Fibronectin regulates morphology, cell organization and gene expression of rat fetal hepatocytes in primary culture

Background/Aims: The extracellular matrix regulates hepatic development and regeneration, modulating the maintenance of liver architecture in the differentiated state. The aim of this work was to analyze how different extracellular matrix molecules modulate fetal hepatocyte morphology, growth and differentiation. Methods: We cultured fetal hepatocytes either on plastic or on different extracellular matrix proteins, i.e., collagen I, fibronectin or E-C-L (entactin-collagen IV-laminin) and we analyzed cell attachment, morphological organization, proliferative response and gene expression. Results: Cell attachment was increased by all the extracellular matrix proteins to a similar extent. However, only fibronectin facilitated the formation of elongated cord-like structures, reminiscent of liver plate organization. Immunocytochemical analysis of the cells in these structures revealed high levels of albumin and cytokeratin 18, phenotypical markers of parenchymal hepatocytes. Fibronectin did not block the mitogenic stimuli induced by epidermal growth factor in these cells and the elongated structures appeared either in the absence or in the presence of the mitogen. Cells cultured on fibronectin, regardless of whether epidermal growth factor was present or not, also presented the maximal levels of expression for liver specific genes, such as albumin or alpha-fetoprotein. This expression was coincident with an increased expression of hepatocyte nuclear factor (HNF)-4 and a higher HNF-1α/HNF-1β ratio, when compared with those cells that were cultured on collagen or E-C-L extracellular matrix. Conclusions: These results suggest that fibronectin might play a differential role, as compared to other extracellular matrix proteins, in fetal hepatocyte organization and gene expression.