Cytokeratin-positive hepatocytes in the hilar region: An immunohistochemical study using livers from fetuses and elderly individuals

Background/aims: Cytokeratin-positive primitive hepatocytes or hepatic progenitor cells have been described in the fetal ductal plate, as well as in the adult canals of Hering. We examined the fate of ductal plate cells in the hilar region of the liver. Methods: Using liver sections from 10 fetuses and 15 elderly cadavers, we performed immunohistochemistry for cytokeratins 14 and 19, smooth muscle actin, vimentin and CD34. Results: At 18 weeks of gestation, cytokeratin-positive cells were evident in the ductal plate and liver parenchyma, which were separated by a narrow space. At 25 weeks, most of these positive cells had disappeared, but the remnant cells were aligned along the parenchymal margins facing the hilar portal pedicle in addition to the canals of Hering in the peripheral portal pedicle. The gallbladder bed did not contain cytokeratin 19-positive cells. Notably, even livers in the elderly contained such marginal positive cells in the hilar region. These cells were negative for smooth muscle actin and CD34, but tended to be positive for vimentin. Conclusions: Cytokeratin-positive hepatic progenitor cells are likely to exist along the hilar portal pedicle even in adults. These hilar marginal hepatocytes seem to be derived not from the fetal ductal plate, but from the liver parenchyma.