Introduction: Marfan syndrome (MFS) patients classically develop focal aortic root aneurysms. Aortic root smooth muscle cells (SMCs) develop predominately from second heart field (SHF), whereas ascending aorta/arch SMCs originate from cardiac neural crest (CNC). We previously demonstrated induced pluripotent stem cell (iPSC)-derived SHF SMCs overexpress integrin αV (ITGAV). Therefore, we hypothesize that ITGAV promotes SHF SMC proliferation, contributing to thoracic aortic root aneurysm development. Methods: iPSCs from MFS patients (n=2) and healthy control (n=1) were differentiated into SHF and CNC SMCs. ITGAV-pFAK-pAkt Thr308 levels were detected with western blot and ELISA at baseline and following recombinant TGF-β (2ng/ml) and/or an ITGAV antagonist (GLPG0187, 10nM) for 24 hours. Cell proliferation was measured with quantitative BrdU assay. Results: Baseline ITGAV-pFAK-pAkt Thr308 activation were significantly elevated in MFS SHF lines (n=5 experimental replicates) compared to MFS CNC (n=5) or control SHF (n=4, p<0.05). Addition of recombinant TGF-β to SMC differentiation media further enhanced pFAK-pAkt Thr308 levels in MFS SHF. Treatment with GLPG0187 reduced pFAK-pAkt Thr308 in MFS SHF and CNC, confirming ITGAV-mediated signaling promotes pathologic FAK- Akt Thr308 activation. SMCs from MFS SHF (n=6) had increased proliferation compared to other SMCs (p<0.01 vs MFS CNC and control SHF) which was reversed to the same level as control SHF (p=0.132) with GLPG0187 treatment. Conclusions: The integrin-FAK-Akt Thr308 signaling pathway is activated in iPSC SMCs from MFS patients specifically from the SHF lineage, which is further exacerbated by TGF-β. Mechanistically, this pathway promotes SMC proliferation in vitro . ITGAV blockade via GLPG0187 may be a promising therapeutic approach for MFS aneurysmal growth.