SMAD3 and renal fibrosis: Immunohistochemistry, western blotting, and quantitative real-time PCR revealed that, compared with control UUO mice, CRP Tg/Smad3 WT mice developed severe renal fibrosis by increasing both mRNA and protein levels of collagen I, fibronectin, and α-smooth muscle actin (α-SMA) (Figure 3 and 4A).