ABSTRACT
We have studied the effect of retinol on an established murine cell line (GRX), representative of liver connective tissue cells. This cell line has myofibroblast characteristics; under retinol treatment it is induced into the lipocyte (Ito-cell) phenotype. Retinol decreased the proliferation rate in the entire cell population. It increased cell adherence to the substrate, which was correlated with the increased secretion of fibronectin. Collagen secretion was specifically decreased, whilst the total protein secretion remained stable. Heparan sulphate was decreased in the pericellular compartment, but other glycosaminoglycans were not affected by retinol treatment. Modulations of pericellular components induced by retinol may alter the relations among liver mesenchymal cells, and may be related to vitamin-A-induced modifications of the homoeostasis of hepatic connective tissue and hepatic fibrosis.
Subject(s)
Liver/drug effects , Vitamin A/pharmacology , Animals , Cell Adhesion/drug effects , Cell Count , Cell Line , Collagen/biosynthesis , Connective Tissue/drug effects , Connective Tissue/metabolism , Fibronectins/biosynthesis , Glycosaminoglycans/biosynthesis , Liver/metabolism , Mice , Mitosis/drug effectsABSTRACT
We have studied collagen synthesis and secretion in an established liver connective tissue cell line (GRX) that can be induced in vitro to express either the myofibroblastic or the fat-storing (lipocyte) phenotype. In lipocytes, collagen synthesis was reduced. Their intracellular collagen degradation corresponded to 15% of newly synthesized collagen. In myofibroblasts, collagen synthesis was high but its secretion was considerably altered by intracellular collagen degradation, which attained up to 60% of newly synthesized collagen. In this in vitro model, we have provided direct evidence that hepatic lipocytes, involved mainly in lipid and retinol metabolism, have a low basal level of collagen synthesis. Myofibroblastic phenotype correlates with increased collagen synthesis and may be directly related to increased collagen deposition in hepatic fibrosis. Modulation of the phenotype of liver connective tissue cells are possibly one of the major points of control in normal and pathological deposition of collagen in liver parenchyma.
