ABSTRACT
Transforming growth factor-β1(TGF-β1)is an important factor in tissue fibrosis. TGF-β1 directly ac- tivates Smad signaling which triggers the overexpression of profibrotic genes. A large number of studies have shown that the dysregulation of TGF-β1/Smad pathway is an important pathogenic mechanism in tissue fibrosis. Smad2 and Smad3 are the two major downstream regulators that promote TGF-β1-mediated tissue fibrosis,whereas Smad7 acts as a nega- tive feedback regulator of the TGF-β1/Smad pathway,blocking TGF-β1-mediated fibrosis. In addition,the recent re- searches have shown that microRNA(miRNA)can regulate the TGF-β1/Smad signaling pathway,and affect the process of tissue fibrosis. This article reviews the role of TGF-β1/Smad signaling pathway in renal,hepatic,pulmonary and myo- cardial fibrosis,as well as the regulation of TGF-β1/Smad signaling pathway by miRNA.