Abstract 14908: Anatomic Validation of Induced Pluripotent Stem Cell-derived Aortic Smooth Muscle Cell Model of Loeys Dietz Syndrome

Introduction: Mutations in TGF-beta (TGF-ß) signaling genes lead to aortic root aneurysm in Loeys Dietz syndrome (LDS). Smooth muscle cells (SMCs) in the proximal aorta develop from two embryologic origins: second heart field (SHF) and neural crest (NC). Induced pluripotent stem cell (iPSC) models simulate these lineages, but direct correlation to clinical disease is lacking. Hypothesis: iPSC-derived SMCs accurately model lineage-specific aortopathy in LDS. Methods: We generated SMC lines from root and ascending aortic surgical tissue and iPSC-derived SMCs through SHF and NC-specific pathways from an LDS patient ( TGFBR1 mutation). Lineage-specific TGF-ß responses were determined by western blot/ELISA. RNA sequencing and RT-PCR identified SMC transcriptomes. Results: Aortic root SMCs showed greater canonical TGF-ß activation (p-SMAD2/3) versus ascending at baseline and with TGF-ß stimulation ( Figure ). Synonymous results were seen in SHF versus NC SMCs from the iPSC pathway. RNAseq identified 1,600 differentially expressed genes between iPSC lineages, including altered TGF-ß receptor and ligand expression profiles. Primary aortic lines validated iPSC data: root SMCs showed enriched TGF-ß receptor 1/2/3 expression (1.7-, 3.9- and 5.9-fold) while ascending SMCs overexpressed TGFB1 and TGFB2 ligands (1.8- and 3.5-fold). Despite discordant TGF-ß activation, SMC contractile gene expression was similar between lineages in aortic and iPSC-SMCs, suggesting alternative downstream effects in LDS aneurysm. Conclusion: iPSC-derived SMCs effectively model lineage-specific aortic root aneurysm pathology, validating this model as a tool for mechanistic testing and therapy discovery.