Severe structural damage of the seemingly non-diseased infrarenal aortic aneurysm neck

ObjectiveThe success of open and endovascular repair of abdominal aortic aneurysms (AAA) is hampered by postoperative dilatation of the anatomical neck of the AAA, which is used for graft attachment. The purpose of this study was to determine whether the macroscopically non-diseased infrarenal aortic neck of AAA is histologically and biochemically altered at the time of operative repair.MethodsWe harvested full-thickness aortic wall samples as longitudinal stripes spanning from AAA neck to aneurysmal sac in 22 consecutive patients undergoing open surgical AAA repair. Control tissue was obtained from five organ donors and five deceased subjects undergoing autopsy without evidence of aneurysmal disease. We assessed aortic media thickness, number of intact elastic lamellar units, media destruction, and neovascularization grade and performed immunohistochemistry for matrix metalloproteinase (MMP)-9 and phosphorylated c-Jun N-terminal kinase (p-JNK). MMP-9 and p-JNK protein expressions were quantified using Western Blots.ResultsThe median thickness of the aortic media was 1150 μm in control tissue (range, 1000-1300), 510 μm in aortic necks (250-900), and 200 μm in aortic sacs (50-500, P from nonparametric test for trend <.001). The number of intact elastic lamellar units was 33 in controls (range, 33-55), 12 in aortic necks (0-31) and three in aortic sacs (0-10, P < .001). The expression of MMP-9 and p-JNK as assessed by Western Blots (P = .007 and .061, respectively) and zymography (P for trend <.001) were up regulated in both the AAA neck and sac compared with controls. Except for p-JNK expression, differences between tissues were similar after the adjustment for age, gender, and type of sampling.ConclusionThe seemingly non-diseased infrarenal AAA neck in patients with AAA undergoing surgical repair shows histological signs of destruction and upregulation of potential drug targets.

Clinical RelevanceThe long-term durability of endovascular abdominal aortic aneurysm repair is hampered by endoleaks that are independently related to aortic neck dilatation in a substantial subset of patients. Within the present study, we have shown that seemingly non-diseased infrarenal aortic necks in patients whom AAA repair is indicated are characterized by substantial histological destruction, neovascularization and upregulation of proven drug targets such as MMP-9 and p-JNK. Further research assessing the impact of various drug treatments aimed at preventing aortic neck dilatation is warranted.