OBJECTIVETo investigate the transformative potential of hepatic progenitor cells to differentiate into liver stem cells using a normal adult mouse system and to determine the effects of HBx protein in these liver stem cells' differentiation into hepatic cells.

METHODSHepatic progenitor cells were obtained from mice by means of an optimized two-step digestion and perfusion method followed by joint differential centrifugation and density gradient centrifugation. Transformation of the hepatic progenitor cells into liver stem cells was observed by immunofluorescent detection of CD 133, EPCAM, CD49f and CK19. Differentiation of the resultant liver stem cells into hepatic cells and bile duct epithelial cells was observed after DMSO addition by Periodic Acid-Schiff (PAS) staining followed by cell immunofluorescence and flow cytometry. To determine the effects of HBx on these liver stem cells' ability to differentiate into hepatic cells, cell transfection was used followed by observation of morphology and proliferation capacity.

RESULTSCell viability of the isolated hepatic progenitor cells was 78.67+/-4.04%. Stimulation with EGF and collagen led to growth of some of the paving-stone shaped cells attached to the hepatic progenitor cells which had gathered into spherical clumps, as is the nature of stem cells. The liver stem cells showed high expression of CD133, CD49f and CK19, and low expression of EPCAM. Under the effect of DMSO, the liver stem cells differentiated into hepatocytes and bile duct epithelial cells. After HBx transfecfion, the liver stem cells maintained the characteristic shape of stem cells and showed enhanced proliferation.

CONCLUSIONEPCAM-positive adult hepatic progenitor cells can transform into liver stem cells.The HBx protein may play an important role in maintaining the stability of liver stem cells in the adult mouse.