XENOTRANSPLANTATION OF MICROENCAPSULATED CANINE ISLETS INTO DIABETIC RATS

Islets of Langerhans were isolated in high yields from canine pancreat a. In the procedure, the pancreata were perfused and digested with col lagenase, and the islets were then purified on histopaque density grad ients. As many as 60,000 islets were isolated from a single pancreas. Islets were encapsulated in alginate-polylysine-alginate membranes wit h the aid of an air-jet droplet generator. In vitro studies demonstrat ed that the isolated and encapsulated islets secreted insulin in respo nse to glucose and IBMX challenge for at least 9 weeks. In in vivo stu dies 6 diabetic Wistar rats were transplanted with 5,000 to 8,000 enca psulated islets each. The diabetic condition was reversed in all recip ients for up to 112 days. In control animals, which received free, une ncapsulated islets, the xenografts remained functional for fewer than 21 days. Microencapsules retrieved from normoglycemic transplant recip ients 1 and 2 months posttransplantation were shown indicate a contain viable islet tissue, and no cellular overgrowth was observed on capsu lar surfaces. The results of the study indicate a considerable clinica l potential of microencapsulated canine islet xenografts.