Role of growth factors in diabetic kidney disease.

Diabetic nephropathy (DN) is one of the major microvascular complications of diabetes and one of the leading causes of death among patients with diabetes. DN is characterized by excessive amassing of extracellular matrix with thickening of glomerular and tubular basement membranes and increased amount of mesangial matrix, which ultimately progress to glomerulosclerosis and tubulo-interstitial fibrosis. The high intracellular glucose environment due to an increased cellular uptake of glucose activates several pathways related to the production of advanced glycation endproducts, cytokines, chemokines, growth factors, reactive oxidative species, which are all final mediators of renal damage in human and experimental diabetes. Several growth factors have been implicated in the pathogenesis of DN, through complex intra-renal systems. Transforming growth factor beta, connective tissue growth factor, vascular endothelial growth factor, growth hormone and insulin-like growth factors are among those best known and investigated. There are also data, even though limited, on the involvement of other two growth factors, epidermal growth factor and platelet derived growth factor, in the pathogenesis of DN. These growth factors, which are generally expressed in the normal kidney and whose levels increase in relation to diabetes, have been implicated in the control of renal matrix composition, cell hypertrophy, proliferation and survival, modulation of cells of the immune system, and enzymes involved in glucose metabolism. The development of specific inhibitors of growth factors has provided further evidence for the involvement of growth factors in the development and progression of DN and further studies might help in developing new potential therapeutical interventions.