title: Cryopreservation of microencapsulated porcine pancreatic islets: in vitro and in vivo studies.
abstract: 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.
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Toronto, Ontario, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Zhou
authors.forename: I
authors.initials: I
authors.lastname: Vacek
authors.forename: A M
authors.initials: AM
authors.lastname: Sun
mesh_terms: 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*
chemical_list: D001786:Blood Glucose