Comparison of two methods of pancreas islets immunoisolation.

The efficacy of two methods of Langerhans islets immunoisolation was compared. For this purpose the function of islets encapsulated with alginate/polyethylenimine/protamine/heparin (APPH) or with alginate/poly-L-lisine/alginate (APA) membranes was assessed: in vitro according to their survival and response to glucose challenges, and in vivo according to their capability to provide sufficient insulin delivery to maintain normal fasting blood glucose following xenotransplantation to streptozotocin diabetic mice. In vitro insulin secretion and the response to glucose challenge of APPH and APA encapsulated islets were comparable to free islets. In vivo intraperitoneal concordant xenotransplantation of APA encapsulated rat islets reversed the diabetic state of streptozotocin diabetic mice for a longer period, than APPH islet grafts. This study clearly demonstrated the inadequacy of in vitro methods in the prediction of in vivo results of islets transplantation.