Male and female C57BL/6J mice between 8-14 weeks of age were used for these experiments. This protocol has received ethical approval from the Animal Care Committee at the University of Calgary and follows all animal care guidelines.
1. Mouse preparation and surgery
<ol>
	<li>Sterilize surgical tools (via bead sterilizer or autoclave).</li>
	<li>Weigh mouse for presurgical weight and analgesic dose.</li>
	<li>Place the mouse in an induction box with 4% isoflurane and 800 mL/min of oxygen. Confirm the anesthetic plane by pinching the toes and observing the animal for lack of reflex.</li>
	<li>Inject analgesic subcutaneously (0.1 mg/kg of Buprenorphine) (see Table of Materials).</li>
	<li>Place the mouse on a heated surgical pad during surgery and maintain anesthesia with 3% isoflurane delivered via nose cone. Apply ophthalmic ointment to avoid dry eyes to each eye.</li>
	<li>Shave the hair from the chest and neck surgical areas.</li>
	<li>Restrain the paws of the mouse and position them on the surgical table.</li>
	<li>Intubate the mouse by inserting a smooth tipped 23 G catheter into the trachea through the mouth and the pharynx.
	<ol>
		<li>Ventilate the mouse following intubation with 2% isoflurane and 100% oxygen as a carrier gas using a commercial Ventilator (see Table of Materials) set at a rate of 110 breaths/min, a tidal volume of 250 &#181;L, and positive end-expiratory pressure (PEEP) of 4 mmHg.</li>
	</ol>
	</li>
	<li>Roll the mouse 30% on its right side to position the left side of the chest for surgery.</li>
	<li>Clean the surgical area with 3 alternating scrubs of 70% ethanol and betadine in a circular motion(seeTable of Materials). Place sterile surgical drapes around the surgical area.</li>
	<li>Make a 2-3 cm lateral incision in the skin of the chest to visualize the pectoralis muscles on the left side. Cut the pectoralis major and minor using a 1 cm incision from the midline outward to visualize the intercostal muscles between the third and fourth ribs. 
	NOTE: Care should be taken to avoid excess bleeding from the pectoralis muscle through cauterization of bleeding vessels.</li>
	<li>Make a 2 cm incision in the left intercostal muscle to introduce air (by passive air movement) into the chest cavity to allow the heart and lungs to fall away from the surgical incision. Further, expand the opening with the help of a cautery device (see Table of Materials) to incise the intercostal and prevent bleeding 
	NOTE: The ventilator should be temporarily stopped during the period of cauterization to avoid explosive reactions with oxygen. Care is taken not to damage the pericardial sac.</li>
	<li>Using retractors, retract the ribs to expose the heart.</li>
	<li>Observe the pericardium and the underlying heart under a stereomicroscope. 
	NOTE: The mouse pericardium is thin enough to visualize the vasculature of the heart.</li>
	<li>Gently place forceps on the surface of the pericardium to reduce its movement and that of the underlying heart.</li>
	<li>Visually landmark the left anterior descending (LAD) coronary artery by tracing its emergence from under the left appendage.</li>
	<li>Using the micro-needle driver, guide an appropriate suture (see Table of Materials) through the pericardium, under the LAD, with the suture emerging on the other side of the LAD and pericardium. Tie the suture to restrict the blood flow through the coronary artery and trim the excess suture with the help of scissors (Figure 1A). 
	NOTE: Upon restricting blood flow to the coronary artery, blanching of the anterior portion of the left ventricle should be visible. This procedure represents a permanent ligation model. However, a transient ligation approach with different ischemia periods could also be applied at this stage.</li>
	<li>Below the incision site within the sterile area, introduce a 24 G catheter percutaneously into the chest (remove the guide needle after entering the chest cavity). Then, close the ribs followed by muscle layers and skin using an appropriate suture (a taper needle for muscle, conventional cutting needle for skin).</li>
	<li>Once the chest is closed, evacuate the remaining air from the chest cavity via the 24 G catheter using gentle suction with a 3 mL syringe and chest compressions. Once the air is removed, withdraw the 24 G catheter.</li>
	<li>Reduce the isoflurane to 1%.</li>
	<li>Turn off the isoflurane while maintaining ventilation with oxygen to allow the mouse to recover from anesthesia. Once the animal shows signs of breathing independently, remove the 23 G tracheal tube from the mouth and place the mouse in a recovery cage to be monitored for resumption of normal breathing.</li>
	<li>Allow the mouse to recover in the cage with a portion of the cage placed on a warming pad to provide an external heat source.</li>
	<li>Provide maintenance injections of analgesic (Buprenorphine 0.1 mg/kg, subcutaneously) every 12 h for 72 h post-surgery.</li>
	<li>Monitor the health status of mice daily for 7 days, which includes evaluating incisions and animal discomfort. 
	&#8203;NOTE: Due to the invasiveness of this procedure (thoracotomy), the administration of antibiotics may be necessary.</li>
</ol>
2. Functional assessment of cardiac function by echocardiography (ECG)
<ol>
	<li>Induce and maintain the mouse under general anesthesia with 1.5-2% isoflurane and 800 mL/min of oxygen.</li>
	<li>Place mouse in a supine position on a heated stage platform and attach the paws to the ECG leads.</li>
	<li>Shave the chest of the mouse.</li>
	<li>Acquire echocardiography images using a 40 MHz linear transducer probe and contact gel and analyze with the appropriate software (see Table of Materials).</li>
	<li>Turn off the isoflurane and allow the mouse to recover on the heating platform before returning the cage to an active state. 
	&#8203;NOTE: Echocardiography assessment is non-invasive and thus can be performed longitudinally throughout the experiment to determine changes before and after coronary ligation.</li>
</ol>
3. Heart tissue collection for fibrosis staining
<ol>
	<li>Sacrifice the mice with inhalation of 100% CO2 and carefully dissect out the heart. 
	NOTE: Using scissors and forceps, this is achieved by cutting through the large vessels entering (vena cava, pulmonary vein) and exiting (pulmonary artery, aorta) the heart to release it from the circulatory system in the thoracic cavity.</li>
	<li>Fix the heart in 10% formalin for at least 24 h.</li>
	<li>Cut samples using a straight razor blade through the right ventricle, interventricular septum, and left ventricle, ensuring that the incision went through the center of the infarct zone. Samples are then sent to the core facility for paraffin embedding.</li>
	<li>Cut tissue sections of 5 &#181;m thickness with a microtome and place them on glass slides for staining.</li>
	<li>Deparaffinize using commercial xylene and graded alcohol washes (2x 99%, 1x 95%, 1x 70%) with deionized water, then rehydrate.</li>
	<li>Stain with 0.1% Sirius red in picric acid for 2 h at room temperature.</li>
	<li>Wash sections with 0.5% acetic acid for 3 min and rinse with 70% ethanol for 1 min.</li>
	<li>Dehydrate the sections using the reverse order of washes outlined in 3.4, with increasing and graded ethanol concentrations then xylene.</li>
	<li>Mount tissue sections with a mounting solution (see Table of Materials) for microscopic evaluation.</li>
</ol>
4. Flow cytometry of heart and pericardial cavity lavage
<ol>
	<li>Sacrifice the mice with inhalation of 100% CO2 to effect.</li>
	<li>Place the mouse on its back and fix the arms and legs to a surgical board using tape.</li>
	<li>Carefully open the left side (right side from the experimenter view) of the thoracic cavity, starting with cutting the diaphragm to about the midpoint and subsequently cutting through the outside ribs towards the sternum. 
	NOTE: Avoid nicking large blood vessels, particularly those that run parallel to the sternum.</li>
	<li>Retract the ribs using a hemostat to expose the underlying heart and pericardium. 
	NOTE: The pericardium is very fragile, so be sure not to catch it with scissors during the cutting.</li>
	<li>Using a PE-10 tubing (see Table of Materials) catheter inserted into the pericardial space near the junction of the left atrium and left ventricle, inject 100 &#181;L of sterile saline into the pericardial cavity.
	<ol>
		<li>Allow saline to pool and collect from the posterior side of the heart, being careful not to puncture or tear the pericardium in the process. Repeat this step twice and place lavage fluid on ice while processing the heart.</li>
	</ol>
	</li>
	<li>Excise the heart by cutting the major vessels (aorta, pulmonary artery, vein, and vena cava) entering and exiting the heart. Remove the right and left atria and weigh the ventricular heart tissue.</li>
	<li>Mince the tissue in small 1 mm2 pieces using scissors and place in 10 mL of digestion buffer containing 450 U/mL of collagenase I, 125 U/mL of collagenase XI, 60 U/mL of DNase I, and 60 U/mL of hyaluronidase in PBS for 1 h at 37 &#176;C on an orbital shaker.</li>
	<li>Pass heart tissue homogenates through a 70 &#181;m cell strainer (see Table of Materials) and spin down at 60 x g for 5 min at 4 &#176;C to remove cardiac parenchymal cells.</li>
	<li>Collect the supernatant, pass through a 40 &#181;m cell strainer (see Table of Materials) for a single cell suspension, and spin down at 400 x g for 5 min at 4 &#176;C to pellet the cells.</li>
	<li>Perform fragment crystallizable (Fc) receptor blocking and staining of cellular markers on pericardial and cardiac cells as previously described8.</li>
	<li>Run samples on a flow cytometer.</li>
</ol>
5. Labeling pericardial macrophage using the Intercostal Approach to the Pleural Space (ICAPS) method9
<ol>
	<li>Sterilize surgical tools (via bead sterilizer or autoclave) and spray 70% ethanol before commencing.</li>
	<li>Induce and maintain the mouse under general anesthesia with 1.5-2% isoflurane and 800 mL/min of oxygen. Confirm the anesthetic plane by pinching the toes and observing the animal for lack of reflex.</li>
	<li>Inject analgesic subcutaneously (Buprenorphine 0.1 mg/Kg).</li>
	<li>Place the mouse on a heated surgical pad during surgery.</li>
	<li>Shave the right anterolateral thoracic area.</li>
	<li>Clean the surgical area with ethanol and betadine.</li>
	<li>Make a 3 cm long incision in the skin, and with forceps expose the rib cage.</li>
	<li>Load 5 &#181;L of fluorescent beads (commercially available fluorescent microspheres, 1 &#181;m, see Table of Materials) and 45 &#181;L of saline into a PE-10 tubing syringe catheter with a beveled tip.</li>
	<li>Guide the catheter into the intercostal space as previously described9, slowly inject the bead solution and remove the catheter in one motion.</li>
	<li>Close the skin using staples. 
	NOTE: Staples are used in place of sutures to minimize potential re-opening of the incision.</li>
	<li>Turn off the isoflurane, place the mouse in the recovery cage and monitor for complications over the first 24 h.</li>
</ol>

<ol>
	<li>Virani, S. 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=Heart+disease+and+stroke+statistics-2020+update:+A+report+from+the+American+Heart+Association.">Heart disease and stroke statistics-2020 update: A report from the American Heart Association.</a> Circulation. 141, 139 (2020).</li><li>Iismaa, S. E., 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=Comparative+regenerative+mechanisms+across+different+mammalian+tissues.">Comparative regenerative mechanisms across different mammalian tissues.</a> NPJ Regenerative Medicine. 3 (6), (2018).</li><li>Bayat, 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=Progressive+heart+failure+after+myocardial+infarction+in+mice.">Progressive heart failure after myocardial infarction in mice.</a> Basic Research in Cardiology. 97 (3), 206-213 (2002).</li><li>Virag, J. A., Lust, 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=Coronary+artery+ligation+and+intramyocardial+injection+in+a+murine+model+of+infarction.">Coronary artery ligation and intramyocardial injection in a murine model of infarction.</a> Journal of Visualized Experiments. 52, 2581 (2011).</li><li>De Villiers, C., Riley, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+models+of+myocardial+infarction:+comparing+permanent+ligation+and+ischaemia-reperfusion.">Mouse models of myocardial infarction: comparing permanent ligation and ischaemia-reperfusion.</a> Disease Models &amp; Mechanisms. 13 (11), (2020).</li><li>Borlaug, B. A., Reddy, Y. N. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+the+pericardium+in+heart+failure:+Implications+for+pathophysiology+and+treatment.">The role of the pericardium in heart failure: Implications for pathophysiology and treatment.</a> JACC Heart Failure. 7 (7), 574-585 (2019).</li><li>Pfaller, M. 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=The+importance+of+the+pericardium+for+cardiac+biomechanics:+from+physiology+to+computational+modeling.">The importance of the pericardium for cardiac biomechanics: from physiology to computational modeling.</a> Biomechanics and Modeling in Mechanobiology. 18 (2), 503-529 (2019).</li><li>Deniset, J. F., 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=Gata6(+)+Pericardial+Cavity+Macrophages+Relocate+to+the+Injured+Heart+and+Prevent+Cardiac+Fibrosis.">Gata6(+) Pericardial Cavity Macrophages Relocate to the Injured Heart and Prevent Cardiac Fibrosis.</a> Immunity. 51 (1), 131-140 (2019).</li><li>Weber, G. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immune+targeting+of+the+pleural+space+by+intercostal+approach.">Immune targeting of the pleural space by intercostal approach.</a> BMC Pulmonary Medicine. 15, 14 (2015).</li><li>Nakatani, T., Shinohara, H., Fukuo, Y., Morisawa, S., Matsuda, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pericardium+of+rodents:+pores+connect+the+pericardial+and+pleural+cavities.">Pericardium of rodents: pores connect the pericardial and pleural cavities.</a> The Anatomical Record. 220, 132-137 (1988).</li><li>Tyberg, J. V., 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=The+relationship+between+pericardial+pressure+and+right+atrial+pressure:+an+intraoperative+study.">The relationship between pericardial pressure and right atrial pressure: an intraoperative study.</a> Circulation. 73, 428-432 (1986).</li><li>Hamilton, D. R., Sas, R., Semlacher, R. A., Kieser Prieur, T. M., Tyberg, J. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+between+left+and+right+pericardial+pressures+in+humans:+an+intraoperative+study.">The relationship between left and right pericardial pressures in humans: an intraoperative study.</a> The Canadian Journal of Cardiology. 27, 346-350 (2011).</li><li>Park, D. S. J., 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=Human+pericardial+proteoglycan+4+(lubricin):+Implications+for+postcardiotomy+intrathoracic+adhesion+formation.">Human pericardial proteoglycan 4 (lubricin): Implications for postcardiotomy intrathoracic adhesion formation.</a> The Journal of Thoracic and Cardiovascular Surgery. 156 (4), 1598-1608 (2018).</li></ol>

The authors have no conflicts to disclose.

Inducing an MI in a closed pericardium in rodents is unique and can have potentially significant applications. The procedure relies heavily on the surgeon&#39;s familiarity with the rodent model and rodent cardiac anatomy. Success is also dependent on the care given during three critical steps: intercostal muscle incision and rib retraction (Steps 1.11-1.13), creating the infarct (Step 1.17 ), and animal recovery (Steps 1.22-1.24).
The thoracotomy must be done diligently to avoid puncturing or...

To this day, cardiovascular disease (CVD) is recognized as the leading cause of death globally, resulting in a significant financial burden and reduction in patient quality of life1. Coronary artery disease (CAD) is a sub-type of CVD and plays an essential role in the development of myocardial infarction (MI), which is a chief contributor to mortality. By definition, MI results from irreversible injury to the myocardial tissue due to prolonged conditions of ischemia and hypoxia. Myocardial tissue lacks regeneration capacity, so injuries are permanent and result in the replacement of heart muscle with a fibrotic scar that can be initially protective but ultimately contributes to adverse cardiac remodeling and eventual heart failure2.
Although the management of patients with CAD has dramatically improved over the past few decades, chronic heart failure (CHF) secondary to ischemia affects many patients worldwide. For preventing and managing this epidemic, it is necessary to understand the underlying mechanisms more extensively and develop new therapeutic approaches. Moreover, past findings highlight the limitations of systemic therapy and the necessity of developing precise alternatives. Given investigating the molecular sequelae of MI in humans is affected by the ability to access infarcted tissue, animal models that recapitulate the characteristics and development of human MI and CHF related to CVD are indispensable.
As ideal animal models closely resemble a human disorder for structural and functional characteristics, disease etiology should guide their conception. In CAD, it is the chronic atherosclerotic stenosis of coronary arteries or acute thrombotic occlusion. Different methods have been developed and applied in various species of laboratory animals to induce coronary artery narrowing or occlusion. Such strategies can be broadly classified into two groups: (1) mechanical manipulation of a coronary artery to induce an MI and (2) expediting atherosclerosis to facilitate coronary narrowing leading to an MI. The first strategy usually involves either the ligation of a coronary artery or the placement of a stent within the artery. The second approach tends to rely on modifying the animal&#39;s diet to include high fat/cholesterol food. Some of the limitations of this latter approach include the lack of control on the timing and site of coronary occlusions.
In contrast, the surgical induction of MI or ischemia in an animal model has several advantages, such as location, precise timing, and extent of the coronary event, leading to more reproducible results. The most widely used method is surgical ligation of the left anterior descending coronary artery (LAD). Such models recapitulate human responses to acute ischemic injury, as well as the progression to CHF3. Initially developed in larger animals, LAD surgery on small animals such as rodents has become more feasible with advancements in technology4. In establishing such models, mice have been favored for various reasons, including their relative availability, low expense in housing, and their capacity for genetic manipulation.
Contemporary surgical models of ischemic heart disease using LAD occlusion require the researcher to open the pericardium to temporarily or permanently ligate the artery5. Such strategies result in the disruption of the pericardial space, which plays an essentially mechanical and lubricating function to ensure proper cardiac function. Another disadvantage of opening the pericardium is losing the animal&#39;s native pericardial fluid with its various cellular and protein components6,7. In response, a method to induce MI while keeping the pericardium intact was developed by us. In addition to minimizing the perturbation of this homeostatic environment, this approach allows for tagging and tracing specific cells after causing an MI. In addition, this approach better represents myocardial ischemic injury in the human setting.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Steri-350 Bead Sterilizer</td>
			<td>Inotech</td>
			<td>NC9449759</td>
			<td></td>
		</tr>
		<tr>
			<td>10% Formalin</td>
			<td>Millipore Sigma</td>
			<td>HT501128-4L</td>
			<td></td>
		</tr>
		<tr>
			<td>40 &#181;m Cell strainer</td>
			<td>VWR</td>
			<td>CA21008-949</td>
			<td>Falcon, 352340</td>
		</tr>
		<tr>
			<td>70 &#181;m Cell strainer</td>
			<td>VWR</td>
			<td>CA21008-952</td>
			<td>Falcon, 352350</td>
		</tr>
		<tr>
			<td>ACK Lysis Buffer</td>
			<td>Thermo Fisher</td>
			<td>A1049201</td>
			<td></td>
		</tr>
		<tr>
			<td>BD Insyte-W Catheter Needle 24 G X 3/4&#34;</td>
			<td>CDMV Inc</td>
			<td>108778</td>
			<td></td>
		</tr>
		<tr>
			<td>Betadine (10% povidone-iodine topical solution)</td>
			<td>CDMV Inc</td>
			<td>104826</td>
			<td></td>
		</tr>
		<tr>
			<td>Blunt Forceps</td>
			<td>Fine Science Tools</td>
			<td>FST 11000-12</td>
			<td></td>
		</tr>
		<tr>
			<td>BNP Ophthalmic Ointment</td>
			<td>CDMV Inc</td>
			<td>17909</td>
			<td></td>
		</tr>
		<tr>
			<td>Castroviejo Needle Driver</td>
			<td>Fine Science Tools</td>
			<td>FST 12061-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge 5810R</td>
			<td>Eppendorf</td>
			<td>22625101</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase I</td>
			<td>Millipore Sigma</td>
			<td>SCR103</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase XI</td>
			<td>Millipore Sigma</td>
			<td>C7657</td>
			<td></td>
		</tr>
		<tr>
			<td>Covidien 5-0 Polysorb Suture - CV-11 taper needle</td>
			<td>Medtronic Canada</td>
			<td>GL-890</td>
			<td></td>
		</tr>
		<tr>
			<td>Covidien 5-0 Polysorb Suture - PC-13 cutting needle</td>
			<td>Medtronic Canada</td>
			<td>SL-1659</td>
			<td></td>
		</tr>
		<tr>
			<td>Curved Blunt Forceps</td>
			<td>Fine Science Tools</td>
			<td>FST 11009-13</td>
			<td></td>
		</tr>
		<tr>
			<td>Dako Mounting Medium</td>
			<td>Agilen</td>
			<td>CS70330-2</td>
			<td></td>
		</tr>
		<tr>
			<td>DNase I</td>
			<td>Millipore Sigma</td>
			<td>11284932001</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol, 100%</td>
			<td>Millipore Sigma</td>
			<td>MFCD00003568</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethicon 8-0 Ethilon Suture - BV-130-4 taper needle</td>
			<td>Johnson &#38; Johnson Inc.</td>
			<td>2815G</td>
			<td></td>
		</tr>
		<tr>
			<td>Fiber-Optic Light</td>
			<td>Nikon</td>
			<td>2208502</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine Forceps</td>
			<td>Fine Science Tools</td>
			<td>FST 11150-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluoresbrite&#174; YG Carboxylate Microspheres 1.00 &#181;m</td>
			<td>Polysciences, Inc.</td>
			<td>15702</td>
			<td></td>
		</tr>
		<tr>
			<td>Geiger Thermal Cautery Unit</td>
			<td>World Precision Instruments</td>
			<td>501293</td>
			<td>Model 150-ST</td>
		</tr>
		<tr>
			<td>Hyaluronidase</td>
			<td>Millipore Sigma</td>
			<td>H4272</td>
			<td></td>
		</tr>
		<tr>
			<td>Isofluorane Vaporizer</td>
			<td>Harvard Apparatus</td>
			<td>75-0951</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane USP, 250 mL</td>
			<td>CDMV Inc</td>
			<td>108737</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic Fixator Retraction System</td>
			<td>Fine Science Tools</td>
			<td>18200-20</td>
			<td></td>
		</tr>
		<tr>
			<td>MX550D- 40 MHz probe</td>
			<td>Fujifilm- Visual Sonics</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Needle Driver</td>
			<td>Fine Science Tools</td>
			<td>FST 12002-12</td>
			<td></td>
		</tr>
		<tr>
			<td>PE-10 Tubing</td>
			<td>Braintree Scienctific, Inc.</td>
			<td>PE10 50 FT</td>
			<td></td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>Fine Science Tools</td>
			<td>FST 14184-09</td>
			<td></td>
		</tr>
		<tr>
			<td>SMZ-1B Stereo Microscope</td>
			<td>Nikon</td>
			<td>SMZ1-PS</td>
			<td></td>
		</tr>
		<tr>
			<td>VentElite Small Animal Ventilator</td>
			<td>Harvard Apparatus</td>
			<td>55-7040</td>
			<td></td>
		</tr>
		<tr>
			<td>Vetergesic (10 mL, 0.3mg/mL buprenorphine))</td>
			<td>CDMV Inc</td>
			<td>124918</td>
			<td>controlled drug</td>
		</tr>
		<tr>
			<td>Vevo 2100 Software</td>
			<td>Fujifilm-Visual Sonics</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

an intact pericardium ischemic rodent model

This protocol has shown that the pericardium and its contents play an essential anti-fibrotic role in the ischemic rodent model (coronary ligation to induce myocardial injury). The majority of pre-clinical myocardial infarction models require the disruption of pericardial integrity with loss of the homeostatic cellular milieu. However, recently a methodology has been developed by us to induce myocardial infarction, which minimizes pericardial damage and retains the heart&#39;s resident immune cell population. An improved cardiac functional recovery in mice with an intact pericardial space following coronary ligation has been observed. This method provides an opportunity to study inflammatory responses in the pericardial space following myocardial infarction. Further development of the labeling techniques can be combined with this model to understand the fate and function of pericardial immune cells in regulating the inflammatory mechanisms that drive remodeling in the heart, including fibrosis.

This modified coronary ligation model has been optimized to achieve reproducibility and animal survival. However, due to the significant injury induced in the heart, some expected intra-operative and post-operative mortality are associated with the procedure. The standard mortality is typically higher in males (~25-35%) than in females (~ 10-15%).
Successful induction of an MI with the modified coronary ligation should be evident by changes in the heart&#39;s functional parameters and structur...

Watch this Scientific Journal Video about An Intact Pericardium Ischemic Rodent Model at JoVE.com

An Intact Pericardium Ischemic Rodent Model

This protocol outlines the steps for inducing myocardial infarction in mice while preserving the pericardium and its contents.

This protocol has shown that the pericardium and its contents play an essential anti-fibrotic role in the ischemic rodent model (coronary ligation to ...

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2.3K Views.  Cumming School of Medicine. This protocol outlines the steps for inducing myocardial infarction in mice while preserving the pericardium and its contents.

Video: An Intact Pericardium Ischemic Rodent Model

Gene Transfer for Ischemic Heart Failure in a Preclinical Model

Various emerging technologies are being developed for patients with heart failure. Well-established preclinical evaluations are necessary to determine their efficacy and safety.
Gene therapy using viral vectors is one of the most promising approaches for treating cardiac diseases. Viral delivery of various different genes by changing the carrier gene has immeasurable therapeutic potential.
In this video, the full process of an animal model of heart failure creation followed by gene transfer is presented using a swine model. First, myocardial infarction is created by occluding the proximal left anterior descending coronary artery. Heart remodeling results in chronic heart failure. Unique to our model is a fairly large scar which truly reflects patients with severe heart failure who require aggressive therapy for positive outcomes. After myocardial infarct creation and development of scar tissue, an intracoronary injection of virus is demonstrated with simultaneous nitroglycerine infusion. Our injection method provides simple and efficient gene transfer with enhanced gene expression. This combination of a myocardial infarct swine model with intracoronary virus delivery has proven to be a consistent and reproducible methodology, which helps not only to test the effect of individual gene, but also compare the efficacy of many genes as therapeutic candidates.

A method of gene transfer for the treatment of ischemic heart failure is described using a swine model of myocardial infarction. Our simple and reproducible method enables us to readily evaluate the efficacy of various gene transfers with a very simple and reproducible way.

Various emerging technologies are being developed for patients with heart failure. Well-established preclinical evaluations are necessary to determine ...

An in vivo Rodent Model of Contraction-induced Injury and Non-invasive Monitoring of Recovery

Muscle strains are one of the most common complaints treated by physicians. A muscle injury is typically diagnosed from the patient history and physical exam alone, however the clinical presentation can vary greatly depending on the extent of injury, the patient's pain tolerance, etc. In patients with muscle injury or muscle disease, assessment of muscle damage is typically limited to clinical signs, such as tenderness, strength, range of motion, and more recently, imaging studies. Biological markers, such as serum creatine kinase levels, are typically elevated with muscle injury, but their levels do not always correlate with the loss of force production. This is even true of histological findings from animals, which provide a "direct measure" of damage, but do not account for all the loss of function. Some have argued that the most comprehensive measure of the overall health of the muscle in contractile force. Because muscle injury is a random event that occurs under a variety of biomechanical conditions, it is difficult to study. Here, we describe an in vivo animal model to measure torque and to produce a reliable muscle injury. We also describe our model for measurement of force from an isolated muscle in situ. Furthermore, we describe our small animal MRI procedure.

An in vivo Rodent Model of Contraction-induced Injury and Non-invasive Monitoring of Recovery

An in vivo animal model of injury is described. The method takes advantage of the subcutaneous position of the fibular nerve. Velocity, timing of muscle activation, and arc of motion are all pre-determined and synchronized using commercial software. Post injury changes are monitored in vivo using MR imaging/spectroscopy.

Muscle strains are one of the most  common complaints treated by physicians. A muscle injury is typically diagnosed from the patient history and  physical ...

A Simplified Technique for Producing an Ischemic Wound Model

One major obstacle in current diabetic wound research is a lack of an ischemic wound model that can be safely used in diabetic animals. Drugs that work well in non-ischemic wounds may not work in human diabetic wounds because vasculopathy is one major factor that hinders healing of these wounds. We published an article in 2007 describing a rabbit ear ischemic wound model created by a minimally invasive surgical technique. Since then, we have further simplified the procedure for easier operation. On one ear, three small skin incisions were made on the vascular pedicles, 1-2 cm from the ear base. The central artery was ligated and cut along with the nerve. The whole cranial bundle was cut and ligated, leaving only the caudal branch intact. A circumferential subcutaneous tunnel was made through the incisions, to cut subcutaneous tissues, muscles, nerves, and small vessels. The other ear was used as a non-ischemic control. Four wounds were made on the ventral side of each ear. This technique produces 4 ischemic wounds and 4 non-ischemic wounds in one animal for paired comparisons. After surgery, the ischemic ear was cool and cyanotic, and showed reduced movement and a lack of pulse in the ear artery. Skin temperature of the ischemic ear was 1-10 &deg;C lower than that on the normal ear and this difference was maintained for more than one month. Ear tissue high-energy phosphate contents were lower in the ischemic ear than the control ear. Wound healing times were longer in the ischemic ear than in the non-ischemic ear when the same treatment was used. The technique has now been used on more than 80 rabbits in which 23 were diabetic (diabetes time ranging from 2 weeks to 2 years). No single rabbit has developed any surgical complications such as bleeding, infection, or rupture in the skin incisions. The model has many advantages, such as little skin disruption, longer ischemic time, and higher success rate, when compared to many other models. It can be safely used in animals with reduced resistance, and can also be modified to meet different testing requirements.

We have developed a minimally invasive technique to create a rabbit ischemic ear wound model by dividing the central artery and nerve and the cranial neurovascular bundle. A subcutaneous tunnel then cuts all subcutaneous tissues. This procedure causes minimal skin disruption and can be safely used in diabetic animals.

One major obstacle in current diabetic wound research is a lack of an ischemic wound model that can be safely used in diabetic animals. Drugs that work ...

Using Quantitative Real-time PCR to Determine Donor Cell Engraftment in a Competitive Murine Bone Marrow Transplantation Model

Murine bone marrow transplantation models provide an important tool in measuring hematopoietic stem cell (HSC) functions and determining genes/molecules that regulate HSCs. In these transplant model systems, the function of HSCs is determined by the ability of these cells to engraft and reconstitute lethally irradiated recipient mice. Commonly, the donor cell contribution/engraftment is measured by antibodies to donor- specific cell surface proteins using flow cytometry. However, this method heavily depends on the specificity and the ability of the cell surface marker to differentiate donor-derived cells from recipient-originated cells, which may not be available for all mouse strains. Considering the various backgrounds of genetically modified mouse strains in the market, this cell surface/ flow cytometry-based method has significant limitations especially in mouse strains that lack well-defined surface markers to separate donor cells from congenic recipient cells. Here, we reported a PCR-based technique to determine donor cell engraftment/contribution in transplant recipient mice. We transplanted male donor bone marrow HSCs to lethally irradiated congenic female mice. Peripheral blood samples were collected at different time points post transplantation. Bone marrow samples were obtained at the end of the experiments. Genomic DNA was isolated and the Y chromosome specific gene, Zfy1, was amplified using quantitative Real time PCR. The engraftment of male donor-derived cells in the female recipient mice was calculated against standard curve with known percentage of male vs. female DNAs. Bcl2 was used as a reference gene to normalize the total DNA amount. Our data suggested that this approach reliably determines donor cell engraftment and provides a useful, yet simple method in measuring hematopoietic cell reconstitution in murine bone marrow transplantation models. Our method can be routinely performed in most laboratories because no costly equipment such as flow cytometry is required.

Determining donor cell engraftment presents a challenge in mouse bone marrow transplant models that lack well-defined phenotypical markers. We described a methodology to quantify male donor cell engraftment in female transplant recipient mice. This method can be used in all mouse strains for the study of HSC functions.

Murine bone marrow transplantation models provide an important tool in measuring hematopoietic stem cell (HSC) functions and determining genes/molecules ...

Rat Model of Photochemically-Induced Posterior Ischemic Optic Neuropathy

Posterior Ischemic optic neuropathy (PION) is a sight-devastating disease in clinical practice. However, its pathogenesis and natural history have&#160;remained poorly understood. Recently, we developed a reliable, reproducible animal model of PION and tested the treatment effect of some neurotrophic factors in this model1. The purpose of this video is to demonstrate our photochemically induced model of posterior ischemic optic neuropathy, and to evaluate its effects with retrograde labeling of retinal ganglion cells. Following surgical exposure of the posterior optic nerve, a photosensitizing dye, erythrosin B, is intravenously injected and a laser beam is focused onto the optic nerve surface. Photochemical interaction of erythrosin B and the laser during irradiation damages the vascular endothelium, prompting microvascular occlusion mediated by platelet thrombosis and edematous compression. The resulting ischemic injury yields a gradual but pronounced retinal ganglion cell dieback, owing to a loss of axonal input - a remote, injury-induced and clinically relevant outcome. Thus, this model provides a novel platform to study the pathophysiologic course of PION,&#160;and can be further optimized for testing therapeutic approaches for optic neuropathies as well as other CNS ischemic diseases.

The goal of this protocol is to photochemically induce ischemic injury to the posterior optic nerve in rat. This model is critical to studies of the pathophysiology of posterior ischemic optic neuropathy, and therapeutic approaches for this and other optic neuropathies, as well as of other CNS ischemic diseases.

Posterior Ischemic optic neuropathy (PION) is a sight-devastating disease in clinical practice. However, its pathogenesis and natural history ...

A Piglet Model of Neonatal Hypoxic-Ischemic Encephalopathy

Birth asphyxia, which causes hypoxic-ischemic encephalopathy (HIE), accounts for 0.66 million deaths worldwide each year, about a quarter of the world&#8217;s 2.9 million neonatal deaths. Animal models of HIE have contributed to the understanding of the pathophysiology in HIE, and have highlighted the dynamic process that occur in brain injury due to perinatal asphyxia. Thus, animal studies have suggested a time-window for post-insult treatment strategies. Hypothermia has been tested as a treatment for HIE in pdiglet models and subsequently proven effective in clinical trials. Variations of the model have been applied in the study of adjunctive neuroprotective methods and piglet studies of xenon and melatonin have led to clinical phase I and II trials1,2. The piglet HIE model is further used for neonatal resuscitation- and hemodynamic studies as well as in investigations of cerebral hypoxia on a cellular level. However, it is a technically challenging model and variations in the protocol may result in either too mild or too severe brain injury. In this article, we demonstrate the technical procedures necessary for establishing a stable piglet model of neonatal HIE. First, the newborn piglet (&#60; 24 hr old, median weight 1500 g) is anesthetized, intubated, and monitored in a setup comparable to that found in a neonatal intensive care unit. Global hypoxia-ischemia is induced by lowering the inspiratory oxygen fraction to achieve global hypoxia, ischemia through hypotension and a flat trace amplitude integrated EEG (aEEG) indicative of cerebral hypoxia. Survival is promoted by adjusting oxygenation according to the aEEG response and blood pressure. Brain injury is quantified by histopathology and magnetic resonance imaging after 72 hr.

Hypoxic-ischemic encephalopathy following perinatal asphyxia can be studied using animal models. We demonstrate the procedures necessary for establishing a piglet model of neonatal hypoxic-ischemic encephalopathy.

Birth asphyxia, which causes hypoxic-ischemic encephalopathy (HIE), accounts for 0.66 million deaths worldwide each year, about a quarter of the ...

Demonstration of the Rat Ischemic Skin Wound Model

The propensity for chronic wounds in humans increases with ageing, disease conditions such as diabetes and impaired cardiovascular function, and unrelieved pressure due to immobility. Animal models have been developed that attempt to mimic these conditions for the purpose of furthering our understanding of the complexity of chronic wounds. The model described herein is a rat ischemic skin flap model that permits a prolonged reduction of blood flow resulting in wounds that become ischemic and resemble a chronic wound phenotype (reduced vascularization, increased inflammation and delayed wound closure). It consists of a bipedicled dorsal flap with 2 ischemic wounds placed centrally and 2 non-ischemic wounds lateral to the flap as controls. A novel addition to this ischemic skin flap model is the placement of a silicone sheet beneath the flap that functions as a barrier and a splint to prevent revascularization and reduce contraction as the wounds heal. Despite the debate of using rats for wound healing studies due to their quite distinct anatomic and physiologic differences compared to humans (i.e., the presence of a panniculus carnosus muscle, short life-span, increased number of hair follicles, and their ability to heal infected wounds) the modifications employed in this model make it a valuable alternative to previously developed ischemic skin flap models.

The rat, due to its size, availability, and rather docile behavior, has been utilized as a research model for many years. The goal of this protocol is to utilize the rat as an ischemic skin wound healing model to provide valuable insight into the pathophysiology of chronic wounds.

The propensity for chronic wounds in humans increases with ageing, disease conditions such as diabetes and impaired cardiovascular function, and ...

The Rodent Model of Nonarteritic Anterior Ischemic Optic Neuropathy (rNAION)

Nonarteritic anterior ischemic optic neuropathy (NAION) is a focal ischemic lesion of the optic nerve that affects 1/700 individuals throughout their lifetime. NAION results in optic nerve edema, selective loss of the retinal ganglion cell neurons (RGCs) and atrophy of the optic nerve. A rodent model of NAION that expresses most NAION features and sequelae has been developed, which is applicable to both rats and mice. This model utilizes a focal laser application of 532 nm wavelength to illuminate a photoactive dye, Rose Bengal (RB), to cause capillary damage and leakage at the targeted anterior optic nerve (the laminar region). After rNAION induction, there is an early optic nerve ischemia, optic nerve edema, and intraneural inflammation, followed by selective RGC and axonal loss. Since the optic nerve is a CNS white matter tract, the rNAION model is applicable to mechanistic studies of selective white matter ischemia, as well as neuroprotective analyses and short and long-term mechanisms of glial and neuronal response to ischemia.

The Rodent Model of Nonarteritic Anterior Ischemic Optic Neuropathy rNAION

The following report describes how to replicate the rodent model of nonarteritic anterior ischemic optic neuropathy (rNAION), using the appropriate dye, contact lens and laser parameters. We also reveal the appropriate steps for evaluating the rNAION lesion in vivo.

Nonarteritic anterior ischemic optic neuropathy (NAION) is a focal ischemic lesion of the optic nerve that affects 1/700 individuals throughout their ...

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 ...

Oxygen-Induced Retinopathy Model for Ischemic Retinal Diseases in Rodents

One of the commonly used models for ischemic retinopathies is the oxygen-induced retinopathy (OIR) model. Here we describe detailed protocols for the OIR model induction and its readouts in both mice and rats. Retinal neovascularization is induced in OIR by exposing rodent pups either to hyperoxia (mice) or alternating levels of hyperoxia and hypoxia (rats). The primary readouts of these models are the size of neovascular (NV) and avascular (AVA) areas in the retina. This preclinical in vivo model can be used to evaluate the efficacy of potential anti-angiogenic drugs or to address the role of specific genes in the retinal angiogenesis by using genetically manipulated animals. The model has some strain and vendor specific variation in the OIR induction which should be taken into consideration when designing the experiments.

Oxygen-induced retinopathy (OIR) can be used to model ischemic retinal diseases such as retinopathy of prematurity and proliferative diabetic retinopathy and to serve as a model for proof-of-concept studies in evaluating antiangiogenic drugs for neovascular diseases. OIR induces robust and reproducible neovascularization in the retina that can be quantified.

One of the commonly used models for ischemic retinopathies is the oxygen-induced retinopathy (OIR) model. Here we describe detailed protocols for the OIR ...