Local increase of beta 1-integrin expression in cocultures of immortalized hepatocytes and sinusoidal endothelial cells.

The expression and spatial arrangement of beta 1-integrins was determined on two immortalized liver cell lines held in coculture, namely the epithelial cell line mHepR1 and a sinusoidal endothelial cell line. On mHepR1 cells the distribution of beta 1-integrins was restricted to the basolateral plasma membrane domains, a staining pattern that is typical of polarized epithelial cells. On the endothelial cell line the beta 1-integrins were distributed all over the cell surface. In coculture the endothelial cells tended to cover over the epithelial cells. Epithelial cells located in their vicinity exhibited an increased staining of beta 1-integrins at basolateral plasma membrane domains, which was most prominent with regard to the alpha 2-subunit. When mHepR1 cells were cultivated on various types of extracellular matrix also synthesized by the endothelial cells only collagen IV was found to increase the intensity of beta 1-integrin expression at the cell surface. The results indicate that beta 1-integrin expression in epithelial cell colonies can locally be modulated by interactions with non-parenchymal cells. In addition, the data suggest that mHepR1 cells may be a favorable system for analyzing basic functions of beta 1-integrins in polarized epithelial cells.