Ongoing angiogenesis in blood vessels of the abdominal aortic aneurysm

ABSTRACT

Pathogenesis of the abdominal aortic aneurysm has been attributed to neovascularization of the aortic wall. However, it is not clear whether angiogenesis persists in the aneurysm. In sections of aneurysms, we determined the immunohistochemical distributions of the alpha v beta 3 integrin, tenascin and endothelial nitric oxide synthase (eNOS), which are markers respectively, of angiogenesis, matrix remodeling and vasoregulatory function. In addition, we used reverse transcription followed by in situ PCR, to determine the distribution of alpha v mRNA. All aneurysm specimens exhibited extensive increases of wall vascularization as compared with the control aortic wall, and showed the presence of perivascular inflammatory exudates containing macrophages and lymphocytes. The neovascularization consisted of thick-walled vessels in the media and adventitia, and capillaries in the subintima. The majority of vessels stained positively for the alpha v beta 3 antigen and eNOS. Tenascin was deposited as bands that circumscribed thick-walled vessels. The distribution of av mRNA was extensive and was positive even in those vessels that failed to stain for the alpha v beta 3 protein. No staining was evident in control aortas for the alpha v beta 3 antigen, tenascin or alpha v mRNA. The upregulation of av mRNA and the alpha v beta 3 integrin in blood vessels surrounded by a matrix expressing tenascin, indicates that angiogenesis is an ongoing process in the mature aortic aneurysm.