Cryopreservation of microencapsulated porcine pancreatic islets: in vitro and in vivo studies.
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 islets 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+/-118 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.
Zhou
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D
Department of Physiology, Faculty of Medicine, University of Toronto, Ontario, Canada.
Vacek
I
I
Sun
A M
AM
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D015925:Cryopreservation / Q000379:methods*; D003921:Diabetes Mellitus, Experimental / Q000601:surgery; D004339:Drug Compounding; D005069:Evaluation Studies as Topic; D007515:Islets of Langerhans; D016381:Islets of Langerhans Transplantation; D051379:Mice; D008810:Mice, Inbred C57BL; D010529:Peritoneal Cavity / Q000601:surgery; D013552:Swine; D014021:Tissue Preservation / Q000379:methods*
D001786:Blood Glucose