TGFB1 and renal fibrosis: The findings of present study show that (1) treatment with the coumarin derivative osthole (7-Methoxy-8-(3-methylbut-2-enyl)-2-chromenone) reduces fibroblast activation and proliferation in vitro and in vivo; (2) OST treatment blocks EMT program in injured kidney from UUO mouse; (3) OST administration suppresses activation of TGF-β1/Smad signaling pathway in fibroblasts and renal tissue (4) as well as inflammatory response in obstructed kidneys after UUO, which contribute to renal fibrosis.