The expression of matrix metalloproteinase-9 and the pathological changes of vascular smooth muscle cell in patients with acute ascending aortic dissection / 中华胸心血管外科杂志

ABSTRACT

Objective Ascending aortic dissection(AAD),for which the pathogenesis remains unknown,is life-threatening.Matrix metalloproteinase-9(MMP-9)and the pathological changes of vascular smooth muscle cells(VSMCs)have been reported to have roles the pathogenesis.The study examined the expression of matrix metalloproteinase-9(MMP-9)and the pathological changes of,VSMCs in patients with AAD.Methods AAD samples were taken from 35 patients(disease group)in acute phase during aortic replacement operation for AAD and control samples were corresponding part of ascending aorta(control group,n=21)collected from the donor hearts for transplantation.Transmission electron microscepe,hematoxylin-eosin(H-E)staining.Mallory staining were used for observing the pathological changes of VSMCs and matrix in the affected aortic wall.The immunohistochemicai staining of MMP-9 was carried out in both groups and semi-quantified by staining intensity analysis.The affected patients were further grouped according to the diameter of dissected aorta as with a AAD of <55 mm or with a AAD of≥55 mm.The associations of clinical factors,such as smoking status,hypertensive disease and aneurysm diameter,with the expression of MMP-9 were analyzed.Results Increased synthetic function of VSMCs with decreased density,disrupted elastic fibers and fibrosis in the dissected aortic wall were observed in the disease group,but not in the control group.MMP-9 was scarcely expressed in the aortic wall of the patients in the control group,though it was notably expressed in the VSMCs of disease group.Both subgroups presented more MMP-9 than the control group(both P<0.001).In the disease group,sub-group with a AAD diameter of ≥55 mm presented more MMP-9 than that with a diameter of <55 mm(P<0.05).MMP-9 expression was positively correlated with a history of hypertension(P<0.01)or a great aneurysm diameter(P<0.05).MMP-9 expression was not associated with age,smoking status or other clinical factors.Conclusion Increased secretion of VSMCs and the expression of MMP-9 induced by elevated blood pressure may lead to the destruction of matrix proteins.The resulting fibrosis of the aortic wall would decrease the tensile strength of the wall.When the fibrotic aortic wall dilated further,the increased expression of MMP-9 would aggravate the damage to the wall.It can be speculated that acute AAD would occur as a result of partial tearing of the aortic intima.