Disruption Of Osteoprotegerin Has Complex Effects On Medial Destruction And Adventitial Fibrosis During Mouse Abdominal Aortic Aneurysm Formation

Aortic aneurysm refers to dilatation of the aorta due to loss of elasticity and degenerative weakening of its wall. A preventive role for osteoprotegerin (Opg) in the development of abdominal aortic aneurysm has been reported in the CaCl2-induced aneurysm model, whereas Opg was found to promote suprarenal aortic aneurysm in the AngII-inducedApoEknockout mouse aneurysm model. To determine whether there is a common underlying mechanism to explain the impact of Opg deficiency on the vascular structure of the two aneurysm models, we analyzed suprarenal aortic tissue of 6-month-oldApoE(-/-)Opg(-/-)mice after AngII infusion for 28 days. Less aortic dissection and aortic lumen dilatation, more adventitial thickening, and higher expression of collagen I and Trail were observed inApoE(-/-)Opg(-/-)mice relative toApoE(-/-)Opg(+/+) mice. An accumulation of alpha-smooth muscle actin and vimentin double-positive myofibroblasts was noted in the thickened adventitia ofApoE(-/-)Opg(-/-)mice. Our results suggest that fibrotic remodeling of the aorta induced by myofibroblast accumulation might be an important pathological event which tends to limit AngII-induced aortic dilatation inApoE(-/-)Opg(-/-)mice.