The vascular protective properties of endogenous Lrp1 have been attributed to its limitation of smooth muscle cell response to platelet-derived growth factor (PDGF) and TGF-β stimulation, with the former contributing to the atherosclerosis phenotype and the latter affecting elastic layer integrity and aneurysm similar to that observed with Marfan syndrome [17]. Here, TGFB1 is linked to Marfan syndrome.