This may reflect a buildup of proteoglycan substrate, which has been shown to occur in patients with thoracic aortic aneurysm or dissection, including those with MFS.52 Notably, our experiments showed for the first time that a reduction of MFAP4 in SMCs leads to a parallel reduction in the expression of versican, as well as several different changes in the ADAMTS enzyme family. Here, MFAP4 is linked to thoracic aortic aneurysm.