Rat stellate cells regulate proliferation of rat hepatocytes in culture

This study was aimed to reveal the stellate cell derived factors that regulate hepatocyte proliferation in culture. Rat hepatocytes and stellate cells were cultured in serum free Williams-E medium. We used hepatocyte monoculture and two different co-cultures of hepatocytes and stellate cells ; 1) co-culture on the same surface (Co-mix.) and 2) co-culture without contact between hepatocytes and stellate cells using a culture insert (Co-sep.) . Changes in the number and the DNA synthesis of hepatocytes was estimated. Although the number of hepatocyte decreased to 76% of the original at 48 h after starting mono-culture, it was kept at 106% in Co-mix and increased to 135% in Co-sep. The hepatocyte DNA synthesis was enhanced by carbenoxolone, gap junction blocker, in Co-mixo and reduced by NK 1 in each coculture. PD 153035, an EGF receptor specific inhibitor, had no effect. HeparitinaseI (20 mU/ml) and sodium chrolate (25 mM) reduced the hepatocyte DNA synthesis in Co-sepo to 71%. Activation of MAPK was induced in hepatocytes stimulated by conditioned mediums. These results indicated that hepatocyte proliferation was stimulated in the presence of stellate cells through HGF, extracellular heparan sulfate, and heparan sulfate proteoglycan, and might be negatively regulated by gap junction dependent mechanism.