Interactions between glomerular mesangial cells, cytokines, and extracellular matrix.

This brief overview summarizes recent information on the interactions of glomerular mesangial cells (MC) with soluble cytokines and nonsoluble extracellular matrix (ECM). The presently available knowledge stems largely from glomerular cell culture studies and from experimental work with laboratory animals. ECM production by MC appears to be regulated primarily by the paracrine or autocrine effects of cytokines, such as interleukin 1, platelet-derived growth factor, and transforming growth factor beta. However, ECM itself also affects the behavior of cultured MC, e.g., with regard to cell replication and the production of ECM components and other proteins. At present, little is known about the recognition of ECM and cytokines by MC that allows these interactions to take place. First results indicate that MC, like other cell types, possess surface proteins belonging to the beta 1 integrin family, which serve as specific receptors for ECM molecules. Receptors for the cytokines platelet-derived growth factor, insulin-like growth factor 1, epidermal growth factor, and transforming growth factor beta have also been demonstrated on MC. The expression of various receptors on MC appears to be affected by the ECM substratum. Thus, it is becoming apparent that mesangial ECM is not only important as a mechanical scaffold of the glomerular capillary tuft but that it also contains and conveys information relevant for the regulation of the MC phenotype, e.g., by modulating the MC response to cytokines. The available evidence suggests that alterations of ECM composition in glomerular disease can directly or indirectly affect MC behavior, e.g., by promoting cell replication and further accumulation of ECM, eventually resulting in progressive mesangial and glomerular sclerosis.