SMAD3 and Hepatic fibrosis: Smad2/Smad3, a downstream factor of Smad signaling, is considered a key regulator of TGF-β signaling in tissue fibrogenesis (Yao et al., 2012), and more importantly, Smad7 is a potential major transcriptional repressor of HSC activation and liver fibrosis in vitro and in vivo, regulating Smad2/Smad3 phosphorylation (Xu et al., 2016).