Name: intramyocardial transplantation of msc-loading injectable hydrogels after myocardial infarction in a murine model
Uploaded: 2020-09-20T15:00:00
Description: Watch this Scientific Journal Video about Intramyocardial Transplantation of MSC-Loading Injectable Hydrogels after Myocardial Infarction in a Murine Model at JoVE.com

This research is supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by Ministry of Education (NRF-2018R1D1A1A02049346)

All animal research procedures were provided in accordance with the Laboratory Animals Welfare Act, the Guide for the Care and Use of Laboratory Animals and the Guidelines and Policies for Rodent Experiments provided by the Institutional Animal Care and Use Committee (IACUC) in the School of Medicine of The Catholic University of Korea.
1. Preparation of MSCs and injectable gelatin hydrogels
<ol>
	<li>Culture MSCs in a 100 mm culture dish at 37 &#176;C and 5% CO2. When MSCs growth...

<ol>
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N., Yan, W., Srivastava, A., Desiderio, V., Dhingra, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+injectable+hydrogels+for+cardiac+stem+cell+therapy+and+tissue+engineering.">Application of injectable hydrogels for cardiac stem cell therapy and tissue engineering.</a> Reviews in Cardiovascular Medicine. 20 (4), 221-230 (2019).</li><li>Gaetani, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epicardial+application+of+cardiac+progenitor+cells+in+a+3D-printed+gelatin/hyaluronic+acid+patch+preserves+cardiac+function+after+myocardial+infarction.">Epicardial application of cardiac progenitor cells in a 3D-printed gelatin/hyaluronic acid patch preserves cardiac function after myocardial infarction.</a> Biomaterials. 61, 339-348 (2015).</li><li>Gao, 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=Myocardial+Tissue+Engineering+With+Cells+Derived+From+Human-Induced+Pluripotent+Stem+Cells+and+a+Native-Like,+High-Resolution,+3-Dimensionally+Printed+Scaffold.">Myocardial Tissue Engineering With Cells Derived From Human-Induced Pluripotent Stem Cells and a Native-Like, High-Resolution, 3-Dimensionally Printed Scaffold.</a> Circualtion Research. 120 (8), 1318-1325 (2017).</li><li>Hasan, A., 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=Injectable+Hydrogels+for+Cardiac+Tissue+Repair+after+Myocardial+Infarction.">Injectable Hydrogels for Cardiac Tissue Repair after Myocardial Infarction.</a> Advanced Science. 2 (11), 1500122 (2015).</li><li>Wu, R., Hu, X., Wang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concise+Review:+Optimized+Strategies+for+Stem+Cell-Based+Therapy+in+Myocardial+Repair:+Clinical+Translatability+and+Potential+Limitation.">Concise Review: Optimized Strategies for Stem Cell-Based Therapy in Myocardial Repair: Clinical Translatability and Potential Limitation.</a> Stem Cells. 36 (4), 482-500 (2018).</li><li>Lee, 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=In+situ+forming+gelatin-based+tissue+adhesives+and+their+phenolic+content-driven+properties.">In situ forming gelatin-based tissue adhesives and their phenolic content-driven properties.</a> Journal of Materials Chemistry B. 1 (18), 2407-2414 (2013).</li><li>Lee, Y., Bae, J. W., Lee, J. W., Suh, W., Park, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enzyme-catalyzed+in+situ+forming+gelatin+hydrogels+as+bioactive+wound+dressings:+effects+of+fibroblast+delivery+on+wound+healing+efficacy.">Enzyme-catalyzed in situ forming gelatin hydrogels as bioactive wound dressings: effects of fibroblast delivery on wound healing efficacy.</a> Journal of Materials Chemistry B. 2 (44), 7712-7718 (2014).</li><li>Lee, S. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+Crosslinkable+Gelatin+Hydrogels+for+Vasculogenic+Induction+and+Delivery+of+Mesenchymal+Stem+Cells.">In situ Crosslinkable Gelatin Hydrogels for Vasculogenic Induction and Delivery of Mesenchymal Stem Cells.</a> Advanced Functional Materials. 24 (43), 6771-6781 (2014).</li><li>Jung, B. K., 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=A+hydrogel+matrix+prolongs+persistence+and+promotes+specific+localization+of+an+oncolytic+adenovirus+in+a+tumor+by+restricting+nonspecific+shedding+and+an+antiviral+immune+response.">A hydrogel matrix prolongs persistence and promotes specific localization of an oncolytic adenovirus in a tumor by restricting nonspecific shedding and an antiviral immune response.</a> Biomaterials. 147, 26-38 (2017).</li><li>Kim, G., 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=Tonsil-derived+mesenchymal+stem+cell-embedded+in+situ+crosslinkable+gelatin+hydrogel+therapy+recovers+postmenopausal+osteoporosis+through+bone+regeneration.">Tonsil-derived mesenchymal stem cell-embedded in situ crosslinkable gelatin hydrogel therapy recovers postmenopausal osteoporosis through bone regeneration.</a> PLoS One. 13 (7), 0200111 (2018).</li><li>Kim, C. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MSC-Encapsulating+in+situ+Cross-Linkable+Gelatin+Hydrogels+To+Promote+Myocardial+Repair.">MSC-Encapsulating in situ Cross-Linkable Gelatin Hydrogels To Promote Myocardial Repair.</a> ACS Applied Bio Materials. 3 (3), 1646-1655 (2020).</li><li>Meirelles Lda, S., Nardi, N. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Murine+marrow-derived+mesenchymal+stem+cell:+isolation,+in+vitro+expansion,+and+characterization.">Murine marrow-derived mesenchymal stem cell: isolation, in vitro expansion, and characterization.</a> Br J Haematol. 123 (4), 702-711 (2003).</li><li>Ojha, 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=Characterization+of+the+structural+and+functional+changes+in+the+myocardium+following+focal+ischemia-reperfusion+injury.">Characterization of the structural and functional changes in the myocardium following focal ischemia-reperfusion injury.</a> Am J Physiol Heart Circ Physiol. 294 (6), 2435-2443 (2008).</li><li>Takagawa, 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=Myocardial+infarct+size+measurement+in+the+mouse+chronic+infarction+model:+comparison+of+area-+and+length-based+approaches.">Myocardial infarct size measurement in the mouse chronic infarction model: comparison of area- and length-based approaches.</a> Journal of Applied Physiology. 102 (6), 2104-2111 (2007).</li><li>Terrovitis, 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+Quantification+and+Optimization+of+Acute+Cell+Retention+by+In+vivo+Positron+Emission+Tomography+After+Intramyocardial+Cardiac-Derived+Stem+Cell+Delivery.">Noninvasive Quantification and Optimization of Acute Cell Retention by In vivo Positron Emission Tomography After Intramyocardial Cardiac-Derived Stem Cell Delivery.</a> Journal of the American College of Cardiology. 54 (17), 1619-1626 (2009).</li><li>Dib, N., Khawaja, H., Varner, S., McCarthy, M., Campbell, A. <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> Journal of Cardiovascular Translational Research. 4 (2), 177-181 (2011).</li></ol>

Injectable GH hydrogels have great potential for in vivo applications because of their ability to homogenously incorporate diverse therapeutic agents in situ. Furthermore, their physical and biochemical properties can be easily manipulated based on disease-dependent requirements. In this respect, injectable hydrogels have been proposed to address the major limitations in current cardiac stem cell therapy hampered by poor survival and cell retention (i.e., &#60; 10% within 24 h post-transplantation) in the injured heart<s...

Cardiac stem cell therapy has emerged as a potential approach for myocardial repair and regeneration1,2. Despite the recent positive results in animal models and clinical trials, the application of stem cell-based therapy for myocardial repair is limited due to low retention and poor survival of injected cells at the infarcted heart tissues3,4. As a result, the use of cell-based tissue engineering, including injectable biomaterials5, cardiac patches6, and cell sheets7, has been intensively studied to improve cell retention and integration within the host myocardium.
Among the various potential approaches to bioengineered cardiac tissue repair, injectable hydrogels combined with appropriate cell types, such as mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and induced pluripotent stem cells (iPSCs), are an attractive option to effectively deliver cells into myocardial regions8,9. Gelatin, a well-known natural polymer, can be used as an injectable matrix due to its great biocompatibility, considerable biodegradability, and reduced immunogenicity when compared with a wide range of biomaterials used in biomedical applications. Although gelatin-based injectable platforms have great potential, their applicability in vivo remains limited based on their low mechanical stiffness and easy degradability in the physiological environment.
To overcome these limitations, a novel and simple design of gelatin-based hydrogels consisting of hydroxyphenyl propionic acid has been proposed for in vivo applications. Gelatin-hydroxyphenyl propionic acid (GH) conjugates can be cross-linked in situ in the presence of an enzyme, horseradish peroxidase (HRP), and subsequently encapsulate various drugs, biomolecules, or cells within the hydrogel, suggesting great potential in tissue engineering applications10,11,12,13,14. In addition, we have recently investigated the therapeutic effects of GH hydrogels containing encapsulated MSCs and demonstrated their use in successful cardiac repair and regeneration after MI in a murine model15. In this protocol, we describe a simple technique for the encapsulation and in vitro three-dimensional (3D) proliferation of MSCs within GH hydrogels. We also introduce a surgical procedure designed to generate a murine MI model via coronary artery ligation and intramyocardial transplantation of MSC-loading GH hydrogels into the infarcted heart.

<table>
	<tbody>
		<tr>
			<td>4 % paraformaldehyde (PFA)</td>
			<td>Intron</td>
			<td>IBS-BP031-2</td>
			<td></td>
		</tr>
		<tr>
			<td>5-0 silk suture</td>
			<td>AILEE</td>
			<td>SK534</td>
			<td></td>
		</tr>
		<tr>
			<td>8-0 polypropylene suture</td>
			<td>ETHICON</td>
			<td>M8732H</td>
			<td></td>
		</tr>
		<tr>
			<td>8-well chamber slide</td>
			<td>Nunc LAB-TEK</td>
			<td>154534</td>
			<td></td>
		</tr>
		<tr>
			<td>Angiocath Plus (22GA) catheter</td>
			<td>BD Angiocath Plus</td>
			<td>REF382423</td>
			<td></td>
		</tr>
		<tr>
			<td>Antibiotic-antimyocotic</td>
			<td>Gibco</td>
			<td>15240-062</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>GYROGEN</td>
			<td>1582MGR</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal microscope</td>
			<td>Zeiss</td>
			<td>LSM 510</td>
			<td></td>
		</tr>
		<tr>
			<td>Cover slipe</td>
			<td>MARIENFELD</td>
			<td>101242</td>
			<td></td>
		</tr>
		<tr>
			<td>Deluxe High Temperature Cautery kit</td>
			<td>Bovie</td>
			<td>QTY1</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Gibco</td>
			<td>11995-065</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS</td>
			<td>Gibco</td>
			<td>14040-133</td>
			<td></td>
		</tr>
		<tr>
			<td>Dual-syringe</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>EOSIN</td>
			<td>SIGMA-ALDRICH</td>
			<td>HT110116</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>EMSURE</td>
			<td>K49350783 739</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>Gibco</td>
			<td>16000-044</td>
			<td></td>
		</tr>
		<tr>
			<td>Fechtner conjunctiva forceps titanium</td>
			<td>WORLD PRECISISON INSTRUMENTS</td>
			<td>WP1820</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescein isothiocyanate isomer I (FITC)</td>
			<td>SIGMA-ALDRICH</td>
			<td>F7250</td>
			<td></td>
		</tr>
		<tr>
			<td>Forcep</td>
			<td>HEBU</td>
			<td>HB0458</td>
			<td></td>
		</tr>
		<tr>
			<td>Hair removal cream</td>
			<td>Ildong Pharmaceutical</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Heating pad</td>
			<td>Stoelting</td>
			<td>50300</td>
			<td>Homeothermic Blanket System</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td>50301</td>
			<td>Replacement Heating Pad for 50300 (10 X 12.5cm)</td>
		</tr>
		<tr>
			<td>Hematoxylin</td>
			<td>SIGMA-ALDRICH</td>
			<td>HHS80</td>
			<td></td>
		</tr>
		<tr>
			<td>Horseradish peroxide (HRP; 250-330 U/mg)</td>
			<td>SIGMA-ALDRICH</td>
			<td>P8375</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrogen peroxide (H2O2; 30 wt % in H2O)</td>
			<td>SIGMA-ALDRICH</td>
			<td>216763</td>
			<td></td>
		</tr>
		<tr>
			<td>Iodine</td>
			<td>Green Pharmaceutical</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>LIVE/DEAD cell staining kit</td>
			<td>Thermo Fisher</td>
			<td>R37601</td>
			<td></td>
		</tr>
		<tr>
			<td>Mechanical ventilator</td>
			<td>Harvard Apparatus</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro centrifuge</td>
			<td>HANIL</td>
			<td>Micro 12</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro needle holder</td>
			<td>KASCO</td>
			<td>37-1452</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro scissor</td>
			<td>HEBU</td>
			<td>HB7381</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>OLYMPUS</td>
			<td>SZ61</td>
			<td></td>
		</tr>
		<tr>
			<td>MT staining kit</td>
			<td>SIGMA-ALDRICH</td>
			<td>HT1079-1SET</td>
			<td>Weigert&#8217;s iron hematoxylin solution</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td>HT15-1KT</td>
			<td>Trichrome Stain (Masson) Kit</td>
		</tr>
		<tr>
			<td>Paraffin</td>
			<td>LK LABKOREA</td>
			<td>H06-660-107</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS buffer</td>
			<td>Gibco</td>
			<td>10010-023</td>
			<td></td>
		</tr>
		<tr>
			<td>PHK26 staining kit</td>
			<td>SIGMA-ALDRICH</td>
			<td>MINI26</td>
			<td></td>
		</tr>
		<tr>
			<td>Slide scanner</td>
			<td>Leica</td>
			<td>SCN400</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical scissor</td>
			<td>HEBU</td>
			<td>HB7454</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical tape</td>
			<td>3M micopore</td>
			<td>1530-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue cassette</td>
			<td>Scilab Korea</td>
			<td>Cas3003</td>
			<td></td>
		</tr>
		<tr>
			<td>Transducer gel</td>
			<td>SUNGHEUNG</td>
			<td>SH102</td>
			<td></td>
		</tr>
		<tr>
			<td>Trout-Barraquer needle holder curved</td>
			<td>KASCO</td>
			<td>50-3710c</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrasound system</td>
			<td>Philips</td>
			<td>Affiniti 50</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylene</td>
			<td>JUNSEI</td>
			<td>25175-0430</td>
			<td></td>
		</tr>
	</tbody>
</table>

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.

To effectively deliver MSCs to the infarcted myocardium, MSC-loading in situ cross-linkable hydrogels described in Figure 1 were used in this protocol. Prior to in vivo transplantation, the proliferation and survival of MSCs in GH hydrogels were confirmed by a 3D in vitro live/dead cell staining assay (live: green; dead: red). As shown in Figure 2, representative images exhibited sufficient MSCs proliferation, showing branched networks within GH hydrogels. In ad...

Watch this Scientific Journal Video about Intramyocardial Transplantation of MSC-Loading Injectable Hydrogels after Myocardial Infarction in a Murine Model at JoVE.com

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

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 ...

This method can help address key issues in current exacerbated cardiac therapy, such as low applicability to low retention and survival of transplanted cells in infarcted hearts. To address this issue, this method can provide a reliable technique to study intramyocardial transplantation with stem cells using injectable hydrogels in a murine model, which is an excellent platform to use for investigating cardiac tissue repair and regeneration after myocardial infraction. The main advantage of this technique is that it is a feasible method to improve the retention and survival of transplanted stem cells after intra-myocardial transplantation using in-situ cross-link cover injectable hydrogels.These hydrogels offer diverse opportunities for cardiac tissue engineering, such as delivering not only stem cells, but also growth factors, genetic materials and drugs to maximize their therapeutic effect in infarcted heart tissues. Demonstrating the procedure for in-vitro experiment will be Eunmi Lee, a research technologist from my laboratory. Eun-Hye Park and Eunhwa Seong research technologists will demonstrate the procedure for in-vivo experiments.Culture mesenchymal stem cells, or MSCs in a 100 millimeter culture dish at 37 degrees Celsius and 5%carbon dioxide. When the cells reach 80%confluence, wash the dish twice with DPBS and incubate them with one milliliter of trypsin substitute at 37 degrees Celsius for three minutes. Then add nine milliliters of culture medium to the cells and centrifuge them at 500 times G for three minutes.Discard the resulting supernatant. Resuspend the cells in one milliliter of PBS and maintain the cell suspension on ice. Dilute 10 microliters of cell suspension with 10 microliters of trypan blue and determine the cell concentration using an automated cell counter.Resuspend the MSCs to a density of one times 10 to the seventh cells per milliliter and transfer them to a one milliliter tube. Prepare a 6.25%GH conjugate solution in PBS and separate it into two vials. Next mix the GH solutions with either six micrograms per milliliter of HRP or 0.07%hydrogen peroxide.Briefly centrifuge the cell suspension at 1000 times G and carefully aspirate the resulting supernatant. Then mix the cell pellet with GH solution A.Load the MSCs in GH solution A and GH solution B into either side of a dual syringe. Plate 300 microliters of the combined GH solutions with MSCs at a final density of 5 million cells per milliliter onto an eight well chamber slide.After in situ hydrogel formation and subsequent MSC encapsulation via enzymatic cross-linking add 700 microliters of DMEM containing 10%FBS and 1%antibiotic antimycotic solution. Incubate the slide at 37 degrees Celsius and 5%carbon dioxide and replace the culture medium every two to three days. Prior to surgery, depolate the mouse chest using hair removal cream and sterilize the skin with iodine.Place the mouse on an operating table and intubate it by inserting a catheter into the trachea to provide supplemental oxygen via mechanical ventilation. Gently cut through the skin using surgical scissors. Then penetrate the intercostal muscles with micro scissors.Separate the second and third left ribs using a 5-O silk suture to maintain an open chest cavity. Carefully ligate the left anterior descending coronary artery using a needle holder with an 8-0 polypropylene suture and cut the suture using electrocautery. Observe an immediate color change in the anterior left ventricular wall.After inducing the myocardial infarction, inject 10 microliters of the MSC loading GH solutions into two different points at the infarct border zone. Restore the opened chest cavity and close the muscles and skin using 5-0 sutures. Remove the tracheal tube and place the mouse in a cage under an infrared lamp during recovery.Perform an echocardiography and measure corresponding lines for LV anterior wall, LV internal and LV posterior wall to obtain cardiac wall thickness, chamber dimension, and fractional shortening. Prior to in vivo transplantation, the proliferation and survival of MSCs in GH hydragels were confirmed by a 3D in vitro live dead cell staining assay. Representative images exhibited sufficient MSC proliferation showing branched networks within GH hydrogels.An extensive multicellular 3D structure of MSCs was clearly observed at day 14, indicating that GH hydrogels could provide a proper microenvironment for the encapsulated cells. After the induction of myocardial infarction, MSC loading GH hydrogels were intramyocardially transplanted into the peri-infarct areas. The MSCs and gel were appropriately sustained within the infarcted region.MSCs were well-integrated into GH hydrogels. To verify the therapeutic effects of the MSC loading GH hydrogels, the changes in cardiac function and structure were evaluated by echocardiography and histological analysis at day 28 post transplantation, and compared among the different treatment groups. The representative echocardiography showed improved cardiac functions, including fractional shortening, ejection fraction, and end systolic volume in the MSC gel treated group.In addition, histological analysis exhibited less fibrosis, thicker infarcted walls and a smaller infarct size in the MSC gel treated group than in the other groups indicating that this protocol significantly attenuated LV remodeling. Using this technique, we achieved long term stem cells in and proliferation and led to significant improvement in the cardiac structure and function following myocardial infarction in murine model. This technique can be extended for use in large animals and to clinical translation as a new strategy for prevention of a post infarct heart failure by providing cardiac tissue repair and regeneration.

intramyocardial-transplantation-msc-loading-injectable-hydrogels

Research

JoVE Journal

Medicine

Acute Myocardial Infarction in Rats

With heart failure leading the cause of death in the USA (Hunt), biomedical research is fundamental to advance medical treatments for cardiovascular diseases. Animal models that mimic human cardiac disease, such as myocardial infarction (MI) and ischemia-reperfusion (IR) that induces heart failure as well as pressure-overload (transverse aortic constriction) that induces cardiac hypertrophy and heart failure (Goldman and Tarnavski), are useful models to study cardiovascular disease. In particular, myocardial ischemia (MI) is a leading cause for cardiovascular morbidity and mortality despite controlling certain risk factors such as arteriosclerosis and treatments via surgical intervention (Thygesen). Furthermore, an acute loss of the myocardium following myocardial ischemia (MI) results in increased loading conditions that induces ventricular remodeling of the infarcted border zone and the remote non-infarcted myocardium. Myocyte apoptosis, necrosis and the resultant increased hemodynamic load activate multiple biochemical intracellular signaling that initiates LV dilatation, hypertrophy, ventricular shape distortion, and collagen scar formation. This pathological remodeling and failure to normalize the increased wall stresses results in progressive dilatation, recruitment of the border zone myocardium into the scar, and eventually deterioration in myocardial contractile function (i.e. heart failure). The progression of LV dysfunction and heart failure in rats is similar to that observed in patients who sustain a large myocardial infarction, survive and subsequently develops heart failure (Goldman). The acute myocardial infarction (AMI) model in rats has been used to mimic human cardiovascular disease; specifically used to study cardiac signaling mechanisms associated with heart failure as well as to assess the contribution of therapeutic strategies for the treatment of heart failure. The method described in this report is the rat model of acute myocardial infarction (AMI). This model is also referred to as an acute ischemic cardiomyopathy or ischemia followed by reperfusion (IR); which is induced by an acute 30-minute period of ischemia by ligation of the left anterior descending artery (LAD) followed by reperfusion of the tissue by releasing the LAD ligation (Vasilyev and McConnell). This protocol will focus on assessment of the infarct size and the area-at-risk (AAR) by Evan's blue dye and triphenyl tetrazolium chloride (TTC) following 4-hours of reperfusion; additional comments toward the evaluation of cardiac function and remodeling by modifying the duration of reperfusion, is also presented. Overall, this AMI rat animal model is useful for studying the consequence of a myocardial infarction on cardiac pathophysiological and physiological function.

The rat model of acute myocardial infarction (AMI) is useful to study the consequence of a MI on cardiac pathophysiological and physiological function.

With heart failure leading the cause of death in the USA (Hunt), biomedical research is fundamental to advance medical treatments for cardiovascular ...

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 ...

Myocardial Infarction and Functional Outcome Assessment in Pigs

Introduction of newly discovered cardiovascular therapeutics into first-in-man trials depends on a strictly regulated ethical and legal roadmap. One important prerequisite is a good understanding of all safety and efficacy aspects obtained in a large animal model that validly reflect the human scenario of myocardial infarction (MI). Pigs are widely used in this regard since their cardiac size, hemodynamics, and coronary anatomy are close to that of humans. Here, we present an effective protocol for using the porcine MI model using a closed-chest coronary balloon occlusion of the left anterior descending artery (LAD), followed by reperfusion. This approach is based on 90 min of myocardial ischemia, inducing large left ventricle infarction of the anterior, septal and inferoseptal walls. Furthermore, we present protocols for various measures of outcome that provide a wide range of information on the heart, such as cardiac systolic and diastolic function, hemodynamics, coronary flow velocity, microvascular resistance, and infarct size. This protocol can be easily tailored to meet study specific requirements for the validation of novel cardioregenerative biologics at different stages (i.e. directly after the acute ischemic insult, in the subacute setting or even in the chronic MI once scar formation has been completed). This model therefore provides a useful translational tool to study MI, subsequent adverse remodeling, and the potential of novel cardioregenerative agents.

This protocol describes the porcine myocardial infarction (MI) model using a 90 min closed-chest coronary balloon occlusion of the left anterior descending artery (LAD), followed by reperfusion. Furthermore, the protocol for several outcome parameters, such as cardiac function, hemodynamics, microvascular resistance, and infarct size, are also presented.

Introduction of newly discovered cardiovascular therapeutics into first-in-man trials depends on a strictly regulated ethical and legal roadmap. One ...

A Hydrogel Construct and Fibrin-based Glue Approach to Deliver Therapeutics in a Murine Myocardial Infarction Model.

The murine MI model is widely recognized in the field of cardiovascular disease, and has consistently been used as a first step to test the efficacy of treatments in vivo1. The traditional, established protocol has been further fine-tuned to minimize the damage to the animal. Notably, the pectoral muscle layers are teased away rather than simply cut, and the thoracotomy is approached intercostally as opposed to breaking the ribs in a sternotomy, preserving the integrity of the ribcage. With these changes, the overall stress on the animal is decreased. 
Stem cell therapies aimed to alleviate the damage caused by MIs have shown promise over the years for their pro-angiogenic and anti-apoptotic benefits. Current approaches of delivering cells to the heart surface typically involve the injection of the cells either near the damaged site, within a coronary artery, or into the peripheral blood stream2-4. While the cells have proven to home to the damaged myocardium, functionality is limited by their poor engraftment at the site of injury, resulting in diffusion into the blood stream5. This manuscript highlights a procedure that overcomes this obstacle with the use of a cell-encapsulated hydrogel patch. The patch is fabricated prior to the surgical procedure and is placed on the injured myocardium immediately following the occlusion of the left coronary artery. To adhere the patch in place, biocompatible external fibrin glue is placed directly on top of the patch, allowing for it to dry to both the patch and the heart surface. This approach provides a novel adhesion method for the application of a delicate cell-encapsulating therapeutic construct.

This protocol aims to alleviate the limitation of poor cell engraftment for stem cell treatment of myocardial infarctions through the use of a hydrogel system and a fibrin-based glue. With this approach, cell-to-tissue contact post-infarction can be maintained, increasing the therapeutic potential of beneficial agents at the site of injury.

The murine MI model is widely recognized in the field of cardiovascular disease, and has consistently been used as a first step to test the efficacy of ...

Primary Outcome Assessment in a Pig Model of Acute Myocardial Infarction

Mortality after acute myocardial infarction remains substantial and is associated with significant morbidity, like heart failure. Novel therapeutics are therefore required to confine cardiac damage, promote survival and reduce the disease burden of heart failure. Large animal experiments are an essential part in the translational process from experimental to clinical therapies. To optimize clinical translation, robust and representative outcome measures are mandatory. The present manuscript aims to address this need by describing the assessment of three clinically relevant outcome modalities in a pig acute myocardial infarction (AMI) model: infarct size in relation to area at risk (IS/AAR) staining, 3-dimensional transesophageal echocardiography (TEE) and admittance-based pressure-volume (PV) loops. Infarct size is the main determinant driving the transition from AMI to heart failure and can be quantified by IS/AAR staining. Echocardiography is a reliable and robust tool in the assessment of global and regional cardiac function in clinical cardiology. Here, a method for three-dimensional transesophageal echocardiography (3D-TEE) in pigs is provided. Extensive insight into cardiac performance can be obtained by admittance-based pressure-volume (PV) loops, including intrinsic parameters of myocardial function that are pre- and afterload independent. Combined with a clinically feasible experimental study protocol, these outcome measures provide researchers with essential information to determine whether novel therapeutic strategies could yield promising targets for future testing in clinical studies.

Reliable and accurate outcome assessment is the key for translation of preclinical therapies into clinical treatment. The current paper describes how to assess three clinically relevant primary outcome parameters of cardiac performance and damage in a pig acute myocardial infarction model.

Mortality after acute myocardial infarction remains substantial and is associated with significant morbidity, like heart failure. Novel therapeutics are ...

Myocardial Infarction in Neonatal Mice, A Model of Cardiac Regeneration

Myocardial infarction induced by coronary artery ligation has been used in many animal models as a tool to study the mechanisms of cardiac repair and regeneration, and to define new targets for therapeutics. For decades, models of complete heart regeneration existed in amphibians and fish, but a mammalian counterpart was not available. The recent discovery of a postnatal window during which mice possess regenerative capabilities has led to the establishment of a mammalian model of cardiac regeneration. A surgical model of mammalian cardiac regeneration in the neonatal mouse is presented herein. Briefly, postnatal day 1 (P1) mice are anesthetized by isoflurane and placed on an ice pad to induce hypothermia. After the chest is opened, and the left anterior descending coronary artery (LAD) is visualized, a suture is placed around the LAD to inflict myocardial ischemia in the left ventricle. The surgical procedure takes 10-15 min. Visualizing the coronary artery is crucial for accurate suture placement and reproducibility. Myocardial infarction and cardiac dysfunction are confirmed by triphenyl-tetrazolium chloride (TTC) staining and echocardiography, respectively. Complete regeneration 21 days post myocardial infarction is verified by histology. This protocol can be used to as a tool to elucidate mechanisms of mammalian cardiac regeneration after myocardial infarction.

This protocol describes a highly reproducible model of cardiac regeneration by surgical induction of myocardial infarction in the left ventricle of postnatal day 1 mice. The method involves induction of hypothermic anesthesia and ligation of the left anterior descending coronary artery.

Myocardial infarction induced by coronary artery ligation has been used in many animal models as a tool to study the mechanisms of cardiac repair and ...

Murine Left Anterior Descending (LAD) Coronary Artery Ligation: An Improved and Simplified Model for Myocardial Infarction

Ischemic heart disease (IHD), or acute coronary syndrome (ACS), is one of the leading causes of death in the United States. IHD is characterized by reduced blood supply to the heart, resulting in the loss of oxygen to and the ensuing necrosis of the heart muscle. The MI model has gained popularity for its use as a short-term ischemia-reperfusion model and a long-term permanent ligation model. Below, we describe a reliable method for the permanent ligation of the LAD. With mouse genetic engineering technology becoming more advanced, and with an increasing availability of quality murine surgical instruments, the mouse has become a popular model for MI surgeries. Our surgical model incorporates the use of an easily reversible anesthetic for the rapid recovery of the mouse; a minimally invasive endotracheal intubation without involving a tracheotomy; and a thoracentesis through the original thoracotomy site without creating an additional incision in the chest, as is done in some other methods, to effectively remove excess blood and air from the chest cavity. This method is comparatively less invasive than other methods, which dramatically reduces surgical and post-surgical complications and mortality and improves reproducibility.

Murine Left Anterior Descending LAD Coronary Artery Ligation: An Improved and Simplified Model for Myocardial Infarction

We provide a reliable method for left anterior descending artery (LAD) ligation in a mouse model. This method is comparatively less invasive than other methods, involving endotracheal intubation, a left-sided thoracotomy approach, and thoracentesis. This method can be used as a model for both acute and chronic myocardial infarction (MI).

Ischemic heart disease (IHD), or acute coronary syndrome (ACS), is one of the leading causes of death in the United States. IHD is characterized by ...

Murine Myocardial Infarction Model using Permanent Ligation of Left Anterior Descending Coronary Artery

Myocardial infarction (MI) and acute coronary diseases are among the most prominent causes of death in population with western lifestyle. The murine models of MI with permanent ligation of left-anterior descending (LAD) coronary artery closely mimics MI in humans. Murine models benefit from the extensive genetic engineering available nowadays. Here we propose a reproducible murine surgical model of myocardial infarction by permanent LAD coronary ligation. Our technique comprises anesthesia with ketamine/xylazine that can be rapidly reversed by administration of an antagonist, intubation without tracheotomy for mechanical-assisted ventilation, ventilation with application of extrinsic positive end-expiratory pressure (PEEP) to avoid alveolar collapse, a thoracotomy method limiting to the minimum surgical lesions made to skeletal muscles, and lung inflation without thoracentesis. This method is sparsely invasive, reproducible and reduces post-surgery mortality and complications.

Herein we describe a surgical procedure showing how to achieve permanent ligation of the left-anterior descending coronary artery in mice. This model is of high relevance to investigate the pathophysiology of myocardial infarction and the concomitant biological processes.

Myocardial infarction (MI) and acute coronary diseases are among the most prominent causes of death in population with western lifestyle. The murine ...

A Cryoinjury Model to Study Myocardial Infarction in the Mouse

The use of animal models is essential for developing new therapeutic strategies for acute coronary syndrome and its complications. In this article, we demonstrate a murine cryoinjury infarct model that generates precise infarct sizes with high reproducibility and replicability. In brief, after intubation and sternotomy of the animal, the heart is lifted from the thorax. The probe of a handheld liquid nitrogen delivery system is applied onto the myocardial wall to induce cryoinjury. Impaired ventricular function and electrical conduction can be monitored with echocardiography or optical mapping. Transmural myocardial remodeling of the infarcted area is characterized by collagen deposition and loss of cardiomyocytes. Compared to other models (e.g., LAD-ligation), this model utilizes a handheld liquid nitrogen delivery system to generate more uniform infarct sizes.

This article demonstrates a model to study cardiac remodeling after myocardial cryoinjury in mice.

The use of animal models is essential for developing new therapeutic strategies for acute coronary syndrome and its complications. In this article, we ...

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.

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, ...