OBJECTIVETo investigate the expression of matrix metalloproteinase-9 (MMP-9) in the arachnoid membrane around posterior communicating artery aneurysms.

METHODSTwelve patients with posterior communicating artery aneurysms undergoing surgical intervention in our hospital between November, 2010 and November, 2011 were enrolled as the case group along with 6 concurrent patients with severely head trauma or epilepsy as controls. The expression of MMP-9 in the aneurysmal walls and the arachnoid membrane was examined in immunohistochemistry, and HE staining and Sirus red staining were performed to examine the pathological changes.

RESULTSThe perianeurysmal arachnoid membrane showed tissue destruction and disruption of the connections between the membrane and the artery wall with local detachment. Compared with that in the control group, the level of MMP-9 in the arachnoid membrane was significantly higher in the case group (P<0.05), but significantly lower than that in the aneurysm wall within the same sample (P<0.05). No differences were found in the levels of MMP-9 in the aneurysm patients with different ages or Hunt-Hess scale scores.

CONCLUSIONMMP-9 is closely related with the formation of posterior communicating artery aneurysms by causing degradation of extracellular matrix of the vascular wall and the arachnoid membrane.