Induced Cell Clustering Enhances Islet β Cell Formation from Human Cultures Enriched for Pancreatic Ductal Epithelial Cells

Abstract

A better understanding of the culture conditions that stimulate in vitro β-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 β cells. While the initial epithelial cell cultures were devoid of any β 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 ∼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 (r² = 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 β cells in vitro.