Aortic aneurysm progression in Fbn1C1039G/+ and Fbn1mgR/mgR mice is largely driven by increased latent TGF-β activation and signaling secondary to loss of TGF-β-LLC sequestration in the ECM (Figure 1), a molecular phenotype that is replicated in cultured primary smooth muscle cell isolated from Fbn1 mutant aortas [46,47]. Here, TGFB1 is linked to aortic aneurysm.