Name: implantation of hipsc-derived cardiac-muscle patches after myocardial injury in a guinea pig model
Uploaded: 2019-03-18T13:00:00
Description: Watch this Scientific Journal Video about Implantation of hiPSC-derived Cardiac-muscle Patches after Myocardial Injury in a Guinea Pig Model at JoVE.com

No funding was received for this study

Animals received humane care in compliance with the Guide for the Principles of Laboratory Animals, prepared by the Institute of Laboratory Animal Resources, and published by the National Institutes of Health. All animal protocols were approved by the responsible local authority (&#8216;&#8216;Amt f&#252;r Gesundheit und Verbraucherschutz, Hansestadt Hamburg&#8217;&#8217;/ Animal protocol # 109/16).
1. Obtain Animals
<ol>
	<li>Commercially obtain female Guinea pigs weighing 500&#8211;600 g.<...

<ol>
	<li>Kirklin, J. 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=Seventh+INTERMACS+annual+report:+15,000+patients+and+counting.">Seventh INTERMACS annual report: 15,000 patients and counting.</a> The Journal of heart and lung transplantation: the official publication of the International Society for Heart Transplantation. 34, 1495-1504 (2015).</li><li>Soonpaa, M. H., Field, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Survey+of+studies+examining+mammalian+cardiomyocyte+DNA+synthesis.">Survey of studies examining mammalian cardiomyocyte DNA synthesis.</a> Circulation research. 83, 15-26 (1998).</li><li>Shiba, Y., Hauch, K. D., Laflamme, M. 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+applications+for+human+pluripotent+stem+cells.">Cardiac applications for human pluripotent stem cells.</a> Current pharmaceutical design. 15, 2791-2806 (2009).</li><li>Shiba, 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=Human+ES-cell-derived+cardiomyocytes+electrically+couple+and+suppress+arrhythmias+in+injured+hearts.">Human ES-cell-derived cardiomyocytes electrically couple and suppress arrhythmias in injured hearts.</a> Nature. 489, 322-325 (2012).</li><li>Chong, J. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+embryonic-stem-cell-derived+cardiomyocytes+regenerate+non-human+primate+hearts.">Human embryonic-stem-cell-derived cardiomyocytes regenerate non-human primate hearts.</a> Nature. 510, 273-277 (2014).</li><li>Kattman, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stage-specific+optimization+of+activin/nodal+and+BMP+signaling+promotes+cardiac+differentiation+of+mouse+and+human+pluripotent+stem+cell+lines.">Stage-specific optimization of activin/nodal and BMP signaling promotes cardiac differentiation of mouse and human pluripotent stem cell lines.</a> Cell stem cell. 8, 228-240 (2011).</li><li>Watanabe, T., Rautaharju, P. M., McDonald, T. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ventricular+action+potentials,+ventricular+extracellular+potentials,+and+the+ECG+of+guinea+pig.">Ventricular action potentials, ventricular extracellular potentials, and the ECG of guinea pig.</a> Circulation research. 57, 362-373 (1985).</li><li>Weinberger, 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=Cardiac+repair+in+guinea+pigs+with+human+engineered+heart+tissue+from+induced+pluripotent+stem+cells.">Cardiac repair in guinea pigs with human engineered heart tissue from induced pluripotent stem cells.</a> Science translational medicine. 8, 363ra148 (2016).</li><li>Shiba, 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=Electrical+Integration+of+Human+Embryonic+Stem+Cell-Derived+Cardiomyocytes+in+a+Guinea+Pig+Chronic+Infarct+Model.">Electrical Integration of Human Embryonic Stem Cell-Derived Cardiomyocytes in a Guinea Pig Chronic Infarct Model.</a> Journal of Cardiovascular Pharmacology and Therapy. 19, 368-381 (2014).</li><li>van Laake, L. 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=Human+embryonic+stem+cell-derived+cardiomyocytes+survive+and+mature+in+the+mouse+heart+and+transiently+improve+function+after+myocardial+infarction.">Human embryonic stem cell-derived cardiomyocytes survive and mature in the mouse heart and transiently improve function after myocardial infarction.</a> Stem cell research. 1, 9-24 (2007).</li><li>Zimmermann, W. 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=Engineered+heart+tissue+grafts+improve+systolic+and+diastolic+function+in+infarcted+rat+hearts.">Engineered heart tissue grafts improve systolic and diastolic function in infarcted rat hearts.</a> Nature medicine. 12, 452-458 (2006).</li><li>Johns, T. N., Olson, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+myocardial+infarction.+I.+A+method+of+coronary+occlusion+in+small+animals.">Experimental myocardial infarction. I. A method of coronary occlusion in small animals.</a> Annals of surgery. 140, 675-682 (1954).</li><li>van den Bos, E. J., Mees, B. M., de Waard, M. C., de Crom, R., Duncker, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+model+of+cryoinjury-induced+myocardial+infarction+in+the+mouse:+a+comparison+with+coronary+artery+ligation.">A novel model of cryoinjury-induced myocardial infarction in the mouse: a comparison with coronary artery ligation.</a> Heart and circulatory physiology. , H1291-H1300 (2005).</li></ol>

A variety of small animal models are available to study the effect that cell transplantation exerts on injured hearts9,10,11. We chose a guinea pig model because of all small animal models its (electro)physiology resembles most closely that of humans. The advantages of small animal models are simple housing, manageable costs, and few workforces. In comparison with mice and rats, guinea pigs&#180; cardiac (electro)physiology is m...

The number of patients with heart failure is increasing in our aging population. For end-stage heart failure, orthotopic heart transplantation is the only curative treatment option. However, especially in European countries, there is an increasing organ donor shortage. Therefore, alternative treatment options are necessary. Recent achievements in mechanical circulatory support are promising, but especially in the long-term run, limited by its side effects like bleeding, pump thrombosis and infectious complications1.
The endogenous regeneration capacity of the adult human heart is extremely limited. Therefore, cardiac regeneration therapies might become an alternative treatment option for end-stage heart failure patients2,3. Different techniques including stem cell-based cell injection or tissue engineering approaches have been described3,4,5.
Human induced pluripotent stem cells (hiPSC), as well as human embryonic stem cells (hESC) can be effectively differentiated to spontaneously beating human cardiomyocytes6, which has been a major achievement in the field of cardiac regenerative therapies.
To replace myocardium after a myocardial infarction and to improve the function of a failing heart, survival of a suitable number of cardiomyocytes and their mechanical and electrical coupling with the native heart is essential. To investigate the potential of cardiac regenerative therapies with human iPS cell derived cardiomyocytes, a suitable research model is needed. The ideal model should be cost-effective and have a human-like physiology and electrophysiology. Large animal models like pigs would be ideal from that point of view, however, those experiments are very expensive and large amounts of cardiomyocytes would be necessary to replace a relevant number of cardiomyocytes in order to see effects on the left ventricular function in a pig infarction model.
To answer elementary biological questions towards human cell-based cardiac regeneration, e.g., cell survival, vascularization, and electrical coupling, small animal models are more suitable. From the available small animal models, the guinea pig is the most useful species, as compared to rats and mice, as their electrophysiology more closely resembles the situation in humans7. In this guinea pig model, we induced a transmural cryoinjury of the left ventricle. One week after induction of myocardial infarction implantation of a three-dimensional, spontaneously beating hiPS-cell derived cardiomyocyte patch was performed. Cardiomyocyte cell survival was evaluated 28 days after implantation by histological examination.

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implantation of hipsc-derived cardiac-muscle patches after myocardial injury in a guinea pig model

Due to the limited regeneration capacity of the heart in adult mammals, myocardial infarction results in an irreversible loss of cardiomyocytes. This loss of relevant amounts of heart muscle mass can lead to the heart failure. Besides heart transplantation, there is no curative treatment option for the end-stage heart failure. In times of organ donor shortage, organ independent treatment modalities are needed. Left-ventricular assist devices are a promising therapy option, however, especially as destination therapy, limited by its side-effects like stroke, infections and bleedings. In recent years, several cardiac repair strategies including stem cell injection, cardiac progenitors or myocardial tissue engineering have been investigated. Recent improvements in cell biology allow for the differentiation of large amounts of cardiomyocytes derived from human induced pluripotent stem cells (iPSC). One of the cardiac repair strategies currently under evaluation is to transplant artificial heart tissue. Engineered heart tissue (EHT) is a three-dimensional in vitro created cardiomyocyte network, with functional properties of native heart tissue. We have created EHT-patches from hiPSC derived cardiomyocytes. Here we present a protocol for the induction of left ventricular myocardial cryoinjury in a guinea pig, followed by implantation of hiPSC derived EHT on the left ventricular wall.

This guinea pig model is a suitable model to investigate cardiac regeneration after implantation of hiPSC derived EHT-patches. It reproducibly leads to large transmural myocardial injuries. Scar size is evaluated by histology four weeks after cryoinjury. Mason trichrome staining reveals large transmural scars (Figure 2). Scar size was similar over a large number of injured animals reflecting a high degree of reproducibility8. On average 25% of the left ventricular myo...

Watch this Scientific Journal Video about Implantation of hiPSC-derived Cardiac-muscle Patches after Myocardial Injury in a Guinea Pig Model at JoVE.com

Implantation of hiPSC-derived Cardiac-muscle Patches after Myocardial Injury in a Guinea Pig Model

Here we present a protocol for the induction of left ventricular cryoinjury followed by the implantation of a cardiac muscle patch, derived from human iPS-cell cardiomyocytes in a guinea pig model.

Due to the limited regeneration capacity of the heart in adult mammals, myocardial infarction results in an irreversible loss of cardiomyocytes. This loss ...

The aim of the method is to evaluate the functional consequences of engineered heart tissue implantation in a small animal cryoinfarction model. The advantage of this method is that it allows for the induction of relatively reproducible myocardial infarctions with stable infarction sizes. After confirming a lack of response to toe pinch, place the anesthetized guinea pig on a 40 to 42 degrees Celsius warming platform in the supine position.Apply eye ointment and shave and depilate the thorax. Apply 25 degrees Celsius ultrasound transducer gel to the exposed skin and place the transducer from an echocardiography system onto the thorax to acquire two-dimensional parasternal long axis views in B mode from the right neck toward the left leg at the plane of the aortic valve with a concurrent visualization of the left ventricle apex to investigate the pre-operative left ventricular function. Then turn the transducer 90 degrees to obtain a short axis B mode view at the mid papillary level.After the last image has been obtained, transfer the guinea pig to the surgical table and tape the limbs in a spread eagle position. Disinfect the exposed skin with two sequential iodine-based and 80%ethanol scrubs and make a 1.5 centimeter vertical incision in the tracheal area. Bluntly dissect the muscles covering the trachea.When the trachea can be observed, puncture the air tube with an 18 gauge IV cannula and insert the flexible part of the cannula as a tracheal tube. Connect the tracheal tube to an animal respirator for continuous ventilation during the procedure and count the rib spaces starting at the first intercostal space to locate the fifth intercostal space. Make a two centimeter horizontal incision on the fifth intercostal space on the left side of the guinea pig and remove the subcutaneous tissues before dissecting the muscles with an electrocautery until the intercostal muscles are reached.Gently dissect the intercostal muscles with tweezers and small scissors until the pleural space is reached and the left lung can be visualized. Insert a retractor between the ribs and open the retractor carefully until a good view of the heart is obtained. Open the pericardium approximately one centimeter in the region of the anterior left ventricular wall and place a compress on the left lung to protect the lung from damage when inducing the cryoinjury of the left ventricle.Next, cool the tip of an eroded metal stamp with a cross-sectional diameter of 0.5 centimeters in liquid nitrogen for three minutes before pressing the probe onto the left anterior wall of the heart for 30 seconds. Then place a 200 degrees Celsius electric soldering iron inside the stamp to warm the stamp so that the metal can be removed from the tissue. After the third stamp application, remove the retractor from the intercostal space and clamp the outflow tube of the ventilator for two seconds to inflate the lungs with maximum pressure to avoid atelectasis of the lung.Then close the ribs with two 4-0 sutures, the muscles over the ribs with a 5-0 running suture and the skin with 5-0 suture single stitches. After removing the tracheal tube, use a single 8-0 suture to close the puncture site at the trachea and close the wound with three single stitch 5-0 sutures. Seven days after cryoinjury, remove sutures and make a two centimeter horizontal skin incision in the scar area of the left lateral side and use electrocautery to gently dissect the extra pleural adhesions.Carefully open the pleural space with scissors and insert a rib spreader to expose the heart. Visually identify the region of the infarction by its pale color compared to the healthy surrounding myocardium and place an engineered heart tissue patch over the infarction region. Secure the patch with two 8-0 sutures at both sides in the non-infarcted area of the heart and inflate the lungs with pressure to avoid atelectasis of the lungs.Then remove the retractor from the intercostal space and close the animal as demonstrated. Four weeks after engineered heart tissue implantation, perform transthoracic echocardiography as demonstrated to evaluate changes in the left ventricle function overtime. Mason trichrome staining four weeks after cryoinjury reveals large transmural scars over 25%of the left ventricular myocardium on average.Dystrophin staining demonstrates large myocardial grafts that have partially re-muscularized to the scar and staining for human Ku80 that confirms the human origin of the newly formed myocardium. Transthoracic echocardiography monitoring of the implanted engineered heart tissue reveals an improvement in the left ventricle ejection fraction, fractional area shortening, and a decrease in left ventricular and diastolic diameter. It is essential to carefully open the pleural cavity in this kind of re-do operation as adhesions between the thoracic wall and the left ventricle can be present and there's a certain risk to injure the left ventricular myocardium.After the implantation of the human engineered heart tissue, several methods can be used to monitor for changes in left ventricular ejection fraction. Besides echocardiography, an invasive measurement of pressure volume loops can be used to monitor those changes. This method allows to investigate all aspects of human engineered tissue implantation.Functional consequences as well as potential risks like arrhythmias can be evaluated in this small animal model.

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Research

JoVE Journal

Medicine

Assessment of Right Ventricular Structure and Function in Mouse Model of Pulmonary Artery Constriction by Transthoracic Echocardiography

Emerging clinical data support the notion that RV dysfunction is critical to the pathogenesis of cardiovascular disease and heart failure1-3. Moreover, the RV is significantly affected in pulmonary diseases such as pulmonary artery hypertension (PAH). In addition, the RV is remarkably sensitive to cardiac pathologies, including left ventricular (LV) dysfunction, valvular disease or RV infarction4. To understand the role of RV in the pathogenesis of cardiac diseases, a reliable and noninvasive method to access the RV structurally and functionally is essential.
A noninvasive trans-thoracic echocardiography (TTE) based methodology was established and validated for monitoring dynamic changes in RV structure and function in adult mice. To impose RV stress, we employed a surgical model of pulmonary artery constriction (PAC) and measured the RV response over a 7-day period using a high-frequency ultrasound microimaging system. Sham operated mice were used as controls. Images were acquired in lightly anesthetized mice at baseline (before surgery), day 0 (immediately post-surgery), day 3, and day 7 (post-surgery). Data was analyzed offline using software.
Several acoustic windows (B, M, and Color Doppler modes), which can be consistently obtained in mice, allowed for reliable and reproducible measurement of RV structure (including RV wall thickness, end-diastolic&#160;and end-systolic dimensions), and function (fractional area change, fractional shortening, PA peak velocity, and peak pressure gradient) in normal mice and following PAC.
Using this method, the pressure-gradient resulting from PAC was accurately measured in real-time using Color Doppler mode and was comparable to direct pressure measurements performed with a Millar high-fidelity microtip catheter. Taken together, these data demonstrate that RV measurements obtained from various complimentary views using echocardiography are reliable, reproducible and can provide insights regarding RV structure and function. This method will enable a better understanding of the role of RV cardiac dysfunction.

Right ventricle (RV) dysfunction is critical to the pathogenesis of cardiovascular disease, yet limited methodologies are available for its evaluation. Recent advances in ultrasound imaging provide a noninvasive and accurate option for longitudinal RV study. Herein, we detail a step-by-step echocardiographic method using a murine model of RV pressure overload.

Emerging clinical data support the notion that RV dysfunction is critical to the pathogenesis of cardiovascular disease and heart failure1-3. Moreover, ...

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 Femoral Artery Wire Injury with Implantation of a Perivascular Drug Delivery Patch

Percutaneous interventions including balloon angioplasty and stenting have been used to restore blood flow in vessels with occlusive vascular disease. While these therapies lead to the rapid restoration of blood flow, these technologies remain limited by restenosis in the case of bare metal stents and angioplasty, or reduced healing and possibly enhanced risk of thrombosis in the case of drug eluting stents. A key pathophysiological mechanism in the formation of restenosis is intimal hyperplasia caused by the activation of vascular smooth muscle cells and inflammation due to arterial stretch and injury. Surgeries that induce arterial injury in genetically modified mice are useful for the mechanistic study of the vascular response to injury but are often technically challenging to perform in mouse models due to the their small size and lack of appropriate sized devices. We describe two approaches for a surgical technique that induces endothelial denudation and arterial stretch in the femoral artery of mice to produce robust neointimal hyperplasia. The first approach creates an arteriotomy in the muscular branch of the femoral artery to obtain vascular access. Following wire injury this arterial branch is ligated to close the arteriotomy. A second approach creates an arteriotomy in the main femoral artery that is later closed through localized cautery. This method allows for vascular access through a larger vessel and, consequently, provides a less technically demanding procedure that can be used in smaller mice. Following either method of arterial injury, a degradable drug delivery patch can be placed over or around the injured artery to deliver therapeutic agents.

We describe a surgical technique that produces wire injury in the femoral artery of mice to induce neointimal hyperplasia to serve as a model testing system for the perivascular delivery of therapeutic compounds for the inhibition of restenosis.

Percutaneous interventions including balloon angioplasty and stenting have been used to restore blood flow in vessels with occlusive vascular disease. ...

Early Detection of Drug-Induced Renal Hemodynamic Dysfunction Using Sonographic Technology in Rats

The kidney normally functions to maintain hemodynamic homeostasis and is a major site of damage caused by drug toxicity. Drug-induced nephrotoxicity is estimated to contribute to 19- 25% of all clinical cases of acute kidney injury (AKI) in critically ill patients. AKI detection has historically relied on metrics such as serum creatinine (sCr) or blood urea nitrogen (BUN) which are demonstrably inadequate in full assessment of nephrotoxicity in the early phase of renal dysfunction. Currently, there is no robust diagnostic method to accurately detect hemodynamic alteration in the early phase of AKI while such alterations might actually precede the rise in serum biomarker levels. Such early detection can help clinicians make an accurate diagnosis and help in in decision making for therapeutic strategy. Rats were treated with Cisplatin to induce AKI. Nephrotoxicity was assessed for six days using high-frequency sonography, sCr measurement and upon histopathology of kidney. Hemodynamic evaluation using 2D and Color-Doppler images were used to serially study nephrotoxicity in rats, using the sonography. Our data showed successful drug-induced kidney injury in adult rats by histological examination. Color-Doppler based sonographic assessment of AKI indicated that resistive-index (RI) and pulsatile-index (PI) were increased in the treatment group; and peak-systolic velocity (mm/s), end-diastolic velocity (mm/s) and velocity-time integral (VTI, mm) were decreased in renal arteries in the same group. Importantly, these hemodynamic changes evaluated by sonography preceded the rise of sCr levels. Sonography-based indices such as RI or PI can thus be useful predictive markers of declining renal function in rodents. From our sonography-based observations in the kidneys of rats that underwent AKI, we showed that these noninvasive hemodynamic measurements may consider as an accurate, sensitive and robust method in detecting early stage kidney dysfunction. This study also underscores the importance of ethical issues associated with animal use in research.

Early stage hemodynamic dysfunction is critical to the development of kidney disease. Yet, detection methodologies are limited. Recent advances in sonography provide a noninvasive, accurate option for early detection of kidney injury. This study outlines a step-by-step, sonographic methodology for detecting kidney dysfunction using a drug-induced nephrotoxicity rat model.

The kidney normally functions to maintain hemodynamic homeostasis and is a major site of damage caused by drug toxicity. Drug-induced nephrotoxicity is ...

Ultrasound Based Assessment of Coronary Artery Flow and Coronary Flow Reserve Using the Pressure Overload Model in Mice

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow reserve (CFR) in humans. Reduced CFR is accompanied by marked intramyocardial and pericoronary fibrosis and is used as an indication of the severity of dysfunction. This study explores, step-by-step, the real-time changes measured in the coronary flow velocity, CFR and systolic to diastolic peak velocity (S/D) ratio in the setting of an aortic banding model in mice. By using a Doppler transthoracic imaging technique that yields reproducible and reliable data, the method assesses changes in flow in the septal coronary artery (SCA), for a period of over two weeks in mice, that previously either underwent aortic banding or thoracotomy. 
During imaging, hyperemia in all mice was induced by isoflurane, an anesthetic that increased coronary flow velocity when compared with resting flow. All images were acquired by a single imager. Two ratios, (1) CFR, the ratio between hyperemic and baseline flow velocities, and (2) systolic (S) to diastolic (D) flow were determined, using a proprietary software and by two independent observers. Importantly, the observed changes in coronary flow preceded LV dysfunction as evidenced by normal LV mass and fractional shortening (FS). 
The method was benchmarked against the current gold standard of coronary assessment, histopathology. The latter technique showed clear pathologic changes in the coronary artery in the form of peri-coronary fibrosis that correlated to the flow changes as assessed by echocardiography. 
The study underscores the value of using a non-invasive technique to monitor coronary circulation in mouse hearts. The method minimizes redundant use of research animals and demonstrates that advanced ultrasound-based indices, such as CFR and S/D ratios, can serve as viable diagnostic tools in a variety of investigational protocols including drug studies and the study of genetically modified strains.

Coronary flow reserve (CFR) is useful for assessment of myocardial oxygen demand and evaluation of cardiovascular risk. This study establishes a step-by-step transthoracic Doppler echocardiographic (TTDE) method for longitudinal monitoring of the changes in CFR, as measured from coronary artery in mice, under the experimental pressure overload of aortic banding.

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow ...

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 ...

Cochlear Implantation in the Guinea Pig

Cochlear implants are highly efficient devices that can restore hearing in subjects with profound hearing loss. Due to improved speech perception outcomes, candidacy criteria have been expanded over the last few decades. This includes patients with substantial residual hearing that benefit from electrical and acoustical stimulation of the same ear, which makes hearing preservation during cochlear implantation an important issue. Electrode impedances and the related issue of energy consumption is another major research field, as progress in this area could pave the way for fully implantable auditory prostheses. To address these issues in a systematic way, adequate animal models are essential. Therefore, the goal of this protocol is to provide an animal model of cochlear implantation, which can be used to address various research questions. Due to its large tympanic bulla, which allows easy surgical access to the inner ear, as well as its hearing range which is relatively similar to the hearing range of humans, the guinea pig is a commonly used species in auditory research. Cochlear implantation in the guinea pig is performed via a retroauricular approach. Through the bullostomy a cochleostomy is drilled and the cochlear implant electrode is inserted into the scala tympani. This electrode can then be used for electrical stimulation, determination of electrode impedances and the measurement of compound action potentials of the auditory nerve. In addition to these applications, cochlear implant electrodes can also be used as drug delivery devices, if a topical delivery of pharmaceutical agents to the cells or fluids of the inner ear is intended.

The goal of this protocol is to provide an animal model of cochlear implantation, which can be used to address a multitude of research questions. Potential applications include the evaluation of pharmaceutical interventions or electrical stimulation for beneficial effects on hearing thresholds or electrode impedances.

Cochlear implants are highly efficient devices that can restore hearing in subjects with profound hearing loss. Due to improved speech perception ...

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 ...

Model of Ischemic Heart Disease and Video-Based Comparison of Cardiomyocyte Contraction Using hiPSC-Derived Cardiomyocytes

Ischemic heart disease is a significant cause of death worldwide. It has therefore been the subject of a tremendous amount of research, often with small-animal models such as rodents. However, the physiology of the human heart differs significantly from that of the rodent heart, underscoring the need for clinically relevant models to study heart disease. Here, we present a protocol to model ischemic heart disease using cardiomyocytes differentiated from human induced pluripotent stem cells (hiPS-CMs) and to quantify the damage and functional impairment of the ischemic cardiomyocytes. Exposure to 2% oxygen without glucose and serum increases the percentage of injured cells, which is indicated by staining of the nucleus with propidium iodide, and decreases cellular viability. These conditions also decrease the contractility of hiPS-CMs as confirmed by displacement vector field analysis of microscopic video images. This protocol may furthermore provide a convenient method for personalized drug screening by facilitating the use of hiPS cells from individual patients. Therefore, this model of ischemic heart disease, based on iPS-CMs of human origin, can provide a useful platform for drug screening and further research on ischemic heart disease.

We present a model of ischemic heart disease using cardiomyocytes derived from human induced pluripotent stem cells, together with a method for quantitative evaluation of tissue damage caused by ischemia. This model can provide a useful platform for drug screening and further research on ischemic heart disease.