Valve-Dependent Regional Heterogeneity of Wall Mechanics and Collagen Remodeling in Ascending Thoracic Aortic Aneurysms

Figure 1. Regional correlation of biomechanical properties between outer and inner curvature. Scatter plots comparing paired measurements from outer curvature (y-axis) versus inner curvature (x-axis) for patients with tricuspid aortic valve (TAV, red), bicuspid aortic valve (BAV, blue), and non-aneurysmal controls from heart transplantation (HTx, green). Parameters shown: (A) elastic modulus, (B) ultimate tensile strength, (C) ultimate strain, (D) breaking strength, (E) breaking strain, and (F) wall thickness. Dashed line indicates line of identity. Linear regression lines with 95% confidence intervals are shown for each group. Coefficients of determination (R2) and p-values are provided per panel.

Figure 2. Regional elastin content. Quantification of elastin area (%) from Elastica van Gieson-stained sections comparing outer curvature (OC) versus inner curvature (IC) in (A) TAV, (B) BAV, and (C) HTx with representative histological images. Data presented as mean ± SD. Statistical comparison by paired t-test. ** p < 0.01. Scale bar = 100 µm.

Figure 3. Regional gene expression of collagens and elastin. RT-qPCR analysis of COL1A1, COL3A1, COL4A1, COL5A1, COL11A1, and ELN expression at the outer curvature normalized to inner curvature (IC = 1, dashed line) in BAV (blue) and TAV (red). Asterisks above bars indicate significant difference from IC. Brackets indicate BAV vs. TAV comparison. No between-group difference reached significance after multivariable adjustment and FDR correction (Supplementary Table S3). Data presented as mean ± SEM. p-values were calculated using t-test. * p < 0.05, ** p < 0.01, *** p < 0.001.

Figure 4. Experimental workflow. Outer and inner curvature tissue from ascending aortic surgical specimens were sampled and divided for three analyses. Dogbone specimens underwent uniaxial tensile testing, homogenized tissue was processed for RT-qPCR of collagen and elastin genes, and paraffin-embedded sections were stained with HE and Elastica van Gieson for histological evaluation.