As shown in Figure 3C,D,G,H, by IHC staining of lung tissues from ALI mice, TGF-β and Pho-Smad2/3 expressions were significantly increased in the MC group compared to the NC group (p < 0.001, p < 0.0001); in the AMSC-treated groups compared to the MC group, TGF-β and Pho-Smad2/3 expressions were significantly decreased (p <  0.01~p < 0.0001). Here, SMAD2 is linked to acute respiratory distress syndrome.