Apoptosis in dissociation between DNA synthesis and cellular functions of activated hepatic stellate cells - A study with carbon tetrachloride-induced rat liver injury

It is widely believed that DNA synthesis and expressions of smooth muscle a actin and TGF-beta are all together increased in activated hepatic stellat e cells both in vitro and in vivo. Our previous reports disclosed that thes e increases did not always coexist under experimental conditions. Liver nec rosis was induced in rats by oral administration of carbon tetrachloride. H epatic stellate cells were isolated from these rats 2 days later. When thes e cells were cultured on plastic dishes for 3 days, they showed marked DNA synthesis and smooth muscle alpha actin and TGF-beta mRNA expressions asses sed by H-3-thymidine incorporation and Northern blotting, respectively. In the cells further cultured for 7 days, the DNA synthesis was decreased, whe reas both smooth muscle cy actin and TGF-beta mRNA expressions were increas ed, compared to the cells cultured for 3 days. The cells cultured for 10 da ys showed apoptotic nuclei positive for nick-end labeling, and DNA extracte d from the cells revealed laddering patterns on agarose gels by electrophor esis. Apoptotic nuclei were also immunohistochemically found in stellate ce lls in the liver of rats 4 days after the intoxication We conclude that apo ptosis developed in activated hepatic stellate cells both in vitro and in v ivo, and this may contribute to the discrepancy between DNA synthesis and c ellular functions of the cells. (C) 2001 Academic Press.