Sustained proliferation of PDX-1(+) cells derived from human islets

Ex vivo expansion of human beta-cells is an important step toward the devel opment of cell-based insulin delivery systems in type 1 diabetes. Here, we report that human pancreatic endocrine cells can be expanded through 15 cel l doublings in vitro for an estimated total 30,000-fold increase in cell nu mber. mie believe that the cells resulting from these cultures are of beta- cell origin, since they uniformly express the transcription factor PDX-1 (S TF-1, IDX-1, IPF-1), which is initially seen only in cells positive for ins ulin and negative for the ductal cell marker cytokeratin (CK)-19. To rule o ut the possibility that PDX-1 expression might be induced by the culture co nditions used here, cells from isolated human pancreatic ducts were culture d under the same conditions as the islet cells. Cells in these cultures exp ressed CK-19 but not PDX-1. Although the expanded beta-cells continued to e xpress PDX-1, insulin expression was lost over time. Whether reexpression o f islet-specific genes in vitro is essential for successful cell transplant ation remains to be determined.