Changes with age in the metabolism of sulfated glycosaminoglycans in guinea pig cardiac valves

Inhibition by glycosaminoglycans of CaCO3 (calcite) crystallization

Of a range of glycosaminoglycans, heparin and heparan sulphate were the most effective inhibitors in vitro of CaCO3 (calcite) crystallization as assayed by conductimetric measurements. The possible role of such glycosaminoglycans in modulating calcium-salt crystallizations in vivo is discussed.

The collagen of heart valve

A hydroxylysine-rich type I collagen has been isolated from pepsin-digested porcine heart valve. The ratio of alpha1 to alpha2 in the isolated molecule was 2:1. The component alpha chains exhibited unusual chromatographic behavior in comparison to corresponding chains from human dermis and lathyritic rat skin collagen. The composition of component cyanogen bromide peptides identified the alpha chains as authentic type I chains and demonstrated hydroxylysine enrichment throughout the length of the chain. delta6-Dehydro-5,5'dihydroxylysinonorleucine, a collagen cross-link derived from two hydroxylysyl residues and ordinarily found in hard tissue collagens was found to be the predominant cross-link in heart valve.

Aging changes in the human aortic valve in relation to dystrophic calcification

To elucidate the pathogenesis of aging changes and their relation to age associated calcification, a morphological study of 27 human aortic valves was carried out. Nine valves were obtained from immediate autopsies and 18 valves from routine autopsies done within four hours after death. Calcium deposition was present deep in the zona fibrosa along a zone of lipid accumulation. Fibrocytes in the zona fibrosa showed predominant age associated changes, i.e., a massive accumulation of residual bodies in the cytoplasm probably derived from autophagic vacuoles. Light microscopic lipid accumulation corresponded with both intracellular accumulation of electron dense spherules and membranous vesicles derived from degenerate fibrocytes. Calcium deposition in various stages, including needle shaped hydroxyapatite crystals, was seen in close association with these cellular degradation products rather than collagen or elastic fibers. Dystrophic calcification in the aortic valve appears to result from cellular aging and death followed by petrification of cellular degradation products, which may progress to calcific aortic stenosis.