Name: delayed intramyocardial delivery of stem cells after ischemia reperfusion injury in a murine model
Uploaded: 2020-09-03T13:00:00
Description: Watch this Scientific Journal Video about Delayed Intramyocardial Delivery of Stem Cells after Ischemia Reperfusion Injury in a Murine Model at JoVE.com

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
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	<li>Autoclave all surgical instr...

<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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K., Nahrendorf, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardioimmunology:+the+immune+system+in+cardiac+homeostasis+and+disease.">Cardioimmunology: the immune system in cardiac homeostasis and disease.</a> Nature Reviews Immunology. 18 (12), 733-744 (2018).</li><li>Zhang, Z., 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=Mesenchymal+Stem+Cells+Promote+the+Resolution+of+Cardiac+Inflammation+After+Ischemia+Reperfusion+Via+Enhancing+Efferocytosis+of+Neutrophils.">Mesenchymal Stem Cells Promote the Resolution of Cardiac Inflammation After Ischemia Reperfusion Via Enhancing Efferocytosis of Neutrophils.</a> Journal of the American Heart Association. 9 (5), 014397 (2020).</li><li>Saxena, A., Russo, I., Frangogiannis, N. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammation+as+a+therapeutic+target+in+myocardial+infarction:+learning+from+past+failures+to+meet+future+challenges.">Inflammation as a therapeutic target in myocardial infarction: learning from past failures to meet future challenges.</a> Translational Research. 167 (1), 152-166 (2016).</li><li>Prabhu, S. D., Frangogiannis, N. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Biological+Basis+for+Cardiac+Repair+After+Myocardial+Infarction:+From+Inflammation+to+Fibrosis.">The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis.</a> Circulation Research. 119 (1), 91-112 (2016).</li><li>Dominici, 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=Minimal+criteria+for+defining+multipotent+mesenchymal+stromal+cells.+The+International+Society+for+Cellular+Therapy+position+statement.">Minimal criteria for defining multipotent mesenchymal stromal cells. The International Society for Cellular Therapy position statement.</a> Cytotherapy. 8 (4), 315-317 (2006).</li></ol>

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.

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			<td height="17" style="height:17px;">Monoject 1 mL hypodermic syringe</td>
			<td>Coviden</td>
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			<td>Fine Science Tools</td>
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			<td>Fine Science Tools</td>
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			<td>Kent Scientific</td>
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			<td>Johnson &#38; Johnson</td>
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			<td>Cardinal Health</td>
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			<td height="17" style="height:17px;">Vetflo vaporizer</td>
			<td>Kent Scientific</td>
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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...

Watch this Scientific Journal Video about Delayed Intramyocardial Delivery of Stem Cells after Ischemia Reperfusion Injury in a Murine Model at JoVE.com

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, ...

Ischemic damage induces a hostile pro-inflammatory environment affecting the survival of transplanted cells. Our protocol presents an alternative method for providing biologics by circumventing the initial immune response to injury. The main advantage of this protocol is that it makes it possible to administer therapeutics one week following injury, mimicking treatment in the clinical environment.Our primary focus is on the ischemia reperfusion injury model and transplantation of STEM cells. However, this approach can also be utilized for models of inflammatory disease that involves the introduction of biological therapies. Begin by autoclaving all surgical instruments.If multiple surgeries are to be performed in one session, clean the instruments after each animal and re-sterilize them using a hot bead sterilizer. Subcutaneously administer analgesic, weigh the animal, and input the weight into the ventilator. Shave the left side of the chest from the sternum to the level of the shoulder and apply depilatory cream to remove excess fur.To prevent lung collapse, maintain the positive end expiratory pressure at two centimeters of water for the ischemia reperfusion procedure and change it to three centimeters of water for the delayed injection of cells procedure. After anesthetizing the mouse, intubate it with a 20 gauge endotracheal tube and transfer it to a controlled heating pad to maintain a body temperature of 35 to 37 degrees Celsius. Place the mouse in lateral recumbency with cranial end on the left and caudal end on the right.Scrub the surgical area alternating between povidone iodine and alcohol swabs three times and apply ophthalmic ointment to both eyes. Use a number 10 blade scalpel to make a vertical incision 2.5 millimeters to the right of the leftmost nipple in the field of view, then use scissors to cut through the superficial muscle layers until the intercostal muscle and ribs are visible. While lifting the ribs and surrounding tissue, cut through the intercostal space between the fourth and fifth ribs, then insert the eyelid retractor into the open space.Retract the pericardium using curved forceps, moving the lung upwards and out of the view. Pass a 9-0 nylon suture through the myocardium beneath the LAD artery 2.5 millimeters distal to the left auricle maintaining smooth and consistent movement to prevent tearing of the tissue or puncturing a major blood vessel. Tie a loose square knot, then place one centimeter of polyethylene tubing within the loose knot.Secure the suture around the tubing and confirm ischemia by pallor and ventricular arrhythmia, then release after 35 minutes. After removing the tubing, wait for five minutes to confirm re-perfusion of the myocardium. Place a 24 gauge IV catheter tube into the thoracic cavity one intercostal space to the right of the opening.Use 6-0 absorbable sutures to close the intercostal incision in a simple interrupted pattern and the muscle layer in a continuous suture pattern. After closing the superficial muscle layer, remove the chest tube while withdrawing the air from the thoracic cavity with a one milliliter tuberculin syringe. Close the skin incision with a 6-0 absorbable suture in a continuous horizontal mattress pattern.When finished, administer 1.5 milliliters of warm saline subcutaneously and apply triple antibiotic ointment to the incision site to prevent infection. Transfer the mouse to a bedding free cage or a cage with covered bedding on a warm pad and a temperature of 35 to 37 degrees Celsius until it is fully recovered. After preparing and intubating the mouse as previously described, remove the suture from the skin layer with scissors and forceps, then use a number 10 scalpel to make an incision in the same location as the previous surgery.Continue to cut through the scar tissue until the muscle layer suture is visible, then use the scissors and forceps to remove the suture and cut the muscle layer open. Remove the sutures holding the ribs together and continue cutting through the intercostal muscle from the previous incision. Place the eyelid retractor into the intercostal space and locate the area of the previous ligation.Load 300, 000 mesenchymal STEM cells suspended in 20 microliters of PBS into a 30 gauge insulin syringe and bend the needle slightly to achieve the proper angle for injection. 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, then slowly inject the cells into the myocardium, wait three seconds and remove the needle. Observe the heart closely for three minutes to make sure that there is no abnormal reaction to the cells such as ventricular fibrillation.After three minutes, place a 24 gauge IV catheter tube into the thoracic cavity one intercostal space to the right of the opening. Close the intercostal muscle and skin layers and remove the chest tube as previously described. Administer 1.5 milliliters of warm saline subcutaneously and apply triple antibiotic ointment to the incision site to prevent infection.Transfer the mouse to a bedding free cage or cage with covered bedding on a warm pad until it is fully recovered. Post-operative echocardiogram and electrocardiogram were performed on the day proceeding STEM cell implantation, confirming infarction and decreased ventricular contractile function. 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 increased.Masson trichrome staining of myocardial tissue seven days post-injury showed increased collagen deposition and thinning of the left ventricular wall in hearts of mice that received ischemic injury. In vivo bioluminescent imaging or BLI was performed on the day after mesenchymal STEM cell implantation. Successful delivery of MSCs is exemplified by the BLI signal compared to mice that had induced ischemia reperfusion injury but did not receive MSCs.When attempting this protocol, keep in mind that small intentional movements when cutting through the intercostals, ligating the vessel, and injecting cells are vital for preventing undue damage to the heart or the lung in the field of view. These procedures offer the ability to monitor cardiac function after transplantation through ultrasound, cell viability via bioluminescence imaging, or further molecular or biochemical techniques depending on the therapy used.

delayed-intramyocardial-delivery-stem-cells-after-ischemia

Research

JoVE Journal

Medicine

Normothermic Cardiac Arrest and Cardiopulmonary Resuscitation: A Mouse Model of Ischemia-Reperfusion Injury

Acute Kidney Injury (AKI) is a common, highly lethal, complication of critical illness which has a high mortality1-4 and which is most 
frequently caused by whole-body hypoperfusion.5,6 Successful reproduction of whole-body hypoperfusion in rodent models has been fraught with 
difficulty.7-9,9,10 Models which employ focal ischemia have repeatedly demonstrated results which do not translate to the clinical setting, and larger 
animal models which allow for whole body hypoperfusion lack access to the full toolset of genetic manipulation possible in the mouse.11,12 However, in recent 
years a mouse model of cardiac arrest and cardiopulmonary resuscitation has emerged which can be adapted to model AKI.13 This model reliably reproduces 
physiologic, functional, anatomic, and histologic outcomes seen in clinical AKI, is rapidly repeatable, and offers all of the significant advantages of a murine surgical 
model, including access to genetic manipulative techniques, low cost relative to large animals, and ease of use. Our group has developed extensive experience 
with use of this model to assess a number of organ-specific outcomes in AKI.14,15

A powerful model for perioperative and critical care related acute kidney injury is presented. Using whole body hypoperfusion induced by cardiac arrest it is possible to nearly replicate the histologic and functional changes of clinical AKI.

Acute Kidney Injury (AKI) is a common, highly lethal, complication of critical illness which has a high mortality1-4 and which is most 
frequently caused ...

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 ...