Culturing Free-Floating and Fibrin-Embedded Islets with Endothelial Cells: Effects on Insulin Secretion and Apoptosis

There is a need to develop methods to culture isolated endocrine pancreatic islets in vitro, as their capacity to secrete insulin typically declines following isolation and they usually undergo apoptosis. In this study, the effects on insulin secretion and apoptosis were tested for two co-culture systems of endocrine porcine islets (1) embedded in fibrin with porcine liver microvascular endothelial cells (PLMEC) and (2) seeded on PLMEC monolayers. The addition of endothelial cells in fibrin resulted in better preserved islet integrity, higher insulin secretion over 7 days, improved glucose-stimulated insulin secretion (GSIS), less loss of insulin-expressing cells over 7 days, and reduced apoptosis, the latter only for 2 days. Seeding islets on PLMEC monolayers had marginal improvement of the insulin secretion over 7 days. It improved GSIS for 2 days, but not over 7 days, as it did not affect the loss of insulin-expressing cells over 7 days. When compared to freely-floating islets in tissue culture polystyrene, the apoptosis level of islets seeded on PLMEC monolayers was on par and slightly decreased over 2 and 7 days, respectively. For both islets co-seeded with PLMEC in fibrin and those cultured on PLMEC monolayers, insulin secretion decreased over 7 days.