Differential distribution of vasa vasorum in different vascular beds in humans

Objective: Vasa vasorum (VV) have been implicated to play a role in the pathogenesis of atherosclerosis. This study was designed to describe the distribution of VV density in different vascular beds in humans and to investigate the association between VV density and the known distribution of atherosclerosis in human arteries. Methods: Forty-two human arteries, harvested at autopsy or after explantation, were analyzed by three-dimensional microscopic-computed tomography (micro-CT). VV density, endothelial-surface-fraction (Σ VV endothelial-surface-area/vessel-wall-volume) and vascular-area-fraction (Σ VV area/vessel-wall-area) were calculated for coronary, renal and femoral arteries. Representatively five coronary, renal and femoral arteries were stained for endothelial cells (von Willebrand-Factor), macrophages (CD68), vascular endothelial growth factor (VEGF) and collagen (Sirius Red). Results: Coronary arteries showed a higher VV density compared to renal and femoral arteries (2.12 ± 0.26 n/mm² versus 0.61 ± 0.06 n/mm² and 0.66 ± 0.11 n/mm²; P < 0.05 for both) as well as a higher endothelial-surface-fraction and vascular-area-fraction. Histology showed a positive correlation between histologically derived VV density and CD68-positive cells/area (r = 0.54, P < 0.01), VEGF-immunoreactivity/area (r = 0.55, P < 0.01) and a negative correlation between VV density and collagen I content (r = 0.66, P < 0.05). Conclusion: This micro-CT study highlights a higher VV density in coronary than in peripheral arteries, supporting the relation between VV density and the susceptibility to atherosclerosis in different vascular beds in humans.