TRANSFORMING-GROWTH-FACTOR-BETA (TGF-BETA) AND EGF PROMOTE CORD-LIKE STRUCTURES THAT INDICATE TERMINAL DIFFERENTIATION OF FETAL HEPATOCYTESIN PRIMARY CULTURE

When fetal hepatocytes were cultured in the presence of transforming g rowth factor-beta (TGF-beta 1) and epidermal growth factor (EGF), some morphological changes were observed. Under these conditions, cells mi grated, from typical clusters that hepatocytes adopt in culture, to fo rm elongated, cord-like structures similar to the hepatic acinus organ ization. Immunocytochemical analysis of these cells revealed high leve ls of albumin and cytokeratin 18, phenotypic markers of parenchymal he patocytes. Although some of the cells in the cord-like structures pres ented 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 pheno type, In addition to these morphological effects, flow cytometric anal ysis of the cells revealed a larger size, granularity and intracellula r lipid content (as a parameter related to liver metabolic function), in TGF-beta + EGF-treated hepatocytes, Western blot analysis of the al bumin levels revealed that both expression and secretion of albumin we re increased in FGF + TGF-beta-treated cells. Finally, all these chang es 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 cooperati ve action between TGF-beta and EGF might modulate terminal maturation of fetal hepatocytes. (C) 1998 Academic Press.