OBJECTIVELiver regeneration occurs through hepatocytes after acute liver injury. However, severe liver injury activates bipotential oval cells from canals of Hering which can differentiate into hepatocytes and biliary epithelial cells. Most models of oval cell activation have employed potential carcinogens to inhibit hepatocyte replication in the face of a regenerative stimulus. Oval cells must be able to withstand the toxic milieu of the damaged liver. ATP binding cassette transporters are cytoprotective efflux pumps that may contribute to the protection of these cells. The aim of this study was to determine the ABC transporter expressions in hepatic oval cells.

METHODSA rat model was established by feeding 2-acetylaminofluorene combined with partial hepatectomy to activate hepatic oval cells. Oval cells were isolated and purified using selective enzymatic digestion and density gradient centrifugation from the heterogeneous hepatic cell population. The expressions of ABC transporter gene, including MDR1, MRP1 and Bcrp1, in isolated hepatic oval cells and hepatocytes were measured by quantitative real-time reverse transcription-polymerase chain reaction and those in rat liver tissues were measured by immunohistochemistry.

RESULTSCompared to those in the rat hepatocytes, mRNA expressions of the genes encoding MDR1, MRP1 and Bcrp1 were increased up to 9-, 1.5- and 13.8-folds in hepatic oval cells. Immunohistochemical staining of rat liver slides demonstrated that the expression of MDR1 proteins was found around periportal areas, and Bcrp1 protein was found located on cell membranes.

CONCLUSIONHepatic oval cells express high levels of the ABC transporter gene that may have cytoprotective functions during severe hepatotoxicity.