Natural and Prosthetic Heart Valve Calcification: Morphology and Chemical Composition Characterization

Abstract

Calcification is the most common cause of damage and subsequent failure of heart valves. Although it is a common phenomenon, little is known about it, and less about the inorganic phase obtained from this type of calcification. This article describes the scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy and Ca K-edge X-ray absorption near edge structure (XANES) characterization performed in natural and bioprosthetic heart valves calcified in vivo (in comparison to in vitro-calcified valves). SEM micrographs indicated the presence of deposits of similar morphology, and XANES results indicate, at a molecular level, that the calcification mechanism of both types of valves are probably similar, resulting in formation of poorly crystalline hydroxyapatite deposits, with Ca/P ratios that increase with time, depending on the maturation state. These findings may contribute to the search for long-term efficient anticalcification treatments.

Collagen Mineralization in Human Aortic Valve Stenosis: A Field Emission Scanning Electron Microscopy and Energy Dispersive Spectroscopy Analysis

“…EDX analysis demonstrates that these abnormal formations principally contain calcium and phosphorus with trace amounts of magnesium (Mg), sodium (Na) and sulfur (S) (B). microstructural characteristics of collagen fibers in the calcified heart valves [2][3][4]7]. In this context, the pathobiology of collagen has been mainly investigated in the tissue engineering research area, with the goal to identify and characterize the mechanisms governing the structural deterioration of prosthetic and bioprosthetic heart valves substitutes [8,9].…”

“…Although first described by Monckeberg nearly a century ago, to date little is known regarding the molecular and cellular events that control the stenosing process with only a few reports dealing with the structural appearance of mineralized collagen in the calcifying tissue of native aortic valve [2][3][4]. Therefore, in the present study we have investigated the morphological association between collagen and minerals in human aortic valves that undergo dystrophic calcification by using scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX).…”

Calcification of aortic human valves studied in situ by Raman microimaging: following mineralization from small grains to big deposits

“…[2][3][4] For a long time calcification has been considered to be a passive calcium accumulation, but currently, it is perceived as an active process, [2,3,5] similar to bone formation. [5][6][7] The combination of the interrelated effects induced by arterial hypertension, hypercholesterolemia, cigarette smoking, diabetes and complex genetic background, primarily bicuspid aortic valve, and the biology of valves, [8,9] has been suggested as a major pathogenetic pathway of calcification leading to the osteoblast phenotype. [8,10,11] Skeletal bone formation appears to be regulated by the extracellular matrix resulting in calcium apatite deposition.…”

Characterization of Porcine Aortic Valvular Interstitial Cell ‘Calcified’ Nodules

“…Nevertheless, a relationship between in vitro nodule formation and pathological aortic valve calcification has not been clearly established, and the cellular composition and nature of the material that comprises such nodules has yet to be determined. The hard material that accumulates on human calcified valves has been identified as a mixture of calcium phosphate phases [21]–[23], thus similar mineral species should be identifiable in a cell-mediated model of aortic valve calcification. The calcified material found in diseased human valves has been suggested to be a result of an osteoblast like mineralization and/or via a dystrophic calcification mechanism [16], [24].…”