Many organs depend on highly regenerative stem cells for tissue renewal after injury or during normal turnover. During embryonic development a common endodermal pre-cursor/stem cell gives rise to both the hepatic and pancreatic parenchyma, including the ductular, exocrine and endocrine components of the pancreas. The isolation and purification of this hepato-pancreatic stem cell would greatly advance the understanding of the biology of the pancreas and possibly generate a therapeutic agent for the treatment of diabetes. The hematopoietic stem cell was identified by a biological assay, the ability to reconstitute the blood and immune system of a host after lethal irradiation. Unfortunately, a transplantation based in vivo repopulation assay for pancreatic stem cells has not been developed. However, several independent lines of evidence suggest that adult mouse pancreas continues to contain cells which can give rise to hepatocytes under certain experimental conditions. The fumarylacetoacetate hydrolase knockout mouse represents a robust liver repopulation assay in which permits the identification of cells that have the capacity to regenerate the liver. Preliminary data have shown that adult murine pancreas contains cells, which have high liver repopulating capacity (pancreatic liver stem cells). We hypothesize that the repopulating activity is a primitive endodermal precursor capable of giving rise to multiple cell types including hepatocytes, bile ducts, pancreatic ducts, acinar cells and endocrine cells. This application pertains to the use of liver repopulation as a surrogate assay for primitive murine pancreatic stem cells. The assay will be used to develop methods for their optimal isolation. Monoclonal antibodies useful for FACS sorting of pancreatic cells will be generated. We will apply cell-sorting methods to enrich pancreatic liver stem cells.
