Within the vascular wall, endothelial cells, vascular smooth muscle cells and fibroblasts are surrounded by a complex and structured network of secreted macromolecules and proteins, the extracellular matrix. The extracellular matrix provides a structural framework essential for the functional properties of tissues. In each tissue, the three-dimensional organisation of the extracellular matrix molecules - elastin, collagens, proteoglycans and structural glycoproteins - synthesized during development and growth is optimal for these functions. Reciprocal interactions between matrix and cells are essential to growth, development and remodeling. In adult tissues, proteases are constitutively expressed but have a very low activity and the turnover of elastic and collagen fibers is very low. During ageing, the interaction of environmental factors (glucose, lipids, calcium...) and modifications of the biosynthesis and degradation processes lead to modifications of extracellular matrix homeostasis and consequently to alterations of tissue functionality. The extracellular matrix of old large elastic arteries undergoes several modifications. The elastic lamellae are fragmented or degraded and calcify, whereas more rigid proteins, such as collagen, accumulate and cause fibrosis. These alterations are associated with the stiffening of arteries, which results in the development of isolated systolic hypertension. © 2012.
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