Transforming growth factor-β and the progression of renal disease.

Transforming growth factor-β (TGF-β) is a profibrotic cytokine found in chronic renal diseases, which initiates and modulates a variety of pathophysiological processes. It is synthesized by many renal cell types and exerts its biological functions through a variety of signalling pathways, including the Smad and MAPK pathways. In renal diseases, TGF-β is upregulated and induces renal cells to produce extracellular matrix proteins leading to glomerulosclerosis as well as tubulointerstitial fibrosis. Different types of renal cells undergo different pathophysiological changes induced by TGF-β, leading to apoptosis, hypertrophy and abnormalities of podocyte foot processes, which ultimately result in renal dysfunction. In this review, we describe the effects of TGF-β on different renal cell types and the means by which TGF-β participates in the pathomechanisms of glomerular and tubulointerstitial diseases.