Inflammatory changes in the aneurysm wall: a review.
ABSTRACT Rupture of a saccular intracranial artery aneurysm (IA) causes subarachnoid hemorrhage, a significant cause of stroke and death. The current treatment options, endovascular coiling and clipping, are invasive and somewhat risky. Since only some IAs rupture, those IAs at risk for rupture should be identified. However, to improve the imaging of rupture-prone IAs and improve IA treatment, IA wall pathobiology requires more thorough knowledge. Chronic inflammation has become understood as an important phenomenon in IA wall pathobiology, featuring inflammatory cell infiltration as well as proliferative and fibrotic remodulatory responses. We review the literature on what is known about inflammation in the IA wall and also review the probable mechanisms of how inflammation would result in the degenerative changes that ultimately lead to IA wall rupture. We also discuss current options in imaging inflammation and how knowledge of inflammation in IA walls may improve IA treatment.
- SourceAvailable from: Eduardo Anglés-Cano[show abstract] [hide abstract]
ABSTRACT: Acquired abdominal aortic aneurysms are usually associated with a mural thrombus through which blood continues to flow. Some early data suggest that aneurysmal evolution correlates with the biological activity of the thrombus. Our hypothesis was therefore that the thrombus could adsorb blood components and store, release, and participate in the activation of proteases involved in aneurysmal evolution. For this purpose, we have explored both the metalloproteinase and fibrinolytic systems in the thrombus and the wall of human aneurysms. We have first investigated blood clot formation and lysis in vitro. Spontaneous clotting induces a release of promatrix metalloproteinase (pro-MMP)-9 into the serum that was fourfold higher than in paired control plasma (P < 0.001). Fibrinolysis progressively released more MMP-9 in a time-dependent manner (P < 0.01). After selective isolation, we demonstrated that polymorphonuclear leukocytes are the main source of MMP-9 release during clot formation. Protease content was then analyzed in 35 mural thrombi and walls of human abdominal aortic aneurysms sampled during surgical repair. In 15 aneurysms, the liquid phase at the interface between the thrombus and the wall was sampled separately. Both thrombus and wall contained MMP-2 and MMP-9 but the ratio MMP-9/MMP-2 was higher in the thrombus than in the wall. The liquid interface also contained active MMP-9. Immunohistochemistry of the thrombus confirmed these findings, showing the presence of polymorphonuclear leukocytes at the luminal pole of the thrombus, co-localizing with MMP-9 storage. In contrast, MMP-3 and MMP-7 were only present in the aneurysmal wall. Plasminogen was present in the mural thrombus but plasmin activity was present in both thrombus and wall. In the liquid interface, plasmin-alpha(2)-anti-plasmin complexes were detected demonstrating in vivo the activation of plasminogen. In contrast, u-PA and t-PA were detectable only in the wall, suggesting that plasminogen present in the thrombus could be activated by factors secreted by the arterial wall. This was demonstrated in vitro, in which co-incubation of thrombus and wall extracts generated plasmin in the presence of a fibrin matrix and activated MMPs. In conclusion, our study strongly suggests that the mural thrombus, by trapping polymorphonuclear leukocytes and adsorbing plasma components could act as a source of proteases in aneurysms that may play a critical role in enlargement and rupture.American Journal Of Pathology 12/2002; 161(5):1701-10. · 4.52 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Kyoto University (京都大学) 0048 新制・課程博士 博士(医学) 甲第14457号 医博第3302号 新制/医/972 UT51-2009-D169 2009-03-23 京都大学大学院医学研究科脳統御医科学系専攻 (主査)教授 金子 武嗣, 教授 林 拓二, 教授 開 祐司 学位規則第4条第1項該当01/2007;
- [show abstract] [hide abstract]
ABSTRACT: A cerebral aneurysm (CA) causes catastrophic subarachnoid hemorrhage. Degradation of extracellular matrix in arterial walls is a prominent feature of cerebral aneurysms. We investigated the expression and role of cysteine cathepsins, collagen- and elastin- degrading proteinases, in CA progression. CAs were induced in Sprague-Dawley rats with or without cysteine cathepsin inhibitor, NC-2300. Expression of cathepsin B, K, S, and cystatin C, an endogenous inhibitor of cysteine cathepsins, in aneurysmal walls was examined in quantitative RT-PCR and immunohistochemistry. The activity of cysteine cathepsins and collagenase I and IV in aneurysmal walls was also assessed. Finally, expression of cysteine cathepsins and cystatin C in human CAs was examined. Quantitative RT-PCR and immunohistochemistry revealed upregulated expression of cathepsin B, K, and S in the late stage of aneurysm progression. In contrast, cystatin C expression was reduced with aneurysm progression. Treatment with NC-2300 resulted in the decreased incidence of advanced CAs. The activity of cysteine cathepsins and collagenase I and IV in aneurysmal walls was reduced and elastin content was increased in the NC-2300-treated group. Finally, immunohistochemistry for cysteine cathepsins and cystatin C expression in human CAs showed the same expression pattern as in the rat study. Data obtained by using NC-2300 revealed an important role of cysteine cathepsins in the progression of CAs. Our findings strongly suggest that an imbalance between cysteine cathepsins and their inhibitor may cause the excessive breakdown of extracellular matrix in the arterial walls leading to the progression and rupture of CAs.Stroke 09/2008; 39(9):2603-10. · 6.16 Impact Factor