Abstract 640: Overexpression of Vasohibin-2 Exacerbates Development of Angiotensin II-Induced Thoracic Aortic Aneurysms Independent of VeEGF

Objective: Chronic angiotensin II (AngII) infusion promotes both thoracic (TAAs) and abdominal aortic aneurysms (AAAs) in mice. Vasohibin-2 (VASH2) is known to cause angiogenesis at the sprouting front of neovascularization. The purpose of this study was to examine whether VASH2 influenced AngII-induced TAAs. Methods: Male C57BL/6J mice (10-week-old) were injected with VASH2 or LacZ expressing adenovirus (Ad; 7.5 x 10 9 vp/100 μL) via tail vein at 2 week intervals. One week after the first injection, subcutaneous infusion of either AngII (1,000 ng/kg/min) or saline by mini osmotic pumps was started for 3 weeks. Consequently, mice were divided into 4 groups: AngII + Ad VASH2 (n=22), AngII + Ad LacZ (n=21), saline + Ad VASH2 (n=10), saline + Ad LacZ (n=8). Next, in order to examine whether VASH2 affected TAAs via VEGF regulation, bevacizumab was intraperitoneally administrated into mice; AngII + Ad VASH2 + saline (n=15), AngII + Ad VASH2 + bevacizumab (n=15). TAAs were evaluated in all mice by en face method. Third, human aortic smooth muscle cells (hSMCs) were infected with Ad VASH2 or Ad LacZ, stimulated with or without AngII to evaluate further mechanism. Result: Intima area of aortic arch was significantly larger in AngII + Ad VASH2 group than in AngII + Ad LacZ group (19.78 ± 0.40 mm 3 vs 17.74 ± 0.44 mm 3 , P < 0.001). Gelatin zymography demonstrated that AngII upregulated latent MMP-2 expression, and activated MMP-2 most prominently in AngII + VASH2 group. Protein expression of p21 and p53 in thoracic aortas was enhanced in AngII + VASH2 group. Positive TUNEL staining was observed in thoracic aortic wall of AngII + VASH2 group. No significant difference in intima area of aortic arch between AngII + Ad VASH2 + saline group and AngII + Ad VASH2 + bevacizumab group. In vitro, the same results were observed regarding protein expression of p21 and p53, and TUNEL staining. In addition, Annexin-V staining was detected only in AngII + VASH2 group. Conclusion: Overexpression of VASH2 accelerated development of AngII-induced TAAs in vivo. VASH2-induced cell apoptosis may influence AngII-induced TAA formation independent of VEGF.