A, Representative western blots of aortic TGF‐β1, p‐SMAD2, and SMAD2. B, Quantitative data of aortic activated TGF‐β1 protein abundance (P<0.001 for main treatment effect, P<0.001 for main genotype effect, P<0.001 for treatment×genotype, by 2‐way ANOVA) (left panel). Quantitative data of aortic p‐SMAD2/SMAD2 ratio (P<0.001 for main treatment effect, P<0.001 for main genotype effect, P<0.01 for treatment×genotype, by two‐way ANOVA). Graph (right panel) showing mean±SEM with individual data for knockout and WT mice with angiotensin II or saline infusion. *P<0.05 and ***P<0.001 by Bonferroni post hoc tests following 2‐way ANOVA. C, Photomicrographs of immunostaining collagen type I. Morphometric analysis shows relative collagen I immunostaining area (%) (P<0.001 for main treatment effect, P<0.001 for main genotype effect, P<0.001 for treatment×genotype, by 2‐way ANOVA). Graph (far right panel) showing mean±SEM with individual data for knockout and WT mice with angiotensin II or saline infusion. ***P<0.001 by Bonferroni post hoc tests following 2‐way ANOVA. D, Representative western blots of aortic collagen I. Quantitative data of aortic collagen I (P<0.01 for main treatment effect, P>0.05 for main genotype effect, P<0.0001 for treatment×genotype, by 2‐way ANOVA). Graph (right panel) showing mean±SEM with individual data points for knockout and WT mice with angiotensin II or saline infusion. ***P<0.001 by Bonferroni post hoc tests following 2‐way ANOVA. Scale bar=100 μm. Ang II indicates angiotensin II; KO, knockout; L, lumen; M, media; MW, molecular weight; p‐SMAD2, phosphorylated mother against decapentaplegic homolog 2; SMAD2, mother against decapentaplegic homolog 2; TGF‐β1, transforming growth factor beta 1; and WT, wild‐type.