We would like to thank Mark Smith for his assistance with radiographic imaging. This work is supported by the NIH T32 Grant for Interdisciplinary Research in Cardiovascular Disease (BOA), the American Heart Association (SMC), and the NIH R35 Grant (DKS).

The protocols for animal handling were approved by the Institutional Animal Care and Use Committee of the University of Maryland, Baltimore (animal protocol number 0116024) and conducted according to AAALAC International standards.
1. Preparation of Reagents
<ol>
	<li>Heparin
	<ol>
		<li>Dilute 250 &#181;L of 1000 U/mL heparin sulfate in 50 mL of phosphate buffered saline to make a final concentration of 5 U/mL.</li>
		<li>Warm the heparinized (5 U/mL) phosphate buffered saline, which will replace the blood in the vasculature in a water bath set to 37 &#176;C.</li>
		<li>Prepare the pressure-controlled pump by connecting the required tubing and 2 empty 10-mL syringes, 1 for the heparinized-saline buffer and 1 for the contrast agent.</li>
		<li>Fill the tubing with the warm heparinized phosphate buffered saline and remove the air bubbles from the tubing of the pressure pump.</li>
	</ol>
	</li>
	<li>Contrast agent 
	NOTE: Please refer to the Table of Materials for the contrast agent kit constituents.
	<ol>
		<li>Mix a pigmented compound with a diluent to achieve a 1:6 dye to diluent ratio.</li>
		<li>Immediately prior to use (step 2.3.12), add 200 &#181;L of a curing agent to each 5-mL aliquot of the diluted pigmented compound and mix them well (4% by volume). 
		NOTE: The manufacturer reported the working time is 40 min. As the silicone-rubber contrast agent begins to polymerize 20 min after the addition of the curing agent, it is important to prepare the solution immediately prior to its infusion.</li>
	</ol>
	</li>
	<li>BAPN drinking water
	<ol>
		<li>Dissolve &#946;-aminopropionitrile (BAPN) in drinking water to create a final concentration of 3 g/L (adapted from protocols previously described in the literature)9,16,17.</li>
		<li>Administer the BAPN-containing drinking water to a group of mice once they are 4 weeks of age until the time of perfusion for micro-CT.</li>
	</ol>
	</li>
</ol>
2. Surgical Procedure
<ol>
	<li>Animal preparation
	<ol>
		<li>Wean the mice at 3 weeks of age, maintain them on a 12 h light/12 h dark cycle, and feed them standard rodent chow. For the BAPN-treated group, administer freshly prepared BAPN drinking water for 16 - 26 weeks ad libitum. Provide the control animals with standard drinking water ad libitum.</li>
	</ol>
	</li>
	<li>Anesthetic technique 
	NOTE: 24 h prior to the CT analysis, the following procedure is performed. Surgical procedures are enacted to prepare the specimen for a postmortem intracardiac perfusion.
	<ol>
		<li>Induce an anesthesia via an induction tank with 100% O2 and 3% isoflurane delivered via a precision vaporizer. After the anesthesia induction, discontinue the isoflurane and flush the chamber with O2. Maintain the anesthesia with 2 - 2.5% isoflurane and 1 L/min of O2 via a nose cone.</li>
		<li>Attach both the induction chamber and the facemask to a charcoal scavenger for waste gas adsorption to protect personnel. Ensure an adequate anesthetic plane by demonstrating that there is no response to noxious stimuli (toe pinch).</li>
		<li>Prepare an operative field consisting of a surgical tray and the necessary surgical instruments.</li>
		<li>Transfer the animal to the surgical field and position it in dorsal recumbency.</li>
	</ol>
	</li>
	<li>Operative technique
	<ol>
		<li>Using scissors, make a midline incision through the skin and soft tissue from midway between the pubic symphysis to the sternal notch, extending through the skin and soft tissue overlying the sternum.</li>
		<li>Using scissors, create a hole in the diaphragm at the xiphoid process to enter the thoracic cavity.</li>
		<li>Use scissors to dissect the diaphragm of the ventral chest wall, bilaterally.</li>
		<li>Cut through the costal cartilages to separate the ribs from the sternum at the right sternal border.</li>
		<li>Apply a fine hemostatic clamp to the tip of the sternum (near the xiphoid process) and move the hemostat cranially so that it is positioned over the head of the mouse. This will retract the thymus and sternum away from the heart, exposing the heart and great vessels for further manipulation.</li>
		<li>Sharply dissect any attachments between the heart and the chest wall.</li>
		<li>Connect the 27-gauge IV catheter needle to a syringe pre-loaded with 10 mL of heparinized phosphate buffered saline (5 U/mL) and fill all tubing with the buffer in order to remove the air bubbles from the tubes of the pressure pump.</li>
		<li>Use care while preparing the fluid as bubbles in the fluid line may impede the filling of smaller vessels. Limit the number of vessels that are damaged during the animal preparation, as this will cause the contrast agent to leak out of the severed vessels, changing the volume required for a complete filling and introducing artifacts to the final imaging.</li>
		<li>Puncture the left ventricle with a 27-gauge needle that is stabilized with a right-angle clamp. Immediately incise the right ventricle or the inferior vena cava to drain the heparin solution and blood. 
		NOTE: Heparin is used as an anticoagulant to prevent the blood from clotting in the vessels after the animal&#39;s death.</li>
		<li>Perfuse the animal at a constant rate of 2 mL/minute using a single syringe pump. Note the visible blanching of the organs. Continue the perfusion until the perfusate draining from the venous circulation is free of blood (about 5 - 6 mL). Stop the pump.</li>
		<li>Disconnect the IV catheter tubing from the 10-mL syringe, taking care not to disrupt the needle&#39;s position in the left ventricle.</li>
		<li>Immediately after the complete exsanguination, separate the contrast agent solution into 5-mL aliquots and add the curing agent at this time (see step 1.2). Mix them well. Draw up 5 mL of the contrast agent mix into a 10-mL syringe and perfuse the animal with it.</li>
		<li>For a complete filling of the vessels (arteries and veins), continue the infusion past the point when it can be seen exiting the venous solution. Look for signs of a successful perfusion including the visualization of a casting agent in the coronary arteries, pulmonary arteries, intestine, and liver vasculature.</li>
		<li>The contrast agent will cure after approximately 20 min at room temperature. Upon curing, harvest the individual organs, as needed, and fix them in 10% neutral buffered formalin. Fix whole carcasses if the samples are not used for micro-CT scanning the following day. If the carcasses will be used the subsequent day, position them on a metal tray and place them in a refrigerator at 4 &#176;C to cure overnight.</li>
	</ol>
	</li>
</ol>
3. Micro-CT Scanning and Parameters
NOTE: The specific image acquisition parameters will be dependent upon the machine in use.
<ol>
	<li>Acquire X-ray computed tomography images of each mouse the day following the perfusion using a micro-CT scanner using an X-ray tube voltage of 55 kVp, a current of 150 &#956;A, a system magnification factor of 2.19, and a CCD camera pixel binning factor of 2. This yields an effective pixel size of 29 &#181;m.
	<ol>
		<li>Lay the mouse carcass supine on the micro-CT scanner table and obtain a scout X-ray scan.</li>
		<li>Focus the detector field of view of 57.4 mm (axial) x 37.1 mm (transaxial) on the torso to image the full length of the aorta.</li>
		<li>Acquire 180 image projections with a rotation increment of 2 degrees and a time per projection of 2800 ms.</li>
	</ol>
	</li>
	<li>Reconstruct the images using a modified Feldkamp algorithm; the reconstructed voxel size is 29 x 29 x 29 &#181;m3 (slice thickness = 29 &#181;m) using the Multimodal 3D Visualization plug-in for the software used here.</li>
</ol>
4. Post-processing and Rendering
<ol>
	<li>Convert the CT data to a DICOM format using the appropriate software.</li>
	<li>Analyze the images to identify whether an aneurysm was present. Measure the minor axis diameter at the widest point of the aortic arch, descending thoracic aorta, and abdominal aorta as previously described18 (Figure 1). 
	NOTE: In our study, images were analyzed by two independent observers (one blinded) utilizing a DICOM viewer to identify whether an aneurysm was present. The minor axis diameter was measured at the widest point of the aortic arch, descending thoracic aorta, and abdominal aorta as previously described19 (Figure 1). Mean non-aneurysmal arterial segments of BAPN-untreated mice established normal vessel diameters serving as the age-matched control values.</li>
	<li>Aneurysms are defined as a localized or diffuse dilation of the aortic segments to diameters greater than 50% of the reference diameter. Locate these based on the above measurements.</li>
</ol>

<ol>
	<li>Meszaros, I., 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=Epidemiology+and+clinicopathology+of+aortic+dissection.">Epidemiology and clinicopathology of aortic dissection.</a> CHEST. 117 (5), 1271-1278 (2000).</li><li>Kochanek, K. 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=Deaths:+final+data+for+2009.">Deaths: final data for 2009.</a> National Vital Statistics Reports. 60 (3), 1-116 (2011).</li><li>Li, J. S., Li, H. Y., Wang, L., Zhang, L., Jing, Z. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+beta-aminopropionitrile-induced+aortic+dissection+model+in+rats+by+different+administration+and+dosage.">Comparison of beta-aminopropionitrile-induced aortic dissection model in rats by different administration and dosage.</a> Vascular. 21 (5), 287-292 (2013).</li><li>Huffman, M. D., Curci, J. A., Moore, G., Kerns, D. B., Starcher, B. C., Thompson, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+importance+of+connective+tissue+repair+during+the+development+of+experimental+abdominal+aortic+aneurysms.">Functional importance of connective tissue repair during the development of experimental abdominal aortic aneurysms.</a> Surgery. 128 (3), 429-438 (2000).</li><li>Wu, D., Shen, Y. H., Russel, L., Coselii, J. S., LeMaire, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+mechanisms+of+thoracic+aortic+dissection.">Molecular mechanisms of thoracic aortic dissection.</a> Journal of Surgical Research. 184 (2), 907-924 (2013).</li><li>Bruel, A., Ortoft, G., Oxlund, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibition+of+cross-links+in+collagen+is+associated+with+reduced+stiffness+of+the+aorta+in+young+rats.">Inhibition of cross-links in collagen is associated with reduced stiffness of the aorta in young rats.</a> Atherosclerosis. 140 (1), 135-145 (1998).</li><li>Martinez-Revelles, 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=Lysyl+oxidase+induces+vascular+oxidative+stress+and+contributes+to+arterial+stiffness+and+abnormal+elastin+structure+in+hypertension:+Role+of+p38MAPK.">Lysyl oxidase induces vascular oxidative stress and contributes to arterial stiffness and abnormal elastin structure in hypertension: Role of p38MAPK.</a> Antioxidants &amp; Redox Signaling. 27 (7), 379-397 (2017).</li><li>Kumar, D., Trent, M. B., Boor, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Allylamine+and+beta-aminopropionitrile+induced+aortic+medial+necrosis:+Mechanisms+of+synergism.">Allylamine and beta-aminopropionitrile induced aortic medial necrosis: Mechanisms of synergism.</a> Toxicology. 125 (2-3), 107-115 (1998).</li><li>Ren, W., 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=&#946;-Aminopropionitrile+monofumarate+induces+thoracic+aortic+dissection+in+C57BL/6+mice.">&#946;-Aminopropionitrile monofumarate induces thoracic aortic dissection in C57BL/6 mice.</a> Scientific Reports. 6, 28149 (2016).</li><li>Kanematsu, 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=Pharmacologically-induced+thoracic+and+abdominal+aortic+aneurysms+in+mice.">Pharmacologically-induced thoracic and abdominal aortic aneurysms in mice.</a> Hypertension. 55 (5), 1267-1274 (2010).</li><li>Weyers, J. J., Carlson, D. D., Murry, C. E., Schwartz, S. M., Mahoney, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retrograde+Perfusion+and+Filling+of+Mouse+Coronary+Vasculature+as+Preparation+for+Micro+Computed+Tomography+Imaging.">Retrograde Perfusion and Filling of Mouse Coronary Vasculature as Preparation for Micro Computed Tomography Imaging.</a> J Vis Exp. (60), e3740 (2012).</li><li>Cortell, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silicone+rubber+for+renal+tubular+injection.">Silicone rubber for renal tubular injection.</a> Journal of Applied Physics. 26 (1), 158-159 (1969).</li><li>Bentley, M. D., Ortiz, M. C., Ritman, E. L., Romero, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+microcomputed+tomography+to+study+microvasculature+in+small+rodents.">The use of microcomputed tomography to study microvasculature in small rodents.</a> American Journal of Physiology - Regulatory, Integrative and Comparative Physiology. 282 (5), R1267-R1279 (2002).</li><li>Marxen, M., 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=MicroCT+scanner+performance+and+considerations+for+vascular+specimen+imaging.">MicroCT scanner performance and considerations for vascular specimen imaging.</a> Medical Physics. 31 (2), 305-313 (2004).</li><li>Yang, J., Yu, L. X., Rennie, M. Y., Sled, J. G., Henkelman, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+structural+and+hemodynamic+analysis+of+vascular+trees.">Comparative structural and hemodynamic analysis of vascular trees.</a> American Journal of Physiology - Heart and Circulatory Physiology. 298 (4), H1249-H1259 (2010).</li><li>Jia, L. X., 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=Mechanical+stretch-induced+endoplasmic+reticulum+stress,+apoptosis,+and+inflammation+contribute+to+thoracic+aortic+aneurysm+and+dissection.">Mechanical stretch-induced endoplasmic reticulum stress, apoptosis, and inflammation contribute to thoracic aortic aneurysm and dissection.</a> The Journal of Pathology. 236 (3), 373-383 (2015).</li><li>Kurihara, 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=Neutrophil-derived+matrix+metalloproteinase+9+triggers+acute+aortic+dissection.">Neutrophil-derived matrix metalloproteinase 9 triggers acute aortic dissection.</a> Circulation. 126 (25), 3070-3080 (2012).</li><li>Dillavou, E. D., Buck, D. G., Muluk, S. C., Makaroun, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+versus+three-dimensional+CT+scan+for+aortic+measurement.">Two-dimensional versus three-dimensional CT scan for aortic measurement.</a> Journal of Endovascular Therapy. 10 (3), 531-538 (2003).</li><li>Muratoglu, S. C., 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=LRP1+protects+the+vasculature+by+regulating+levels+of+connective+tissue+growth+factor+and+HtrA1.">LRP1 protects the vasculature by regulating levels of connective tissue growth factor and HtrA1.</a> Arterioclerosis, Thrombosis, and Vascular Biology. 33, 2137-2146 (2013).</li><li>Badea, C. T., Dragova, M., Holdsworth, D. W., Johnson, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+small+animal+imaging+using+micro-CT+and+digital+subtraction+angiography.">In vivo small animal imaging using micro-CT and digital subtraction angiography.</a> Phys Med Biol. 53 (19), R319-R350 (2008).</li><li>Zhou, Y. 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=Ultrasound-guided+left-ventricular+catheterization:+A+novel+method+of+whole+mouse+perfusion+for+microimaging.">Ultrasound-guided left-ventricular catheterization: A novel method of whole mouse perfusion for microimaging.</a> Laboratory Investigation. 84, 385-389 (2004).</li></ol>

The authors have nothing to disclose.

Micro-CT imaging can be used to provide highly detailed and three-dimensional reconstructions of vascular pathology in animal models. Through the use of intravascular contrast-enhanced media, non-enhanced soft tissues, such as the lumen of a blood vessel, can be differentiated from those that are enhancing. While laser Doppler, microangiography, magnetic resonance angiography, histology with confocal, or two-photon microscopy may be used to assess vascular beds, they typically focus on a limited area of study and/or are ...

The incidence of aortic dissection is 3 cases per 100,000 per year1. Aortic dissection and aneurysmal diseases account for over 10,000 deaths in the United States each year, accounting for 1 - 2% of all deaths in Western countries2. Aortic dissection is initiated by a tear in the intimal layer of the vessel with the propagation of blood through the layers of the aortic wall under physiologic pressures. Elevated patient pulse pressures are associated with an increased incidence of dissection and complications. Increased wall shear stress is associated with the aortic wall expansion leading to an aneurysm formation3,4. Consequences of aortic dissection include the occlusion of blood flow to distant organs including the brain, kidneys, bowels, and limbs, the formation of chronic aneurysms, rupture, or death5,6,7.
At present, the biochemical and cellular processes involved in the initiation and progression of aortic aneurysms and dissections are still poorly understood. Reproducible animal models of aortic aneurysm and dissection are key to understanding their pathophysiology. &#946;-aminopropionitrile (BAPN) is a lysyl oxidase inhibitor, which prevents the cross-linking of elastin and collagen and has been shown to significantly alter the structure of the vessel wall extracellular matrix and its biomechanical integrity6,8. Rodents treated with BAPN have been utilized as a common animal model of aortic aneurysm and dissection9,10.
Vascular imaging modalities are instrumental in identifying vascular pathology, confirming vessel patency, and evaluating organ perfusion. Recently, micro-computed tomography (micro-CT) has been utilized to study the vasculature of mice and similarly sized animals. Unlike bone, the axial imaging of blood vessels by computed tomography is limited, as intraluminal blood is inherently relatively radiolucent. When combined with intravascular contrast agents, however, micro-CT enables detailed three-dimensional reconstructions of animal vasculatures for the study of macro-anatomic vascular pathology11.
The selected contrast agent (see the Table of Materials) is a radiopaque silicone rubber that contains lead chromate and lead sulfate. Upon perfusion in the presence of a catalyst, it quickly hardens to form a cast of the vasculature with minimal alterations in the macro-anatomic architecture of the vessels, making the vasculature highly radiopaque in contrast to the background tissues when examined radiographically. This contrast agent is advantageous because it is easy to handle and avoids the tissue degradation and vessel loss due to breakage often associated with vascular cast corrosion. As it cures with minimal shrinkage12, vessels cleared of blood remain patent and allow for an accurate assessment of the animal macro-vasculature in non-survival experiments. Previous work has successfully used radiopaque silicone rubber-contrast in a variety of animal studies. Specifically, applicability in visualizing the coronary, glomerular, placental, and cerebral circulations11,12,13,14,15 has been shown. In this paper, we detail the methodology of open left-ventricular puncture for the intravascular perfusion of lead-based radiopaque silicone rubber to quantitatively characterize BAPN-induced aortic pathology in a mouse model by micro-CT.

<table>
	<tbody>
		<tr>
			<td>Microfil</td>
			<td>Flow Tech, Inc</td>
			<td>MV-122</td>
			<td>We use yellow, a different color can be ordered as desired. Kit includes MV-Compound, MV-Diluent, and MV-Curing Agent.</td>
		</tr>
		<tr>
			<td>Heparin (1000 U/mL)</td>
			<td>Sagent Pharmaceuticals</td>
			<td>25021-400-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline</td>
			<td>Corning</td>
			<td>21-031-CV</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Vet One, MWI</td>
			<td>502017</td>
			<td></td>
		</tr>
		<tr>
			<td>3-Aminopropionitrile fumarate salt</td>
			<td>Sigma-Aldrich</td>
			<td>A3134</td>
			<td></td>
		</tr>
		<tr>
			<td>Single syringe pump</td>
			<td>Fisher Scientific</td>
			<td>14-831-200</td>
			<td></td>
		</tr>
		<tr>
			<td>27-gauge scalp vein set needle</td>
			<td>Exel Int</td>
			<td>26709</td>
			<td>27G x 3/4&#34;, 12&#34; tube</td>
		</tr>
		<tr>
			<td>Inveon Micro-CT scanner</td>
			<td>Siemens Medical Solutions</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Osirix MD</td>
			<td>Pimxmeo SARL</td>
			<td></td>
			<td>Version 8.0.2</td>
		</tr>
		<tr>
			<td>Inveon Research Workplace</td>
			<td>Siemens Medical Solutions</td>
			<td></td>
			<td>Version 4.2</td>
		</tr>
		<tr>
			<td>Rodent Chow</td>
			<td>Harlan Teklad</td>
			<td>2018sx</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

In order to evaluate this protocol, 20 male adult mice, of mixed background as previously described19 and of 20 - 30 weeks of age, with or without BAPN treatment, were perfused with a lead-based radiopaque silicone rubber (see the Table of Materials) using the protocol detailed above. They underwent micro-CT scanning on the following day (Figure 1 and Figure 2). There were...

Watch this Scientific Journal Video about Quantitative Micro-CT Analysis of Aortopathy in a Mouse Model of ÃŽÂ²-aminopropionitrile-induced Aortic Aneurysm and Dissection at JoVE.com

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

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 ...

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9.5K Views.  University of Maryland School of Medicine. 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.

Video: Quantitative Micro-CT Analysis of Aortopathy in a Mouse Model of β-aminopropionitrile-induced Aortic Aneurysm and Dissection

A New Murine Model of Endovascular Aortic Aneurysm Repair

Endovascular aneurysm exclusion is a validated technique to prevent aneurysm rupture. Long-term results highlight technique limitations and new aspects of Abdominal aortic aneurysm (AAA) pathophysiology. There is no abdominal aortic aneurysm endograft exclusion model cheap and reproducible, which would allow deep investigations of AAA before and after treatment. We hereby describe how to induce, and then to exclude with a covered coronary stentgraft an abdominal aortic aneurysm in a rat. The well known elastase induced AAA model was first reported in 19901 in a rat, then described in mice2. Elastin degradation leads to dilation of the aorta with inflammatory infiltration of the abdominal wall and intra luminal thrombus, matching with human AAA. Endovascular exclusion with small covered stentgraft is then performed, excluding any interactions between circulating blood and the aneurysm thrombus. Appropriate exclusion and stentgraft patency is confirmed before euthanasia by an angiography thought the left carotid artery. Partial control of elastase diffusion makes aneurysm shape different for each animal. It is difficult to create an aneurysm, which will allow an appropriate length of aorta below the aneurysm for an easy stentgraft introduction, and with adequate proximal and distal neck to prevent endoleaks. Lots of failure can result to stentgraft introduction which sometimes lead to aorta tear with pain and troubles to stitch it, and endothelial damage with post op aorta thrombosis. Giving aspirin to rats before stentgraft implantation decreases failure rate without major hemorrhage. Clamping time activates neutrophils, endothelium and platelets, and may interfere with biological analysis.

Histological and biochemical modifications after aneurysm endograft exclusion are still unclear. We describe a new model of endograft implantation on a murine aneurysm. Through thrombus analysis with and without persistant circulating blood stream interface, and new endovascular biomaterials evaluation, this model will help to better understand endovascular aneurysm exclusion pathobiology.

Endovascular aneurysm exclusion is a validated technique to prevent aneurysm rupture. Long-term results highlight technique limitations and new aspects of ...

Quantitative Analysis and Characterization of Atherosclerotic Lesions in the Murine Aortic Sinus

Atherosclerosis is a disease of the large arteries and a major underlying cause of myocardial infarction and stroke. Several different mouse models have been developed to facilitate the study of the molecular and cellular pathophysiology of this disease. In this manuscript we describe specific techniques for the quantification and characterization of atherosclerotic lesions in the murine aortic sinus and ascending aorta. The advantage of this procedure is that it provides an accurate measurement of the cross-sectional area and total volume of the lesion, which can be used to compare atherosclerotic progression across different treatment groups. This is possible through the use of the valve leaflets as an anatomical landmark, together with careful adjustment of the sectioning angle. We also describe basic staining methods that can be used to begin to characterize atherosclerotic progression. These can be further modified to investigate antigens of specific interest to the researcher. The described techniques are generally applicable to a wide variety of existing and newly created dietary and genetically-induced models of atherogenesis.

We describe procedures to quantify and characterize atherosclerotic lesions in mouse models using precision sectioning of the aortic sinus and ascending aorta combined with histochemical and immunohistochemical analysis.

Atherosclerosis is a disease of the large arteries and a major underlying cause of myocardial infarction and stroke. Several different mouse models have ...

Using the Sleeve Technique in a Mouse Model of Aortic Transplantation - An Instructional Video

Orthotopic aortic transplantation using the sleeve technique reduces injury to the aorta with failure rate of only 10-20%. The time to anastomose the aorta in mice using the sleeve method was short and easy averaging 20 min, permitting studies of iso/allo grafts. The following article describes the aortic transplantation procedure used in our laboratory. The mice were anesthetized with a mixture of 1.5% volume isoflurane and 100% oxygen through a face mask. At this point, the segment of the aorta between the renal arteries and its bifurcation was separated from the vena cava, freely prepared and clampedat the proximal and distal segments with a single silk suture. Prior to the removal of the aorta, a saline solution containing heparin was injected into the inferior vena cava. Then the aorta was cut between the clamps and a saline heparin solution was used to flush the lumen. The sleeve technique with monofilament sutures was used in order to transplant the abdominal aorta in the orthotopic position.

We present an orthotopic aortic transplantation model using the sleeve technique in mice. It is a very rapid anastomosis method, which can be employed in studies of vascular disease.

Orthotopic aortic transplantation using the sleeve technique reduces injury to the aorta with failure rate of only 10-20%. The time to anastomose the ...

Dissection of the Mouse Pancreas for Histological Analysis and Metabolic Profiling

We have been investigating the pancreas specific transcription factor, 1a cre-recombinase; lox-stop-lox- Kristen rat sarcoma, glycine to aspartic acid at the 12 codon (Ptf1acre/+;LSL-KrasG12D/+) mouse strain as a model of human pancreatic cancer. The goal of our current studies is to identify novel metabolic biomarkers of pancreatic cancer progression. We have performed metabolic profiling of urine, feces, blood, and pancreas tissue extracts, as well as histological analyses of the pancreas to stage the cancer progression. The mouse pancreas is not a well-defined solid organ like in humans, but rather is a diffusely distributed soft tissue that is not easily identified by individuals unfamiliar with mouse internal anatomy or by individuals that have little or no experience performing mouse organ dissections. The purpose of this article is to provide a detailed step-wise visual demonstration to guide novices in the removal of the mouse pancreas by dissection. This article should be especially valuable to students and investigators new to research that requires harvesting of the mouse pancreas by dissection for metabolic profiling or histological analyses.

This video article provides a detailed demonstration of the procedures required to successfully remove the pancreas from a mouse by dissection for histological analysis and metabolic profiling.

We have been investigating the pancreas specific transcription factor, 1a cre-recombinase; lox-stop-lox- Kristen rat sarcoma, glycine to aspartic acid at ...

Creation of a Rodent Model of Abdominal Aortic Aneurysm by Blocking Adventitial Vasa Vasorum Perfusion

The adventitial vasa vasorum (VV) provides oxygen and nourishment to the aortic wall. Hypoxia in the aortic wall can cause enlarged abdominal aortic aneurysms (AAAs). This article introduces and describes a standard protocol used to induce AAAs through adventitial VV hypoperfusion created with a combination of polyurethane catheter insertion into the aortic lumen and suture ligation of the infrarenal abdominal aorta.
The protocol involves the use of male rats weighing 300-400 g, which are provided food and water ad libitum. After laparotomy with a ventral midline abdominal incision, exfoliation of the aorta is performed, which blocks blood flow from the perivascular tissue. Aortotomy involving a small incision adjacent to the renal artery branches is performed, and a polyurethane catheter is inserted using an 18-gauge indwelling needle. After repairing the incision, tight ligation of the aorta over the catheter blocks VV blood flow from the proximal direction through the aortic wall without disturbing the aortic blood flow. This technique can induce an AAA with progressive aortic dilatation.
The greatest benefit of this model is that VV hypoperfusion causes tissue hypoxia and the development of an infrarenal AAA, which has morphological and pathological characteristics similar to those of a human AAA.

Polyurethane catheter insertion into the aortic lumen and suture ligation of the aorta induce chronic hypoxia due to hypoperfusion of the adventitial vasa vasorum. This article describes a novel animal model of abdominal aortic aneurysm (AAA) with characteristics similar to those of AAA in humans.

The adventitial vasa vasorum (VV) provides oxygen and nourishment to the aortic wall. Hypoxia in the aortic wall can cause enlarged abdominal aortic ...

Induction and Micro-CT Imaging of Cerebral Cavernous Malformations in Mouse Model

Mutations in the CCM1 (aka KRIT1), CCM2, or CCM3 (aka PDCD10) gene cause cerebral cavernous malformation (CCM) in humans. Mouse models of CCM disease have been established by tamoxifen induced deletion of Ccm genes in postnatal animals. These mouse models provide invaluable tools to investigate molecular mechanism and therapeutic approaches for CCM disease. An accurate and quantitative method to assess lesion burden and progression is essential to harness the full value of these animal models. Here, we demonstrate the induction of CCM disease in a mouse model and the use of the contrast enhanced X-ray micro computed tomography (micro-CT) method to measure CCM lesion burden in mouse brains. At postnatal day 1 (P1), we used 4-hydroxytamoxifen (4HT) to activate Cre recombinase activity from the Cdh5-CreErt2 transgene to cleave the floxed allele of Ccm2. CCM lesions in mouse brains were analyzed at P8. For micro-CT, iodine based Lugol&#39;s solution was used to enhance contrast in brain tissue. We have optimized the scan parameters and utilized a voxel dimension of 9.5 &#181;m, which lead to a minimum feature size of approximately 25 &#181;m. This resolution is sufficient to measure CCM lesion volume and number globally and accurately, and provide high-quality 3-D mapping of CCM lesions in mouse brains. This method enhances the value of the established mouse models to study the molecular basis and potential therapies for CCM and other cerebrovascular diseases.

This protocol demonstrates the induction of cerebral cavernous malformation disease in a mouse model and uses contrast enhanced micro computed tomography to measure lesion burden. This method enhances the value of established mouse models to study the molecular basis and potential therapies for cerebral cavernous malformation and other cerebrovascular diseases.

Mutations in the CCM1 (aka KRIT1), CCM2, or CCM3 (aka PDCD10) gene cause cerebral cavernous malformation (CCM) in humans. Mouse models of CCM disease have ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

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 ...

Imaging and Analysis of Oil Red O-Stained Whole Aorta Lesions in an Aneurysm Hyperlipidemia Mouse Model

Apolipoprotein E (Apoe)- or low density lipoprotein receptor (Ldlr)-deficient hyperlipidemic mice are the two most commonly used models for atherosclerosis research. They are used to study the impact of a various genetic factors and different cell types on atherosclerotic lesion formation and as well as test the development of new therapies. Isolation, excision of the whole aorta, and quantification of Oil Red O-stained atherosclerotic lesions are basic morphometric methods used to evaluate atherosclerotic burden. The goal of this protocol is to describe an optimized, step-by-step surgical method to dissect, perfuse-fix, isolate, stain, image and analyze atherosclerotic lesions in mouse aortas with Oil Red O. Because atherosclerotic lesions can form anywhere in the entire aortic tree, this whole aorta Oil Red O staining method has the advantage of evaluating lipid-laden plaques in the entire aorta and all branches in a single mouse. In addition to Oil Red O staining, fresh isolated whole aortas can be used for variety of in vitro and in vivo experiments and cell isolations.

This protocol provides a step-by-step procedure to analyze atherosclerotic burden in mice. Investigators can use this protocol to compare the abundance, location, and size of atherosclerotic lesions in different animals.