Optimizing Temperature and Oxygen Supports Long-term Culture of Human Islets

Background Islet transplantation is a promising treatment for type-1 diabetes; however, donor shortage is a concern. Even when a pancreas is available, low islet yield limits the success of transplantation. Islet culture enables pooling of multiple low-yield isolations into an effective islet mass, but isolated islets rapidly deteriorate under conventional culture conditions. Oxygen depletion in the islet core, which leads to central necrosis and volume loss, is one of the major reasons for this deterioration. Methods To promote long-term culture of human islets in PIM-R medium (used for islet research), we adjusted temperature (12, 22, and 37°C) and oxygen concentration (21% and 50%). We simulated the oxygen distribution in islets based on islet oxygen consumption rate and dissolved oxygen in the medium. We determined the optimal conditions for oxygen distribution and volume maintenance in a 2-week culture and assessed viability and insulin secretion compared to noncultured islets. In vivo islet engraftment was assessed by transplantation into diabetic NOD-SCID mouse kidneys. We validated our results using CMRL 1066 medium (used for clinical islet transplantation). Results Simulation revealed that 12°C–50% oxygen PIM-R culture supplied oxygen effectively into the islet core. This condition maintained islet volume at >90% for 2 weeks. There were no significant differences in viability and function in vitro or diabetic reversal rate in vivo between 2-week cultured and noncultured islets. Similar results were obtained using CMRL 1066. Conclusion By optimizing temperature and oxygen concentration, we cultured human islets for 2 weeks with minimal loss of volume and function. Corresponding author: Hirotake Komatsu, MD, PhD, Division of Developmental and Translational Diabetes and Endocrinology Research, Department of Diabetes and Metabolic Research, Beckman Research Institute of City of Hope, 1500 E. Duarte Rd., Duarte, CA 91010, USA. E-mail: hkomatsu@coh.org Authorship Hirotake Komatsu designed the study, collected and analyzed data, and wrote the manuscript. Jeffrey Rawson, Leonard Medrano, Colin A. Cook, Alyssa Barriga, Nelson Gonzalez, and Mayra Salgado collected data. Keiko Omori, Fouad Kandeel, Yu-Chong Tai, and Yoko Mullen reviewed and edited the manuscript. Disclosure: All authors certify that there is no conflict of interest with any financial organization regarding the material discussed in the manuscript. Funding: This study was supported by a grant from the Nora Eccles Treadwell Foundation (Title of Grant: CURE OF DIABETES, Grant Period: July 1, 2012–June 30, 2020, P.I.: Yoko Mullen, MD, PhD). Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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