The experiments were performed on female C57BL/6 mice, age 10-12 weeks and 20-25 g body weight. All animal procedures complied with the standards stated in the Guide for the Care and Use of Laboratory Animals (Institute of Laboratory Animal Resources, National Academy of Sciences, Bethesda, MD, USA) and were approved by the Mayo Clinic College of Medicine Institutional Animal Care and Use Committee (IACUC).
1. Preparation and intubation
<ol>
	<li>Autoclave all surgical instruments before surgery. If multiple surgeries are to be performed in one session, clean the instruments after each animal and re-sterilize using a hot bead sterilizer.</li>
	<li>Anesthetize the mice with 3.5-4% isoflurane at 1 L/min O2 in an induction chamber.</li>
	<li>Administer Buprenorphine SR 1 mg/kg (analgesic) subcutaneously, weigh the animal, and input the weight into the ventilator.</li>
	<li>Shave the left side of the chest from the sternum to the level of the shoulder and apply depilatory cream to remove excess fur.</li>
	<li>For the ischemia reperfusion procedure maintain the positive end-expiratory pressure (PEEP) on the ventilator at 2 cmH2O. For the delayed injection of cells procedure change the PEEP to 3 cmH2O to prevent lung collapse.</li>
	<li>Intubate the animal using a 20 G endotracheal tube, transfer to a controlled heating pad to maintain a body temperature of 35-37 &#176;C.</li>
	<li>Place the mouse on a ventilator in lateral recumbency with cranial end on the left and caudal end on the right.</li>
	<li>Maintain anesthesia at 2-2.5% isoflurane at 1 L/min O2 for the remainder of the procedure.</li>
	<li>Scrub the surgical area alternating between povidone-iodine and alcohol swabs three times and apply ophthalmic ointment to both eyes.</li>
</ol>
2. Ischemia reperfusion injury
<ol>
	<li>Using a #10 blade scalpel make a vertical incision 2.5 mm to right of the leftmost nipple in the field of view.</li>
	<li>Using scissors cut through the superficial muscle layers until the intercostal muscles and ribs are visible.</li>
	<li>While lifting the ribs and surrounding tissue, cut through the intercostal space between the 4th and 5th ribs, then insert the eyelid retractor into the open space.</li>
	<li>Retract the pericardium using curved forceps, moving the lung upwards and out of view.</li>
	<li>Visualize LAD artery and, using a 9-0 nylon suture, pass through the myocardium beneath the artery 2.5 mm distal to the left auricle and tie a loose square knot.</li>
	<li>Cut 1 cm of polyethylene tubing and place it within the loose knot.</li>
	<li>Secure the suture around the tubing, confirm ischemia, then release after 35 min. 
	NOTE: Confirm ischemia by pallor and ventricular arrhythmia.</li>
	<li>After releasing the ligation and removing the tubing, wait for 5 min to confirm reperfusion of the myocardium.</li>
	<li>Place a 24 G I.V. catheter tube into the thoracic cavity one intercostal space to right of the opening.</li>
	<li>Close the intercostal incision with a 6-0 absorbable suture in a simple interrupted pattern.</li>
	<li>Close the muscle layer with a 6-0 absorbable suture in a continuous suture pattern.</li>
	<li>After closing the superficial muscle layer, remove the chest tube while withdrawing the air from thoracic cavity using a 1 mL tuberculin syringe.</li>
	<li>Close the skin incision with a 6-0 absorbable suture in a continuous horizontal mattress pattern 
	NOTE: Nylon sutures and a discontinuous suture pattern may also be used for the skin layer.</li>
	<li>Administer 1.5 mL of warm saline subcutaneously and apply triple-antibiotic ointment to the incision site to prevent infection.</li>
	<li>Turn off isoflurane and allow the animal to breathe through the ventilator on 100% O2 until it can breathe continuously without aid.</li>
	<li>Transfer the mouse to a bedding-free cage or a cage with covered bedding (paper towel or drape) on a warm pad with a temperature of 35-37 &#176;C until fully recovered.</li>
</ol>
3. Mouse mesenchymal stem cell delivery
NOTE: The strain of mice used for the procedure are an inbred line and are deemed genetically identical. The mesenchymal stem cells were obtained from animals of the same strain and, by protocol design, immunosuppression was not induced1.
<ol>
	<li>Complete the preparation and intubation steps as done previously for the first procedure.</li>
	<li>Remove the suture from the skin layer using scissors and forceps.</li>
	<li>With a #10 scalpel, make an incision in the same location as the previous surgery.</li>
	<li>Continue to use the scalpel to cut through scar tissue until muscle layer suture is visible</li>
	<li>Using the scissors and forceps remove the suture and cut the muscle layer open.</li>
	<li>Visualize and remove the sutures holding the ribs together and continue cutting through the intercostal muscle from the previous incision. 
	NOTE: The lungs may have adhered to the chest wall, if this occurs, use blunt or curved forceps to carefully separate and release them.</li>
	<li>Place the eyelid retractor into the intercostal space and locate the area of the previous ligation.</li>
	<li>Load the mesenchymal stem cells (3.0 x 105), suspended in 20 &#181;L PBS, into a 30 G insulin syringe, bend the needle slightly as needed for the proper angle to inject. 
	NOTE: Mesenchymal stem cells (MSCs) were isolated from the adipose tissue of 4-6-week-old C56BL/6 mice. Early passage cells (p3) were transduced with a vector expressing the firefly luciferase gene under the CMV promoter to allow in vivo cell viability monitoring. Adipose-derived mouse MSC were characterized by flow cytometry and the cells were positive for CD44, CD29, CD90 and CD105 but negative for the hematopoietic marker CD4514. Prior to the injection, MSCs were cultured for at least one passage to avoid the loss of cells from the thawing process.</li>
	<li>Moving in the direction from the apex towards the base of the heart insert the syringe into the peri-infarct region until the needle opening is completely inside the myocardium.</li>
	<li>Once inside slowly inject the cells into the myocardium, wait 3 s, then remove the needle.</li>
	<li>Observe the heart closely for 3 min to be sure of no abnormal reactions to the cells such as ventricular fibrillation.</li>
	<li>Place a 24 G IV catheter tube into the thoracic cavity one intercostal space to right of the opening.</li>
	<li>Close the intercostal, muscle, and skin layers and remove the chest tube in the same method as the first procedure.</li>
	<li>Administer 1.5 mL of warm saline subcutaneously and apply triple-antibiotic ointment to the incision site to prevent infection.</li>
	<li>Turn off isoflurane and allow animal to breathe through the ventilator on 100% O2 until it is able to breathe continuously without aid.</li>
	<li>Transfer the mouse to a bedding-free cage or a cage with covered bedding (paper towel or drape) on a warm pad with a temperature of 35-37 &#176;C until fully recovered.</li>
</ol>
4. Post-operative care following both procedures
<ol>
	<li>Observe the animal continuously until spontaneous breathing, sternal recumbency and normal movement is established.</li>
	<li>Continue observation every 15-30 min for at least 3 h on the day of the surgery.</li>
	<li>Check the mice for wound dehiscence or abnormal pain once daily for 5 days, then 2-3 times weekly.</li>
	<li>If the animal shows signs of pain (i.e. arched back, minimal movement, grimacing, or scruffy fur) after 72 h post-op, provide an additional dose of the Buprenorphine SR analgesic.</li>
</ol>

<ol>
	<li>Franchi, 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=The+Myocardial+Microenvironment+Modulates+the+Biology+of+Transplanted+Mesenchymal+Stem+Cells.">The Myocardial Microenvironment Modulates the Biology of Transplanted Mesenchymal Stem Cells.</a> Molecular Imaging Biology. , (2020).</li><li>Bergmann, O., 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=Evidence+for+cardiomyocyte+renewal+in+humans.">Evidence for cardiomyocyte renewal in humans.</a> Science. 324 (5923), 98-102 (2009).</li><li>Writing Group, 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=Heart+Disease+and+Stroke+Statistics-2016+Update:+A+Report+From+the+American+Heart+Association.">Heart Disease and Stroke Statistics-2016 Update: A Report From the American Heart Association.</a> Circulation. 133 (4), 38 (2016).</li><li>Gersh, B. J., Simari, R. D., Behfar, A., Terzic, C. M., Terzic, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+cell+repair+therapy:+a+clinical+perspective.">Cardiac cell repair therapy: a clinical perspective.</a> Mayo Clinic Protocol. 84 (10), 876-892 (2009).</li><li>Terzic, A., Behfar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regenerative+heart+failure+therapy+headed+for+optimization.">Regenerative heart failure therapy headed for optimization.</a> European Heart Journal. 35 (19), 1231-1234 (2014).</li><li>Beegle, 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=Hypoxic+preconditioning+of+mesenchymal+stromal+cells+induces+metabolic+changes,+enhances+survival,+and+promotes+cell+retention+in+vivo.">Hypoxic preconditioning of mesenchymal stromal cells induces metabolic changes, enhances survival, and promotes cell retention in vivo.</a> Stem Cells. 33 (6), 1818-1828 (2015).</li><li>Kubli, D. A., Gustafsson, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondria+and+mitophagy:+the+yin+and+yang+of+cell+death+control.">Mitochondria and mitophagy: the yin and yang of cell death control.</a> Circulation Research. 111 (9), 1208-1221 (2012).</li><li>Psaltis, P. 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=Noninvasive+monitoring+of+oxidative+stress+in+transplanted+mesenchymal+stromal+cells.">Noninvasive monitoring of oxidative stress in transplanted mesenchymal stromal cells.</a> JACC Cardiovascular Imaging. 6 (7), 795-802 (2013).</li><li>Peet, C., Ivetic, A., Bromage, D. I., Shah, A. 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The authors have nothing to disclose.

Over 85 million people worldwide are affected by cardiovascular disease3. The high prevalence of these ischemic events warrants further development and expansion of alternative therapies for promoting the regeneration of damaged tissue. Traditional methods utilize the ischemia reperfusion procedure in an acute setting with subsequent administration of therapeutics1. Inflammatory reactions are at its peak between 3-4 days postdating a cardiac ischemic event, with infiltratio...

Cardiovascular disease remains the most common cause of morbidity and mortality worldwide. Cardiac ischemic events have been found to be detrimental to the overall function of the myocardium and surrounding cells1. Only&#160;&#160; &#820;0.45-1.0% of cardiomyocytes will regenerate every year after myocardial damage occurs2. Despite the growing demand and inherent focus on developing treatments, therapies aiding in the regeneration of injured tissue have been difficult to establish and still require further optimization3,4,5. Stem cell therapies have been introduced as an alternative path to rejuvenate damaged tissue after an ischemic event; however, advancement of these therapies has been challenged by the limited survival and retention of the cells to an injured area6.
The microenvironment of the heart after an ischemic event can be characterized as hypoxic, pro-oxidant, and pro-inflammatory, presenting hostile conditions for therapeutic stem cells to adapt to for survival7,8. As an immune response is triggered following injury, na&#239;ve lymphocytes, macrophages, neutrophils and mast cells attempt to repair the damage by removing dying cells and modulating the process for tissue remodeling9,10,11. Within the first 3 days post-ischemia, inflammation is at its peak with the release of pro-inflammatory cytokines with high numbers of neutrophils and monocytes in the area10,12. After 7 days, much of the inflammation has subsided and the transition to reparative cells begins, continuing until the remodeling cascade is complete, approximately 14 days in mice13. Our surgical method is a potential alternative approach to the introduction of biologics into the myocardium to bypass the peak innate immune response after ischemia reperfusion injury. At the same time, it will allow for the study of any treatments in a condition of subacute/chronic ischemia where there may be different variables to consider compared to acute myocardial infarction.

<table border="0" cellpadding="0" cellspacing="0" style="width:973px;" width="973">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="17">
			<td height="17" style="height:17px;width:322px;">0.9% NaCl Irrigation, USP</td>
			<td style="width:191px;">Baxter</td>
			<td style="width:132px;">0338-0048-04</td>
			<td style="width:328px;"></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">11x12&#34; Press n&#39; Seal surgical drape, autoclavable</td>
			<td>SAI Infusion Technologies</td>
			<td>PSS-SD</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">24G 3/4&#34; IV catheter tube</td>
			<td>Jelco</td>
			<td>4053</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">28G x 1/2&#34; 1mL allergy syringe</td>
			<td>BD</td>
			<td>305500</td>
			<td>Injection of analgesic</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">30G x 1/2&#34; 3/10cc insulin syringe</td>
			<td>Ulticare</td>
			<td>08222.0933.56</td>
			<td>Injection of stem cells</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">6-0 S-29, 12&#34; Vicryl suture</td>
			<td>Ethicon</td>
			<td>J556G</td>
			<td>Intercostal, superficial muscle and skin layer incision closure</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">9-0 BV100-4, 5&#34; Ethilon suture</td>
			<td>Ethicon</td>
			<td>2829G</td>
			<td>Ligation of the LAD artery</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Absorbent underpad</td>
			<td>Thermo Fischer Scientific</td>
			<td>14-206-64</td>
			<td>For underneath the animal</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Alcohol prep pads, 2 ply, medium</td>
			<td>Coviden</td>
			<td>6818</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Anti-fog face mask</td>
			<td>Halyard</td>
			<td>49235</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Bonn Strabismus scissors, curved, blunt</td>
			<td>Fine Science Tools</td>
			<td>14085-09</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Buprenorphine HCL SR LAB 1mg/ml, 5 ml</td>
			<td>ZooPharm Pharmacy</td>
			<td></td>
			<td>Buprenorphine narcotic analgesic formulated in a polymer that slows absorption extending duration of action (72 hours duration of activity).</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Castroviejo needle holders, curved</td>
			<td>Fine Science Tools</td>
			<td>12061-01</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Curity sterile gauze sponges</td>
			<td>Coviden</td>
			<td>397310</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Delicate suture tying forceps, 45 angle bent</td>
			<td>Fine Science Tools</td>
			<td>11063-07</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Electric Razor</td>
			<td>Wahl</td>
			<td></td>
			<td>Fur removal</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Isoflurane 100 ml</td>
			<td>Cardinal Health</td>
			<td>PI23238</td>
			<td>Anesthetic</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Lab coat</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Monoject 1 mL hypodermic syringe</td>
			<td>Coviden</td>
			<td>8881501400</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Moria iris forceps, curved, serrated (x2)</td>
			<td>Fine Science Tools</td>
			<td>11370-31</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Moria speculum retractor</td>
			<td>Fine Science Tools</td>
			<td>17370-53</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Mouse endotracheal intubation kit</td>
			<td>Kent Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Nair depilatory cream</td>
			<td>Johnson &#38; Johnson</td>
			<td></td>
			<td>Fur removal</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Optixcare eye lube plus</td>
			<td>Aventix</td>
			<td></td>
			<td>Sterile ocular lubricant</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Physiosuite ventilator</td>
			<td>Kent Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">PolyE Polyethylene tubing</td>
			<td>Harvard Apparatus</td>
			<td>72-0191</td>
			<td>Temporary compression of LAD artery</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Povidone-iodine swabs</td>
			<td>PDI</td>
			<td>S41125</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Scalpel, 10-blade</td>
			<td>Bard-Parker</td>
			<td>371610</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Sterile 3&#34; cotton tipped applicators</td>
			<td>Cardinal Health</td>
			<td>C15055-003</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Sterile 6&#34; tapered cotton tip applicators</td>
			<td>Puritan</td>
			<td>25-826-5WC</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Sterile gloves</td>
			<td>Cardinal Health</td>
			<td>N8830</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Sterilization pouches</td>
			<td>Medline</td>
			<td>MPP100525GS</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Surgery cap</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Surgical Microscope</td>
			<td>Leica</td>
			<td>M125</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Suture tying forceps, straight (x2)</td>
			<td>Fine Science Tools</td>
			<td>10825-10</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Transpore surgical tape</td>
			<td>3M</td>
			<td>1527-1</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Triple antibiotic ointment</td>
			<td>G&#38;W Laboratories</td>
			<td>11-2683ILNC2</td>
			<td>Topical application to prevent infection</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Vannas-T&#252;bingen Spring Scissors, curved</td>
			<td>Fine Science Tools</td>
			<td>15004-08</td>
			<td></td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;">Vetflo vaporizer</td>
			<td>Kent Scientific</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

delayed intramyocardial delivery of stem cells after ischemia reperfusion injury in a murine model

There is significant interest in the use of stem cells (SCs) for the recovery of cardiac function in individuals with myocardial injuries. Most commonly, cardiac stem cell therapy is studied by delivering SCs concurrently with the induction of myocardial injury. However, this approach presents two significant limitations: the early hostile pro-inflammatory ischemic environment may affect the survival of transplanted SCs, and it does not represent the subacute infarction scenario where SCs will likely be used. Here we describe a two-part series of surgical procedures for the induction of ischemia-reperfusion injury and delivery of mesenchymal stem cells (MSCs). This method of stem cell administration may allow for the longer viability and retention around damaged tissue by circumventing the initial immune response. A model of ischemia reperfusion injury was induced in mice accompanied by the delivery of mesenchymal stem cells (3.0 x 105), stably expressing the reporter gene firefly luciferase under the constitutively expressed CMV promoter, intramyocardially 7 days later. The animals were imaged via ultrasound and bioluminescent imaging for confirmation of injury and injection of cells, respectively. Importantly, there was no added complication rate when performing this two-procedure approach for SC delivery. This method of stem cell administration, collectively with the utilization of state-of-the-art reporter genes, may allow for the in vivo study of viability and retention of transplanted SCs in a situation of chronic ischemia commonly seen clinically, while also circumventing the initial pro-inflammatory response. In summary, we established a protocol for the delayed delivery of stem cells into the myocardium, which can be used as a potential new approach in promoting regeneration of the damaged tissue.

Ischemia reperfusion injury was induced in mice on day 0, followed by a post-operative echocardiogram and electrocardiogram on the day preceding stem cell implantation. Ultrasound and electrocardiogram analysis confirmed infarction and decreased ventricular contractile function (Figure 1A-D). Further examination of the data showed the ejection fraction and fractional shortening were decreased in mice that received ischemic injury, while the end-diastolic and systolic volumes...

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Delayed Intramyocardial Delivery of Stem Cells after Ischemia Reperfusion Injury in a Murine Model

Stems cells are continuously investigated as potential treatments for individuals with myocardial damage, however, their decreased viability and retention within injured tissue can impact their long-term efficacy. In this manuscript we describe an alternative method for stem cell delivery in a murine model of ischemia reperfusion injury.

There is significant interest in the use of stem cells (SCs) for the recovery of cardiac function in individuals with myocardial injuries. Most commonly, ...

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4.5K Views.  Mayo Clinic. Stems cells are continuously investigated as potential treatments for individuals with myocardial damage, however, their decreased viability and retention within injured tissue can impact their long-term efficacy. In this manuscript we describe an alternative method for stem cell delivery in a murine model of ischemia reperfusion injury.

Video: Delayed Intramyocardial Delivery of Stem Cells after Ischemia Reperfusion Injury in a Murine Model

A Murine Closed-chest Model of Myocardial Ischemia and Reperfusion

Surgical trauma by thoracotomy in open-chest models of coronary ligation induces an immune response which modifies different mechanisms involved in ischemia and reperfusion. Immune response includes cytokine expression and release or secretion of endogenous ligands of innate immune receptors. Activation of innate immunity can potentially modulate infarct size. We have modified an existing murine closed-chest model using hanging weights which could be useful for studying myocardial pre- and postconditioning and the role of innate immunity in myocardial ischemia and reperfusion. This model allows animals to recover from surgical trauma before onset of myocardial ischemia.
Volatile anesthetics have been intensely studied and their preconditioning effect for the ischemic heart is well known. However, this protective effect precludes its use in open chest models of coronary artery ligation. Thus, another advantage could be the use of the well controllable volatile anesthetics for instrumentation in a chronic closed-chest model, since their preconditioning effect lasts up to 72 hours. Chronic heart diseases with intermittent ischemia and multiple hit models are other possible applications of this model.
For the chronic closed-chest model, intubated and ventilated mice undergo a lateral blunt thoracotomy via the 4th intercostal space. Following identification of the left anterior descending a ligature is passed underneath the vessel and both suture ends are threaded through an occluder. Then, both suture ends are passed through the chest wall, knotted to form a loop and left in the subcutaneous tissue. After chest closure and recovery for 5 days, mice are anesthetized again, chest skin is reopened and hanging weights are hooked up to the loop under ECG control.
At the end of the ischemia/reperfusion protocol, hearts can be stained with TTC for infarct size assessment or undergo perfusion fixation to allow morphometric studies in addition to histology and immunohistochemistry.

Surgical trauma induces an inflammatory response. Cytokines and endogenous ligands are known to modulate myocardial infarct size following ischemia and reperfusion. We present a modified closed-chest model of murine ischemia and reperfusion using hanging weights to minimize effects of thoracotomy.

Surgical trauma by thoracotomy in open-chest models of coronary ligation induces an immune response which modifies different mechanisms involved in ...

Ischemia-reperfusion Model of Acute Kidney Injury and Post Injury Fibrosis in Mice

Ischemia-reperfusion induced acute kidney injury (IR-AKI) is widely used as a model of AKI in mice, but results are often quite variable with high, often unreported mortality rates that may confound analyses. Bilateral renal pedicle clamping is commonly used to induce IR-AKI, but differences between effective clamp pressures and/or renal responses to ischemia between kidneys often lead to more variable results. In addition, shorter clamp times are known to induce more variable tubular injury, and while mice undergoing bilateral injury with longer clamp times develop more consistent tubular injury, they often die within the first 3 days after injury due to severe renal insufficiency. To improve post-injury survival and obtain more consistent and predictable results, we have developed two models of unilateral ischemia-reperfusion injury followed by contralateral nephrectomy. Both surgeries are performed using a dorsal approach, reducing surgical stress resulting from ventral laparotomy, commonly used for mouse IR-AKI surgeries. For induction of moderate injury BALB/c mice undergo unilateral clamping of the renal pedicle for 26 min and also undergo simultaneous contralateral nephrectomy. Using this approach, 50-60% of mice develop moderate AKI 24 hr after injury but 90-100% of mice survive. To induce more severe AKI, BALB/c mice undergo renal pedicle clamping for 30 min followed by contralateral nephrectomy 8 days after injury. This allows functional assessment of renal recovery after injury with 90-100% survival. Early post-injury tubular damage as well as post injury fibrosis are highly consistent using this model.

We describe models of moderate and severe ischemia-reperfusion-induced kidney injury in which the mice undergo unilateral renal pedicle clamping followed by simultaneous or delayed contralateral nephrectomy, respectively. These models consistently give rise to renal dysfunction and post-injury fibrosis, but injury severity and survival are dependent on mouse background, age and surgical equipment.

Ischemia-reperfusion induced acute kidney injury (IR-AKI) is widely used as a model of AKI in mice, but results are often quite variable with high, often ...

Intramyocardial Cell Delivery: Observations in Murine Hearts

Previous studies showed that cell delivery promotes cardiac function amelioration by release of cytokines and factors that increase cardiac tissue revascularization and cell survival. In addition, further observations revealed that specific stem cells, such as cardiac stem cells, mesenchymal stem cells and cardiospheres have the ability to integrate within the surrounding myocardium by differentiating into cardiomyocytes, smooth muscle cells and endothelial cells.
Here, we present the materials and methods to reliably deliver noncontractile cells into the left ventricular wall of immunodepleted mice. The salient steps of this microsurgical procedure involve anesthesia and analgesia injection, intratracheal intubation, incision to open the chest and expose the heart and delivery of cells by a sterile 30-gauge needle and a precision microliter syringe.
Tissue processing consisting of heart harvesting, embedding, sectioning and histological staining showed that intramyocardial cell injection produced a small damage in the epicardial area, as well as in the ventricular wall. Noncontractile cells were retained into the myocardial wall of immunocompromised mice and were surrounded by a layer of fibrotic tissue, likely to protect from cardiac pressure and mechanical load.

Intramyocardial cell delivery in murine models of cardiovascular diseases, such as hypertension or myocardial infarction, is widely used to test the therapeutic potential of different cell types in regenerative studies. Therefore, a detailed description and a clear visualization of this surgical procedure will help to define the limits and advantages of cardiovascular cell therapeutic analyses in small rodents.

Previous studies showed that cell delivery promotes cardiac function amelioration by release of cytokines and factors that increase cardiac tissue ...

A Murine Model of Myocardial Ischemia-reperfusion Injury through Ligation of the Left Anterior Descending Artery

Acute or chronic myocardial infarction (MI) are cardiovascular events resulting in high morbidity and mortality. Establishing the pathological mechanisms at work during MI and developing effective therapeutic approaches requires methodology to reproducibly simulate the clinical incidence and reflect the pathophysiological changes associated with MI. Here, we describe a surgical method to induce MI in mouse models that can be used for short-term ischemia-reperfusion (I/R) injury as well as permanent ligation. The major advantage of this method is to facilitate location of the left anterior descending artery (LAD) to allow for accurate ligation of this artery to induce ischemia in the left ventricle of the mouse heart. Accurate positioning of the ligature on the LAD increases reproducibility of infarct size and thus produces more reliable results. Greater precision in placement of the ligature will improve the standard surgical approaches to simulate MI in mice, thus reducing the number of experimental animals necessary for statistically relevant studies and improving our understanding of the mechanisms producing cardiac dysfunction following MI. This mouse model of MI is also useful for the preclinical testing of treatments targeting myocardial damage following MI.

We introduce a surgical method to induce experimental ischemia/reperfusion (I/R) injury to simulate myocardial infarction (MI) in mouse models that allows for more clarity in positioning of the ligation on the left anterior descending artery (LAD) to increase the reproducibility of MI experiments in mice.

Acute or chronic myocardial infarction (MI) are cardiovascular events resulting in high morbidity and mortality. Establishing the pathological mechanisms ...

Murine Model of Intestinal Ischemia-reperfusion Injury

Intestinal ischemia is a life-threatening condition associated with a broad range of clinical conditions including atherosclerosis, thrombosis, hypotension, necrotizing enterocolitis, bowel transplantation, trauma and chronic inflammation. Intestinal ischemia-reperfusion (IR) injury is a consequence of acute mesenteric ischemia, caused by inadequate blood flow through the mesenteric vessels, resulting in intestinal damage. Reperfusion following ischemia can further exacerbate damage of the intestine. The mechanisms of IR injury are complex and poorly understood. Therefore, experimental small animal models are critical for understanding the pathophysiology of IR injury and the development of novel therapies.
Here we describe a mouse model of acute intestinal IR injury that provides reproducible injury of the small intestine without mortality. This is achieved by inducing ischemia in the region of the distal ileum by temporally occluding the peripheral and terminal collateral branches of the superior mesenteric artery for 60 min using microvascular clips. Reperfusion for 1 hr, or 2 hr after injury results in reproducible injury of the intestine examined by histological analysis. Proper position of the microvascular clips is critical for the procedure. Therefore the video clip provides a detailed visual step-by-step description of this technique. This model of intestinal IR injury can be utilized to study the cellular and molecular mechanisms of injury and regeneration.

Here we describe the detailed procedure of intestinal ischemia-reperfusion in mice which results in reproducible injury without mortality to encourage the standardization of this technique across the field. This model of intestinal ischemia-reperfusion injury can be utilized to study the cellular and molecular mechanisms of injury and regeneration.

Intestinal ischemia is a life-threatening condition associated with a broad range of clinical conditions including atherosclerosis, thrombosis, ...

A Mouse Model of Retinal Ischemia-Reperfusion Injury Through Elevation of Intraocular Pressure

Retinal ischemia-reperfusion (I/R) is a pathophysiological process contributing to cellular damage in multiple ocular conditions, including glaucoma, diabetic retinopathy, and retinal vascular occlusions. Rodent models of I/R injury are providing significant insights into mechanisms and treatment strategies for human I/R injury, especially with regard to neurodegenerative damage in the retinal neurovascular unit. Presented here is a protocol for inducing retinal I/R injury in mice through elevation of intraocular pressure (IOP). In this protocol, the ocular anterior chamber is cannulated with a needle, through which flows the drip of an elevated saline reservoir. Using this drip to raise IOP above systolic arterial blood pressure, a practitioner temporarily halts inner retinal blood flow (ischemia). When circulation is reinstated (reperfusion) by removal of the cannula, severe cellular damage ensues, resulting ultimately in retinal neurodegeneration. Recent studies demonstrate inflammation, vascular permeability, and capillary degeneration as additional elements of this model. Compared to alternative retinal I/R methodologies, such as retinal arterial ligation, retinal I/R injury by elevated IOP offers advantages in its&#160;anatomical specificity, experimental tractability, and technical accessibility, presenting itself as a valuable tool for examining neuronal pathogenesis and therapy in the retinal neurovascular unit.

This article describes a procedure for inducing retinal ischemia-reperfusion injury by elevated intraocular pressure in mice. Retinal ischemia-reperfusion injury by elevated intraocular pressure serves to model human pathologies characterized by compromised oxygen and nutrient delivery in the retina, enabling researchers to examine potential cellular mechanisms and treatments for human diseases of the retinal neurovascular unit.

Retinal ischemia-reperfusion (I/R) is a pathophysiological process contributing to cellular damage in multiple ocular conditions, including glaucoma, ...

Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via recanalization of the coronary artery is the most effective strategy for reducing the size of ischemic myocardium. The coronary microvasculature cannot be visualized and imaged&#160;in vivo, but there are several invasive and noninvasive techniques that can be used to assess parameters which depend directly on coronary microvascular function. The endothelial function after ischemia reperfusion can be assessed also at the level of the coronary circulation via the coronary flow reserve (CFR).&#160;In this study, peak velocity of left anterior descending (LAD) coronary arteries was measured in rats in vivo via Transthoracic Doppler Echocardiography during resting and stress challenge (induced by Dobutamine). A normal heart can increase its coronary blood flow up to four times above the resting values during stress induction. Following ischemia reperfusion, we found a significantly diminished CFR, which can be used as a marker of coronary microvascular dysfunction. CFR has opened a window on the importance of microvascular dysfunction and has been shown to predict cardiovascular risk independent of whether the severe obstructive disease is present.

Coronary flow reserve (CFR), is defined as the ratio of maximal coronary blood flow to the resting coronary blood flow. We present a protocol for evaluating CFR in rats via ultrasound, which offers the opportunity to predict cardiovascular risk factors in the absence of obstructive coronary disease.

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via ...

A Pre-clinical Rat Model for the Study of Ischemia-reperfusion Injury in Reconstructive Microsurgery

Ischemia-reperfusion injury is the main cause of flap failure in reconstructive microsurgery. The rat is the preferred preclinical animal model in many areas of biomedical research due to its cost-effectiveness and its translation to humans. This protocol describes a method to create a preclinical free skin flap model in rats with ischemia-reperfusion injury. The described 3 cm x 6 cm rat free skin flap model is easily obtained after the placement of several vascular ligatures and the section of the vascular pedicle. Then, 8 h after the ischemic insult and completion of the microsurgical anastomosis, the free skin flap develops the tissue damage. These ischemia-reperfusion injury-related damages can be studied in this model, making it a suitable model for evaluating therapeutic agents to address this pathophysiological process. Furthermore, two main monitoring techniques are described in the protocol for the assessment of this animal model: transit-time ultrasound technology and laser speckle contrast analysis.

Here, we describe a pre-clinical animal model for studying the pathophysiology of ischemia-reperfusion injury in reconstructive microsurgery. This free skin flap model based on the superficial caudal epigastric vessels in the rat may also allow for the evaluation of different therapies and compounds to counteract ischemia-reperfusion injury-related damage.

Ischemia-reperfusion injury is the main cause of flap failure in reconstructive microsurgery. The rat is the preferred preclinical animal model in many ...

Tracking Superparamagnetic Iron Oxide-labeled Mesenchymal Stem Cells using MRI after Intranasal Delivery in a Traumatic Brain Injury Murine Model

Stem cell-based therapies for brain injuries, such as traumatic brain injury (TBI), are a promising approach for clinical trials. However, technical hurdles such as invasive cell delivery and tracking with low transplantation efficiency remain challenges in translational stem-based therapy. This article describes an emerging technique for stem cell labeling and tracking based on the labeling of the mesenchymal stem cells (MSCs) with superparamagnetic iron oxide (SPIO)&#160;nanoparticles, as well as intranasal delivery of the labeled MSCs. These nanoparticles are fluorescein isothiocyanate (FITC)-embedded and safe to label the MSCs, which are subsequently delivered to the brains of TBI-induced mice by the intranasal route. They are then tracked non-invasively in vivo by real-time magnetic resonance imaging (MRI). Important advantages of this technique that combines SPIO for cell labeling and intranasal delivery include (1) non-invasive, in vivo MSC tracking after delivery for long tracking periods, (2) the possibility of multiple dosing regimens due to the non-invasive route of MSC delivery, and (3) possible applications to humans, owing to the safety of SPIO, non-invasive nature of the cell-tracking method by MRI, and route of administration.

Presented here is a protocol for non-invasive mesenchymal stem cell (MSC) delivery and tracking in a mouse model of traumatic brain injury. Superparamagnetic iron oxide&#160;nanoparticles are employed as a magnetic resonance imaging (MRI) probe for MSC labeling and non-invasive in vivo tracking following intranasal delivery using real-time MRI.

Stem cell-based therapies for brain injuries, such as traumatic brain injury (TBI), are a promising approach for clinical trials. However, technical ...

Intramyocardial Transplantation of MSC-Loading Injectable Hydrogels after Myocardial Infarction in a Murine Model

One of the major issues facing current cardiac stem cell therapies for preventing postinfarct heart failure is the low retention and survival rates of transplanted cells within the injured myocardium, limiting their therapeutic efficacy. Recently, the use of scaffolding biomaterials has gained attention for improving and maximizing stem cell therapy. The objective of this protocol is to introduce a simple and straightforward technique to transplant bone marrow-derived mesenchymal stem cells (MSCs) using injectable hydroxyphenyl propionic acid (GH) hydrogels; the hydrogels are favorable as a cell delivery platform for cardiac tissue engineering applications due to their ability to be cross-linked in situ and high biocompatibility. We present a simple method to fabricate MSC-loading GH hydrogels (MSC/hydrogels) and evaluate their survival and proliferation in three-dimensional (3D) in vitro culture. In addition, we demonstrate a technique for intramyocardial transplantation of MSC/hydrogels in mice, describing a surgical procedure to induce myocardial infarction (MI) via left anterior descending (LAD) coronary artery ligation and subsequent MSC/hydrogels transplantation.

Stem cell-based therapy has emerged as an efficient strategy to repair injured cardiac tissues after myocardial infarction. We provide an optimal in vivo application for stem cell transplantation using gelatin hydrogels that are able to be enzymatically cross-linked.

One of the major issues facing current cardiac stem cell therapies for preventing postinfarct heart failure is the low retention and survival rates of ...