CHARACTERIZATION AND FUNCTIONAL-STUDIES ON RAT-LIVER FAT-STORING CELL-LINE AND FRESHLY ISOLATED HEPATOCYTE COCULTURE SYSTEM

We developed and characterized a coculture system composed of a fat-st oring cell clone (CFSC-2G) and freshly isolated hepatocytes that can r eproduce in vitro some of the physical and functional relationships ob served in vivo. Hepatocytes in the coculture are polarized, are smalle r in size than hepatocytes plated on plastic, maintain a cuboidal shap e, and have a tendency to form cords. Fat-storing cells, which are ini tially extended, retract and leave spaces that resemble liver sinusoid s. Both cell types in the coculture system are functional for at least two weeks as determined by the expression of high levels of liver-spe cific protein mRNAs as well as by the production and secretion of live r-specific proteins into the culture medium. The hepatocytes maintain relatively high levels of asialoglycoprotein receptor on their cell su rface and form functional gap junctional complexes with fat-storing ce lls. Hence, this coculture system retains a number of differentiated f unctions of hepatocytes, making it a useful model to study cell-cell i nteractions in culture and to analyze regulation of hepatocyte functio ns.