In vivo magnetic resonance imaging of-large spontaneous aortic aneurysms in old apolipoprotein E-deficient mice

Old ApoE-deficient mice were studied in vivo by magnetic resonance imaging (MRI) to prospectively evaluate vascular remodeling associated with atherosclerotic lesions. Material and Methods: Old female ApoE^-/- mice on a normal diet were followed by MRI at 2 Tesla for a 3-month period and killed for histopathology. Aortic dimensions were measured and compared. Results: High-quality in vivo MR images were obtained at 2 Tesla with in plane spatial resolution of 86 x 86 μm². On MRI, aortic lumen enlargement (>1.5-fold dilation) was seen in 10 of 13 mice, located predominantly in the suprarenal portion of the aorta. The mean maximal diameter of the aneurysms and of the aorta above and below the aneurysm were, respectively, 1.12±0.32 mm and 0.53±0.08 mm by MRI and 1.3±0.41 mm and 0.55±0.15 mm by histology. Matched histologic cross-sections of the aortic wall showed medial degradation with rupture of the internal elastic lamina at multiple sites, associated with fibrolipidic plaque containing cholesterol crystals. Conclusions: Aortic lumen enlargement was diagnosed in old ApoE^-/- mice at sites with advanced atherosclerotic plaques. MRI has potential both as an in vivo imaging technique for screening mouse models for vascular wall pathology and to follow arterial remodeling associated with the disease progression.