Thoracic aortopathy in Marfan syndrome overlaps with mechanisms seen in bicuspid aortic valve disease

Figure 1. Transverse histologic sections of the ascending aortic wall in a non-dilated bicuspid aortic valve patient (A), in a Marfan syndrome patient (B) and in a non-dilated tricuspid aortic valve patient (C; 5 μm) stained with resorcin fuchsin. The intimal, medial, and adventitial layer are depicted with an arrow in the figure. The intimal layer is indicated with a red line in (A–C). The intimal layer is formed by a single layer of a lamina elastica interna in the bicuspid (A) and Marfan patient (B), whereas the intima is significantly thicker in the tricuspid aortic valve patient (C), graph (D). Elastic lamellae are fine and neatly organized without fragmentation or degeneration. BA, non-dilated bicuspid aortic valve; MFS, Marfan syndrome; TA, non-dilated tricuspid aortic valve; and RF, resorcin fuchsin, ***p<0.001. Scale bar is shown in the figures.

Figure 2. Transverse histologic sections of a non-dilated dilated bicuspid (A), Marfan syndrome (B) and a non-dilated tricuspid ascending aortic wall (C; 5 μm) stained with MOVAT pentachrome staining. (A) shows mucoid extracellular matrix accumulation which stains light blue (indicated with the red arrows) in the MOVAT pentachrome staining, the vascular smooth muscle cells are red, elastic fibers are seen in dark purple, collagen and reticulin in yellow, and nuclei in black. Mucoid extracellular matrix accumulation was significantly greater in the bicuspid (A) and Marfan patients (B) as compared to the non-dilated tricuspid aortic valve group (C), graph (D). BA, non-dilated bicuspid aortic valve; BAD, dilated bicuspid aortic valve; MEMA, mucoid extracellular matrix accumulation; MFS, Marfan syndrome; TA, non-dilated tricuspid aortic valve; and TAD, dilated tricuspid aortic valve, *p<0.05. Scale bar is shown in the figures.

Figure 3. Transverse histologic sections of a dilated tricuspid ascending aortic wall (A,C,D,G) and a dilated bicuspid aortic valve (J; 5 μm) stained with hematoxylin eosin (A,D,G,J), resorcin fuchsin (C). (A) shows overall medial degeneration, which is indicated with the red arrows. Overall medial degeneration was significantly greatest in the dilated tricuspid aortic valve and Marfan syndrome group, graph (B). Elastic fiber fragmentation is indicated with the red arrows in (C). In (D), the vascular smooth muscle cells are surrounded by a blue circle, the areas with loss of smooth muscle cell nuclei are indicated with an arrow. Smooth muscle cell nuclei loss was significantly greatest in the dilated tricuspid aortic valve and Marfan syndrome groups, graph (E), which was confirmed with the caspase-3 staining shown in (F). Elastic fiber thinning was significantly greatest in the bicuspid and Marfan groups (I). In (J) in comparison a dilated ascending aortic wall is shown in the bicuspid aortic valve without features of overall medial degeneration, smooth muscle cell nuclei loss and adventitial inflammatory cells. BA, non-dilated bicuspid aortic valve; BAV, bicuspid aortic valve; EFF/L,…

Figure 4. Transverse histologic sections of a non-dilated ascending aortic wall in bicuspid aortic valve (A), Marfan syndrome (B) and tricuspid aortic valve (C); and a dilated ascending aortic wall in bicuspid aortic valve (F), Marfan syndrome (G) and tricuspid aortic valve (H; 5 μm); stained with alpha smooth muscle actin (A–C) and smoothelin (F–H). Alpha smooth muscle actin expression was significantly highest in the non- and dilated tricuspid aortic valve patients (A–D). Level of expression was lower in the bicuspid and Marfan patients as individual cells expressed less alpha smooth muscle actin as pointed out with the arrows highlighting cells (blue nuclei) which are devoid of expression. Smooth muscle 22 alpha expression was also significantly higher in the tricuspid aortic valve groups as compared to the bicuspid and Marfan patients (E). Smoothelin expression was significantly highest in the non-dilated tricuspid aortic valve patients (F–I). Lamin A/C expression is shown in (Figure 5E) with significantly highest expression the non-dilated and dilated tricuspid patients. αSMA, alpha smooth muscle actin; BA, non-dilated bicuspid aortic valve; BAD, dilated bicuspid aortic valve; SM22α,…

Figure 5. Transverse histologic sections of a dilated tricuspid (A) and Marfan (Figure 4B) ascending aortic wall (5 μm); stained with fibrillin-1. Fibrillin-1 expression was significantly highest in the tricuspid aortic valve patients as compared to the Marfan and bicuspid patient groups (A–C). Expression was found extracellular in the tricuspid aortic valve patients (red arrows in A) as compared to the intracellular expression in the Marfan patients (red arrows in B). BA, non-dilated bicuspid aortic valve; BAD, dilated bicuspid aortic valve; FBN1, fibrillin-1; TA, non-dilated tricuspid aortic valve. TAD, dilated tricuspid aortic valve, *p<0.05, **p<0.01. Scale bar shown in the figures.

Figure 6. Ascending aortic wall pathology in TAV, MFS, and BAV. The figure summarizes the intimal, medial and adventitial pathology in tricuspid aortic valve, Marfan syndrome and bicuspid aortic valve patients. Marfan syndrome pathology overlaps with mechanisms seen in the tricuspid and bicuspid aortic valve. TAV, tricuspid aortic valve; MFS, Marfan syndrome; BAV, bicuspid aortic valve; αSMA, alpha smooth muscle actin; SM22α, smooth muscle 22 alpha; and VSMC, vascular smooth muscle cell.