Meng’s Team explored the function of Smad4 in regulating TGF-β signaling in mice with unilateral ureteral obstruction and noticed that Smad4 activates Smad3, which leads to the activation of downstream promoters and promotes the co-ligation of Smad3 with the COL1A2 promoter, confirming the Smad3 and Smad4 play a promoting role in liver fibrosis [67]. Here, SMAD3 is linked to Hepatic fibrosis.