The cellular composition of explanted bioprosthetic heart valves in infective endocarditis

OBJECTIVE: To perform immunohistochemical typing of cells as a component of bioprosthetic (BP) heart valves explanted during reoperations for prosthetic valve endocarditis. MATERIAL AND METHODS: The authors investigated 8 models of KemCor and PeriCor artificial heart valves produced by NeoCor Company (Kemerovo, Russia), which were explanted from the mitral position due to infection of xenogeneic implanted material. The following markers: CD3 (T-lymphocytes), CD20 (B-lymphocytes), CD34 and VEGFR2 (endotheliocytes), CD68 (monocytes/macrophages), vimentin (fibroblasts), and α-smooth muscle actin (smooth muscle cells), were used for immunohistochemical typing of cells as a component of the analyzed samples. RESULTS: Recipient cells were found to colonize devitalized BP tissues in infective endocarditis. This process simultaneously involved several types of cells performing their functions in infectious lesion and its initiation of BP remodeling. Macrophages contributed to the sanitation of the foci of infection and destruction of BP xenotissue; endotheliocytes ensured neovascularization and resistance of the implanted valve surface to infection; fibroblasts played a role in the neoplastic transformation of collagen, and smooth muscle cells were likely to take on the role in forming the elastic framework of a leaflet and in ensuring the mechanical properties of the bioprosthesis. CONCLUSION: In the time course of development of prosthetic endocarditis, the recipient cells populate xenovalve leaflets that are a modified extracellular matrix obtained from the porcine aortic valve complex. This process is a consequence of the destruction of the BP surface and deep components. The observed cellular reactions are likely to be adaptive and to be aimed at eliminating microorganisms and regenerating structural damages.