Effect of prolonged in vitro exposure to high glucose on neonatal porcine pancreatic islets

Prolonged exposure to high glucose can influence the function, growth, and survival of pancreatic beta-cells. In this study, we examine the effects of prolonged in vitro exposure to high glucose on neonatal porcine P-cells, a potentially useful source of insulin-producing cells for clinical islet transplantation. Neonatal porcine islets were prepared by culturing collagenase-digested pancreases for I week in 5.6 mM glucose, followed by an additional week in either 5.6, 10.0, or 28.0 mM glucose. An additional 2 days of culture in 5.6 mM glucose followed for recovery from high glucose. The 7-day culture period in 28.0 mM glucose failed to irreversibly impair glucose responsiveness and also caused a modest increase in beta-cell mass. Immunostaining revealed that precursor cell differentiation was responsible for the increase in beta-cell mass rather than beta-cell proliferation. Islet cell survival was also assessed by a DNA fragmentation assay (TUNEL stain) to determine beta-cell susceptibility to apoptosis after exposure to high glucose. Interestingly, although the total number of apoptotic islet cells did not drastically change after a week of culture in either 5.6, 10.0, or 28.0 mM glucose (25% TUNEL-positive), neither did the percentage of apoptotic beta-cells. These encouraging results further support the use of neonatal porcine islets for clinical transplantation because of their ability to resist the cytotoxic effects of high glucose on islet function and survival.