Vasa vasorum in the tunica media and tunica adventitia of the porcine aorta.

Vasa vasorum supply both the tunica adventitia and the tunica media of major arteries with nutrients and oxygen. We estimated the density of von Willebrand factor-positive profiles of vasa vasorum visible in transversal histological sections of 123 tissue samples collected from five anatomical positions in the porcine aortae of growing pigs (n=25). The animals ranged in age from 0 to 230 days. The tunica media of the thoracic aorta had a greater vasa vasorum density, with microvessels penetrating deeper towards the lumen than in the abdominal aorta. The density of vasa vasorum gradually decreased with age in both the media and the adventitia. The relative depth into which the vasa vasorum penetrated and where they branched remained constant during the ageing and growth of the media. The ratio of the tunica media and tunica adventitia thicknesses did not change in the single aortic segments during ageing. The media of older animals received fewer but equally distributed vasa vasorum. A greater density of vasa vasorum in the media was correlated with greater media thickness and a greater elastin fraction (data on elastin taken from another study on the same samples). Immunohistochemical quantification revealed deeper penetration of vasa vasorum towards the adluminal layers of the tunica media that were hitherto reported to be avascular. The complete primary morphometric data, in the form of continuous variables, have been made available as a supplement. Mapping of the vasa vasorum profile density and position has promising illustrative potential for studies on atherosclerotic and inflammatory neovascularization, aortic aneurysms, and drug distribution from arterial stents in experimental porcine models.