Collagen polymorphism in cultured rat kidney mesangial cells

Studies have been performed to evaluate both the relative amounts and the molecular forms of the collagens synthesized by cultured rat kidney mesangial (RKM) cells. The collagens secreted into the culture medium and extracted from the cell layers of cultured RKM cells were isolated after limited pepsin digestion and differential salt fractionation. Polyacrylamide gel electrophoresis under denaturing conditions of the RKM cell collagens indicated the presence of components corresponding to the chains present in types I, III, IV, and V collagen. Analysis of each fraction by carboxymethyl-trisacryl chromatography revealed that approximately 95% of the total collagen synthesized by the cultured mesangial cells was type I and that approximately one-half of this genetic type of collagen was present as type I trimers. The type IV molecules synthesized by RKM cells exhibited the molecular structure [alpha 1(IV)]3, whereas the type V molecules had the molecular composition [alpha 1(V)]2 alpha 2(V). Furthermore, in contrast to the type I and V collagens which were identified in both the secreted and cell-associated fractions, no type III or type IV components were detected among the collagens retained by the cells. These data establish the relative proportions of the collagens synthesized by cultured mesangial cells and suggest that the process of cell culture may induce a wound-healing or sclerosing phenotype in the glomerular mesangial cell.