Biological Niches within Human Calcified Aortic Valves: Towards Understanding of the Pathological Biomineralization Process

Figure 3

Scanning electron microscopy (SEM) micrographs of extracellular matrix fibers altered architecture. (a) Extracellular matrix fibers are arranged in a loose network () or in compact but disorganized bundles (×). Filaments are thicker than normal and show a rough appearance due to the presence of mineral deposits. This is evidence of alteration in normal extracellular matrix deposition process. The three-dimensional mesh creates a microenvironment in which extracellular fluid stagnates, and physicochemical processes of calcium deposition may have taken place. (b) In the foreground, a horseshoe-shaped collagen bundle is visible. In the background wavy, twisted, and bent collagen bundles are present. The space among bundles is crossed by single collagen fibers. This unusual arrangement indicates modification in normal extracellular matrix deposition, and consequently the existence of areas in valve tissue with different stress resistance. Filaments are also thicker due to mineral deposit presence.

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