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

Calcific aortic stenosis is a slowly progressive disorder characterized by an important extracellular matrix remodeling with fibrosis and massive deposition of minerals (primarily calcium) in the valve leaflet. The main structural components of human aortic valve are the large, thick collagen bundles that withstand the diastolic loading. Collagen has been studied in a number of reports that aim to clarify the mechanisms underlying the structural deterioration of heart valve substitutes, however to date, little is known regarding the morphological interaction between collagen and mineral crystals in the calcifying tissue of native aortic valve. Here, we have analyzed a total of 12 calcified native aortic valves by using scanning electron microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) to depict the morphological appearance of mineralized collagen and to determine the location of calcium phosphate minerals in the collagen matrix of the valve cusp. Our results demonstrate that crystals probably nucleate and grow in the interior of the collagen fibers in the absence of surface events.