Quantitative CT imaging of the spatio-temporal distribution patterns of vasa vasorum in aortas of apoE^-/-/LDL^-/- double knockout mice

Objective: To investigate the distribution of vasa vasorum (VV) relative to advanced atherosclerotic lesions (calcified, fibrotic or hemorrhaged) along the aortic wall of apoE^-/-/LDL^-/- mice at the age of 25 and 80 weeks using high-resolution nano-CT. Methods: Aortas from male apoE^-/-/LDL^-/- mice at the age of 25 weeks (n=4) and 80 weeks (n=7) were infused in situ with contrast agent and harvested for scanning with nano-CT. The spatial distribution of vasa vasorum [number and area/cross-section (mm²)] was compared to aortic luminal cross-sectional area and plaque cross-sectional area in the ascending aorta, aortic arch and descending aorta. Results were complemented with co-localized histology. Results: The number and total luminal cross-sectional area of VV showed a significant decrease in the ascending aorta and aortic arch from 25 to 80 weeks but not in the descending aorta. The number and cross-sectional area of VV showed significant local differences depending on whether it was near a fibrotic, and hemorrhaged or calcified plaque in animals at the age of 80 weeks. Area of VV progressively increased along the aorta from least in the ascending aorta < aortic arch < descending aorta in animals at the age of 80 weeks and is inverse in animals aged 25 weeks. Conclusion: Atherosclerotic lesion type is correlated to the number and cross-sectional area of VV in different aortic segments in apoE^-/-/LDL^-/- mice. The chronological development of VV along the aorta proceeds distally from the ascending aorta and aortic arch.