This research was supported by funding from the National Natural Science Foundation of China (NSFC, 81730010, 91839302, 81921001, 31930056, and 91529203) and the National Key R&#38;D Program of China (2019YFA 0801600).

Animal studies were performed in compliance with the guidelines of the Institutional Animal Care and Use Committee of Peking University Health Science Center and were approved by the Biomedical Ethics Committee of Peking University (LA2015142). All the mice for surgery were anesthetized with isoflurane (1.5%-2%), and anesthesia was carefully monitored to avoid pain or discomfort for the mice.
1. Preparation
<ol>
	<li>Cut 0.3 cm wide strips of powder-free rubber gloves and gauze.</li>
	<li>Purchase 8-10-week-old C57BL/6J male mice. House the animals in an air-conditioned environment with a 12 h light-dark cycle and free access to food and water.</li>
	<li>Autoclave the gauze, cotton swabs, scissors, and forceps prior to surgery.</li>
	<li>Obtain betadine, 70% ethanol, and antiseptic hand wash.</li>
	<li>Put on a mask, gown, and sterile gloves.</li>
</ol>
2. Surgical procedure
<ol>
	<li>Feed chewable carprofen tablets (5 mg/kg dose) to an 8-10-week-old C57BL/6J mouse 2-4 h before surgery. Then, place the mouse in an induction chamber (206 mm x 210 mm x 140 mm) with isoflurane at a flow rate of 1.5%-2%.
	<ol>
		<li>Monitor the mouse for about 5 min until respiration is visibly slowed. Ensure that the mouse has no response to pain stimulation before surgery.</li>
	</ol>
	</li>
	<li>Apply an ophthalmic ointment to the eyes and provide thermal support with a heating pad or blanket. Confirm the depth of anesthesia with a toe pinch every 15 minutes during the surgical procedure.</li>
	<li>Shave the abdominal hair of the mouse using an electric clipper or hair removal cream. Swab and wipe the shaved area with betadine, followed by 70% ethanol, several times in a circular motion. Change gloves to maintain sterility.</li>
	<li>Use scissors to make a ~1.5 cm incision at the lower abdomen along the midline of the abdomen.</li>
	<li>Use a sterile cotton swab moistened with normal saline to carefully remove the intestine until the infrarenal aorta is visible.</li>
	<li>Dissect the connective tissue and fat from the infrarenal aorta for an approximately 0.5 cm section. Note the small vessels to the dorsal side and avoid tearing them. There is no need to separate the abdominal aorta from the abdominal main vein.</li>
	<li>Pack a piece of the saline-soaked rubber glove strip under the abdominal aorta and abdominal main vein. Use a cotton swab to wipe off excess liquid.</li>
	<li>Pack a piece of gauze soaked with 0.5 M CaCl2 on the adventitia of the infrarenal abdominal vasculature for 10 min. For the sham mouse group, replace the 0.5 M CaCl2 with normal saline.</li>
	<li>Remove the gauze and pack another piece of gauze soaked with PBS solution for 5 min to generate CaPO4 crystals in situ in the adventitia of the aorta.</li>
	<li>Carefully remove the rubber glove strip and gauze. Reset the intestinal tract of the mouse.</li>
	<li>Suture the abdominal incision and skin with a 5-0 suture.</li>
	<li>Place the mouse on a heating pad until the mouse regains consciousness. Provide postsurgical pain recovery housing and analgesia, according to the local animal ethics committee.</li>
	<li>House the mouse for another 14 days. Monitor the mouse closely after the surgery and observe at least 1x every day subsequently. Perform a necropsy immediately if any mice die during this period.</li>
</ol>
3. Harvesting for imaging of aortas
<ol>
	<li>14 days after the surgery, sacrifice the mice using CO2.</li>
	<li>Cut open the mouse thoracic and abdominal cavities ventrally and cut open the right atrium.</li>
	<li>Perfuse the mice with PBS buffer through the left ventricle of the heart to remove blood in the aorta, and then perfuse with 4% paraformaldehyde as previously described8.</li>
	<li>Harvest the aorta under the stereoscope.</li>
	<li>Place harvested aortas in tubes containing 5 mL of 4% paraformaldehyde for 48 h.</li>
	<li>Remove adventitial tissue and fat carefully under the stereoscope and pin the aorta on a black wax plate with insect needles.</li>
	<li>Acquire aortic images.</li>
</ol>
4. Evaluation of the degradation of the elastic fibers
<ol>
	<li>Cut the aortic aneurysm tissues into serial cryosections (7 &#181;m thick).</li>
	<li>Analyze the elastic fibers using a commercial elastic van Gieson (EVG) staining kit according to the manufacturer&#39;s protocol.</li>
	<li>Grade the elastin degradation. Grade 1: &#60;25% degradation; grade 2: 25% to 50% degradation; grade 3: 50% to 75% degradation; or grade 4: &#62;75% degradation.</li>
</ol>

<ol>
	<li>Kent, K. C. <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+aneurysms.">Abdominal aortic aneurysms.</a> The New England Journal of Medicine. 371, 2101-2108 (2014).</li><li>Patelis, N., 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=Animal+models+in+the+research+of+abdominal+aortic+aneurysms+development.">Animal models in the research of abdominal aortic aneurysms development.</a> Physiological Research. 66 (6), 899-915 (2017).</li><li>Gertz, S. D., Kurgan, A., Eisenberg, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aneurysm+of+the+rabbit+common+carotid+artery+induced+by+periarterial+application+of+calcium-chloride+in+vivo.">Aneurysm of the rabbit common carotid artery induced by periarterial application of calcium-chloride in vivo.</a> Journal of Clinical Investigation. 81 (3), 649-656 (1988).</li><li>Yamanouchi, 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=Accelerated+aneurysmal+dilation+associated+with+apoptosis+and+inflammation+in+a+newly+developed+calcium+phosphate+rodent+abdominal+aortic+aneurysm+model.">Accelerated aneurysmal dilation associated with apoptosis and inflammation in a newly developed calcium phosphate rodent abdominal aortic aneurysm model.</a> Journal of Vascular Surgery. 56 (2), 455-461 (2012).</li><li>Wang, Y. T., 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=Influence+of+apolipoprotein+E,+age+and+aortic+site+on+calcium+phosphate+induced+abdominal+aortic+aneurysm+in+mice.">Influence of apolipoprotein E, age and aortic site on calcium phosphate induced abdominal aortic aneurysm in mice.</a> Atherosclerosis. 235 (1), 204-212 (2014).</li><li>Zhao, G., 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=Unspliced+xbp1+confers+VSMC+homeostasis+and+prevents+aortic+aneurysm+formation+via+foxo4+interaction.">Unspliced xbp1 confers VSMC homeostasis and prevents aortic aneurysm formation via foxo4 interaction.</a> Circulation Research. 121 (12), 1331-1345 (2017).</li><li>Jia, Y., 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=Targeting+macrophage+TFEB-14-3-3+epsilon+interface+by+naringenin+inhibits+abdominal+aortic+aneurysm.">Targeting macrophage TFEB-14-3-3 epsilon interface by naringenin inhibits abdominal aortic aneurysm.</a> Cell Discovery. 8 (1), 21 (2022).</li><li>Gage, G. J., Kipke, D. R., Shain, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whole+animal+perfusion+fixation+for+rodents.">Whole animal perfusion fixation for rodents.</a> Journal of Visualized Experiments. (65), e3564 (2012).</li><li>Yu, 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=CYLD+deubiquitinates+nicotinamide+adenine+dinucleotide+phosphate+oxidase+4+contributing+to+adventitial+remodeling.">CYLD deubiquitinates nicotinamide adenine dinucleotide phosphate oxidase 4 contributing to adventitial remodeling.</a> Arteriosclerosis, Thrombosis, and Vascular Biology. 37 (8), 1698-1709 (2017).</li><li>Altobelli, E., Rapacchietta, L., Profeta, V. F., Fagnano, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Risk+factors+for+abdominal+aortic+aneurysm+in+population-based+studies:+A+systematic+review+and+meta-analysis.">Risk factors for abdominal aortic aneurysm in population-based studies: A systematic review and meta-analysis.</a> International Journal of Environmental Research and Public Health. 15 (12), 2805 (2018).</li><li>Theivacumar, N. S., Stephenson, M. A., Mistry, H., Valenti, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diabetes+mellitus+and+aortic+aneurysm+rupture:+A+favorable+association.">Diabetes mellitus and aortic aneurysm rupture: A favorable association.</a> Vascular and Endovascular Surgery. 48 (1), 45-50 (2014).</li><li>Tanaka, T., Takei, Y., Yamanouchi, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperglycemia+suppresses+calcium+phosphate-induced+aneurysm+formation+through+inhibition+of+macrophage+activation.">Hyperglycemia suppresses calcium phosphate-induced aneurysm formation through inhibition of macrophage activation.</a> Journal of the American Heart Association. 5 (3), 003062 (2016).</li><li>Lu, H., 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=Subcutaneous+angiotensin+II+infusion+using+osmotic+pumps+induces+aortic+aneurysms+in+mice.">Subcutaneous angiotensin II infusion using osmotic pumps induces aortic aneurysms in mice.</a> Journal of Visualized Experiments. (103), e53191 (2015).</li><li>Urry, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutral+sites+for+calcium+ion+binding+to+elastin+and+collagen:+A+charge+neutralization+theory+for+calcification+and+its+relationship+to+atherosclerosis.">Neutral sites for calcium ion binding to elastin and collagen: A charge neutralization theory for calcification and its relationship to atherosclerosis.</a> Proceedings of the National Academy of Sciences of the United States of America. 68 (4), 810-814 (1971).</li><li>Li, Z. Q., 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=Runx2+(runt-related+transcription+factor+2)-mediated+microcalcification+is+a+novel+pathological+characteristic+and+potential+mediator+of+abdominal+aortic+aneurysm.">Runx2 (runt-related transcription factor 2)-mediated microcalcification is a novel pathological characteristic and potential mediator of abdominal aortic aneurysm.</a> Arteriosclerosis, Thrombosis, and Vascular Biology. 40 (5), 1352-1369 (2020).</li><li>Kelly, M. J., Igari, K., Yamanouchi, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Osteoclast-like+cells+in+aneurysmal+disease+exhibit+an+enhanced+proteolytic+phenotype.">Osteoclast-like cells in aneurysmal disease exhibit an enhanced proteolytic phenotype.</a> International Journal of Molecular Sciences. 20 (19), 4689 (2019).</li></ol>

Periaortic application of CaPO4 is a robust approach to induce AAA in mice. Several studies have used the CaPO4 model and consistently reported that this is a rapid and reproducible method to study AAA in mice7,9. This model is considered to recapitulate part of the features of human aortic aneurysm and provide mechanistic insights into AAA pathogenesis, including inflammation and extracellular matrix degradation.
<p class="jove_content"...

An abdominal aortic aneurysm (AAA) is a lethal cardiovascular disease characterized by permanent dilation of the abdominal aorta, with high mortality rates once rupture occurs. AAA is associated with aging, smoking, male gender, hypertension, and hyperlipidemia1. Several pathological processes have been shown to contribute to AAA formation, including extracellular matrix fiber proteolysis, immune cell infiltration, and loss of vascular smooth muscle cells. Currently, the pathological mechanisms of AAA remain elusive, and there are no proven drugs for the treatment of AAA1. Research into human AAA is limited due to the existence of few human aortic samples; thus, several chemical modification-induced animal AAA models have been established and widely adopted, including subcutaneous angiotensin II (AngII) infusion, perivascular or intraluminal elastase incubation, and perivascular calcium phosphate application2. A commonly used mouse model is the application of calcium phosphate (CaPO4) to the adventitia of the infrarenal abdominal aorta, which is cost-effective and does not require genetic modification.
Direct periaortic application of CaCl2 to the carotid artery of rabbits to induce aneurysmal change was initially reported by Gertz et al.3 and was later applied to the abdominal aortas of mice. The model was developed by Yamanouchi et al. to accelerate aortic dilation by using CaPO4 crystals in mice4. Infiltration of CaPO4 into mice aortas recapitulates many pathological features observed in human AAAs, including profound macrophage infiltration, extracellular matrix degradation, and calcium deposition. The risk factors of human AAA, such as hyperlipidemia, also augment CaPO4-induced AAA in mice5. In contrast to AngII perfusion-induced AAA in ApoE-/- or LDLR-/- mice, CaPO4-induced AAA occurs in the infrarenal aortic region, which mimics human AAA. Currently, this method has been widely applied to assess susceptibility to AAA development in genetically modified mice and evaluate the anti-AAA effects of drugs6,7.

<table><tbody><tr><td>CaCl&lt;sub&gt;2&lt;/sub&gt;</td><td>MECKLIN</td><td>C805225</td><td></td></tr><tr><td>NaCl</td><td>Biomed</td><td>SH5001-01</td><td></td></tr><tr><td>PBS</td><td>HARVEYBIO</td><td>MB5051</td><td></td></tr><tr><td>Small animal ventilator</td><td>RWD</td><td>H1550501-012</td><td></td></tr></tbody></table>

a calcium phosphate-induced mouse abdominal aortic aneurysm model

An abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease that occurs worldwide and is characterized by irreversible dilation of the abdominal aorta. Currently, several chemically induced murine AAA models are used, each simulating a different aspect of the pathogenesis of AAA. The calcium phosphate-induced AAA model is a rapid and cost-effective model compared to the angiotensin II- and elastase-induced AAA models. The application of CaPO4 crystals to the mouse aorta results in elastic fiber degradation, loss of smooth muscle cells, inflammation, and calcium deposition associated with aortic dilation. This article introduces a standard protocol for the CaPO4-induced AAA model. The protocol includes material preparation, the surgical application of the CaPO4&#160;to the adventitia of the infrarenal abdominal aorta, the harvesting of aortas to visualize aortic aneurysms, and histological analyses in mice.

14 days after CaPO4 application, the C57BL/6J male mice were euthanized, and their aortas were harvested and cleaned. The morphology of the aortas was imaged to visualize AAA formation. As shown in Figure 1A-B, the application of CaPO4 led to dilation of the infrarenal abdominal aorta. Histologically, CaPO4 resulted in a dramatic degradation of elastic fibers, as illustrated by elastin breaks (Figure 1C</...

Watch this Scientific Journal Video about A Calcium Phosphate-Induced Mouse Abdominal Aortic Aneurysm Model at JoVE.com

A Calcium Phosphate-Induced Mouse Abdominal Aortic Aneurysm Model

This protocol describes a calcium phosphate-induced abdominal aortic aneurysm (AAA) mouse model to study the pathological features and molecular mechanisms of AAAs.

An abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease that occurs worldwide and is characterized by irreversible dilation of the ...

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3.8K Views.  Peking University. This protocol describes a calcium phosphate-induced abdominal aortic aneurysm (AAA) mouse model to study the pathological features and molecular mechanisms of AAAs.

Video: A Calcium Phosphate-Induced Mouse Abdominal Aortic Aneurysm Model

Creation of Murine Experimental Abdominal Aortic Aneurysms with Elastase 

Transient intraluminal infusion of porcine pancreatic elastase into the infrarenal segment of the abdominal aorta is the most widely used animal model of abdominal aortic aneurysm (AAA) ever since it was first described in rats by Anidjar and colleagues.1 The rationale for its development was based on the disrupted nature of elastin observed in AAAs. This rat model has been modified to produce AAAs in the infrarenal aortic region of mice.2 The model has the ability to add broad insight into the pathobiology of AAA due to the emergence of numerous transgenic and gene knockout mice. Moreover, it is a viable platform to test potential therapeutic agents for AAA. In this video, we demonstrate the elastase infusion AAA procedure used in our laboratory. 
Mice are anesthetized using 2.5% isoflurane, and a laparotomy is performed under sterile conditions. The abdominal aortais isolated with the assistance of an operating stereomicroscope (Leica). After placing temporary ligatures around the proximal and distal aorta, an aortotomy is created at the bifurcation with the tip of a 30-gauge needle. A heat-tapered segment of PE-10 polyethylene tubing is introduced through the aortotomy and secured. The aortic lumen is subsequently perfused for 5-15 minutes at 100 mm Hg with saline containing type I porcine pancreatic elastase (4.5 U/mL; Sigma Chemical Co.). After removing the perfusion catheter, the aortotomy is repaired without constriction of the lumen.

Creation of Murine Experimental Abdominal Aortic Aneurysms with Elastase

This video shows how to induce abdominal aortic aneurysms (AAA) in mice via transient intraluminal infusion of porcine pancreatic elastase into the infrarenal segment of the abdominal aorta. The model has the ability to add broad insight into the pathobiology of AAA due to the emergence of numerous transgenic and gene knockout mice.

Transient intraluminal infusion of porcine pancreatic elastase into the infrarenal segment of the abdominal aorta is the most widely used animal model of ...

Aortic Ring Assay

Angiogenesis, the sprouting of blood vessels from preexisting vasculature is associated with both natural and pathological processes. Various angiogenesis assays involve the study of individual endothelial cells in culture conditions (1). The aortic ring assay is an angiogenesis model that is based on organ culture. In this assay, angiogenic vessels grow from a segment of the aorta (modified from (2)). Briefly, mouse thoracic aorta is excised, the fat layer and adventitia are removed, and rings approximately 1 mm in length are prepared. Individual rings are then embedded in a small solid dome of basement matrix extract (BME), cast inside individual wells of a 48-well plate. Angiogenic factors and inhibitors of angiogenesis can be directly added to the rings, and a mixed co-culture of aortic rings and other cell types can be employed for the study of paracrine angiogenic effects. Sprouting is observed by inspection under a stereomicroscope over a period of 6-12 days. Due to the large variation caused by the irregularities in the aortic segments, experimentation in 6-plicates is strongly advised. Neovessel outgrowth is monitored throughout the experiment and imaged using phase microscopy, and supernatants are collected for measurement of relevant angiogenic and anti-angiogenic factors, cell death markers and nitrite.

Angiogenesis, the sprouting of blood vessels from pre-existing vasculature, is associated with both natural and pathological processes. Here we demonstrate an aortic ring assay that allows angiogenic potentiators and inhibitors to be directly added to aortic rings in culture. Sprouting and neovessel outgrowth can be determined by inspecting the aortic rings over a period of 6-12 days.

Angiogenesis, the sprouting of blood vessels from preexisting vasculature is associated with both natural and pathological processes. Various angiogenesis ...

Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation

Cardiovascular disease is the leading cause of morbidity and mortality in the world. Atherosclerotic plaques, consisting of lipid-laden macrophages and calcification, develop in the coronary arteries, aortic valve, aorta, and peripheral conduit arteries and are the hallmark of cardiovascular disease. In humans, imaging with computed tomography allows for the quantification of vascular calcification; the presence of vascular calcification is a strong predictor of future cardiovascular events. Development of novel therapies in cardiovascular disease relies critically on improving our understanding of the underlying molecular mechanisms of atherosclerosis. Advancing our knowledge of atherosclerotic mechanisms relies on murine and cell-based models. Here, a method for imaging aortic calcification and macrophage infiltration using two spectrally distinct near-infrared fluorescent imaging probes is detailed. Near-infrared fluorescent imaging allows for the ex vivo quantification of calcification and macrophage accumulation in the entire aorta and can be used to further our understanding of the mechanistic relationship between inflammation and calcification in atherosclerosis. Additionally, a method for isolating and culturing animal aortic vascular smooth muscle cells and a protocol for inducing calcification in cultured smooth muscle cells from either murine aortas or from human coronary arteries is described. This in vitro method of modeling vascular calcification can be used to identify and characterize the signaling pathways likely important for the development of vascular disease, in the hopes of discovering novel targets for therapy.

Vascular calcification is an important predictor of and contributor to human cardiovascular disease. This protocol describes methods for inducing calcification of cultured primary vascular smooth muscle cells and for quantifying calcification and macrophage burden in animal aortas using near-infrared fluorescence imaging.

Cardiovascular disease is the leading cause of morbidity and mortality in the world.  Atherosclerotic plaques, consisting of lipid-laden macrophages and ...

Medicine

Quantitative Micro-CT Analysis of Aortopathy in a Mouse Model of &#946;-aminopropionitrile-induced Aortic Aneurysm and Dissection

Aortic aneurysm and dissection is associated with significant morbidity and mortality in the population and can be highly lethal. While animal models of aortic disease exist, in vivo imaging of the vasculature has been limited. In recent years, micro-computerized tomography (micro-CT) has emerged as a preferred modality for imaging both large and small vessels both in vivo and ex vivo. In conjunction with a method of vascular casting, we have successfully used micro-CT to characterize the frequency and distribution of aortic pathology in &#946;-aminopropionitrile-treated C57/Bl6 mice. Technical limitations of this method include variations in the quality of the perfusion introduced by poor animal preparation, the application of proper methodologies for vessel size quantification, and the non-survivability of this procedure. This article details a methodology for the intravascular perfusion of a lead-based radiopaque silicone rubber for the quantitative characterization of aortopathy in a mouse model of aneurysm and dissection. In addition to visualizing aortic pathology, this method may be used for examining other vascular beds in vivo or vascular beds removed post-mortem.

This article describes a detailed methodology of using a radiopaque lead-based silicone rubber to perfuse the murine vasculature for aortic diameter quantification in a mouse model of aortic aneurysm and dissection.

Aortic aneurysm and dissection is associated with significant morbidity and mortality in the population and can be highly lethal. While animal models of ...

Ultrasound Imaging of the Thoracic and Abdominal Aorta in Mice to Determine Aneurysm Dimensions

Contemporary high-resolution ultrasound instruments have sufficient resolution to facilitate the measurement of mouse aortas. These instruments have been widely used to measure aortic dimensions in mouse models of aortic aneurysms. Aortic aneurysms are defined as permanent dilations of the aorta, which occur most frequently in the ascending and abdominal regions. Sequential measurements of aortic dimensions by ultrasound are the principal approach for assessing the development and progression of aortic aneurysms in vivo. Although many reported studies used ultrasound imaging to measure aortic diameters as a primary endpoint, there are confounding factors, such as probe position and cardiac cycle, that may impact the accuracy of data acquisition, analysis, and interpretation. The purpose of this protocol is to provide a practical guide on the use of ultrasound to measure the aortic diameter in a reliable and reproducible manner. This protocol introduces the preparation of mice and instruments, the acquisition of appropriate ultrasound images, and data analysis.

Ultrasound imaging has become a common modality to determine the luminal dimensions of thoracic and abdominal aortic aneurysms in mice. This protocol describes the procedure to acquire reliable and reproducible two-dimensional ultrasound images of the ascending and abdominal aorta in mice.

Contemporary high-resolution ultrasound instruments have sufficient resolution to facilitate the measurement of mouse aortas. These instruments have been ...

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.

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. ...

Porcine Model of Infrarenal Abdominal Aortic Aneurysm

Large animal models to study abdominal aortic aneurysms are sparse. The purpose of this model is to create reproducible, clinically significant infrarenal abdominal aortic aneurysms (AAA) in swine. To achieve this, we use a combination of balloon angioplasty, elastase and collagenase, and a lysyl oxidase inhibitor, called &#946;-aminopropionitrile (BAPN), to create clinically significant infrarenal aortic aneurysms, analogous to human disease.
Noncastrated male swine are fed BAPN for 7 days prior to surgery to achieve a steady state in the blood. A midline laparotomy is performed and the infrarenal aorta is circumferentially dissected. An initial measurement is recorded prior to aneurysm induction with a combination of balloon angioplasty, elastase (500 units)/collagenase (8000 units) perfusion, and topical elastase application. Swine are fed BAPN daily until terminal procedure on either postoperative day 7, 14, or 28, at which time the aneurysm is measured, and tissue procured. BAPN + surgery pigs are compared to pigs that underwent surgery alone.
Swine treated with BAPN and surgery had a mean aortic dilation of 89.9% &#177; 47.4% at day 7, 105.4% &#177; 58.1% at day 14, and 113.5% &#177; 30.2% at day 28. Pigs treated with surgery alone had significantly smaller aneurysms compared to BAPN + surgery animals at day 28 (p &#60; 0.0003). The BAPN + surgery group had macroscopic and immunohistochemical evidence of end stage aneurysmal disease.
Clinically significant infrarenal AAA can be induced using balloon angioplasty, elastase/collagenase perfusion and topical application, supplemented with oral BAPN. This model creates large, clinically significant AAA with hallmarks of human disease. This has important implications for the elucidation of AAA pathogenesis and testing of novel therapies and devices for the treatment of AAA. Limitations of the model include variation in BAPN ingested by swine, quality of elastase perfusion, and cost of BAPN.&#160;

This novel model creates robust infrarenal abdominal aortic aneurysms in swine using a combination of balloon angioplasty, elastase/collagenase perfusion, topical elastase application, and oral compound &#946;-aminopropionitrile administration, which interferes with collagen cross-linking.

Large animal models to study abdominal aortic aneurysms are sparse. The purpose of this model is to create reproducible, clinically significant infrarenal ...

Investigating the Molecular Mechanisms Underlying Murine Abdominal Aortic Aneurysm

A Mouse Abdominal Aortic Aneurysm Model by Periadventitial Calcium Chloride and Elastase Infiltration

Abdominal aortic aneurysm (AAA) is a life-threatening disease associated with high mortality rates. It is characterized by the permanent dilation of the abdominal aorta with at least a 50% increase in arterial diameter. Various animal models of AAA have been introduced to mimic the pathophysiological changes and study the underlying mechanisms of AAA. Among these models, the calcium chloride (CaCl2)- and elastase-induced AAA models are commonly used in mice. However, these methods have certain limitations. Traditional intraluminal porcine pancreatic elastase (PPE) perfusion is associated with high technical difficulty and a high rupture rate, while periadventitial administration of PPE yields inconsistent results. In addition, the CaCl2-induced AAA model lacks human AAA features, such as atherothrombosis and aneurysm rupture. Therefore, the combined application of CaCl2 and PPE has been proposed as an approach to enhance success rates and induce greater diameter increases in AAA animal models. This manuscript presents a comprehensive protocol for establishing a mouse AAA model through periaortic infiltration of PPE and CaCl2 in the infrarenal segment of the abdominal aorta. By following this protocol, we can achieve an AAA formation rate of approximately 90% with technical simplicity and reproducibility. Further ultrasound and histological experiments confirm that this model effectively replicates the morphological and pathological changes observed in human AAA.

Author Spotlight: Development and Characterization of a Mouse Model for Abdominal Aortic Aneurysm

This manuscript presents a protocol for establishing a mouse abdominal aortic aneurysm model using calcium chloride and elastase, combining the advantages of previous modeling methods. This model can be utilized to investigate the pathophysiological mechanisms underlying abdominal aortic aneurysms.

Abdominal aortic aneurysm (AAA) is a life-threatening disease associated with high mortality rates. It is characterized by the permanent dilation of the ...

Mouse Abdominal Aortic Aneurysm Model Induced by Perivascular Application of Elastase

Abdominal aortic aneurysm (AAA), although primarily asymptomatic, is potentially life-threatening as the rupture of AAA usually has a devastating outcome. Currently, there are several distinct experimental models of AAA, each emphasizing a different aspect in the pathogenesis of AAA. The elastase-induced AAA model is the second most used rodent AAA model. This model involves direct infusion or application of porcine pancreatic elastase (PPE) to the infrarenal segment of the aorta. Due to technical challenges, most elastase-induced AAA model nowadays is performed with the external application rather than an intraluminal infusion of PPE. The infiltration of elastase will cause degradation of elastic lamellae in the medial layers, resulting in the loss of aortic wall integrity and subsequent dilation of the abdominal aorta. However, one disadvantage of the elastase-induced AAA model is the inevitable variation of how the surgery is performed. Specifically, the surgical technique of isolating the infrarenal segment of the aorta, the material used for aorta wrapping and PPE incubation, the enzymatic activity of PPE, and the time duration of PPE application can all be important determinants that affect the eventual AAA formation rate and aneurysm diameter. Notably, the difference in these factors from different studies on AAA can lead to reproducibility issues. This article describes a detailed surgical process of the elastase-induced AAA model through direct application of PPE to the adventitia of the infrarenal abdominal aorta in the mouse. Following this procedure, a stable AAA formation rate of around 80% in male and female mice is achievable. The consistency and reproducibility of AAA studies using an elastase-induced AAA model can be significantly enhanced by establishing a standard surgical procedure.

The present protocol describes a standardized surgical method for the elastase-induced AAA model through the direct application of elastase to the adventitia of infrarenal abdominal aorta in mice.

Abdominal aortic aneurysm (AAA), although primarily asymptomatic, is potentially life-threatening as the rupture of AAA usually has a devastating outcome. ...

Abdominal Aortic Aneurysm Development in Mice Using the Elastase and BAPN Method

Advanced Abdominal Aortic Aneurysm Modeling in Mice by Combination of Topical Elastase and Oral &#223;-aminopropionitrile

The topical elastase murine model of abdominal aortic aneurysm (AAA) is enhanced when combined with &#223;-aminopropionitrile (BAPN)-supplemented drinking water to reliably produce true infrarenal aneurysms with behaviors that mimic human AAAs. Topically applying elastase to the adventitia of the infrarenal aorta causes structural damage to the elastic layers of the aortic wall and initiates aneurysmal dilation. Co-administering BAPN, a lysyl oxidase inhibitor, promotes sustained wall degeneration by reducing collagen and elastin crosslinking. This combination results in large AAAs that progressively expand, form intraluminal thrombus, and are capable of rupture. Refining surgical techniques, such as circumferentially isolating the entire infrarenal aortic segment, can help standardize the procedure for a consistent and thorough application of porcine pancreatic elastase despite different operators and anatomic variations between mice. Therefore, the elastase/BAPN model is a refined approach to surgically inducing AAA in mice, which may better recapitulate human aneurysms and provide additional opportunities to study aneurysm growth and rupture risk.

Author Spotlight: Enhanced Murine AAA Model Using Elastase to Mimic Human Aneurysms

This protocol describes a methodical surgical approach to modeling advanced abdominal aortic aneurysms in mice by a combination of directly applying elastase to the infrarenal aorta and administering &#223;-aminopropionitrile through drinking water.

The topical elastase murine model of abdominal aortic aneurysm (AAA) is enhanced when combined with &#223;-aminopropionitrile (BAPN)-supplemented drinking ...

A Calcium Phosphate-Induced Mouse Abdominal Aortic Aneurysm Model

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Chapters in this video

Creation of Murine Experimental Abdominal Aortic Aneurysms with Elastase

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Mouse Abdominal Aortic Aneurysm Model Induced by Perivascular Application of Elastase

Advanced Abdominal Aortic Aneurysm Modeling in Mice by Combination of Topical Elastase and Oral ß-aminopropionitrile