Role of Vasa Vasorum in Nourishment of the Aorta

Abstract

The media of arteries is virtually avascular. Thus, oxygen and nutrients must reach the cells of the media by diffusion from the lumen of the vessel and from adventitial vessels. The thickness of the thoracic aorta of man and dog exceeds the effective diffusion distance of oxygen, but nutrition is supplemented by vasa vasorum which enter into the outer layers of the media. Occlusion of vasa vasorum in dogs produces medial necrosis, which indicates that these vessels are essential for the nourishment of the aorta. Recently the microsphere method has been used to provide the first measurements of blood flow through vasa vasorum. There is substantial flow to the outer layers of media of the thoracic aorta in dogs, with virtually no blood flow in the inner layers. The vessels are very responsive to physiological stimuli: they dilate during infusion of adenosine and constrict during stimulation of sympathetic nerves. During acute increases in arterial pressure, blood flow to the media decreases probably from distortion of vasa vasorum. Vasa vasorum may play a role in disease states. Insufficient blood flow through vasa vasorum may contribute to medial necrosis of the aorta and to aortic atherosclerosis. A role of vasa vasorum in aortic changes in hypertension and other vascular diseases merits further study.

Ruptura dos vasa vasorum e hematoma intramural da aorta: um paradigma em mudança

“…These features are similar to those encountered in small coronary arteries, indicating that VV can regulate their own tone and consequently arterial wall perfusion. [6][7][8] Isolated porcine aortic VV responded to endothelium-dependent vasodilator substance P and to bradykinin similarly to the native artery, confirming the afore mentioned autoregulating aspect.…”

An ex vivo model for functional studies of myofibroblasts

“…11,25,26 In contrast, it has been estimated that less than 1% of the cells in human embryonic aorta are endothelial cells. 27 Since aortic tissue is a relatively pure source of VSMCs, and has the lowest ratio of endothelium to VSMCs in the vertebrate body, 28,29 it is surprising that sprouting aSMA-positive cells have not attracted more attention. Nonetheless, the endothelium is known for its sprouting capabilities 30 and there was a possibility that traces of endothelial cells from the capillary of tunica adventitia might contribute to formation of sprouts.…”

Angiogenesis in Atherogenesis

“…Of interest, arteries whose thickness is beyond the 150 to 200 m diffusion capacity of oxygen are characterized by adventitial vasa vasorum, which can even extend into the outer media in arteries media if the number of lamellar units exceeds 29 or the "critical depth" of 500 m. 92 Plaque neovascularization may, therefore, be the logical extension of the "anatomic" link between vasa vasorum, artery size, and tissue partial oxygen tension. Bjoernhelden et al supported this theory by demonstrating areas of hypoxia in the atherosclerotic plaque.…”