IMMUNOLOCALIZATION OF PUTATIVE HUMAN LIVER PROGENITOR CELLS IN LIVERSFROM PATIENTS WITH END-STAGE PRIMARY BILIARY-CIRRHOSIS AND SCLEROSINGCHOLANGITIS USING THE MONOCLONAL-ANTIBODY OV-6

The term oval cell describes small cells with oval nuclei that arise i n. the periphery of the portal tracts in rat models of hepatocarcinoge nesis and injury and can differentiate into either hepatocytes or bile duct cells, ie, are bipotential. The presence of such cells in human liver is controversial. Here, immunolocalization of OV-6 and two bilia ry markers, cytokeratin 19 (CK-13) acid human epithelial antigen 125 ( HEA-125) is compared in normal adult human livers and in primary bilia ry cirrhosis (PBC) and primary sclerosing cholangitis (PSC) liver sect ions. CK-19 and HEA-125 stained bile ducts and ductules in normal Live r as well as proliferating ductular structures in diseased livers. OV- 6 did not label ducts or ductules in normal liver, but in PBC and PSC stained numerous proliferating ductular and periductular cells and lob ular hepatocytes. In PBC, discrete OV-6-positive cells with a mature b iliary-cell-like morphology were seen integrated into some intact bite ducts as well as occasional small immature oval-like cells. In additi on, in PSC, hepatocytes in regenerating lobules were also strongly sta ined with OV-6, and on close inspection, in both PBC and PSC, oval cel ls and small hepatocytes at the margins of the lobules were strongly l abeled In contrast to the rat liver, OV-6 and CK-13 staining did not a lways co-localize. It is proposed that the small OV-6-positive oval ce lls are analogous to those seen in rat models and may represent human Liver progenitor cells that may differentiate into OV-6-positive ducta l cells or lobular hepatocytes.