Name: murine surgical model of topical elastase induced descending thoracic aortic aneurysm
Uploaded: 2019-08-24T15:00:00
Description: Watch this Scientific Journal Video about Murine Surgical Model of Topical Elastase Induced Descending Thoracic Aortic Aneurysm at JoVE.com

This work was supported by AHA Scientist Development Grant 14SDG18730000 (M.S.), NIH K08 HL098560 (G.A.) and RO1 HL081629 (G.R.U.) grants. This project was supported by the Thoracic Surgery Foundation for Research and Education (TSFRE) Research Grant (PI: G. Ailawadi). The content is solely the responsibility of the authors and does not necessarily represent the views of the NHLBI or the TSFRE. We thank Anthony Herring and Cindy Dodson for their knowledge and technical expertise.

Animal protocols were approved by the University of Virginia Institutional Animal Care and Use Committee (No. 3634).
1. Induction of anesthesia and intubation
<ol>
	<li>Place an 8-10-week-old male C57BL/6 mouse in a closed chamber with continuous flow of 5% isoflurane and oxygen mixture for 5 min, until respirations are visibly slowed. 
	NOTE: Different strains, genders and ages of mice can be used depending on the experimental protocol. Female mice may be more difficult to intubate bec...

<ol>
	<li>Coady, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=What+is+the+appropriate+size+criterion+for+resection+of+thoracic+aortic+aneurysms.">What is the appropriate size criterion for resection of thoracic aortic aneurysms.</a> Journal of Thoracic and Cardiovascular Surgery. 113 (3), 489-491 (1997).</li><li>Aggarwal, S., Qamar, A., Sharma, V., Sharma, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abdominal+aortic+aneurysm:+A+comprehensive+review.">Abdominal aortic aneurysm: A comprehensive review.</a> Experimental and Clinical Cardiology. 16 (1), 11-15 (2011).</li><li>Bickerstaff, L. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thoracic+aortic+aneurysms:+a+population-based+study.">Thoracic aortic aneurysms: a population-based study.</a> Surgery. 92 (6), 1103-1108 (1982).</li><li>Cheng, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endovascular+aortic+repair+versus+open+surgical+repair+for+descending+thoracic+aortic+disease+a+systematic+review+and+meta-analysis+of+comparative+studies.">Endovascular aortic repair versus open surgical repair for descending thoracic aortic disease a systematic review and meta-analysis of comparative studies.</a> Journal of the American College of Cardiology. 55 (10), 986-1001 (2010).</li><li>Walsh, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endovascular+stenting+versus+open+surgery+for+thoracic+aortic+disease:+systematic+review+and+meta-analysis+of+perioperative+results.">Endovascular stenting versus open surgery for thoracic aortic disease: systematic review and meta-analysis of perioperative results.</a> Journal of Vascular Surgery. 47 (5), 1094-1098 (2008).</li><li>Absi, T. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+patterns+of+gene+expression+distinguishing+ascending+aortic+aneurysms+from+abdominal+aortic+aneurysms:+complementary+DNA+expression+profiling+in+the+molecular+characterization+of+aortic+disease.">Altered patterns of gene expression distinguishing ascending aortic aneurysms from abdominal aortic aneurysms: complementary DNA expression profiling in the molecular characterization of aortic disease.</a> The Journal of Thoracic and Cardiovascular Surgery. 126 (2), 344-357 (2003).</li><li>Ailawadi, G., Eliason, J. L., Upchurch, G. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Current+concepts+in+the+pathogenesis+of+abdominal+aortic+aneurysm.">Current concepts in the pathogenesis of abdominal aortic aneurysm.</a> Journal of Vascular Surgery. 38 (3), 584-588 (2003).</li><li>Ikonomidis, J. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+murine+model+of+thoracic+aortic+aneurysms.">A murine model of thoracic aortic aneurysms.</a> Journal of Surgical Research. 115 (1), 157-163 (2003).</li><li>Daugherty, A., Manning, M. W., Cassis, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Angiotensin+II+promotes+atherosclerotic+lesions+and+aneurysms+in+apolipoprotein+E-deficient+mice.">Angiotensin II promotes atherosclerotic lesions and aneurysms in apolipoprotein E-deficient mice.</a> Journal of Clinical Investigation. 105 (11), 1605-1612 (2000).</li><li>Trachet, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ascending+Aortic+Aneurysm+in+Angiotensin+II-Infused+Mice:+Formation,+Progression,+and+the+Role+of+Focal+Dissections.">Ascending Aortic Aneurysm in Angiotensin II-Infused Mice: Formation, Progression, and the Role of Focal Dissections.</a> Arteriosclerosis, Thrombosis, and Vascular Biology. 36 (4), 673-681 (2016).</li><li>Johnston, W. 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The thoracic and abdominal aorta are cellularly and embryologically distinct, which is relevant to aneurysmal disease14,15,16. Therefore, a specific animal model to study TAA is needed. Though other murine dTAA models have been published8, ours is the only model to create descending thoracic aortic dilatation which can be considered truly aneurysmal (over 50% dilation). Furthermore, our model is relativel...

The purpose of this method is to study the development, pathophysiology, and structural changes in the murine descending thoracic aorta during aortic aneurysm formation. Our model offers a reproducible and consistent method to induce thoracic aortic aneurysms (dTAA) in mice thereby allowing for the testing of various genetic and pharmacologic inhibitors. This work can help identify drugs and gene-therapies which could be translated to a viable treatment strategy for humans with dTAA disease.
dTAAs form when the wall of the thoracic aorta becomes weakened and dilates over time until reaching a critical diameter when tearing or rupture can then occur. Clinically, dTAA can progress in silence, increasing in size until the structure of the aortic wall is so distorted that it eventually fails, with catastrophic consequences. Concerningly, symptoms usually develop only when the aneurysm has reached a perilous size (100-150% dilation) and is at high risk for dissection or rupture1,2. dTAA rupture is almost universally lethal3, and elective surgical repair carries significant morbidity4,5. Furthermore, most patients carry the diagnosis of an aortic aneurysm for approximately 5 years before surgical repair6,7. This window represents an opportune time to intervene non-surgically. Thus, medical therapies to treat or slow progression of dTAA are needed and would represent a significant advancement to the field of aneurysm research. There are currently no medical treatments for dTAA available, mostly because of an incomplete understanding of dTAA pathogenesis.
Over the last 20 years, several dTAA animal models have been developed, but each of these models were distinct from our own and did not produce robust aneurysms. A murine dTAA model most similar to ours was developed by Ikonomidis et al.8, which includes direct application of CaCl2 to the adventitia of the aorta. Though our model was adapted from many of the techniques set forth by Ikonomidis, our model is unique in three separate ways. First, in our model the aorta is exposed to topical elastase for 3-5 minutes, compared to 15 minutes of CaCl2 exposure. Second, aortic dilation occurs in 2 weeks, compared to 16 weeks in the CaCl2 model. Last, our model consistently produces aneurysms of approximately 100% dilatation, compared to the aortic dilatations of 20-30% produced by CaCl2 application (which cannot be truly considered aneurysms as they are defined as an increase in aortic diameter &#62;50%). There are other non-surgical murine models of aneurysm formation, such as the Apo E knockout mouse, which form robust aneurysms with infusion of angiotensin II. However, these mice develop supra-renal or ascending thoracic aortic aneurysms rather than aneurysms specifically in the descending thoracic aorta9,10.
The rational for this protocol is to have a simple, inexpensive, and time suitable way to study dTAA in a murine model. The mouse model provides a unique opportunity to utilize many genetic and cell-specific knockouts that have been found to be impactful in other vascular diseases. The use of our specific TAA model has been well received and experiments utilizing it have been published in high impact journals11,12. To this point, the model has been used to investigate possible genetic and pharmacologic treatments that had a significant effect in the abdominal aortic aneurysm (AAA) murine models; however, as our lab has expanded use of the dTAA model, we are finding targets unique to dTAA formation which could be used as targeted therapies in humans.
This model is most appropriate for labs that have murine micro-surgical capabilities. Though it is technically challenging, it can be executed consistently even by researchers with no prior surgical experience. For a researcher with no murine surgical experience the model can be mastered in approximately 20 operative sessions (or approximately 50 mice). For the researcher with prior surgical experience, the model can be mastered in 5 operative sessions (approximately 20 mice). We believe with a high-quality video, the time to mastery can be further reduced. After proficiency is achieved, the procedure can be completed in 35 minutes for the surgery, and 20 minutes for the terminal harvest. The surgeons in our lab can complete 10-12 full surgeries per day, with an operative mortality rate of 5-10%. The most common cause of mortality is lung injury upon entry to the chest, anesthetic toxicity, or tear of the aorta during dissection. In addition to dTAA research, this model also serves as a guide for safe and easy access to the thoracic aorta and lung hilum for researchers studying other interventions in the chest.&#160;

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			<td height="21" style="height:21px;width:243px;">Angiocatheter (22G)</td>
			<td style="width:191px;"></td>
			<td style="width:161px;"></td>
			<td style="width:167px;">Used for ET Tube</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Dumont Tweezers; Pattern #7 x2</td>
			<td style="width:191px;">Roboz</td>
			<td style="width:161px;">RS-4982</td>
			<td style="width:167px;"></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Graefe Tissue Forceps</td>
			<td style="width:191px;">Roboz</td>
			<td style="width:161px;">RS-5158</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Harms Forceps x2</td>
			<td style="width:191px;">Roboz</td>
			<td style="width:161px;">RS-5097</td>
			<td></td>
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			<td height="42" style="height:42px;width:243px;">Intracardiac Needle Holder; Extra Delicate; Carbide Jaws; 7&#34; Length</td>
			<td style="width:191px;">Roboz</td>
			<td style="width:161px;">RS-7800</td>
			<td></td>
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			<td height="21" style="height:21px;width:243px;">&#160;KL 1500 LED Light Source</td>
			<td style="width:191px;">Leica</td>
			<td style="width:161px;">150-400</td>
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			<td height="21" style="height:21px;width:243px;">&#160;M205A Dissction Microscope</td>
			<td style="width:191px;">Leica</td>
			<td style="width:161px;">CH 94-35</td>
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			<td height="42" style="height:42px;width:243px;">Iris Scissors, 11cm, Tungsten Carbide</td>
			<td style="width:191px;">World Precision Instruments</td>
			<td style="width:161px;">500216-G</td>
			<td style="width:167px;"></td>
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			<td height="42" style="height:42px;width:243px;">Metal Clip board</td>
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			<td style="width:167px;">Use with the Mouse Retractor Set&#160;</td>
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			<td height="42" style="height:42px;width:243px;">Mouse Retractor Set</td>
			<td style="width:191px;">Kent</td>
			<td style="width:161px;">SURGI-5001</td>
			<td style="width:167px;">Need 2 short and 1 tall fixators</td>
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		<tr height="84">
			<td height="84" style="height:84px;width:243px;">Mouse Ventilator MiniVent Type 845, 115 V, Power Supply with US Connector</td>
			<td style="width:191px;">Harvard Apparatus</td>
			<td style="width:161px;">73-0043</td>
			<td style="width:167px;">MiniVent Ventilator for Mice (Model 845), Single Animal, Volume Controlled</td>
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			<td height="42" style="height:42px;width:243px;">Sigma Aldrich</td>
			<td style="width:191px;">Elastase from porcine pancreas</td>
			<td style="width:161px;">E0258-50MG</td>
			<td style="width:167px;">Can be purchased in various size bottles</td>
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			<td height="63" style="height:63px;width:243px;">Small Vessel Cauterizer Kit</td>
			<td style="width:191px;">Fine Science Tools</td>
			<td style="width:161px;">18000-00</td>
			<td style="width:167px;">Recommend using rechargable AA batteries</td>
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			<td height="42" style="height:42px;width:243px;">Spring Scissors, 10.5cm</td>
			<td style="width:191px;">World Precision Instruments</td>
			<td align="right" style="width:161px;">14127</td>
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			<td height="21" style="height:21px;width:243px;">Steril Swabs (Sponges)</td>
			<td style="width:191px;">Sugi</td>
			<td align="right" style="width:161px;">31603</td>
			<td style="width:167px;">Can be cut to size</td>
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			<td height="21" style="height:21px;width:243px;">Surgi Suite Surgical Platform</td>
			<td style="width:191px;">Kent</td>
			<td style="width:161px;"></td>
			<td style="width:167px;">Attach to clip board&#160;</td>
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			<td height="21" style="height:21px;width:243px;">Tech IV Isoflurane Vap</td>
			<td style="width:191px;">Jorgensen&#160;Laboratories&#160;</td>
			<td style="width:161px;">J0561A</td>
			<td style="width:167px;">Anesthesia vaporizer&#160;</td>
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murine surgical model of topical elastase induced descending thoracic aortic aneurysm

According to the Center for Disease Control, aortic aneurysms (AAs) were considered a leading cause of death in all races and both sexes from 1999-2016. An aneurysm forms as a result of progressive weakening and eventual dilation of the aorta, which can rupture or tear once it reaches a critical diameter. Aneurysms of the descending aorta in the chest, called descending thoracic aortic aneurysms (dTAA), make up a large proportion of aneurysm cases in the United States. Uncontained dTAA rupture is almost universally lethal, and elective repair has a high rate of morbidity and mortality. The purpose of our model is to study dTAA specifically, to elucidate the pathophysiology of dTAA and to search for molecular targets to halt the growth or reduce the size of dTAA. By having a murine model to study thoracic pathology precisely, targeted therapies can be developed to specifically test dTAA. The method is based on the placement of porcine pancreatic elastase (PPE) directly on the outer murine aortic wall after surgical exposure. This creates a destructive and inflammatory reaction, which weakens the aortic wall and allows for aneurysm formation over weeks to months. Though murine models possess limitations, our dTAA model produces robust aneurysms of predictable size. Furthermore, this model can be used to test genetic and pharmaceutical targets which may arrest dTAA growth or prevent rupture. In human patients, interventions such as these could help avoid aneurysm rupture, and difficult surgical intervention.

The application of our protocol results in robust dTAA in mice compared to saline controls. The TAAs developed are fusiform in shape and occur only in the treated portion of the aorta (Figure 1 and Figure 2)11. Figure 2 shows an example of a video micrometry measurement at tissue harvest. Using Equation 1, the aortic dilation is 130% in this example.
The original study by Johnston ...

Watch this Scientific Journal Video about Murine Surgical Model of Topical Elastase Induced Descending Thoracic Aortic Aneurysm at JoVE.com

Murine Surgical Model of Topical Elastase Induced Descending Thoracic Aortic Aneurysm

We describe a surgical protocol to consistently induce robust descending thoracic aortic aneurysms in mice. The procedure involves left thoracotomy, thoracic aorta exposure, and placement of a sponge soaked in porcine pancreatic elastase on the aortic wall.

According to the Center for Disease Control, aortic aneurysms (AAs) were considered a leading cause of death in all races and both sexes from 1999-2016. ...

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