SYNOPSIS
Spheroids were formed for human fetal hepatocytes on poly-L-glutamic acid-coated polystyrene dishes that had a negatively charged surface at neutral pH. The optimum concentration of poly-L-glutamic acid solution for coating the surface of the dish was 1mg/ml. The optimum cell density of inoculation for the spheroid formation was 3.4X104 cells/cm2 (4.0 X105 cells/35mm-dish). The cytoskeletal actin filaments of the cells were reorganized from stress fiber in the monolayer to cortical actin in the spheroid. The spheroid formation was inhibited by cytochalasin D, which is an inhibitor of actin polymerization. Furthermore, the activity (6.6 pmol/106nuclei/min) of cytochrome P450 1A1/2 of cells in the spheroid was almost threefold higher than that of those in the monolayer, and was comparable with that of human mature hepatocytes of primary culture. These results suggest that the reorganization of actin filaments in hepatocytes would be essential for the spheroid formation, and the spheroid culture seems to be suitable for the expression of differentiated functions of human hepatocytes.
Key words:human fetal hepatocyte, spheroid, cytochrome P450