Tissue culture of human fetal pancreas. Effects of nicotinamide on insulin production and formation of isletlike cell clusters.

Human fetal pancreas (HFP) is a potential source of beta-cells for transplantation to insulin-dependent diabetic patients. We have previously described a method for tissue culture of HFP that results in the in vitro development of isletlike cell clusters (ICCs) containing a minority of insulin-positive cells. Recently we found that nicotinamide, an inhibitor of poly(ADP-ribose) synthetase, induces an increased islet cell DNA replication both in vivo and in vitro. In this study, this culture technique was used to evaluate the effects of addition of 10 mM nicotinamide on HFP explants cultured in RPMI-1640 medium plus 10% human serum. ICCs developed in 11 of 19 consecutive cultures with nicotinamide increased the yield of ICCs by 40%. Also, the insulin content of ICCs increased approximately 50% with nicotinamide supplementation, although measurements of DNA indicated an unchanged number of cells in each ICC. Neither the rates of insulin release in response to 16.7 mM glucose plus 5 mM theophylline nor the (pro)insulin or total protein biosynthesis rates were affected by nicotinamide addition. The combined results of this study suggest that nicotinamide is useful for stimulating the formation of ICCs from HFP.