Serial, noninvasive, in vivo magnetic resonance microscopy detects the development of atherosclerosis in apolipoprotein E-deficient mice and its progression by arterial wall remodeling

Purpose: To test the ability of serial, in vivo magnetic resonance microscopy (MRM) to detect the development of atherosclerosis and quantify its progression in apolipoprotein E-deficient mice. Materials and Methods: The abdominal aortae of six ApoE(-/-) and three wild-type (WT) control mice were imaged by MRM at 9.4T. Proton density weighted images were obtained (TR = 2000, TE = 9 msec) using four signal averages. The image resolution was 109 x 109 x 500 mum(3). The six ApoE(-/-) mice underwent serial MRM three to five times over a period less than or equal to 44 weeks. Multiple, anatomically aligned MRM slices (N = 6-11 per time point, total 202) were compared serially in each animal. Results: The abdominal aorta remained free of atherosclerosis until 20 weeks of age but thereafter, atherosclerosis was identified in all ApoE(-/-) mice (P < 0.05 to P < 0.001), but no WT controls. Lesion progression was accompanied by positive remodeling in which atherosclerosis within the aortic wall was accommodated by an increase in total cross sectional area (P < 0.01), while lumen area was unchanged. Conclusion: Serial MRM demonstrated the development and progression of atherosclerosis in mouse aorta. Importantly, progression of atherosclerosis could be identified within individual animals. By following the same aortic lesions over time, MRM demonstrated that progression of atherosclerosis in mice is associated with positive arterial remodeling.