Functional characterization of CD49f⁺ hepatic stem/progenitor cells in adult mice liver

Hepatic Stem/progenitor cells (HSPCs) have gained a large amount of interest for treating acute liver disease. However, the isolation and identification of HSPCs are unclear due to the lack of cell-specific surface markers. To isolate adult HSPCs, we used cell surface-marking antibodies, including CD49f and Sca-1. Two subsets of putative HSPCs, Lin^-CD45^-Sca-1^-CD49f⁺ (CD49f⁺) and Lin^-CD45^-Sca-1⁺CD49f^- (Sca-1⁺) cells, were isolated from adult mice liver by flow cytometry. Robust proliferative activity and clonogenic activity were found in both CD49f⁺ and Sca-1⁺ cells through colony-forming tests and cell cycle analyses. Immunofluorescence staining revealed that CD49f⁺ cells expressed ALB and CK-19 while Sca-1⁺ cells expressed only ALB, indicating that CD49f⁺ cells were bipotential and capable of differentiating into hepatocyte and cholangiocyte. Consequently, PAS stain showed that differentiated CD49f⁺ and Sca-1⁺ cells synthesised glycogen, indicating they could differentiate into functional hepatocytes. mRNA expression profile indicated that both CD49f⁺ and Sca-1⁺ cells showed differential expression of genes that are associated with liver progenitor function such as Sox9 and EpCam. Moreover, two subsets of putative HSPCs were activated by DDC and we found that their abundance and proliferation increased with age. In summary, we hypothesized that CD49f⁺ cells were a type of potential HSPCs and may be utilised for clinical stem cell therapy.