Clonal expansion of hepatic progenitor cells and differentiation into hepatocyte-like cells.

Hepatic progenitor cells (HPCs) in adult liver are promising for treatment of liver diseases. A biliary-derived HPC population in adult mice has been characterized by co-expression of stem cell marker Sry (sex determining region Y)-box 9 (SOX9) and biliary marker cytokeratin 7 (CK7). However, isolation of these HPCs in adult healthy liver without any selection procedures remains a big challenge in this field. Here, by establishing a simple and efficient method to isolate and expand the CK7(+)SOX9(+) HPCs in vitro as clones, we acquired a stable and largely scalable cell source. The CK7(+)SOX9(+) progenitor cells were then further induced to differentiate into hepatocyte-like cells with expression of mature hepatocyte markers albumin (Alb) and hepatocyte nuclear factor 4 alpha (HNF4 alpha), both in vitro and in vivo in the presence of hepatocyte growth factor (HGF) and fibroblast growth factor 9 (FGF9). Furthermore, we found that the HPCs are highly responsive to transforming growth factor-beta (TGF-beta) signals. Collectively, we identified and harvested a CK7(+)SOX9(+) progenitor cell population from adult mouse liver by a simple and efficient approach. The exploration of this HPC population offers an alternative strategy of generating hepatocyte-like cells for cell-based therapies of acute and chronic liver disorders.