COMPARATIVE-ANALYSIS OF MITOGENIC AND MORPHOGENIC EFFECTS OF HGF AND EGF ON RAT AND HUMAN HEPATOCYTES MAINTAINED IN COLLAGEN GELS

Hepatocytes maintained in collagen gels remain differentiated for prol onged periods of time compared to cells maintained on conventional cul tures. Previous studies with other culture systems in which chemical s upplements or substratum modifications enhanced hepatocyte differentia tion showed that in all of these systems hepatocytes do not respond to mitogens. In this study it is shown that hepatocytes maintained betwe en two layers of collagen gels respond to mitogens HGF (also known as scatter factor (HGF/SF)) and epidermal growth factor (EGF). Cell densi ty did not affect the responsiveness to mitogens as in conventional cu ltures. In addition both mitogens (HGF more pronounced) induce charact eristic morphogenic changes in which hepatocytes form processes and jo in in formation of cords. Hepatocytes respond to mitogens for up to 6 days in culture at which point they become refractory to further mitog enic stimulation. This occurs despite electron microscopic evidence th at these cells are fully viable when they become refractory to mitogen esis. The refractory state is not modified by substitution of one grow th factor for the other or by addition of growth factors at different times. Hepatocytes in the refractory state become again responsive to mitogens when the collagen gels are dispersed by collagenase and the c ells are replated on conventional substrates. (C) 1993 Wiley-Liss, Inc .