CALCIFIED DEPOSIT FORMATION IN INTIMAL THICKENINGS OF THE HUMAN AORTA

The formation of calcified deposits in intimal thickenings of human ao rta was studied by electron microscopy. Microzones of calcification we re detected in about 20% of fatty streaks studied and were located pre dominantly in the deep musculoelastic layer of the intima, Calcified d eposits formed only on previously existing structures including extrac ellular vesicles and unesterified cholesterol. Calcified deposits in t he musculoelastic layer of the intima localised inside altered elastin fibres, but initiating the calcification of elastin required the prio r accumulation of cholesterol esters inside elastin fibres. Go-localiz ation of calcified deposits and elastin fibres was followed by destruc tion of elastin. The present study suggests that at an early stage in the development of atherosclerotic lesions, calcified deposits are for med by a physicochemical process which is not strongly controlled by t he intimal cells. The recognition of calcified deposits in intimal thi ckenings supports the hypothesis that a subset of fatty streaks might progress to fibrous plaques in human atherosclerosis.