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

Background/Aims: The extracellular matrix regulates hepatic development and regeneration, modulating the maintenance of liver architecture in the diff erentiated state. The aim of this work was to analyze how different extrace llular matrix molecules modulate fetal hepatocyte morphology, growth and di fferentiation. Methods: We cultured fetal hepatocytes either on plastic or on different ex tracellular matrix proteins, i,e,, collagen I, fibronectin or E-C-L (entact in-collagen IV-laminin) and we analyzed cell attachment, morphological orga nization, proliferative response and gene expression. Results: Cell attachment was increased by all the extracellular matrix prot eins to a similar extent, However, only fibronectin facilitated the formati on of elongated cord-like structures, reminiscent of liver plate organizati on. Immunocytochemical analysis of the cells in these structures revealed h igh levels of albumin and cytokeratin 18, phenotypical markers of parenchym al hepatocytes. Fibronectin did not block the mitogenic stimuli induced by epidermal growth factor in these cells and the elongated structures appeare d either in the absence or in the presence of the mitogen, Cells cultured o n fibronectin, regardless of whether epidermal growth factor was present or not, also presented the maximal levels of expression for liver specific ge nes, such as albumin or alpha-fetoprotein, This expression was coincident w ith an increased expression of hepatocyte nuclear factor (HNF)-4 and a high er HNF-1 alpha/HNF-1 beta ratio, when compared with those cells that were c ultured on collagen or E-C-L extracellular matrix, Conclusions: These results suggest that fibronectin might play a differenti al role, as compared to other extracellular matrix: proteins, in fetal hepa tocyte organization and gene expression.