Cellular interactions promote tissue‐specific function, biomatrix deposition and junctional communication of primary cultured hepatocytes

Hepatocytes, prepared from normal adult rat liver, were seeded onto a collagen substratum and cultured alone or in the presence of rat liver endothelial cells. When hepatocytes were cultured alone in a hormonally defined serum‐free medium, decreased albumin production and rapid morphological deterioration of bile canaliculi structures and gap junctions occurred within 4 to 5 days. In contrast, hepatocytes cocultured with liver mesenchymal cells remained morphologically intact and biochemically functional for at least 4 weeks. They reorganized into small islands, continued to secrete high levels of albumin, did not express α‐fetoprotein (a fetal marker), and remained strongly dye coupled. All of the hepatocytes synthesized albumin and retained their gap junctional channels. No junctional communication was observed between hepatocytes and endothelial cells. Long fibers containing fibronectin, Type I collagen and laminin distributed over the hepatocytes were induced in coculture but never appeared in hepatocytes cultured alone. Moreover, supplementation of the hormonally defined medium with phenobarbital and dimethyl sulfoxide, both of which improve the life span and functional activities of cultured hepatocytes, failed to induce reticulin fiber formation in pure culture of hepatocytes. The modulation of albumin secretion, biomatrix deposition and junctional communication observed in hepatocytes cultured with sinusoidal liver cells was also obtained when hepatocytes were in association with various epithelial or mesenchymal cells [rat liver epithelial cells (T51B), mouse embryonic fibroblasts (NIH 3T3), human or rat dermal fibroblasts and bovine aorta endothelial cells (AG 4762)].