OV-6 EXPRESSION IN PROLIFERATING HUMAN NORMAL AND DISEASED BILIARY EPITHELIAL CELLS IN VITRO

Abstract

144 The monoclonal antibody, OV-6, identifies cells in rodent models which proliferate in response to liver injury and or carcinogens. These cells, called oval cells, are thought to derive from a stem cell compartment and may differentiate into either biliary epithelial cells or hepatocytes in response to injury. We have previously shown that OV-6 is expressed in a sub-population of biliary epithelial cells, peri-portal hepatocytes and a small proportion of intensely stained cells with oval-like cell features in human diseased liver tissue sections. In contrast, OV-6 staining was absent from normal liver tissue sections. In this study, the staining characteristics of OV-6 on isolated human biliary epithelial cells have been investigated in vitro and compared to the biliary cell marker cytokeratin 19 (CK-19) during growth. Biliary epithelial cells were isolated from normal paediatric donor liver (n=6) and cholestatic diseased paediatric explants (n=4). Cells were maintaned in culture for 14 days and stained at a range of time points (2 - 14 days). Biliary epithelial cells from both normal and diseased livers were strongly positive for CK-19 throughout the culture period. In contrast, in biliary epithelial cells isolated from normal liver, OV-6 demonstrated faint staining at day 2 but increased in intensity with further culture. Cells isolated from diseased tissue were positive for OV-6 at all time points tested, although intensity was weaker compared to CK-19. In tissue sections from normal liver, epithelial cells are largely quiescent and are negative for OV-6 staining, whereas under culture conditions when cells are actively proliferating they are positive for OV-6. It is suggested that OV-6 expression is associated with proliferating cells and may reflect hepatic regeneration following injury.