SMAD7 and acute respiratory distress syndrome: It is well known that TGF-β1 is a key cytokine leading to EMT and TGF-β1 overexpression is associated with poorer prognosis in ARDS [25, 35].The downstream effects of TGF-β1 are mediated by Smad2/3, while Smad7 can bind TGF-βR1 and prevent TGF-β-associated Smad signaling [35].