Evolving Mural Defects, Dilatation, and Biomechanical Dysfunction in Angiotensin II–Induced Thoracic Aortopathies

Abstract

BACKGROUND: Thoracic aortopathy associates with extracellular matrix remodeling and altered biomechanical properties. We sought to quantify the natural history of thoracic aortopathy in a common mouse model and to correlate measures of wall remodeling such as aortic dilatation or localized mural defects with evolving microstructural composition and biomechanical properties of the wall. METHODS: We combined a high-resolution multimodality imaging approach (panoramic digital image correlation and optical coherence tomography) with histopathologic examinations and biaxial mechanical testing to correlate spatially, for the first time, macroscopic mural defects and medial degeneration within the ascending aorta with local changes in aortic wall composition and mechanical properties. RESULTS: Findings revealed strong correlations between local decreases in elastic energy storage and increases in circumferential material stiffness with increasing proximal aortic diameter and especially mural defect size. Mural defects tended to exhibit a pronounced biomechanical dysfunction that is driven by an altered organization of collagen and elastic fibers. CONCLUSIONS: While aneurysmal dilatation is often observed within particular segments of the aorta, dissection and rupture initiate as highly localized mechanical failures. We show that wall composition and material properties are compromised in regions of local mural defects, which further increases the dilatation and overall structural vulnerability of the wall. Identification of therapies focused on promoting robust collagen accumulation may protect the wall from these vulnerabilities and limit the incidence of dissection and rupture.

Enhanced expression of miR-20a driven by nanog exacerbated the degradation of extracellular matrix in thoracic aortic dissection

“…In addition to genetic mutations, phenotypic transformation of vascular smooth muscle cells (VSMCs) [ 5 ], dysfunction of endothelial cells [ 6 ], infiltration of immune cells [ 7 ], and abnormal interactions between vascular cells [ 8 ] have been reported to contribute to the pathological remodeling of the aorta, ultimately leading to TAD. Aortic extracellular matrix (ECM) degradation and medial degeneration are key histopathologic features of TAD, yet the detailed mechanisms remain incompletely understood, which significantly hampers progress in drug development [ 9 ]. Therefore, elucidating the pathogenesis of TAD and developing effective conservative treatments are urgent priorities.…”