Hormonally induced formation of extracellular biomatrix in cultured normal and neoplastic liver cells. Effect of dexamethasone.

We have examined by scanning electron microscopy the cell surface of rat hepatocytes (HEP), propagable liver epithelial (CE) cells, Morris # 7777 and # 7795 hepatoma (MH) cells at different times after seeding onto fibronectin-precoated substratum in presence of a defined medium. Upon seeding, HEP exhibited numerous microvilli and at later times, the cells flattened and lost most of these structures. When HEP were cultured in presence of dexamethasone (DEX), numerous microfibrils were observed extending into the substratum and on the cells and formed elaborate extracellular matrices. By indirect immunofluorescence we have demonstrated that these extracellular matrices are composed of fibronectin and collagens (type I, III). In contrast to HEP, sparse or confluent CE cells showed few microvilli and only very low amount of extracellular matrices were observed at confluency, even in presence of DEX. Growing or confluent MH # 7777 cells exhibited some microvilli while MH # 7795 cells showed a lower number of these surface structures at confluency. These hepatoma cell lines produced little extracellular matrices in absence or presence of DEX. Tyrosine aminotransferase (TAT), a liver specific intracellular protein, was inducible in HEP and MH but not in CE cells. Thus, these data demonstrate that the hormonal induction of a liver specific function is accompanied by the production of extracellular matrix only in the case of normal hepatocytes (HEP), but not in the case of cancerous (MH) or epithelial (CE) cells.