大動脈瘤破裂診断システムの開発と破裂予防に関する実験的研究

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Introduction : The first objective of this study is to develop the methodology to estimate aortic aneurysm biomechanically. The second objective is to estimate a significance of matrix metalloproteinase (MMP) compared with biomechanical stress.Methods : We used the elastase-induced rat aneurysmal model. 1) Measurement of the aneurysmal wall motion and geometry by intravascular ultrasound system. 2) Measurement of the wall stiffness by the pipette aspiration. 3) Histological analysis. 4) Measurement of the MMP activity by gelatin zymography.Results : Intra-aortic infusion of elastase produced significant aortic dilatation (control, 1.7±0.26mm, ; 7days, 5.46±1.38 mm ; 14days, 6.46±1.45 mm). No cases ruptured, but the daughter aneurysms were produced in a few cases. Aneurysmal wall motion significant decreased. Most aneurysm lumens contained mural thrombus. The elastic modulus of the maximal dilated position decreased once, and increased significantly. The excessive fibrosis occurred in adventitia of aneurysmal wall. The neutrophils mural infiltration occurred early time. MMP-2 activities increased in aneurysmal wall, but not MMP-9.Conclusions : In this model, instability of aneurysmal wall occur in maximal dilated position at first, and the area move to distal midsection. The balance of wall stress and wall strength is important to aneurysmal dilatation and rupture. MMP-2 needs to vascular remodeling. MMP-9 will destroy wall structure in this model.