Abstract 12566: Aortic Smooth Muscle Cell Focal Adhesion Kinase (FAK) Activation is Prominently Associated With Acute Aortic Dissections in Patients and Mouse Models and Loss of FAK Signaling Augments Dissections in Mice

Abstract

Introduction: Genetic variants predisposing to thoracic aortic disease disrupt proteins either in the extracellular matrix (ECM) or the smooth muscle cell (SMC) contractile unit, and focal adhesions (FAs) are molecular bridges between these aortic wall components. We sought to identify molecular triggers for acute aortic dissection (AAD) in a mouse model with AAD induced by β-aminopropionitrile (BAPN) and patients with type A AAD. Methods: At postnatal day 21 (P21), C57BL/6J mice were exposed to BAPN in drinking water (0.5%) and proximal aortas were harvested for single-cell RNA sequencing (scRNA-seq), proteomics assays and transmission electron microscopic (TEM) analysis at P35. Ascending aortic scRNA-seq assays were performed on AAD patients (n=3) and age-matched, cardiac transplantation donors (n=3). Results: In the BAPN mice, ruptured AAD-deaths started at P36, and 54% of mice died by P49, despite a significant decrease of BP (111/79 to 95/66 mmHg, p<0.0001). ScRNA-seq and KEGG pathway analysis identified increased FA signaling as the top altered pathway in the BAPN-treated SMC clusters. Similarly, FA signaling was identified as a top upregulated pathway in SMCs from patients’ aortas. Western blots confirmed increased level of FAK phosphorylation in BAPN-treated aortas. Proteomics analysis revealed a FAK-interacting protein, cortactin, and apoptotic proteins, annexin A1, A3 and A5 (p<0.01), as the top proteins increased with BAPN treatment, which was consistent with increased TUNEL signal in BAPN-treated aortas (p<0.01). TEM analysis identified collagen deposition between SMCs and elastic fibers and loss of elastic extensions in BAPN-treated aortic media. Importantly, administration of a FAK inhibitor, PF-573228, starting at P30 in BAPN-treated mice significantly increased AAD-deaths (starting at P35 and all mice died by P48) when compared to BAPN-only treated mice (p<0.0001). Conclusions: FA signaling is the major pathway activated in SMCs in mouse pre-dissection aortas and human dissected aortas, thus implicating disruption of SMC-ECM interactions in AADs. Disruption of FAK signaling augments AADs, suggesting that maintenance of FA signaling delays AADs in the ECM-compromised, BAPN-treated aortas.