Human albumin preserves islet mass and function better than whole serum during pretransplantation islet culture.

OBJECTIVE: Human islet transplant protocols frequently include a brief period of islet culture before transplantation. Some investigators have suggested that medium supplementation with human serum might quench collagenase activity and provide better culture conditions when compared with human albumin. We studied the effect of whole serum on islet count, islet equivalence, insulin secretion, and DNA content in human islets. METHODS: Adult human islets isolated from a single pancreas with purity >50% were cultured in identical 150 islet equivalent samples at 37 degrees C using CMRL 1066-based islet medium (Mediatech) supplemented with either 0.5% human albumin or 10% human AB serum. Prior to culture and after 3 days, islets were assessed in vitro using dithizone staining (n = 4), insulin release after static glucose stimulation (n = 8), and DNA content (n = 8). RESULTS: After 3 days, islet mass (defined by the number of islets and islet equivalents counted after dithizone staining) was better preserved in islets cultured in 0.5% human albumin. Although the stimulation index and total DNA content were similar between groups, islets cultured in human albumin demonstrated greater absolute insulin secretion (p = .02) and insulin secretion per cell (p = .02). CONCLUSIONS: When used to supplement CMRL 1066-based islet culture medium, human albumin preserves islet mass and secretory capacity better than whole human serum. Human serum offers no advantage in islet preservation or function.