Induced cell clustering enhances islet beta cell formation from human cultures enriched for pancreatic ductal epithelial cells

A better understanding of the culture conditions that stimulate in vitro beta-cell differentiation from islet precursors would be useful for optimizing the production of tissue-engineered islets. In this study, high- and low-adherent substrates and high- and low-serum media were used to control the clustering of human pancreatic ductal epithelial cells and to determine its effect on their transdifferentiation to beta cells. While the initial epithelial cell cultures were devoid of any beta cells as assessed by dithizone staining, dithizone+ cells were generated during the next 3 weeks under all culture conditions. Although the rate of transdifferentiation was low, a approximately 4-fold greater number and percentage of dithizone+ cells were generated following 23-24 days of culture in the least adherent conditions (low-serum medium, low-adherent substrate), which stimulated cell clustering to the highest degree. Insulin immunohistochemistry data correlated well with the dithizone data (r(2) = 0.99), evidence that dithizone is a reliable measure of insulin+ cells. The preferential distribution of the dithizone+ cells to regions of cell aggregation and the increased efficiency of transdifferentiation in conditions that promote cell clustering suggest that cell-cell interactions and/or cell shape changes are important to the transdifferentiation of adult pancreatic ductal epithelial cells to beta cells in vitro.