LONG-TERM PRESERVATION OF ISLETS OF LANGERHANS IN HYDROPHILIC MACROBEADS

Several obstacles have hindered the successful transplantation of isle ts of Langerhans to human patients in efforts to cure type I diabetes mellitus. One problem is the necessity for short- and long-term storag e of islets after isolation and before transplantation. Current long-t erm storage methods, such as incubation in a physiological medium and cryopreservation, are suboptimal, resulting in significant loss of via ble islet mass or function. Better storage methods are needed, In this study we examined the long-term storage of rat islets in macrobeads c omposed of agarose and collagen, Islets isolated from Wistar-Furth rat s were placed into macrobeads (1000 islets/macrobead) and maintained i n culture for periods of up to 189 days at 37 degrees C. Insulin relea sed from the cultured macrobeads remained constant for periods of at l east 154 days. In one group, insulin release was 1050 mU/24 hr/4 beads on day 3 and 1040 mU/24hr/4 beads on day 154. In another group, insul in release was 1305 mU/24 hr/5 beads on day 17 and 1580 mU/24 hr/5 bea ds on day 112. Xenotransplantation of Wistar Furth islet macrobeads, s tored for 10 to 112 days at 37 degrees C, into 42 B6AF/1 mice with str eptozotocin-induced diabetes resulted in a return to euglycemia in the recipients within 24 hr. Thereafter, euglycemia was maintained for mo re than 100 days in 32/42 of the recipients, and removal of the macrob eads caused a return to hyperglycemia within 48 hr in all animals. In addition, a group of 7 mice receiving macrobeads containing 1000 islet s stored for 84 days had normal glucose tolerance tests (compared with those of 7 nontreated, nontransplanted mice with streptozotocin-induc ed diabetes and 7 normal mice), demonstrating that the islets in the m acrobeads were functioning as they would in an intact pancreas. Finall y, 5 macrobeads transplanted after initial storage of 112 days, remove d from the first recipient after 100 days or more, stored again for 4 days in vitro, and retransplanted into 5 other diabetic mice also rest ored and maintained euglycemia for at least 45 days. Our results indic ate that collagen-agarose macrobeads are capable of preserving rat pan creatic islets for extended periods without loss of in vitro insulin r elease capability or ability to achieve and maintain euglycemia in viv o, As such they should be useful for human islet transplantation effor ts.