Changes in the distribution of laminin, fibronectin, type IV collagen and heparan sulfate proteoglycan during colony formation by chick retinal pigment epithelial cells in vitro.

Retinal pigment epithelial cells isolated by non-enzymatic means from 8 day old chick embryos were grown as explants on glass coverslips in culture. Retinal pigment epithelial cells grown in this way form colonies in which three zones, each containing cells with distinctly different morphology, pigmentation, adhesion pattern and cytoskeletal organization, can be distinguished (Turksen et al., 1983). Using specific antisera against laminin, fibronectin, type IV collagen, and heparan sulfate proteoglycan, we have found differences in the distribution of these basement membrane components in the three zones of each colony. When cells were stained with laminin, type IV collagen and fibronectin antibodies, extensive filamentous arrays were observed on the substratum side of the cells. In contrast to type IV collagen which was deposited to a similar degree in all three zones of each colony, laminin and fibronectin were most prominent in the central zone in which the packed cuboidal differentiated cells are located. In contrast to the other components, the heparan sulfate proteoglycan appeared to be associated primarily with the cell surface. Our results support the general view that basement membrane components could influence cell shape through an effect on the cytoskeleton, and play a role in the maintenance and expression of the differentiated state. Thus retinal pigment epithelial cells might provide a very useful model system for studying the interactions between the cytoskeleton and extracellular matrices and the biosynthesis of the BM components in epithelial cells.