1. Chemical, morphological and mineralogical characterization of aortic valve calcifications D. Miriello°, A. Bloise°, D. Barca°, G. M. Crisci°, I. Perrotta**, F. Conforti*, V. Zuccalà*, G. Donato* °Dip. Scienze della Terra, Università della Calabria *U.O. Anatomia Patologica, Facoltà di Medicina e Chirurgia, Università Magna Graecia **Dipartimendo di Ecologia, Università della Calabria
Introduction
Aortic valve calcification (AVC) is the leading cause for valve replacement in Europe and North America and the third leading cause of cardiovascular disease.
AVC has long been regarded as a passive, degenerative process leading to severe precipitation of calcium phosphate into injured tissue in the absence of a systemic mineral imbalance and strongly associated with diabetes, atherosclerosis and aging.
Recently, a number of studies have evidenced that mineral deposition in the cardiovascular system is an actively regulated phenomenon similar to ossification process, involving the induction of noncollagenous matrix proteins of bone.
Over the past few decades, the prevalence of rheumatic and degenerative etiologies of calcific valve disease have drastically changed with the latter increasing probably due to the longevity of life.
Histopathological and morphological studies of calcified valves have been concerned mainly with the determination of the suitable sites for initial mineral deposition and much remains to be elucidated about the pathophysiological events of AVC and the exact elemental composition of the mineral deposits observed in the dystrophic calcification of aortic valves.
The present study sought to characterize the nature of mineral deposits and the ultrastructural features of calcified human aortic valves in order to provide valuable insight into the pathogenic mechanisms of calcium deposition in valvular tissue.
Identification of the valve calcification
Valve calcifications have been investigated by optical and scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), thermogravimetry (TG), infrared spectrometer (FT-IR). The composition was inspected on valve calcifications cross-sections by EDS-SEM and LA-ICP-MS analyses.
Figure 1: Optical images of the valve calcifications.
Figure 4: a, b, c SEM images showing calcified valves. a b c
Figure 8: SEM images showing (at the given scale) siliceous spherules.
Results
X-ray diffraction show that the valve calcification (Fig. 1 a, b) consists of fluorapatite (JCPDS ) only (Fig. 2). When observed with the SEM, fluoroapatite shows both regular (Fig. 3 a, b, c) and lacking in morphology (Fig. 4 a, b, c). As regards chemical composition, some correlation is observed between elements concentrations (ppm) and removal from the organic-inorganic border (Fig. 5). The DSC and TG curves for the valve calcification are showed in figure 6. Further characterization of the valve calcifications have detected the presence in variable amount of other phases (Fig. 7) also as siliceous spherules (Fig. 8) and needle titanium both crystallized in micrometric size.
Figure 3: a, b, c SEM images showing (at the given scale) fluoroapatite.
Figure 2: X-ray powder diffraction pattern of the calcification showing that it consists of fluorapatite (JCPDS ) only. a b c
Our ultrastructural investigations indicated that cellular and extracellular remodeling was present in the calcified areas and included vacuolization of elastin, disorganization of collagen fibers, and degeneration of valve interstitial cells without inflammatory infiltrate.
Figure 7: SEM-BSE images showing the presence of phases with Cu and Cr.
Figure 6: DSC-TG curves of the calcifications.
Figure 5: LA-ICP-MS analyses.