We have applied an imaging system of phase-contrast X-ray CT to the detection of atherosclerotic plaque components by means of the differences of tissue mass densities. In this study, we investigated the effect of the anti-platelet therapies, widely used for secondly prevention of cardiovascular events, on plaque stability and examined whether this novel technique could detect the changes of plaque components under the therapy. Apolipoprotein E-deficient mice were fed on high-cholesterol diet alone and either with 0.1% cilostazol or clopidogrel for 10 weeks. We assessed atherosclerotic lesion volumes and components at brachiocephalic artery by the phase-contrast X-ray CT imaging and histochemistry. The phase-contrast X-ray CTimaging could reveal that cilostazol and clopidogrel significantly decreased atherosclerotic lesion volumes at brachiocephalic artery (31.2% reduction in cilostazol group and 37.4% reduction in clopidogrel group), compared with control group. In addition, the mass densities calculated by this method revealed the anti-platelet treatment increased stable plaque areas including high collagen content, but decreased unstable plaque areas including lipid and macrophage content. These findings were confirmed by histological analyses. Realtime PCR analyses indicated that anti-platelets inhibited gene expressions of cytokines and adhesion molecules, such as IFNc and ICAM-1. Anti-platelet therapies had a beneficial effect on plaque stability maybe due to anti-inflammatory actions. Phase-contrast X-ray CT imaging could quantify the plaque volume and qualify the plaque components affected by anti-platelet therapies. This novel phase-contrast X-ray CT imaging system could be a plausible method to detect the unstable plaque non-invasively in the future.
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