Phenotypic modulation of rat glomerular visceral epithelial cells by culture substratum

The interaction of cells with their supporting extracellular matrix influences cellular phenotype, cellular proliferation, protein synthetic profile, and specific gene activation. To examine the ability of culture substratum to modulate the phenotype expressed by glomerular epithelial cells (GEC) in culture, GEC were grown on plastic culture plates coated with collagen gels (Type I collagen, Vitrogen) or a complex matrix from the Englebreth-Holm-Swarm tumor (Matrigel). Cultures were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). On untreated plastic, GEC grew in a random pattern. Cells were flat and thin with many filamentous processes. When grown on collagen I gels, GEC grew to confluence as a tight monolayer with typical cobblestone appearance. These cells demonstrated surface microvilli and a central cilium. TEM showed an epithelial appearance with tight junctions. When plated on the surface of Matrigel, GEC formed nests of cells that gradually burrowed into the gel. Proliferation on this matrix was extremely slow. TEM demonstrated that there are surface projections that abut the matrix and that the nests of cells are hollow with a central lumen. SEM demonstrated nests of cells that formed a sphere. Surface microvilli were not as abundant as cells grown on Vitrogen, and cilia were not seen. Cells could be removed from one surface, plated onto another, and would shift phenotype to that observed for subcultures primarily plated onto that surface. Cells on each complex substrate, as well as GEC plated on tissue culture plates coated with individual matrix proteins were biosynthetically labeled with (35S)methionine. The profile and rate of protein synthesis were modified by the plating substrate. These observations demonstrate that rat GEC can be induced to display variable phenotypes in culture that are determined by the plating substrate.(ABSTRACT TRUNCATED AT 250 WORDS)