FBN1 and Marfan syndrome: The increased expression of MMP-9 in the MFS group in this study may also be implicated in the significant reduction of both fibrillin-1 and fibronectin, given that previous studies have shown in different connective tissue pathologies that MMP-9 plays a role in the degradation of fibrillin-1, fibronectin, and elastic fibers [36,44–47].