Role of glomerular mesangial cells in the regulation of glomerular endothelial cell growth

Because of difficulties of propagating and cultivating glomerular endothelial cells (GEN), the role of glomerular mesangial cells (GMC) in the regulation of GEN growth is still unknown. We cloned individually GEN and GMC from the same adult bovine kidneys, and a direct coculture system was established to examine the interactions between GEN and GMC. When cocultured with GMC which was growth arrested by mitomycin C, the GEN growth was inhibited by 63% after 8 days of the beginning of coculture. No inhibitory activity was detected when media conditioned by individual culture of GMC. In contrast, media condi tioned by GEN cocultured with GMC inhibited bromodeoxyuridine (BrdU) uptake of GEN detected by flow cytometry. Addition of anti-transforming growth factor (TGF)-β antibody to media conditioned by coculture blocked the inhibitory actions of conditioned media onGEN growth. Western blotting analysis of conditioned media by coculture revealed an existence of TGF-β in the media. These results indicate that latent TGF-β is produced by these cells and activated in coculture of GEN and GMC.