ABSTRACT
BACKGROUND: Thickening of the pericoronary adipose tissue (PCAT) is a proven risk factor for coronary artery disease, but it is poorly understood whether PCAT stores pro-atherogenic substances with oxidized low-density lipoprotein (oxLDL) and low-density lipoprotein (LDL), and an anti-atherogenic substance with high-density lipoprotein (HDL) and supply them to the coronary intima. METHODS: Using immunohistochemical techniques, the localization of oxLDL, LDL and HDL in PCAT and its adjacent coronary segments was examined in 30 epicardial coronary arteries excised from 11 human autopsy cases. RESULTS: PCAT stored oxLDL and HDL in all, but LDL rarely, in 77 specimens examined, irrespective of the presence or absence of coronary plaques and underlying disease. The percentage (%) incidence of oxLDL, HDL and LDL deposits in intima was, respectively, 28, 10, 35 in 29 normal segments, 80 (p<0.05 vs. normal segments), 12, 75 in 19 white plaques (growth stage), 57, 36, 90 in 15 yellow plaques without necrotic core (NC; mature stage), and 40, 21, 100 (p<0.05 vs. normal segments) in 14 yellow plaques with NC (end-stage of maturation) as classified by angioscopy and histology. In coronary intima, oxLDL deposited in either a dotted or diffuse pattern whereas HDL and LDL showed diffuse patterns. Dotted oxLDL deposits were contained in CD68(+)-macrophages traversing the border of PCAT and adventitia, external and internal elastic laminae. Diffuse oxLDL and HDL deposits colocalized with intimal vasa vasorum. CONCLUSIONS: The results suggested that, as a hitherto unrecognized supplying route, the human PCAT stores oxLDL and HDL and oxLDL is supplied to coronary intima either by CD68(+)-macrophages or vasa vasorum and HDL by vasa vasorum, and that deposition of oxLDL and HDL in the intima increased with plaque growth but the former decreased while the latter increased further with plaque maturation. Molecular therapy targeting PCAT before plaque maturation could be effective in preventing atherosclerosis.
