SMAD2 and Ureteral obstruction: We suggest that in the early stages of the ureteral obstruction ALK1 is regulating the myofibroblast emergence from endothelial cells while after 15 days UUO the fibrotic program is completely established and myofibroblast number is elevated and ALK1 regulates negatively ECM protein synthesis by myofibroblasts through an inhibition of TGF-β1/Smad2/3 pathway (Muñoz-Félix et al., 2014b).