β-Cell differentiation of human pancreatic duct-derived cells after in vitro expansion

β-Cell replacement therapy is a promising field of research that is currently evaluating new sources of cells for clinical use. Pancreatic epithelial cells are potent candidates for β-cell engineering, but their large-scale expansion has not been evidenced yet. Here we describe the efficient expansion and β-cell differentiation of purified human pancreatic duct cells (DCs). When cultured in endothelial growth-promoting media, purified CA19-9(+) cells proliferated extensively and achieved up to 22 population doublings over nine passages. While proliferating, human pancreatic duct-derived cells (HDDCs) downregulated most DC markers, but they retained low CK19 and SOX9 gene expression. HDDCs acquired mesenchymal features but differed from fibroblasts or pancreatic stromal cells. Coexpression of duct and mesenchymal markers suggested that HDDCs were derived from DCs via a partial epithelial-to-mesenchymal transition (EMT). This was supported by the blockade of HDDC appearance in CA19-9(+) cell cultures after incubation with the EMT inhibitor A83-01. After a differentiation protocol mimicking pancreatic development, HDDC populations contained about 2% of immature insulin-producing cells and showed glucose-unresponsive insulin secretion. Downregulation of the mesenchymal phenotype improved β-cell gene expression profile of differentiated HDDCs without affecting insulin protein expression and secretion. We show that pancreatic ducts represent a new source for engineering large amounts of β-like-cells with potential for treating diabetes.