Diversity of hepatic stem cells in the fetal and adult liver.

The liver is an organ with tremendous regenerative capacity. Hepatic stem cells, identified by flow cytometric sorting and single cell-based assays as c-Met (+)CD49f (+/low)c-Kit (-)CD45 (-)TER119 (-) cells in murine fetal livers, possess multilineage differentiation potential and self-renewing capability. These cells can differentiate in vitro as well as in vivo into some epithelia capable of reconstituting tissues within the liver, pancreas, and intestine following appropriate transplantation. The isolated fetal hepatic stem cells are also characterized by the ability to maintain their self-renewal capability in the developing liver. Thus, these cells may be ideal vehicles for delivering therapeutic genes to the liver. We also examined the relationship between fetal hepatic stem cells and hepatic oval cells in the adult liver. These two subtypes shared both multipotential capabilities of differentiation and surface marker expression profiles, suggesting that hepatic oval cells are probably the progeny of fetal hepatic stem cells. We also address the related topics of hepatocyte repopulation, exogenous hepatic stem cells, and transdifferentiation. Topics ranging from the fundamental properties and comprehensive descriptions of hepatic stem cells to current progress in the field are discussed in this brief article and our recent studies are addressed.