CALCIFIED DEPOSIT FORMATION IN INTIMAL THICKENINGS OF THE HUMAN AORTA

The formation of calcified deposits in intimal thickenings of human aorta was studied by electron microscopy. Microzones of calcification were detected in about 20% of fatty streaks studied and were located predominantly in the deep musculoelastic layer of the intima, Calcified deposits formed only on previously existing structures including extracellular vesicles and unesterified cholesterol. Calcified deposits in the musculoelastic layer of the intima localised inside altered elastin fibres, but initiating the calcification of elastin required the prior accumulation of cholesterol esters inside elastin fibres. Go-localization of calcified deposits and elastin fibres was followed by destruction of elastin. The present study suggests that at an early stage in the development of atherosclerotic lesions, calcified deposits are formed by a physicochemical process which is not strongly controlled by the intimal cells. The recognition of calcified deposits in intimal thickenings supports the hypothesis that a subset of fatty streaks might progress to fibrous plaques in human atherosclerosis.