The role of glomerular mesangial cells (MC) and mesangial matrix (MM) in glomerular sclerosis was studied by using rat mesangial cell culture, immunohistochemical studies for laminin, laminin receptors as well as collagen types IV and III. The effect of tumor necrosis factor (TNF) and endothelin (ET) on MC was also studied. Results show that TNF and ET have potent mitogenic effects on MC. The glomerular MC possess the special capability of secreting TNF and ET. TNF and ET can also influence and induce the secretion of each other. The MM is increased in the MC nodular colonies formed after prolonged culture. These colonies are composed of collagen IV and collagen III. Therefore, injuring factors can cause MC and MM to proliferate and produce glomerulosclerosis.