TGFB1 and fibrosis: In many fibrotic diseases, TGF-β1 combines with type I receptors, type II receptors and relays signal transduction through phosphorylation of downstream effectors, such as Smad2/3, to promote MMP expression and collagen deposition, eventually lead to tissue fibrosis (van Caam et al., 2017; Kilari et al., 2018; Zhang et al., 2020).