HUMAN AORTIC FIBROLIPID LESIONS - PROGENITOR LESIONS FOR FIBROUS PLAQUES, EXHIBITING EARLY FORMATION OF THE CHOLESTEROL-RICH CORE

  • 1 January 1985
    • journal article
    • research article
    • Vol. 120  (2) , 193-206
Abstract
The early development of the lipid-rich core and other features of artherosclerotic fibrous plaques was elucidated by examining discrete, small regions of raised intima in human aorta, which often bear a resemblance to both fatty streaks and fibrous plaques. Approximately 1/4 of small raised lesions (< 16 sq mm of surface area) contained little or no stainable lipid, while 3/4 had a characteristic appearance, which included a superficial layer of foam cells, a core of noncrystalline and/or crystalline lipid, and a developed or developing collagenous cap. Total intimal volumes of the lipid-containing lesions, termed fibrolipid lesions, ranged from 3 to 43 .mu.l, with the majority less than 16 .mu.l. Core lipid in the smallest lesions was located in the musculoelastic layer of the intima. In larger lesions the core extended luminally into the elastic hyperplastic layer, and cholesterol crystals were found more frequently. Total cholesterol concentrations in fibrolipid lesions was similar to that in fatty streaks; the ratio of unesterified to total cholesterol was relatively high, similar to that found in fibrous plaques. The formation of a lipid-rich core and cholesterol crystallization are early events in the development of many raised lesions; the consistent association between the superficial layer of foam cells and the deep-lying lipid-rich core raises the possibility of an influence, possibly indirect, of foam-cell lipid metabolism on core formation. The fibrolipid lesion may represent 1 stage in a potential transitional morphologic sequence between fatty streak and fibrous plaque.