A novel rat model of abdominal aortic aneurysm using a combination of intraluminal elastase infusion and extraluminal calcium chloride exposure

Abstract

Objective: An ideal animal model of abdominal aortic aneurysm (AAA) is of great importance for clarifying unknown complex mechanisms of the pathogenesis. We introduce a new, simple technique to create reliable AAAs that simulate human aneurysms. Methods: Experimental models of AAAs were created in 71 rats by means of a 20-minute application of intraluminal elastase (30 U) and extraluminal calcium chloride (0.5M) in the 1-cm segment of infrarenal abdominal aorta (group EC, n ‫؍‬ 26). A single application of elastase (group E, n ‫؍‬ 24) or calcium chloride (group C, n ‫؍‬ 21) was used as control. The treated aorta in each group was measured under physiologic conditions and harvested at 1 and 4 weeks. Successful AAA formation was defined as a dilation ratio >50%. Inflammatory response, elastolytic activity, and histology in the treated aorta were evaluated among the three groups. Results: The surgical procedure in each group was similarly completed for approximate 30 minutes and performed without any technical failure or operative death. At 4 weeks, the dilation ratio and wall thickness were 94.8% ؎ 9.9% and 125.4 ؎ 5.6 m in group EC, 43.3% ؎ 6.3% and 149.6 ؎ 6.5 m in group E, and 10.9% ؎ 4.2% and 152.9 ؎ 7.2 m in group C. The success rate of AAA formation in group EC (92.7%) was significantly higher than that in group E (25.0%) and group C (0.0%). Less elastin content in the aortic wall was observed in group EC. At 1 week, tumor necrosis factor-␣ and interleukin-1␤ messenger RNA (mRNA) expressions were significantly upregulated, and CD3؉ and CD11b؉ cells were significantly infiltrated into the treated aorta of group EC, compared with groups E or C. Gelatinolytic activities and mRNA expressions of matrix metalloproteinase (MMP)-2 and MMP-9 were also significantly activated in group EC. Conclusion: The rat AAA model using a combination of intraluminal elastase infusion and extraluminal calcium chloride exposure is simple and easy to perform and is highly reliable and reproducible to create a saccular aneurysm similar to human AAAs. This model could be more useful to clarify AAA pathogenesis, mechanisms, and treatment interventions in experimental researches. ( J Vasc Surg 2009;50:1423-32.)Clinical Relevance: Abdominal aortic aneurysm (AAA) typically has a silent nature, and its rupture has high morbidity and mortality. There are currently no therapeutic approaches to prevent AAA, and complete mechanisms of AAA formation are still poorly understood. We developed a novel rat AAA model using a combination of intraluminal elastase infusion and extraluminal calcium chloride exposure. This model is simple and easy to perform and is highly reliable and reproducible to create a saccular aneurysm. It could become a powerful tool not only to elucidate etiopathogenetic mechanisms of AAA formation but also to explore new diagnostic and therapeutic possibilities.

Free-radical scavenger edaravone inhibits both formation and development of abdominal aortic aneurysm in rats

“…12 Because we regarded this AAA condition as simulating the pre-existing form or a small AAA in humans, edaravone was given beginning 7 days after aneurysm preparation. The present study showed that edaravone treatment starting at 7 days after aneurysm preparation inhibited AAA further development.…”

“…However, we demonstrated that our AAA model is simple and easy to perform, is highly reliable, and is reproducible to create a saccular aneurysm. 12 The second limitation is the lack of protein analysis for proinflammatory cytokines and MMPs and signal transduction mechanism analysis for the antioxidative effects of edaravone. The most likely mechanism for the protective effect of edaravone is a reduction in oxygen radicals, but further studies are needed, especially with regard to its effects on inflammatory cell infiltration and to exclude other possible mechanisms of AAA regression.…”

“…An experimental AAA model was created by means of simple application of intraluminal elastase and extraluminal calcium chloride, according to our recent report. 12 Briefly, rats anesthetized with an intraperitoneal administration of pentobarbiturate (1 mg/kg) were placed under an operating Leica M651 microscope (Leica Microsystems, Heerburgg, Switzerland; original magnification, ϫ6 to ϫ10). After a midline abdominal incision and an abdominal aorta exposure, 30 units of elastase (135 U/mg; Elastin Products, Owensville, Mo) were applied to the 1-cm infrarenal aorta intraluminally and 0.5 mmol/L of CaCl 2 (Sigma-Aldrich, Tokyo, Japan) extraluminally for 20 minutes.…”

Activation of transglutaminase type 2 for aortic wall protection in a rat abdominal aortic aneurysm formation

“…Experimental AAA model was created by means of a simple application of both intramural elastase and extraluminal calcium chloride, according to our recently described method. 21 Briefly, rats anesthetized with an intra-peritoneal administration of pentobarbiturate (1 mg/kg) were placed under an operating microscope Leica M651 (Leica Microsystems, Heerbrugg, Switzerland) with 6 to 10 times magnification. After a midline abdominal incision and an abdominal aorta exposure, 30 U of elastase (135 U/mg; Elastin Products, Owensville, Mo) was applied to the 1 cm infrarenal aorta intraluminally and 0.5 M of CaCl 2 (Sigma-Aldrich, Tokyo, Japan) extraluminally for 20 minutes.…”

“…The AAA is defined as when the dilation ratio is more than 50%. 21 Quantitative real-time polymerase chain reaction (PCR) analysis. Total RNA was isolated from AAA samples using an RNeasy fibrous tissue mini-kit (Qiagen K.K., Tokyo, Japan) according to manufacturer's instructions.…”