Filipin-positive, oil red O-negative particles in atherosclerotic lesions induced by cholesterol feeding.

In this study, extracellular spherical filipin-positive particles have been demonstrated using the fluorescent cholesterol probe, filipin, in rat, rabbit, and monkey atherosclerotic lesions induced by cholesterol feeding. Examination of tissue sections stained with both filipin (detects unesterified cholesterol) and oil red O (detects esterified cholesterol) demonstrated that extracellular filipin-positive particles did not stain with oil red O. Thus, extracellular filipin-positive particles represent a previously unrecognized structure in which cholesterol accumulates within atherosclerotic lesions.