Expression of vimentin in proliferating and damaged bile ductules and interlobular bile ducts in nonneoplastic hepatobiliary diseases.

Biliary epithelial cells express characteristically cytokeratin in their cytoplasm in normal and diseased livers. The present study disclosed that vimentin was frequently expressed in the cytoplasm of proliferating and damaged bile ductules and interlobular bile ducts, while their normal counterparts were negative for vimentin. Although this expression itself seemed nonspecific to any of the hepatobiliary diseases examined, bile ductules and interlobular bile ducts were frequently positive in chronic cholestatic and necroinflammatory liver diseases. In biliary epithelial cells, vimentin was localized around the nucleus or in the subnuclear regions, when present. Immunoelectron microscopically, reaction products for vimentin and for cytokeratin were found on bundles of intermediate filaments in the cytoplasm of biliary epithelial cells. The former was found mostly in the paranuclear and subnuclear regions, while the latter detected around the desmosomes, in addition to the paranuclear cytoplasm. Vimentin and cytokeratin were also seen together under immunoelectron microscopy on the same intermediate filaments. It seems likely that aberrant expression of vimentin in bile ductules and interlobular bile ducts and heterogeneous antigenic expression of intermediate filaments in the same biliary epithelial cells may be related to proliferation of, reorganization of, or damage to the ductular and ductal biliary cells in a variety of hepatobiliary diseases.