In contrast, when TGF-β signaling was disrupted in 4-week-old mice via tamoxifen induction (with similar efficiency of Cre recombination in greater than 90% of SMCs as adult animals), 75% of the Tgfbr1/2iSMCKO mice developed aneurysms, intimomedial tears, and dissection of the thoracic aorta over a 4-week period (Supplemental Figure 2), similar to previous results with deletion of Tgfbr2 alone (11). Here, TGFB1 is linked to aneurysm.