CRYOPRESERVATION OF MICROENCAPSULATED PORCINE PANCREATIC-ISLETS - IN-VITRO AND IN-VIVO STUDIES

Background If the transplantation of immunoisolated porcine islets int o human diabetics is to become reality, the development of a long-term storage method represents an important prerequisite, However, informa tion on cryogenic storage of porcine islets is scanty and fragmentary, Methods. Porcine pancreatic islets microencapsulated in alginate-poly lysine-alginate membranes were cryopreserved and assessed both in vitr o by static glucose challenge and in vivo in a transplantation study, Two separate methods of islet cryopreservation were compared: method A , using the Bio Cool III freezing machine, and method B, which uses th e Nalgene isopropyl alcohol insulated cooler, Results. Method A was fo und to have better preserved the ability of the microencapsulated cryo preserved islets to respond to high-glucose static challenge (7 out of 10 lots) compared with method B (1 out of 10 lots), Upon exposure to high glucose, the islet batches that did retain the ability to respond to glucose were shown to have secreted an average of 1220+/-73 pM/24 hr/islet of insulin as compared with 1528+/-118 pM/24 hr/islet for fre sh islets, The presence of isobutyl methylxanthine further potentiated insulin secretion to 1805+/-81 pM/24 hr/islet and to 2410+/-104 pM/24 hr/islet for cryopreserved and free islets, respectively. Intraperito neal transplantation of 2000 cryopreserved microencapsulated porcine i slets into streptozotocin-diabetic mice resulted in the reversal of hy perglycemia in 6 out of 10 recipients for the duration of the 90-day s tudy. Conclusions, The effective protection of the delicate porcine en docrine tissue during the cryopreservation process and the subsequent long-term storage were demonstrated with considerable success in this study.