Reduced growth capacity of hepatocytes from c-myc and c-myc/TGF-alpha transgenic mice in primary culture.

We have previously shown that coexpression of c-myc and TGF-alpha in the liver results in accelerated replicative senescence and promotes tumor development in young adult transgenic mice. Here we describe the characteristics of hepatocyte proliferation in primary cultures established from 10-week-old control, c-myc and c-myc/TGF-alpha transgenic mice. A variety of cellular and functional changes occurred in the transgenic livers at this age including enhanced polypoidization and impairment of hepatic functions. Control mouse hepatocytes demonstrated a high level of DNA synthesis in serum-free medium with a maximum at day three in culture at which time 70% of the cells were in S phase. In contrast, DNA synthesis peaked one day later and was reduced by 50% in the cultured c-myc and c-myc/TGF-alpha hepatocytes. Also, higher frequency of apoptosis was observed in the transgenic hepatocytes. However, in hepatocytes isolated from c-myc/TGF-alpha mice, which show early appearance of preneoplastic lesions in vivo, the DNA synthesis continued for 6 days in culture in contrast to a sharp decrease in the labeling index of control and c-myc hepatocytes after 3-4 days in culture. The results suggest that proliferative features of the transgenic hepatocytes in vitro reflect the general properties of these cells in vivo and thus may provide a model for studies on senescence and transformation of hepatocytes.