Examination of the molecular signature associated with islet dysfunction

The aim of this study was to identify the molecular signatures that are predictive of nonfunctional islet preparations. We examined functional outcomes of six islet preparations accepted for research purposes from human donors. Islet were maintained on culture in M-SFM media for 7 to 14 days then transplanted into NOD-SCID mice. At the time of transplant, RNA was extracted from a second aliquot of cultured islets for expression analysis. We also performed gene expression analysis using high-density Affymetrix U133A GeneChips on these preparations. Among 1833 genes selected, hierarchical clustering was performed using the GeneSpring software package (Silicon Genetics, Inc.), where 754 genes (higher in nonfunctional) and 177 genes (lower in nonfunctional) were differentially expressed with tight pattern of expression. Islets with low functionality showed high relative levels of expression of hypoxia-induced genes and increased frequency of expression of proinflammatory and proangiogenic genes, such as vascular endothelial growth factor. Conversely, nonfunctional islets had low levels of insulin-processing message. The general profile of these low-functionality islets shows attempted recovery from hypoxic assault and little effort directed toward insulin production and secretion. Further identification of the molecular signature of nonfunctional islets could allow the development of a potency assay for human transplantation.