AIM: To detect the markers of oval cells in adult rat liver andto enrich them for further analysis of characterization in vitro.METHODS: Rat model for hepatic oval cell proliferation wasestablished with 2-acetylaminofluorene and two third partialhepatectomy (2-AAF/PH).Paraffin embedded rat liversections from model (11 d after hepatectomy) and controlgroups were stained with HE and OV6,cytokeratin19 (CK19),albumin,alpha fetoprotein (AFP),connexin43,and c-kitantibodies by immunohistochemistry.Oval cell proliferationwas measured with BrdU incorporation test.C-kit positiveoval cells were enriched by using magnetic activated cellsorting (MACS).The sorted oval cells were cultured in a lowdensity to observe colony formation and to examine theircharacterization in vitro by immunocytochemistry and RT-PCR.RESULTS: A 2-AAF/PH model was successfully establishedto activate the oval cell compartment in rat liver.BrdUincorporation test of oval cell was positive.The hepatic ovalcells coexpressed oval cell specific marker OV6,hepatocyte-marker albumin and cholangiocyte-marker CK19.They alsoexpressed AFP and connexin 43.C-kit,one hematopoieticstem cell receptor,was expressed in hepatic oval cells athigh levels.By using c-kit antibody in conjunction with MACS,we developed a rapid oval cell isolation protocol.The sortedcells formed colony when cultured in vitro.Cells in the colonyexpressed albumin or CK19 or coexpressed both and BrdUincorporation test was positive.RT-PCR on colony showedexpression of albumin and CK19 gene.CONCLUSION: Hepatic oval cells in the 2-AAF/PH modelhad the properties of hepatic stem/progenitor cells.UsingMACS,we established a method to isolate oval cells.Thesorted hepatic oval cells can form colony in vitro whichexpresses different combinations of phenotypic markers andgenes from both hepatocytes and cholangiocyte lineage. AIM: To detect the markers of oval cells in adult rat liver and to enrich them for further analysis of characterization in vitro. METHODS: Rat model for hepatic oval cell proliferation wasestablished with 2-acetylaminofluorene and two third partial hepatectomy (2-AAF / PH). Paraffin embedded rat liversections from model (11d after hepatectomy) and controlgroups were stained with HE and OV6, cytokeratin 19 (CK19), albumin, alpha fetoprotein (AFP), connexin43, and c- kitantibodies by immunohistochemistry. Oval cell proliferation was measured with BrdU incorporation The sorted oval cells were cultured in a low density to observe colony formation and to examine their characterization in vitro by immunocytochemistry and RT-PCR .RESULTS: A2-AAF / PH model was successfully established to activate the oval cell compartment in rat liver. BrdUincorporation test of oval cell was positive. The hepatic oval cells coexpressed oval cell specific marker OV6, hepatocyte-marker albumin and cholangiocyte-marker CK 19. They alsoexpressed AFP and connexin 43. C-kit, one hematopoieticstem cell receptor, was expressed in hepatic oval cells athigh levels. By using c-kit antibody in conjunction with MACS , we developed a rapid oval cell isolation protocol. The sorted cells were colony when cultured in vitro. Cells in the colonyexpressed albumin or CK19 or coexpressed both and BrdUincorporation test was positive. RT-PCR on colony show expression of albumin and CK19 gene.CONCLUSION: Hepatic oval cells in the 2-AAF / PH modelhad the properties of hepatic stem / progenitor cells. Using MACS, we established a method to isolate oval cells. Thehes hepatic oval cells can form colony in vitro whichexpresses different combinations of phenotypic markers and genes from both hepatocytes and cholangiocyte lineage.