Regulation of cultured rat hepatocyte proliferation by stellate cells

This study using primary culture models was aimed to reveal the stellate cell-derived factors that regulate hepatocyte proliferation.

Rat hepatocytes and stellate cells were cultured in serum-free Williams-E medium. We prepared hepatocyte mono-culture 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.). The change in the number and the DNA synthesis of hepatocytes was evaluated.

The number of hepatocytes decreased to 76% of the original number after 48 h of starting mono-culture, while it remained at 106% in mixed co-culture (Co-mix.) and increased to 135% in separated co-culture (Co-sep.). The hepatocyte DNA synthesis was enhanced by carbenoxolone in Co-mix. and reduced by NK1 in each co-culture. PD153035 had no effect. Heparitinase-I (20 mU/ml) and sodium chrolate (25 mM) reduced the hepatocyte DNA synthesis in Co-sep. to 71.8 and 61.6%, respectively. Activation of mitogen-activated protein kinase was induced in hepatocytes stimulated by conditioned mediums.

Hepatocyte proliferation was stimulated in the presence of stellate cells through hepatocyte growth factor, extracellular heparan sulfate (HS), and HS proteoglycan, and might be negatively regulated by gap junction-dependent mechanism.