Wall Deformation, Wall Shear Stress and Atherosclerosis Around the Intercostal Ostia of C57 Mice

Dorsal surfaces and upstream regions around ostia of aortic branches are favored sites of atherosclerosis. Both asymmetrical stresses in branch walls and disturbed flow patterns have been suggested as contributing to this localization. In the present study, fluorescence images of the thoracic aortic tree of C57 mice were obtained using quantum dot (Qdot) bioconjugate markers for vascular cell adhesion molecule-1 (VCAM-1) and two-photon excitation laser scanning microscopy. The images show that dorsal surfaces and upstream regions of intercostal ostia have a higher intensity of VCAM-1 than the downstream region. We also investigated blood flow patterns and wall shear stress (WSS) in the descending aorta and proximal intercostal branches of C57 mice using micro-CT imaging and ultrasound velocity measurements, combined with computational fluid dynamics (CFD). The latter investigation showed that dynamical wall deformation caused by pulsatile pressure around the ostia induces blood flow patterns which create lower and oscillating WSS in the upstream region and dorsal surface than in the distal region. Comparisons of the Qdot marker and CFD studies demonstrate that the distribution of greater expression of VCAM-1 corresponds with lower and oscillating WSS around the branch ostia. Thus, local wall deformation may contribute to disturbed flow patterns that are known to be associated with increased VCAM-1 expression.