Cryopreservation of microencapsulated porcine pancreatic islets: in vitro and in vivo studies
Zhou, D.; Vacek, I.; Sun, A.M.
Transplantation 64(8): 1112-1116
1997
ISSN/ISBN: 0041-1337 PMID: 9355825 Document Number: 476923
Background: If the transplantation of immunoisolated porcine islets into human diabetics is to become reality, the development of a long-term storage method represents an important prerequisite. However, information on cryogenic storage of porcine is- lets is scanty and fragmentary. Methods: Porcine pancreatic islets microencapsulated in alginate-polylysine-alginate membranes were cryopreserved and assessed both in vitro 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 the Nalgene isopropyl alcohol insulated cooler. Results: Method A was found to have better preserved the ability of the microencapsulated cryopreserved 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+-1188 pM/24 hr/islet for fresh 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. Intraperitoneal transplantation of 2000 cryopreserved microencapsulated porcine islets into streptozotocin-diabetic mice resulted in the reversal of hyperglycemia in 6 out of 10 recipients for the duration of the 90-day study. Conclusions: The effective protection of the delicate porcine endocrine tissue during the cryopreservation process and the subsequent long-term storage were demonstrated with considerable success in this study.