Micro-ultrasound imaging assessment of carotid plaque characteristics in apolipoprotein-E knockout mice

This study was aimed to test the hypothesis that noninvasive assessment of carotid plaques can be achieved by high-resolution micro-ultrasound imaging in apolipoprotein-E knockout (apoE-KO) mice. Forty-two male apoE-KO mice were fed a high-fat diet and atherosclerotic lesions in the left common carotid artery were induced by perivascular placement of constrictive collars. Eight weeks after surgery, all mice were divided into interventional group (n=21) which received mental stress stimulation and intraperitoneal injection of lipopolysaccharide, and control group (n=21) which received only 0.9% sodium chloride solution for 4 weeks. Plaque morphology and flow velocities were evaluated by micro-ultrasonography. The results showed that micro-ultrasound imaging and corresponding cross-sectional histopathology data revealed positive correlations for plaque area, intima-medial thickness (IMT), eccentric index (EI) and remodeling index (RI) (all p<0.05). Ultrasound-derived IMT, EI and RI in the ruptured plaques were significantly greater than those in the nonruptured plaques (all p<0.05). Maximal flow velocity (Vmax) was higher in the ruptured plaque sites compared with nonruptured plaques sites (p<0.001). Multivariate logistic regression analysis revealed that IMT and Vmax were independent predictors of plaque rupture. In conclusion, micro-ultrasound imaging provides a reliable approach to the noninvasive and quantitative assessment of carotid plaques in apoE-KO mice.