Abstract 18901: Critical Role of Endothelial Injury in the Initiation of Aortic Dissection

Introduction: Endothelium forms a protective barrier and maintains vascular hemostasis. However, the role of endothelial injury in aortic aneurysms and dissections (AAD) remains poorly understood. Receptor-interacting protein kinase 3 (RIP3)-mediated necroptosis and gasdermin D (GSDMD)-mediated pyroptosis trigger necrotic cell death. We hypothesize endothelial cell (EC) death induced by necroptosis and pyroptosis contributes to AAD formation. Methods: Endothelial integrity and gene expression were examined in ascending aortic tissues from ascending thoracic aortic aneurysm (ATAA) patients (n=9) and organ donor controls (n=8) by single-cell transcriptome analysis. Effects of EC death on AAD formation were determined in EC-specific Rip3 knockout (EC-Rip3 -/- , n=26), EC-specific Gsdmd knockout (EC-Gsdmd -/- , n=21), and necroptosis/pyroptosis inhibitor necrosulfonamide (NSA) treated mice (n=15) in sporadic AAD models induced by angiotensin II (Ang II) infusion. Evans blue staining and nanoparticle-mediated contrast-enhanced CT (n-CECT) detected endothelial hyperpermeability Results: Single-cell transcriptome and immunostaining analyses revealed significant upregulation of pro-death genes (e.g., RIP3 and GSDMD), but downregulation of cell junction genes (e.g., TJP1 and GJA1) in ECs of ATAA patients compared with controls. In the mouse AAD model, endothelial injury and hyperpermeability were detected 2-5 days after Ang II infusion and were associated with intramural nanoparticle accumulation, elastic fiber fragmentation, and macrophage infiltration. Importantly, EC-Rip3 -/- mice and EC-Gsdmd -/- mice showed preserved EC barrier function, reduced nanoparticle accumulation and elastic fiber fragmentation, and reduced AAD incidence (including aneurysm, dissection, and rupture) compared to their littermate controls (EC-Rip3 -/- mice: 52% vs 23.1%, P=0.033; EC-Gsdmd -/- mice: 52.6% vs 14.3%, P=0.01). Blocking necroptosis/pyroptosis by NSA treatment reduced the incidence (65% vs 27%; P=0.04) and severity of AAD. Conclusions: Endothelial injury and subsequent barrier dysfunction and infiltration are key features of AAD formation. Prevention of EC necrotic cell death can be a potential AAD therapeutic target.