MRI visualized neo-intimal dissection and co-localization of novel apoptotic markers apolipoprotein C-1, ceramide and caspase-3 in a Watanabe hyperlipidemic rabbit model

Purpose Apoptotic arterial wall vascular smooth muscle cell death is known to contribute to plaque vulnerability and rupture. Novel apoptotic markers like apolipoprotein C-I have been implicated in apoptotic human vascular smooth muscle cell death via recruiting a neutral sphingomyelinase (N-SMase)-ceramide pathway. In vivo relevance of these observations in an animal model of plaque rupture has not been shown. Methods and Results Using Watanabe rabbits, we investigated three different groups (group 1, three normal Watanabe rabbits; group 2, six Watanabe rabbits fed with high cholesterol diet for 3 months; group 3, five Watanabe rabbits with similar diet but additional endothelial denudation). We followed progression of atherosclerosis to pharmacologically induced plaque rupture non-invasively using novel 3D magnetic resonance Fast-Field-Echo angiography (TR = 7.2, TE = 3.6 ms, matrix = 512 × 512) and Fast-Spin-Echo vessel wall imaging methods (TR = 3 heart beats, TE = 10.5 ms, matrix = 304 × 304) on 1.5 T MRI. MRI provided excellent image quality with good MRI versus histology vessel wall thickness correlation (r = 0.8). In six animals of group 2/3 MRI detected neo-intimal dissection in the abdominal aorta which was accompanied by immuno-histochemical demonstration of concomitant aforementioned novel apoptotic markers, previously implicated in the apoptotic smooth muscle cell death in vitro. Conclusions Our studies suggest a potential role for the signal transduction pathway involving apolipoprotein C-I for in vivo apoptosis and atherosclerotic plaque rupture visualized by MRI.