Hepatocytes transdifferentiate into biliary epithelial cells following toxicant‐induced biliary epithelium injury

Abstract

Previously we have reported that rats treated with a biliary epithelium (BE) toxicant, methylene dianiline (DAPM), followed by bile duct ligation exhibit extensive transdifferentiation of hepatocytes to biliary epithelial cells. To further characterize the hepatocyte to BE transdifferentiation, we treated male F344 rats with two doses of DAPM (50 and 75 mg/kg, ip) and studied the dynamics of injury and regenerative changes in the liver over a time course of 0 to 15 days. DAPM treatment resulted in dose dependent BE injury as indicated by increase in serum bilirubin and GGT levels. H&E staining revealed massive BE necrosis with extensive inflammation and portal triad edema. PCNA immunohistochemical analysis indicated significant proliferation of BE cells, which continued till day 7 in the high (75 mg/kg) dose. In addition to BE cells, periportal hepatocytes exhibited PCNA positivity indicating increase in hepatocyte proliferation. The periportal hepatocytes also stained positive for AE1/AE3, markers of BE. To further study which growth factor can stimulate transdifferentiation, primary rat hepatocytes were cultured in roller bottles and were stimulated with HGF, EGF, FGF, PDGF, VEGF, SCF, MSP alone, as well as HGF and EGF in combination. None of the growth factors tested except HGF and EGF alone, and HGF and EGF in combination, stimulated formation of bile duct-like structures. Western blot analysis revealed no change in EGFR. Taken together, these data provide evidence for hepatocyte to BE transdifferentiation after DAPM-induced injury and indicate involvement of HGF and EGF-stimulated signaling in hepatocyte transdifferentiation.