TWP was funded by the Irish Cardiac Society Brian McGovern Travelling Fellowship. WTP was funded by R01 HL095712 and an AHA Established Investigator Award.

All described steps were performed under protocols approved by the Institutional Animal Care and Use Committee of Boston Children&#8217;s Hospital.
1. Preparation
<ol>
	<li>Perform baseline cardiac anatomical and functional assessment by echocardiography prior to beginning the injection protocol, as the optimal fixed transducer position for intramyocardial injection may not yield the optimal standard views for delineating anatomy and assessment of function.</li>
	<li>The injection setup is shown in Figures 1A-1C. Place an empty syringe with a sheathed needle, bevel oriented upwards, in the syringe clamp (see Figure 1C) and secure the ultrasound transducer probe in the scan-head clamp (see Figure 1B). Loosen the scan-head clamp ball lock joint (Figure 1B) and manipulate the transducer orientation so that it is aligned parallel to the axis of the needle. Fix the scan-head position by tightening the scan-head clamp ball lock joint. 
	NOTE: For injection in adult mice, a 30 G needle with a 1 in/2.5 cm length is optimal. A 1 ml syringe can be used for larger volumes, while a gastight syringe can be used for more precise control of smaller volumes (5-10 &#181;l).</li>
	<li>Apply ultrasound gel liberally to the transducer tip with a spatula to cover the head along its entirety. Carefully unsheathe the needle and use the needle mount controls to advance the needle directly under the transducer and within the ultrasound gel for visualization. Make minor adjustments using the needle mount control so that the needle is visualized clearly along its length on the ultrasound image. If the transducer was properly aligned parallel to the needle in step 1.4, then the needle should remain within the imaging plane as it is advanced and withdrawn with the injection control knob (Figure 1C).</li>
	<li>In subsequent steps, do not disturb the needle/transducer horizontal alignment by moving either in the horizontal axis. Rather, target specific areas of the heart for injection by changing the vertical (y-axis) position of the needle mount and by moving the animal platform.</li>
	<li>Move the transducer superiorly from the animal platform using the scan height control (Figure 1B) to allow subsequent placement of the anesthetized mouse onto the animal platform. This will not disrupt the x-axis alignment of the transducer to the long axis of the needle.</li>
	<li>Remove the syringe that was used for alignment from the syringe clamp and discard carefully. Load the new needle and syringe with the injectate to the final target volume, allowing for dead space in the syringe tip. Be careful to remove air bubbles. Place the syringe into the syringe clamp without adjusting its x-axis alignment. Fully retract the syringe using the injection control. 
	NOTE: For initial training purposes, the use of Evan&#8217;s blue dye (1%), Trypan blue stain (0.4%) or a suspension of fluorescent microspheres as the injectate can assist the operator in confirming competency and success of targeted injection.</li>
</ol>
2. Injection
<ol>
	<li>Turn on the integrated warmer of the heating platform and set it for 37 &#176;C. Place the animal platform 180&#176; from the usual imaging orientation, with the anesthesia hose clamp and head of the animal closest to the operator. This allows the heart (in the left side of the chest) to be ipsilateral to the syringe clamp and needle. Note: Additional minor clockwise rotational adjustments to the animal platform may be necessary to orient the heart correctly for the parasternal short axis imaging plane that will be used for injection (Figure 2A).</li>
	<li>Prepare mice for echocardiography as previously reported9. Anesthetize the mouse in an induction chamber with 2% isoflurane. Remove chest hair with hair removal cream and apply lubricating gel to both eyes to prevent drying of the sclera.</li>
	<li>Raise the transducer using the scan head height control (Figure 1B). Place the anesthetized mouse supine atop the heated animal platform with the snout within a nose cone delivering 1-3% isoflurane (Figures 2A-2B). Gently insert a rectal probe and tape the four paws to the ECG electrodes, applying electrode gel for electrical contact. 
	NOTE: An appropriate level of anesthesia must be ensured for the humane treatment of the animal. There should be no change in heart rate and no response to placement of the needle through the chest wall. The animal platform&#8217;s integrated homeostatic temperature controls should be used to maintain normothermia (37&#160;&#177; 0.5 &#176;C), as hypothermia will result in relative bradycardia, ventricular dilatation, and possible discomfort.</li>
	<li>Once the mouse is secure on the animal platform, lower the transducer onto the depilated chest using the scan head height control (Figure 1B). The optimal ultrasound setup for injection is for the heart to be visualized in the parasternal short axis orientation, as per standard echocardiographic technique. Rotate the animal platform 20-30&#176; clockwise to obtain the optimal acoustic window for injection in the short axis imaging plane (Figures 2A-2B). Note: Alternatively, injection can be performed from a parasternal long axis orientation by counter-clockwise rotation of the animal platform (Figure 2C).</li>
	<li>Use the animal platform adjustment controls to adjust the field of view and to target any desired injection site in the left ventricular myocardium. Pan back-and-forth from the apex to the base of heart to target the desired injection location in the left ventricular myocardium (Figures 3A-3C). Note: The midpapillary parasternal short-axis view (Figure 3A) offers reproducible landmarks that permit followup imaging of the injection site. Note: Alternatively, the parasternal long axis view can be used to target a predefined injection site (Figure 3D).</li>
	<li>Starting with the syringe in the fully retracted syringe clamp, slowly advance the syringe towards the animal&#8217;s chest by turning the injection control clockwise (Figure 4A). To permit clear ultrasound visualization of both the heart and the needle tip as it approaches the chest, use plenty of ultrasound gel over the left side of the chest and optimize the acoustic window by setting a wide field of view on the echocardiography controls. Set the focal point/zone at the target site for injection. Minor adjustments to the needle mount controls can optimize the image of the needle along its length. 
	NOTE: Some ultrasound machines have a needle guide software function to digitally extend a line along the long axis of the needle through to the target myocardium (Figure 4B). Such a software tool can be helpful but is not essential.</li>
	<li>With the animal appropriately sedated (1-3% isoflurane mixed with 0.5-0.8 L/min 100% oxygen), advance the needle through the chest wall of the mouse and into the myocardium, carefully observing the position of the beveled needle tip at all times. Stop advancing when the needle tip is within the target myocardium (Figure 4C). The whole beveled tip should be securely within the myocardium, to avoid injectate leak into the pericardial space.</li>
	<li>When the tip is in the desired location, deliver the injectate by pushing on the syringe plunger. Deliver the injectate slowly, over 5-30 sec (depending on the volume being delivered). Up to 50 &#181;l of injectate can be delivered without compromising ventricular function. A transient echobright appearance to the injected myocardial region may be evident after successful injection. A brief (seconds) period of relative bradycardia is occasionally noted with injection into the myocardium and quickly resolves.</li>
	<li>Once the injectate has been administered, promptly withdraw the needle by counter-clockwise rotation of the injection control knob. The mouse should be kept under anesthesia for several minutes of echocardiographic observation to confirm preserved ventricular function and no postprocedural complications. If indicated, multiple regions of myocardium can be serially injected by repositioning of the needle&#8217;s angle of approach by adjustment of the animal platform. After intramyocardial injection, the mouse is placed in a cage on its own and allowed to recover from anesthesia under observation.</li>
	<li>Do not leave an animal unattended until it has regained sufficient consciousness to maintain sternal recumbency. Do not return an animal that has undergone intramyocardial injection to the company of other animals until fully recovered. The cage should be placed on a thermoregulated pad with ready provision of water and mouse diet. Postprocedural discomfort is not expected and failure to appropriately resume normal behavior shortly after intervention suggests a potential complication (see Discussion).</li>
	<li>Carefully discard the needle immediately after completion of intramyocardial injection to minimize the risk of sharps injury to the operator or bystanders. Reusing a needle can result in blunting of the tip making it more challenging to pierce the myocardium and resulting in a higher risk of complication.</li>
</ol>

<ol>
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L., 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=Postinfarct+intramyocardial+injection+of+mesenchymal+stem+cells+pretreated+with+TGF-alpha+improves+acute+myocardial+function.">Postinfarct intramyocardial injection of mesenchymal stem cells pretreated with TGF-alpha improves acute myocardial function.</a> Am J Physiol Regul Integr Comp Physiol. 299 (1), 371-378 (2010).</li><li>Zhou, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+injection+of+autologous+mesenchymal+stromal+cells+improves+myocardial+function.">Direct injection of autologous mesenchymal stromal cells improves myocardial function.</a> Biochem Biophys Res Commun. 390 (3), 902-907 (2009).</li><li>Campbell, N. G., Suzuki, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+delivery+routes+for+stem+cell+therapy+to+the+heart:+current+and+future+approaches.">Cell delivery routes for stem cell therapy to the heart: current and future approaches.</a> J Cardiovasc Transl Res. 5 (5), 713-726 (2012).</li><li>Hou, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radiolabeled+cell+distribution+after+intramyocardial,+intracoronary,+and+interstitial+retrograde+coronary+venous+delivery:+implications+for+current+clinical+trials.">Radiolabeled cell distribution after intramyocardial, intracoronary, and interstitial retrograde coronary venous delivery: implications for current clinical trials.</a> Circulation. 112, 150-156 (2005).</li><li>Dib, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recommendations+for+successful+training+on+methods+of+delivery+of+biologics+for+cardiac+regeneration:+a+report+of+the+International+Society+for+Cardiovascular+Translational+Research).">Recommendations for successful training on methods of delivery of biologics for cardiac regeneration: a report of the International Society for Cardiovascular Translational Research).</a> JACC Cardiovasc Interv. 3 (3), 265-275 (2010).</li><li>Dib, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+therapy+for+cardiovascular+disease:+a+comparison+of+methods+of+delivery.">Cell therapy for cardiovascular disease: a comparison of methods of delivery.</a> J Cardiovasc Transl Res. 4 (2), 177-181 (2011).</li></ol>

The authors have nothing to disclose.

Biologics can be delivered to the myocardium by direct intramyocardial injection, intrapericardial injection, or indirect administration via the bloodstream. Recent cell based therapy trials in myocardial infarction models have described an open thoracotomy approach to the delivery of injectate12-14. An important factor in the success of a myocardial therapeutic intervention hinges on the choice of delivery route. The highest local dose of biologic is achieved by intramyocardial delivery15,16. Intra...

Heart disease is the leading cause of death for both men and women in the United States, accounting for 600,000 deaths annually1. Murine models of cardiovascular disease are critically important for investigating pathophysiological mechanisms and for exploring potential therapies. Myocardial delivery of gene therapy vectors, stem cells, modified RNAs, and other therapeutic agents permits investigation of their therapeutic potential for heart disease2-7. Currently, there are limited options for myocardial delivery of therapeutic agents in mouse models6. Intramyocardial injection under direct visualization is commonly used, but requires a sternotomy or thoracotomy and is limited to the exposed region of the heart. While convenient when performed at the time of another experimental manipulation such as LAD ligation, the need for an invasive procedure for intramyocardial delivery limits potential experimental designs and introduces additional effects from the procedure (e.g., fibrosis due to thoracotomy). Percutaneous pericardial delivery of viral vectors has been reported, but the site and distribution of therapeutic agent is not homogeneous and is difficult to control8. Percutaneous coronary injection results in more homogenous distribution of injected material, but efficient and reproducible coronary delivery is challenging in murine models.
Here, we describe a closed chest intramyocardial injection technique that allows minimally invasive, operator controlled targeting of therapeutic agents under ultrasound guidance. The technique is easy to learn, obviates the need for thoracotomy or sternotomy and their attendant experimental complications, and provides greater flexibility on the timing and sites of intramyocardial injection. Thus, echocardiography-assisted intramyocardial injection represents a technically simple and highly effective method of manipulating the myocardium in murine experimental models.

<table><tbody><tr><td>Vevo 2100 ultrasound imaging system&amp;nbsp;</td><td>Visualsonics</td><td></td><td></td></tr><tr><td>Vevo Integrated Rail System III</td><td>Visualsonics</td><td></td><td></td></tr><tr><td>Microscan MS400 transducer</td><td>Visualsonics</td><td></td><td></td></tr><tr><td>Microscan MS550D transducer</td><td>Visualsonics</td><td></td><td></td></tr><tr><td>PrecisionGlide needles</td><td>BD</td><td>305128</td><td>30 G x 1 in/2.5 cm</td></tr><tr><td>1 cc slip tip syringe</td><td>Exel International&amp;nbsp;</td><td>26048</td><td>or equivalent</td></tr><tr><td>Gastight 50 &amp;#956;l glass syringes</td><td>Hamilton</td><td>1705</td><td></td></tr><tr><td>Trypan blue stain (0.4%)</td><td>Gibco&amp;nbsp;</td><td>15250</td><td>or equivalent</td></tr><tr><td>Isoflurane</td><td>Baxter</td><td>AHN3640</td><td>or equivalent</td></tr><tr><td>Aquasonic 100</td><td>Parker Laboratories</td><td>(01-08)</td><td>or equivalent</td></tr><tr><td>Polystyrene microspheres (red fluorescent)</td><td>Life Technologies</td><td>F-8842</td><td>or equivalent</td></tr></tbody></table>

ultrasound-guided transthoracic intramyocardial injection in mice

Murine models of cardiovascular disease are important for investigating pathophysiological mechanisms and exploring potential regenerative therapies. Experiments involving myocardial injection are currently performed by direct surgical access through a thoracotomy. While convenient when performed at the time of another experimental manipulation such as coronary artery ligation, the need for an invasive procedure for intramyocardial delivery limits potential experimental designs. With ever improving ultrasound resolution and advanced noninvasive imaging modalities, it is now feasible to routinely perform ultrasound-guided, percutaneous intramyocardial injection. This modality efficiently and reliably delivers agents to a targeted region of myocardium. Advantages of this technique include the avoidance of surgical morbidity, the facility to target regions of myocardium selectively under ultrasound guidance, and the opportunity to deliver injectate to the myocardium at multiple, predetermined time intervals. With practiced technique, complications from intramyocardial injection are rare, and mice quickly return to normal activity on recovery from anesthetic. Following the steps outlined in this protocol, the operator with basic echocardiography experience can quickly become competent in this versatile, minimally invasive technique.

Murine Intramyocardial Injection with Blue Dye or Fluorescent Microspheres
Injection of Evan&#8217;s blue dye is useful for training purposes. Soon after injection, euthanize the mouse and remove the heart to visualize the location of the injected blue dye. Figure 5 shows an example of a successful injection, with blue dye infiltrating the myocardium at the mid-papillary muscle level (Figure 5A, region enclosed by dotted line). Evans blue dye will wash out of the...

Watch this Scientific Journal Video about Ultrasound-guided Transthoracic Intramyocardial Injection in Mice at JoVE.com

Ultrasound-guided Transthoracic Intramyocardial Injection in Mice

Echocardiography-guided percutaneous intramyocardial injection represents an efficient, reliable, and targetable modality for the delivery of gene transfer agents or cells into the murine heart. Following the steps outlined in this protocol, the operator can quickly become competent in this versatile, minimally invasive technique.

Murine models of cardiovascular disease are important for investigating pathophysiological mechanisms and exploring potential regenerative therapies. ...

ultrasound-guided-transthoracic-intramyocardial-injection-in-mice

Research

JoVE Journal

Medicine

14.8K Views.  Boston Children's Hospital.  Echocardiografie-geleide percutane intramyocardiale injectie vertegenwoordigt een efficiënte, betrouwbare en richtbare modaliteit voor de levering van genoverdracht agentia of cellen in muizen hart. Naar aanleiding van de stappen in dit protocol, kan de operator snel bevoegd in deze veelzijdige, minimaal invasieve techniek geworden. 

Video: Ultrasound-guided Transthoracic Intramyocardial Injection in Mice

Coronary Artery Ligation and Intramyocardial Injection in a Murine Model of Infarction

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo. With the advent of genetic modifications to the whole organism or the myocardium and an array of biological and/or synthetic materials, there is great potential for any combination of these to assuage the extent of acute ischemic injury and impede the onset of heart failure pursuant to myocardial remodeling. 
Here we present the methods and materials used to reliably perform this microsurgery and the modifications involved for temporary (with reperfusion) or permanent coronary artery occlusion studies as well as intramyocardial injections. The effects on the heart that can be seen during the procedure and at the termination of the experiment in addition to histological evaluation will verify efficacy. 
Briefly, surgical preparation involves anesthetizing the mice, removing the fur on the chest, and then disinfecting the surgical area. Intratracheal intubation is achieved by transesophageal illumination using a fiber optic light. The tubing is then connected to a ventilator. An incision made on the chest exposes the pectoral muscles which will be cut to view the ribs. For ischemia/reperfusion studies, a 1 cm piece of PE tubing placed over the heart is used to tie the ligature to so that occlusion/reperfusion can be customized. For intramyocardial injections, a Hamilton syringe with sterile 30gauge beveled needle is used. When the myocardial manipulations are complete, the rib cage, the pectoral muscles, and the skin are closed sequentially. Line block analgesia is effected by 0.25% marcaine in sterile saline which is applied to muscle layer prior to closure of the skin. The mice are given a subcutaneous injection of saline and placed in a warming chamber until they are sternally recumbent. They are then returned to the vivarium and housed under standard conditions until the time of tissue collection. At the time of sacrifice, the mice are anesthetized, the heart is arrested in diastole with KCl or BDM, rinsed with saline, and immersed in fixative. Subsequently, routine procedures for processing, embedding, sectioning, and histological staining are performed. 
Nonsurgical intubation of a mouse and the microsurgical manipulations described make this a technically challenging model to learn and achieve reproducibility. These procedures, combined with the difficulty in performing consistent manipulations of the ligature for timed occlusion(s) and reperfusion or intramyocardial injections, can also affect the survival rate so optimization and consistency are critical.

Numerous genetic manipulations and/or intramyocardial injections of genes, proteins, cells, and/or biomaterials are superimposed upon the dimension of time in studies of acute ischemia/ reperfusion injury and chronic remodeling in mice. This video illustrates the microsurgical procedures for ischemia/reperfusion, permanent coronary artery ligation, and intramyocardial injection studies.

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo.  With the advent of genetic modifications to ...

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 ...

Ultrasound Imaging-guided Intracardiac Injection to Develop a Mouse Model of Breast Cancer Brain Metastases Followed by Longitudinal MRI

Breast cancer brain metastasis, occurring in 30% of breast cancer patients at stage IV, is associated with high mortality. The median survival is only 6 months. It is critical to have suitable animal models to mimic the hemodynamic spread of the metastatic cells in the clinical scenario. Here, we are introducing the use of small animal ultrasound imaging to guide an accurate injection of brain tropical breast cancer cells into the left ventricle of athymic nude mice. Longitudinal MRI is used to assessing intracranial initiation and growth of brain metastases. Ultrasound-guided intracardiac injection ensures not only an accurate injection and hereby a higher successful rate but also significantly decreased mortality rate, as compared to our previous manual procedure. In vivo high resolution MRI allows the visualization of hyperintense multifocal lesions, as small as 310 &#181;m in diameter on T2-weighted images at 3 weeks post injection. Follow-up MRI reveals intracranial tumor growth and increased number of metastases that distribute throughout the whole brain.

A breast cancer brain metastasis mouse model is established with ultrasound imaging-guided intracardiac injection of MDA-MB231/Br-GFP cells. Development of multifocal intracranial metastases has been monitored longitudinally using high-resolution 9.4 T MRI.

Breast cancer brain metastasis, occurring in 30% of breast cancer patients at stage IV, is associated with high mortality. The median survival is only 6 ...

Intramyocardial Injection for the Study of Cardiac Lymphatic Function in Zebrafish

Zebrafish have proved to be an important model for studying cardiovascular formation and function during postembryonic development and regeneration. The present protocol describes a method for injecting fluorescent tracers into the zebrafish myocardium to study interstitial fluid and debris uptake into cardiac lymphatic vessels. To do so, microspheres (200 nm diameter) and quantum dots (&#60;10 nm diameter) are introduced into the myocardium of live zebrafish, which can be tracked using ex vivo confocal microscopy. These tracers are then tracked intermittently over several hours to follow clearance from the myocardium into cardiac lymphatic vessels. Quantum dots&#160;are transported through cardiac lymphatic vessels away from the heart, while larger microspheres&#160;remain at the injection site for over three weeks. This method of intramyocardial injection can be extended to other uses, including the injection of encapsulated MS or hydrogels to locally release cells, proteins, or compounds of interest to a targeted region of the heart.

The present protocol allows efficient and stable delivery of fluorescent microspheres (MS) and quantum dots (QD) into the myocardium of live fish that can be tracked (traced) over time.

Zebrafish have proved to be an important model for studying cardiovascular formation and function during postembryonic development and regeneration. The ...

Developmental Biology

Ultrasound-guided Intracardiac Injection of Human Mesenchymal Stem Cells to Increase Homing to the Intestine for Use in Murine Models of Experimental Inflammatory Bowel Diseases

Crohn&#39;s disease (CD) is a common chronic inflammatory disease of the small and large intestines. Murine and human mesenchymal stem cells (MSCs) have immunosuppressive potential and have been shown to suppress inflammation in mouse models of intestinal inflammation, even though the route of administration can limit their homing and effectiveness 1,3,4,5. Local application of MSCs to colonic injury models has shown greater efficacy at ameliorating inflammation in the colon. However, there is paucity of data on techniques to enhance the localization of human bone marrow-derived MSCs (hMSCs) to the small intestine, the site of inflammation in the SAMP-1/YitFc (SAMP) model of experimental Crohn&#39;s disease. This work describes a novel technique for the ultrasound-guided intracardiac injection of hMSCs in SAMP mice, a well-characterized spontaneous model of chronic intestinal inflammation. Sex- and age-matched, inflammation-free AKR/J (AKR) mice were used as controls. To analyze the biodistribution and the localization, hMSCs were transduced with a lentivirus containing a triple reporter. The triple reporter consisted of firefly luciferase (fl), for bioluminescent imaging; monomeric red fluorescent protein (mrfp), for cell sorting; and truncated herpes simplex virus thymidine kinase (ttk), for positron emission tomography (PET) imaging. The results of this study show that 24 h after the intracardiac administration, hMSCs localize in the small intestine of SAMP mice as opposed to inflammation-free AKR mice. This novel, ultrasound-guided injection of hMSCs in the left ventricle of SAMP mice ensures a high success rate of cell delivery, allowing for the rapid recovery of mice with minimal morbidity and mortality. This technique could be a useful method for the enhanced localization of MSCs in other models of small-intestinal inflammation, such as TNF&#916;RE6. Future studies will determine if the increased localization of hMSCs by intra-arterial delivery can lead to increased therapeutic efficacy.

Murine studies in models of colonic inflammation have demonstrated that a small percentage (1 - 5%) of mesenchymal stem cells (MSC) injected intravenously or intraperitoneally home to the inflamed colon1,2. This study shows that ultrasound-guided intracardiac injections of MSCs result in increased localization to the intestine.

Crohn&#39;s disease (CD) is a common chronic inflammatory disease of the small and large intestines. Murine and human mesenchymal stem cells (MSCs) have ...

Percutaneous Contrast Echocardiography-guided Intramyocardial Injection and Cell Delivery in a Large Preclinical Model

Cell and gene therapy are exciting and promising strategies for the purpose of cardiac regeneration in the setting of heart failure with reduced ejection fraction (HFrEF). Before they can be considered for use, and implemented in humans, extensive preclinical studies are required in large animal models to evaluate the safety, efficacy, and fate of the injectate (e.g., stem cells) once delivered into the myocardium. Small rodent models offer advantages (e.g., cost effectiveness, amenability for genetic manipulation); however, given inherent limitations of these models, the findings in these rarely translate into the clinic. Conversely, large animal models such as rabbits, have advantages (e.g., similar cardiac electrophysiology compared to humans and other large animals), whilst retaining a good cost-effective balance. Here, we demonstrate how to perform a percutaneous contrast echocardiography-guided intramyocardial injection (IMI) technique, which is minimally invasive, safe, well tolerated, and very effective in the targeted delivery of injectates, including cells, into several locations within the myocardium of a rabbit model. For the implementation of this technique, we also have taken advantage of a widely available clinical echocardiography system. After putting in practice the protocol described here, a researcher with basic ultrasound knowledge will become competent in the performance of this versatile and minimally invasive technique for routine use in experiments, aimed at hypothesis testing of the capabilities of cardiac regenerative therapeutics in the rabbit model. Once competency is achieved, the whole procedure can be performed within 25 min after anaesthetizing the rabbit.

Novel therapeutic strategies in cardiac regenerative medicine require extensive and detailed studies in large preclinical animal models before they can be considered for use in humans. Here, we demonstrate a percutaneous contrast echocardiography-guided intramyocardial injection technique in rabbits, which is valuable for hypothesis testing the efficacy of such novel therapies.

Cell and gene therapy are exciting and promising strategies for the purpose of cardiac regeneration in the setting of heart failure with reduced ejection ...

A Minimally Invasive, Accurate, and Efficient Technique for Intrathymic Injection in Mice

Intrathymic injection in mouse models is an important technique for studying thymic and immune function, including genetic and acquired T cell disorders. This requires methods for the direct deposition of reagents and/or cells into the thymus of living mice. Traditional methods of intrathymic injection include thoracic surgery or minimally invasive percutaneous blind injections, both of which have significant limitations. Ultra-high frequency ultrasound imaging devices have made image-guided percutaneous injections possible in mice, greatly improving the injection accuracy of the percutaneous injection approach and enabling the injection of smaller targets. However, image-guided injections rely on the utilization of an integrated rail system, making this a rigid and time-consuming procedure. A unique, safe, and efficient method for percutaneous intrathymic injections in mice is presented here, eliminating reliance on the rail system for injections. The technique relies on using a high-resolution micro-ultrasound unit to image the mouse thymus noninvasively. Using a free-hand technique, a radiologist can place a needle tip directly into the mouse thymus under sonographic guidance. Mice are cleaned and anesthetized before imaging. For an experienced radiologist adept at ultrasound-guided procedures, the learning period for the stated technique is quite short, typically within one session. The method has a low morbidity and mortality rate for the mice and is much faster than current mechanically assisted techniques for percutaneous injection. It allows the investigator to efficiently perform precise and reliable percutaneous injections of thymuses of any size (including very small organs such as the thymus of aged or immunodeficient mice) with minimal stress on the animal. This method enables the injection of individual lobes if desired and facilitates large-scale experiments due to the time-saving nature of the procedure.

The present protocol describes an interventional radiology procedure established for intrathymic injection in mice to avoid the risk of open surgery and improve the accuracy of blind percutaneous injections.

Intrathymic injection in mouse models is an important technique for studying thymic and immune function, including genetic and acquired T cell disorders. ...

Immunology and Infection

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 ...

Ultrasound-Guided Induced Pluripotent Stem Cell-Derived Cardiomyocyte Implantation in Myocardial Infarcted Mice

The key objective of cell therapy after myocardial infarction (MI) is to effectively enhance the cell grafted rate, and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are a promising cell source for cardiac repair after ischemic damage. However, a low grafted rate is a significant obstacle for effective cardiac tissue regeneration after transplantation. This protocol shows that multiple hiPSC-CM ultrasound-guided percutaneous injections into an MI area effectively increase cell transplantation rates. The study also describes the entire hiPSC-CM culture process, pretreatment, and ultrasound-guided percutaneous delivery methods. In addition, the use of human mitochondrial DNA help detect the absence of hiPSC-CMs in other mouse organs. Lastly, this paper describes the changes in cardiac function, angiogenesis, cell size, and apoptosis at the infarcted border zone in mice 4 weeks after cell delivery. It can be concluded that echocardiography-guided percutaneous injection of the left ventricular myocardium is a feasible, relatively invasive, satisfactory, repeatable, and effective cellular therapy.

Ultrasound-guided cell delivery around the site of myocardial infarction in mice is a safe, effective, and convenient way of cell transplantation.

The key objective of cell therapy after myocardial infarction (MI) is to effectively enhance the cell grafted rate, and human induced pluripotent stem ...

A Simple and Efficient Method for In Vivo Cardiac-specific Gene Manipulation by Intramyocardial Injection in Mice

Gene manipulation specifically in the heart significantly potentiate the investigation of cardiac disease pathomechanisms and their therapeutic potential. In vivo cardiac-specific gene delivery is commonly achieved by either systemic or local delivery. Systemic injection via tail vein is easy and efficient in manipulating cardiac gene expression by using recombinant adeno-associated virus 9 (AAV9). However, this method requires a relatively high amount of vector for efficient transduction, and may result in nontarget organ gene transduction. Here, we describe a simple, efficient, and time-saving method of intramyocardial injection for in vivo cardiac-specific gene manipulation in mice. Under anesthesia (without ventilation), the pectoral major and minor muscles were bluntly dissected, and the mouse heart was quickly exposed by manual externalization through a small incision at the fourth intercostal space. Subsequently, adenovirus encoding luciferase (Luc) and vitamin D receptor (VDR), or short hairpin RNA (shRNA) targeting VDR, was injected with a Hamilton syringe into the myocardium. Subsequent in vivo imaging demonstrated that luciferase was successfully overexpressed specifically in the heart. Moreover, Western blot analysis confirmed the successful overexpression or silencing of VDR in the mouse heart. Once mastered, this technique can be used for gene manipulation, as well as injection of cells or other materials such as nanogels in the mouse heart.

A Simple and Efficient Method for In Vivo Cardiac-specific Gene Manipulation by Intramyocardial Injection in Mice

Here we present a protocol for cardiac-specific gene manipulation in mice. Under anesthesia, the mouse hearts were externalized through the fourth intercostal space. Subsequently, adenoviruses encoding specific genes were injected with a syringe into the myocardium, followed by protein expression measurement via in vivo imaging and Western blot analysis.

Gene manipulation specifically in the heart significantly potentiate the investigation of cardiac disease pathomechanisms and their therapeutic potential. ...

Ultrasound-guided Transthoracic Intramyocardial Injection in Mice

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