scholarly journals Ultrastructural pathology of bioprosthetic heart valves with infectious endocarditis

2021 ◽  
Vol 6 (3) ◽  
pp. 25-34
Author(s):  
R. A. Mukhamadiyarov ◽  
I. V. Milto ◽  
A. G. Kutikhin

Aim. To study the ultrastructure of mitral bioprosthetic heart valves (BHVs) which failed due to infective endocarditis.Materials and Methods. Here we examined 7 ethylene glycol diglycidyl ether-treated xenopericardial BHVs excised during repeated BHV replacement because of prosthetic endocarditis. After being fixed in formalin and postfixed in osmium tetroxide, BHVs were dehydrated and stained in uranyl acetate with the subsequent embedding into epoxy resin, grinding, polishing, and lead citrate counterstaining. Upon the sputter coating with carbon, we visualised the BHV microanatomy by means of backscattered scanning electron microscopy at 15 kV voltage.Results. The extracellular matrix underwent degradation and disintegration resulting in loosening, fragmentation, and reduction in the electron density of collagen and elastin fibers. We observed a number of recipient cells (macrophages, multinucleated giant cells, neutrophils, endothelial cells and smooth muscle cells) within the BHVs. The highest number of cells was localized on the valve surfaces. The localization of the recipient cells on the ventricular and atrial surfaces was different. The central part of the valves was abundantly populated by macrophages.Conclusion. Prosthetic endocarditis is accompanied by the migration of recipient cells into the BHV structure, which is the consequence of surface and extracellular matrix disintegration.

2015 ◽  
Vol 70 (6) ◽  
pp. 662-668 ◽  
Author(s):  
Rinat Avkhadievich Mukhamadiyarov ◽  
Natal'ya Vital'evna Rutkovskaya ◽  
Ol'ga Dmitrievna Sidorova ◽  
Leonid Semenovich Barbarash

With the aim to assess the mechanisms of the structural dysfunctions associated with xenograft tissue calcification, we investigated the cellular composition of the explanted xenoaortic epoxy-treated bioprosthetic heart valves. In the leaflets, we revealed multiple cells with retained internal structure. Most of them located on the leaflet surface, at the areas of collagen destruction, and near calcium deposits. Monocytes were the predominant cell fraction on the leaflet surface whilst immune (macrophages, multinucleated giant cells, plasma cells, neutrophils) and connective tissue (fibroblasts, fibrocytes, endothelial, and smooth muscle cells) cells prevailed at the areas of collagen destruction and near calcium deposits. Calcification of the leaflets was accompanied by cellular infiltration, therefore suggesting that pathological mineralization may be associated with cell-mediated processes.


2021 ◽  
Vol 8 (1) ◽  
pp. 10
Author(s):  
Uri Galili ◽  
Kevin R. Stone

This review describes the first studies on successful conversion of porcine soft-tissue bioprostheses into viable permanently functional tissue in humans. This process includes gradual degradation of the porcine tissue, with concomitant neo-vascularization and reconstruction of the implanted bioprosthesis with human cells and extracellular matrix. Such a reconstruction process is referred to in this review as “humanization”. Humanization was achieved with porcine bone-patellar-tendon-bone (BTB), replacing torn anterior-cruciate-ligament (ACL) in patients. In addition to its possible use in orthopedic surgery, it is suggested that this humanization method should be studied as a possible mechanism for converting implanted porcine bioprosthetic heart-valves (BHV) into viable tissue valves in young patients. Presently, these patients are only implanted with mechanical heart-valves, which require constant anticoagulation therapy. The processing of porcine bioprostheses, which enables humanization, includes elimination of α-gal epitopes and partial (incomplete) crosslinking with glutaraldehyde. Studies on implantation of porcine BTB bioprostheses indicated that enzymatic elimination of α-gal epitopes prevents subsequent accelerated destruction of implanted tissues by the natural anti-Gal antibody, whereas the partial crosslinking by glutaraldehyde molecules results in their function as “speed bumps” that slow the infiltration of macrophages. Anti-non gal antibodies produced against porcine antigens in implanted bioprostheses recruit macrophages, which infiltrate at a pace that enables slow degradation of the porcine tissue, neo-vascularization, and infiltration of fibroblasts. These fibroblasts align with the porcine collagen-fibers scaffold, secrete their collagen-fibers and other extracellular-matrix (ECM) components, and gradually replace porcine tissues degraded by macrophages with autologous functional viable tissue. Porcine BTB implanted in patients completes humanization into autologous ACL within ~2 years. The similarities in cells and ECM comprising heart-valves and tendons, raises the possibility that porcine BHV undergoing a similar processing, may also undergo humanization, resulting in formation of an autologous, viable, permanently functional, non-calcifying heart-valves.


2021 ◽  
Vol 10 (3) ◽  
pp. 26-33
Author(s):  
L. A. Bogdanov ◽  
N. Yu. Osyaev ◽  
Yu. D. Bogdanova ◽  
R. A. Mukhamadiyarov ◽  
A. R. Shabaev ◽  
...  

Aim. To analyze the topographic patterns of valvular and atherosclerotic calcification growth.Methods.           Dysfunctional aortic valves (n = 18) and atherosclerotic plaques (n = 20) were fixed in formalin, postfixed in 1% osmium tetroxide, consecutively stained by 2% osmium tetroxide and 2% uranyl acetate, and embedded into epoxy resin (Epon) with the further grinding and polishing ofthe samples. Upon the counterstaining by lead citrate and sputter coating with carbon, samples were visualized by backscattered scanning electron microscopy. Elemental analysis was conducted via energy-dispersive X-ray spectroscopy. Measurement of Ca/P ratio within the mineral deposits was carried out employing a pool table principle (i.e., in the center of the deposit, in the near and far circumferences (clockwise), and in control regions around the mineral deposit). Topographic patterns of calcifications were modeled using the correlation analysis.             Results. Significant correlation was revealed between the Ca/P ratio in the deposit center and in the near and far circumferences of deposit in both in valvular (r = 0,35-0,78 - near circumference; r = 0,63-0,69 - far circumference) and atherosclerotic mineral deposits (r = 0,37-0,56 - near circumference; r = 0,48-0,63 - far circumference), suggesting the hierarchical growth of cardiovascular calcification around the initial nucleation sites.Conclusion.       Valvular and atherosclerotic calcifications development is concentric.


2011 ◽  
Vol 99B (2) ◽  
pp. 217-229 ◽  
Author(s):  
Vincent M. Friebe ◽  
Brandon Mikulis ◽  
Sourav Kole ◽  
Christy S. Ruffing ◽  
Michael S. Sacks ◽  
...  

Author(s):  
Douglas F. Bray

The extracellular matrix (ECM) of fibrous connective tissue is a composite of protein- and carbohydrate-containing structures. Preservation of the protein components is achieved through fixation with glutaraldehyde and osmium tetroxide. Carbohydrates however are inadequately preserved and often lost using these fixatives. Cationic dyes such as ruthenium red, alcian blue, and several others have been used to stabilize and retain carbohydrates, particularly the proteoglycans (PGs), but usually with less than optimal results. The present study documents the improved preservation and staining of PGs and other carbohydratecontaining components of skin ECM using ruthenium hexammine trichloride (RHT).Human neonatal foreskins were cut into 1 mm 3 blocks, fixed for 3 h in cacodylate buffered (0.1M, pH 7.2) 2.5% glutaraldehyde containing 1 mg/ml RHT (Polysciences, U.S.A.), postfixed 1 h in buffered 1% OsO4 also containing 1 mg/ml RHT, dehydrated in ethanol and embedded in Spurrs. In some cases the tissue was digested with chondroitinase ABC (Miles, U.S.A.) prior to fixation. Sections from tissue fixed without RHT were poststained in uranyl acetate and lead citrate. Figs. 2 - 5 are from 0.5 μm sections of tissue immunolabelled with monoclonal antibodies to type VI collagen.


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