The correlation between the deterioration of microstructural evolution and mechanical properties in human ascending aortas with and without dissections

The progression of aortic dissection involves a concomitant deterioration in the mechanical properties and microstructure of the aortic wall. However, the specific histopathological alterations in the aorta of patients with aortic dissection and their contribution to mechanical failure remain poorly understood. This study aims to establish the correlation between histopathological changes and deterioration in the mechanical properties of human ascending aortas from patients with aortic dissection. Human ascending aorta samples from 36 patients (with aortic dissection and non-dissection controls) underwent the peel test, uniaxial tensile test, and histological analysis. The results show a significant reduction in both mechanical properties and load-bearing components. Correlation analysis indicates that the circumferential delamination strength is positively correlated with medial elastic fiber content (r = 0.54), and circumferential tensile strength is positively correlated with collagen content (r = 0.57). Further regression analysis suggests that reduced medial elastic fiber content may contribute to the decrease in circumferential delamination strength associated with pathological changes, whereas the reduction in circumferential tensile strength may be partially explained by the reduction in full-thickness collagen content. These mechanical and compositional alterations also provide a biomechanical basis for explaining the effects of clinical risk factors on aortic dissection. Within the aortic dissection group, advanced age significantly increases the initial aortic modulus, and females exhibit greater accumulation of glycosaminoglycans in the media. Overall, our findings clarify the key microstructural components responsible for the aortic failure in patients with aortic dissection, thereby enriching the understanding of its pathophysiological mechanisms. STATEMENT OF SIGNIFICANCE: This study examined 36 fresh human ascending aortas (22 cases in the aortic dissection (AoD) group and 14 cases in the non-AoD group) to establish the relationship between histopathological changes and deterioration of the mechanical properties. Our findings clarify the key microstructural components responsible for the failure of the dissected aorta, and elucidate the influences of clinical risk factors on the aorta dissection. This work provides new insights into the clinical phenomenon of AoD and deepens our understanding of the mechanical mechanisms underlying AoD.