EFFECTS OF HEPATOCYTE GROWTH-FACTOR ON THE GROWTH AND METABOLISM OF HUMAN HEPATOCYTES IN PRIMARY CULTURE

The effect of recombinant human hepatocyte growth factor (h-rHGF), a potent mitogen for hepatocytes, was investigated in primary cultures of human hepatocytes. Here, we describe a series of experiments to iuvestigate the kinetics of its mitogenic action, as well as its metabolic effects on cultured human hepatocytes. The h-rHGF is a potent signal for initiating DNA synthesis in human hepatocytes, with maximal stimulatory effects at 10 ng/mL (0.1 pmol/L,). The kinetics of DNA synthesis showed a lag of about 48 to 72 hours, followed by a maximum at 96 hours. At least 48 hours of continuous exposure to h-rHGF are required to initiate DNA synthesis in quiescent human hepatocytes, Cell cycle analysis by flow cytometry showed that most of quiescent 2c cells have left G0/G1 and entered the cell cycle (S and G2/M phases) by 96 hours of continuous exposure to h-rHGF. When compared with other growth factors, h-rHGF was a much more potent mitogen. The effects of 10 ng/mL (0.1 pmol/L) h-rHGF on DNA synthesis were only achieved by 1.5 pmol/L epidermal growth factor (EGF), 0.1 mu mol/L insulin, or 1 mu mol/L glucagon. It is noteworthy that the, effect of h-rHGF was potentiated by glucagon but not by insulin or EGF. The stimulatory effect of HGF on DNA synthesis was gradually inhibited by h-rHGF transforming growth factor beta (TGF-beta) in the range 1 to 10 ng/ml. The HGF also influenced the expression of other hepatic genes. This mitogenic factor stimulated the synthesis of the negative acute-phase plasma protein, albumin, and inhibited the synthesis of the positive one, alpha(1)-antichymotrypsin, whereas it moderately influenced the. synthesis of fibrinogen, Although glucagon per se had no effects on cell growth, the synergism between glucagon and h-rHGF could be of relevance facilitating the mobilization of glycogen and the stimulation of human hepatocyte growth.