Sustained exenatide delivery via intracapsular microspheres for improved survival and function of microencapsulated porcine islets

The ability of glucagon-like peptide-1 analogs to enhance glucose-dependent insulin secretion and to inhibit β cell apoptosis could be of potential benefit for islet transplantation. In this study, we investigated the effect of sustained local delivery of exenatide, a synthetic exendin-4, on the in vitro viability and function of encapsulated porcine islets. Prior to encapsulation, we fabricated exenatide-loaded poly(latic-co-glycolic acid) microspheres, and investigated their release behavior with different initial drug-loading amounts. Exenatide-loaded microspheres, exhibiting a sustained release over 21 days, were subsequently chosen and co-encapsulated with porcine islets in alginate microcapsules. During the 21-day period, the islets co-encapsulated with the exenatide-loaded microspheres exhibited improved survival and glucose-stimulated insulin secretion, compared to those without. This suggested that the intracapsular sustained delivery of exenatide via microspheres could be a promising strategy for improving survival and function of microencapsulated porcine islets for islet xenotransplantation.