Bioprosthetic heart valve degeneration: new insights into structural remodeling and calcification

Figures

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  Figure 1. Composition of healthy and diseased native aortic valve versus healthy and degenerated bioprosthetic aortic valve. (A) Schematic of a healthy native aortic valve. The structure is layered, consisting of the collagen-rich fibrosa, proteoglycan-rich spongiosa, and elastin-rich ventricularis. Each layer contains VICs and the surface covered with VECs. (B) Schematic of a healthy bioprosthetic aortic valve. The components are similar to those of a native aortic valve, but the cells are devitalized pericardial fibroblasts. (C) Schematic of a diseased native aortic valve. Collagen becomes altered throughout the valve and calcium deposits within the fibrosa. Macrophages and EVs are present and promote these pathological changes. (D) Schematic of our proposed model of BHV degeneration. Experimentally supported processes are integrated with hypothesized pathways. The dashed arrow indicates a proposed interaction that has not been directly demonstrated in BHVs. Created with BioRender.com.

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  Figure 2. Histological features of explanted bioprosthetic heart valves. (A) Hematoxylin and eosin (H&E) staining of an explanted valve demonstrates host cells predominantly localize near the valve surface (S), with no cells present in the interstitium (I) compared with non-implanted control tissue. Scale bar = 50 µm. (B) Picrosirius Red (PSR) staining under polarized light demonstrates collagen degradation in explanted BHV tissue, characterized by increased green, thin collagen fibers compared with non-implanted control tissue. Scale bar = 100 µm. (C) OsteoSense demonstrates calcification deposits within explanted BHV tissue, characterized by increased white fluorescence compared with non-implanted control tissue. Vimentin immunostaining is shown in pink. Scale bar = 100 µm.