Transforming growth factor-beta (TGF-beta) and EGF promote cord-like structures that indicate terminal differentiation of fetal hepatocytes in primary culture.

When fetal hepatocytes were cultured in the presence of transforming growth factor-beta (TGF-beta 1) and epidermal growth factor (EGF), some morphological changes were observed. Under these conditions, cells migrated, from typical clusters that hepatocytes adopt in culture, to form elongated, cord-like structures similar to the hepatic acinus organization. Immunocytochemical analysis of these cells revealed high levels of albumin and cytokeratin 18, phenotypic markers of parenchymal hepatocytes. Although some of the cells in the cord-like structures presented a cortical ring distribution of F-actin filaments, the cord also presented thick peripheral bundles and cells of the tips showed thin stress fibers oriented to the cell edges, typical of a migratory phenotype. In addition to these morphological effects, flow cytometric analysis of the cells revealed a larger size, granularity and intracellular lipid content (as a parameter related to liver metabolic function), in TGF-beta + EGF-treated hepatocytes. Western blot analysis of the albumin levels revealed that both expression and secretion of albumin were increased in EGF + TGF-beta-treated cells. Finally, all these changes were coincident with an enhancement in the DNA-binding activity for hepatocyte nuclear factors (HNF1, HNF3, and HNF4), as revealed in gel-shift experiments with nuclear extracts. We conclude that a cooperative action between TGF-beta and EGF might modulate terminal maturation of fetal hepatocytes.