Cholesteryl ester-rich inclusions from human aortic fatty streak and fibrous plaque lesions of atherosclerosis. I. Crystalline properties, size and internal structure.

Cholesteryl esters, the major lipid in the lesions of human atherosclerosis, occurred in fatty streaks and fibrous plaques from 42 adults as spherical inclusions whose diameters averaged 1.99 +/- 0.48 and 2.16 +/- 0.62 mu, respectively, and which with polarizing light microscopy resolved into a mixture of various proportions of anisotropic and isotropic forms. Anisotropic forms had diameters of 1.9 +/- 0.4 mu, uniaxial-like symmetry with a formée cross image, a whitish gray interference color under cross polarizer and analyzer, second order blue and first order yellow interference colors with a tint plate, a birefringence of 0.0412 +/- 0.0054 and a refractive index of 1.559 +/- 0.0014. Their probable structural organization is primarily a lyotropic smectic mesophase (liquid crystal) of cholesteryl esters secondarily organized into multiple concentric lamellae. Isotropic forms had diameters of 2.3 +/- 0.6 mu and were optically inactive irrespective of their orientation. At 23 C, fatty streak inclusions from 21 subjects averaged significantly higher in the proportion of anisotropic forms, 85.5 +/- 9.3%, than did fibrous plaque inclusions from 21 subjects, which had 32.4 +/- 16.3% anisotropic forms (P < 0.01).