ABSTRACT
We have isolated a novel progenitor cell population from adult rat pancreatic ducts, termed pancreatic-derived progenitor cells (PDPCs). Here, we report the in vitro culture, selection, and characterization of Thy1.1-positive and Thy1.1-negative PDPC subpopulations. These cells exhibit bipotentiality for differentiation into both pancreatic and hepatic cell types. Significantly, they express Pdx-1. Using a serum-free FGF-4-containing differentiation protocol, we have observed a time course of both morphological and gene expression changes indicative of hepatic lineage differentiation for the Thy1.1-positive subpopulation. These cells express albumin and store glycogen, typical features of mature hepatocytes. The Thy1.1-positive subpopulation could also readily be induced to differentiate into a pancreatic lineage with characteristic morphological changes resulting in three-dimensional islet-like structures and the transcriptional expression of insulin and glucagon in addition to Pdx-1. No morphological evidence of islet-like clusters was observed using the Thy1.1-negative population. However, Thy1.1-negative cells grown in pancreatic differentiation medium did show insulin gene transcription. Glucagon was not expressed in the undifferentiated Thy1.1-negative cells, nor was it induced in vitro after differentiation. The detection of Pdx-1 transcriptional expression in both populations indicates their potential as a novel source of non-beta-cell-derived insulin.
