Vascular aging: from molecular mechanism to clinical significance.

The large and medium-sized arteries in elderly people show varying degrees of intimal and medial change. The medial change is known as age-related medial degeneration and sclerosis (ARMDS). The ARMDS results in systolic hypertension and left ventricular hypertrophy of the heart as a result of loss of arterial elasticity. It also causes aortic dilatation, or even aortic aneurysm. The ARMDS and atherosclerosis are distinct entities, but are often overlapped and confused with each other. The present review mainly focuses on ARMDS and briefly addresses atherosclerosis, and aging of arterioles, capillaries and veins. The smooth muscle cells in the inner half of the aortic media of elderly people degenerate and undergo apoptosis. This causes degradation of elastin fibers and the accumulation of collagen fibers in the media, but the inflammatory infiltrates are scarce. Biochemical studies showed an age-related decrease of elastin and its crosslinks, and an increase of collagen and its crosslink. Because the turnover of elastin is very long, it likely suffers from glycation (Maillard reaction) and glyco-oxidative reaction. The advanced glycation end-products accumulate in the aortic media with increasing age. Alcian-blue positive mucin accumulates in aortic media in elderly people. The major component of the increase of aortic mucin is chondroitin-6-sulfate. Microcalcification is frequent in the inner acellular portion of the aortic media in elderly people. Calcium contents increase with age. In conclusion, the ARMDS is a distinct pathological entity with clinical significance. The pathogenesis of ARMDS is unclear; the mechanical stress of elastin, endothelial dysfunction, and glycation of elastin are proposed.