TGFB1 and renal fibrosis: Given the conception that activation and proliferation of renal resident interstitial fibroblasts are the main events in the origin of myofibroblasts, the primary matrix-producing cells (Strutz and Zeisberg, 2006), cultured renal interstitial fibroblasts were exposed to TGF-β1, the central mediator of renal fibrosis, or serum, a mixture of multiple growth factors, to investigate the anti-activation and anti-proliferation role of OST.