EPITHELIAL-MESENCHYMAL TRANSITION IN CULTURED NEONATAL HEPATOCYTES

When hepatocyte-enriched fractions from neonatal rat livers were cultu red for different times in the absence of added growth factors, a popu lation of highly proliferating and migrating fibroblastlike cells appe ared. Double immunofluorescence with antibodies to cytokeratin and to vimentin showed a progressive reduction in the number of cytokeratin-p ositive cells parallel to an increase in the vimentin-positive cells. Some cells with transitional epithelial or migrating morphology coexpr essed both intermediate filament proteins. Immunofluorescence with ant ibodies against hepatocyte differentiation markers showed that shortly after seeding most of the cells were positive to anti-albumin antibod ies, but after 1 week in culture, only 10% were positive. Cells presen ting albumin and cytokeratin appeared morphologically epithelial. Fibr oblastlike cells were not positive for albumin, but some cells with tr ansitional epithelial morphology presented some labels for albumin and for vimentin, Immunofluorescence with antibodies to glutathione-S-tra nsferase subunit Pi and vimentin showed that many fibroblastlike cells were positive for both markers, some of them binucleate, Cultures per formed in the presence of dexamethasone, absence of arginine, or on co llagen type I matrix had no effect on the behavior of neonatal hepatoc ytes. The appearance of fibroblastlike cells was ontogenically regulat ed because the highest increase in the percentage of vimentin-positive cells was observed in cell cultures from livers of 7- and 15-day-old animals. These data provide evidence that neonatal hepatocytes in cult ure have the potential to dedifferentiate by epithelial-mesenchymal tr ansition and contribute to an understanding of hepatic growth developm ent.