such as selective re-cannulation and distention of identified problem regions) resolved these issues, and MRI was successfully utilized as a guide and assessment tool for improved delivery. Current methods of porcine pancreas distention do not consistently deliver enzyme uniformly or adequately to all regions of the pancreas. Novel methods of enzyme delivery should be investigated and implemented for improved enzyme distribution. MRI serves as a valuable tool to visualize and evaluate the efficacy of current and prospective methods of pancreas distention and enzyme delivery.
• Hering, B. J., Parkey, J., Kandaswamy, R., Jevne, R., Lervik, B., Harmon, J. V., Pakala, P., Papas, K. K., & Sutherland, D. E. (2013, MAY). Long-term survival of human islet allografts in type 1 diabetes.. AMERICAN JOURNAL OF TRANSPLANTATION.
• Kaddis, J. S., Olack, B. J., Ruel, N., Qian, D., Papas, K. K., & Niland, J. C. (2013, JUN). Measuring insulin for comparative assessments in humans: A study by the national islet cell resource center (ICR) consortium. DIABETES.
• Papas, K. K. (2013, January). FACTORS AFFECTING TRANSPLANT OUTCOME IN DIABETIC NUDE MICE RECEIVING HUMAN, PORCINE, AND NON-HUMAN PRIMATE ISLETS: LESSONS FROM 328 TRANSPLANTATIONS.
• Papas, K. K. (2013, March-April). International workshop: islet transplantation without borders enabling islet transplantation in Greece with international collaboration and innovative technology..
• Papas, K. K., Avgoustiniatos, E. S., Scott, W. E., Nelson, R. A., Rozak, P. R., Wildey, G. M., Fraga, D. W., Ansite, J. D., Tanaka, T., & Hering, B. J. (2013, MAY). Quality of research and clinical human islet preparations after culture.. AMERICAN JOURNAL OF TRANSPLANTATION.
• Scott, W. E., Avgoustiniatos, S. S., Ferrer-Fabrega, J., Anazawa, T., Weegman, B. P., Kidder, L. S., Stein, S., Matsumoto, S., Hammer, B. E., Balamurugan, A. N., O'brien, T. D., Murtaugh, M., Tempelman, L., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2013, JAN). Pancreas Oxygen Persufflation Increases ATP-Levels and Improves Islet Viability Compared with Two-Layer Method (TlM). AMERICAN JOURNAL OF TRANSPLANTATION.
• Scott, W. E., Balamurugan, A. N., Ferrer-Fabrega, J., Anazawa, T., Weegman, B. P., Hammer, B. E., Matsumoto, S., Avgoustiniatos, E. S., Maynard, K. S., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2013, SEP-OCT). MRI as a novel tool to develop new methods of pancreas distension to enable homogeneous enzyme distribution for successful islet isolation. XENOTRANSPLANTATION.
• Khorsandi, S. E., Scott, W. E., Jassem, W., Vilca-Melendez, H., Prachalias, A., Papas, K. K., Quaglia, A., Heaton, N., & Srinivasan, P. (2012, OCT). Establishing a technique of Anterograde Liver Persuffulation (A-PSF) for resuscitation of marginal grafts. HEPATOLOGY.
• Kitzmann, J. P., Pepper, A. R., Lopez, B. G., Pawlick, R., Kin, T., O'Gorman, D., Mueller, K. R., Gruessner, A. C., Szot, G. L., Posselt, A. M., Stock, P. G., Wilson, J. R., Shapiro, A. M., & Papas, K. K. (2011, SEP 27). Human Islet Viability and Function is Maintained During High Density Shipment on Silicone Rubber Membrane Vessels. TRANSPLANTATION.
• Min, C., Smith, K. E., Steyn, L. V., Weber, C., Purvis, W. G., Stanton, J. B., Burachek, A. M., Salama, B. F., Korbutt, G. S., Lynch, R. M., Limesand, S. W., & Papas, K. K. (2011, NOV). Comparison of adult, juvenile and neonatal porcine islets demonstrates age dependent beta-cell fraction, insulin content and insulin secretion. XENOTRANSPLANTATION.
• Papas, K. K. (2011, March). Microbiological safety of porcine islets: comparison with source pig..
• Smith, K., Steyn, L. V., Weber, C., Min, C., Purvis, W. G., Stanton, J. B., Burachek, A. M., Salama, B. F., Korbutt, G. S., Lynch, R. M., Limesand, S. W., & Papas, K. K. (2011, NOV). Direct comparison of adult, juvenile, and neonatal porcine islets in vitro reveals age dependent differences in viability and function. XENOTRANSPLANTATION.
• Steyn, L. V., Davis, M. A., Min, C., Smith, K., Purvis, W. G., Stanton, J. B., Loudovaris, T., Weegman, B. P., Mueller, K. R., Kitzmann, J. P., Avgoustiniatos, E. S., Tempelman, L., Limesand, S. W., & Papas, K. K. (2011, NOV). In situ oxygen delivery to islets within an implantable immunoisolating device in vivo enhances viability and function. XENOTRANSPLANTATION.
• Suszynski, T. M., Mueller, K. R., Gruessner, A. C., & Papas, K. K. (2011, SEP 27). Oxygen Consumption Rate of Porcine Pancreatic Acinar and Islet Tissue in Culture. TRANSPLANTATION.
• Weegman, B. P., Scott, W. E., Anazawa, T., Avgoustiniatos, E. S., Yuasa, T., Ferrer-Fabrega, J., Hammer, B. E., Loughnane, M. H., Hering, B. J., Kandaswamy, R., Sutherland, D. E., Suszynski, T. M., & Papas, K. K. (2011, SEP-OCT). Continuous, real-time viability assessment of kidneys based on oxygen consumption. XENOTRANSPLANTATION.
• Einstein, S. A., Weegman, B. P., Kitzmann, J. P., Kirkeide, L. R., Papas, K. K., & Garwood, M. (2010, NOV). Non-invasive assessment of tissue-engineered graft viability with oxygen-17 magnetic resonance spectroscopy. XENOTRANSPLANTATION.
• Papas, K. K., Karatzas, T., Purvis, W. G., Kitzmann, J. P., Gruessner, A. C., O'Gorman, D., Kin, T., Shapiro, J. A., & Tempelman, L. A. (2010, NOV). Pancreas oxygen gas perfusion (persufflation) during preservation improves clinical islet isolation yields and success rates. XENOTRANSPLANTATION.
• Smith, K., Kelly, A. C., Weber, C., Min, C., Smith, B., McCarthy, F., Steyn, L. V., Badarinarayana, V., Strop, P., Lynch, R. M., Limesand, S. W., & Papas, K. K. (2010, NOV). Acute ischemic exposure leads to functional deficits and a transcriptome enriched in inflammatory and hypoxic pathways in human islets. XENOTRANSPLANTATION.
• Smith, K., Steyn, L. V., Weber, C., Min, C., Purvis, W. G., Stanton, J. B., Burachek, A. M., Salama, B. F., Korbutt, G. S., Lynch, R. M., Limesand, S. W., & Papas, K. K. (2010, NOV). In vitro comparison of adult, juvenile, and neonatal porcine islets reveals age dependent resistance to ischemia. XENOTRANSPLANTATION.
• Bansal-Pakala, P., Bellin, M., Hire, K., Appakalai, B., Papas, K. K., Kandaswamy, R., Sutherland, D. E., Bluestone, J. A., & Hering, B. J. (2009, SEP-OCT). Immune mechanisms of teplizumab induction immunotherapy in type 1 diabetic islet allograft recipients. XENOTRANSPLANTATION.
• Elvira, J., Lina, M., Chris, D., Lindy, W., Tina, P. A., Daisy, M., Klearchos, P., Goto, M., Tom, K., Toby, C., Philip, O., Tom, L., & Wayne, H. (2009, AUG). EFFECT OF TRANSPORTATION ON HUMAN ISLETS USING DIFFERENT SPECIALISED SHIPPING CONTAINERS BETWEEN TRANSPLANT CENTRES IN AUSTRALIA. IMMUNOLOGY AND CELL BIOLOGY.
• Hering, B. J., Parkey, J., Kandaswamy, R., Jevne, R., Snead, D., Lervik, B., Harmon, J. V., Tanaka, T., Yonekawa, Y., Matsumoto, S., Balamurugan, A. N., Papas, K. K., Pakala, P., & Sutherland, D. E. (2009, SEP). Analysis of long-term islet allograft function in recipients with type 1 diabetes given depleting t-cell antibodies for induction immunosuppression. XENOTRANSPLANTATION.
• Loganathan, G., Dawra, R. K., Papas, K. K., Pugazhenthi, S., Wiseman, A., Saluja, A. K., Sutherland, D. E., Hering, B. J., & Appakalai, B. (2009, SEP-OCT). Culture of impure human islet fractions in the presence of alpha-1-antitrypsin prevents insulin cleavage and improves islet recovery. XENOTRANSPLANTATION.
• Mueller, K. R., Appakalai, B., Cline, G., Pongratz, R., Hooper, R. L., Weegman, B. P., Taylor, M. J., Graham, M. L., Schuurman, H., & Papas, K. K. (2009, SEP-OCT). Comparison of glucose-stimulated insulin secretion between isolated human, nonhuman primate and porcine islets. XENOTRANSPLANTATION.
• Papas, K. K., Mueller, K. R., Penrod, L. V., Davis, M. A., Kitzmann, J. P., Gruessner, S. G., Suszynski, T. M., Jie, T., Tempelman, L., Limesand, S. W., & Avgoustiniatos, E. S. (2009, SEP 27). Macroencapsulated Human Islet Viability is Drastically Reduced In Vivo as the Number of Islets per Device is Increased. TRANSPLANTATION.
• Scott, W. E., Ferrer-Fabrega, J., Anazawa, T., Weegman, B. P., Stein, S., Matsumoto, S., Stone, J., Balamurugan, A. N., Hammer, B. E., Avgoustiniatos, E. S., Maynard, K. S., Stone, S., Tempelman, L., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2009, SEP-OCT). Pancreas oxygen persufflation increases ATP levels as shown by NMR. XENOTRANSPLANTATION.
• Scott, W. E., Ferrer-Fabrega, J., Avgoustiniatos, E. S., Anazawa, T., Weegman, B. P., Matsumoto, S., O'brien, T. D., Murtaugh, M., Hammer, B. E., Yu, I., Kidder, L. S., Maynard, K. S., Stone, S. G., Tempelman, L., Sutherland, D. E., Hering, B. J., & Papas, K. K. (2009, SEP-OCT). Pancreas persufflation for 6 h and 24 h improves viable islet yields compared with the two-layer method. XENOTRANSPLANTATION.
• Scott, W. E., Turker, T., Suszynski, T. M., Weegman, B. P., Long, R. C., Breidenbach, W. C., & Papas, K. K. (2009, NOV). INVESTIGATION OF PERSUFFLATION (PSF) AS A NOVEL METHOD OF COMPOSITE TISSUE (CT) PRESERVATION FOR REPLANT AND TRANSPLANT IN A PIG MODEL. TRANSPLANT INTERNATIONAL.
• Anazawa, T., Balamurugan, A. N., Ferrer, J., Matsumoto, S., Avgoustiniatos, E. S., Papas, K. K., Sutherland, D. E., & Hering, B. J. (2007, SEP-OCT). Improved method of porcine pancreas procurement with arterial flush and ductal injection enhances islet isolation outcome. XENOTRANSPLANTATION.
• Weegman, B. P., Einstein, S. A., Steyn, L. V., Suszynski, T. M., Firpo, M. T., Graham, M. L., Janacek, J., Eberly, L. E., Garwood, M., & Papas, K. K. (2007, NOV). Continuous oxygen delivery improves oxygenation of tissue-engineered islet grafts in vivo as measured with fluorine-19 magnetic resonance spectroscopy. XENOTRANSPLANTATION.
• Steyn, L. V., Smith, K., Min, C., Purvis, W. G., Stanton, J. B., Davis, M. A., Mueller, K. R., Kitzmann, J. P., Weegman, B. P., Avgoustiniatos, E. S., Tempelman, L., Limesand, S. W., & Papas, K. K. (2006, NOV). Increasing islet density within an immunoisolation device has a detrimental impact on viability in vivo. XENOTRANSPLANTATION.