Myeloperoxidase Associates With Degenerative Remodeling and Rupture of the Saccular Intracranial Aneurysm Wall.

Rupture of a saccular intracranial aneurysm (sIA) is often fatal. Thus, early detection of rupture-prone sIAs is vital. Myeloperoxidase (MPO), derived mainly from neutrophils, associates with sIA rupture, and therefore its role in sIA pathogenesis warrants further studies. We analyzed MPO and its association with other histological markers in 36 (16 unruptured and 20 ruptured) sIA samples by immunohistochemistry. MPO was present in all studied sIAs, and its expression associated with wall inflammatory cell infiltrations (r = 0.50, 0.63, and 0.75, all p < 0.002), degenerative remodeling (p = 0.002) and rupture (p = 0.003). MPO associated strongly with the presence of organized luminal thrombi (p < 0.001), which also stained positive for MPO. Polymorphonuclear MPO+ cells were detected in the sIA walls, indicating neutrophils as MPO-source. MPO correlated strongly with accumulation of oxidized lipids (r = 0.67, p < 0.001) and loss of smooth muscle cells (r = -0.68, p < 0.001), suggesting that MPO is a relevant source of oxidative stress leading to cell death in the sIA wall. Furthermore, MPO associated with erythrocyte fragmentation (r = 0.74, p < 0.001) and iron deposition (p = 0.041), 2 outcomes known to amplify MPO-dependent oxidative stress. Taken together, these results suggest that MPO associates with degenerative remodeling predisposing to sIA wall rupture and may serve as a biomarker of a rupture-prone sIA wall.