This work was supported by grants from the National Natural Science Foundation of China (82073851 to Sun) and the National China Postdoctoral Science Foundation (2021M690074 to Lin).

All procedures were performed according to the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH Publication No. 85-23, revised in 1996) and were approved by the Animal Ethics Committee of Nanfang Hospital, Southern Medical University (Guangzhou, China). Healthy male C57BL/6J mice (8-10 weeks old; body weight, 25-30 g) were obtained from the Animal Center of Southern Medical University. Female mice can also be used, but mixing both genders is not recommended due to the potential influences of sex differences. After arrival, the mice were housed under a 12-h/12-h dark/light cycle (3-4 mice per cage), with ad libitum food and water.
1. Preparation for surgery
<ol>
	<li>Sterilize surgical instruments by autoclaving&#160;before the surgery. Adjust the heating pad to 37 &#176;C.</li>
	<li>Anesthetize the mice by an intraperitoneal injection of 50 mg/kg of pentobarbital (see Table of Materials) to relieve surgical pain. Place the mice in separate boxes for anesthesia induction. Ensure the depth of anesthesia by the absence of a toe-withdrawal response. 
	NOTE: It is also recommended to use 1.5% isoflurane for inhalation anesthesia because it is better for analgesia.</li>
	<li>Place the mice supine on the pad by fixing their incisors with a suture and immobilizing their limbs with adhesive tape. Ensure the depth of anesthesia again by checking the reflex.</li>
	<li>Remove hair from the neck to xiphoid with a depilatory cream. Disinfect the surgical area 3 times with alternating antiseptic scrub and 75% alcohol and&#160;then drape the surgical field.</li>
	<li>Perform intubation following the steps below.
	<ol>
		<li>Adjust the breathing frequency of the animal with a mini ventilator (see Table of Materials) to 150/min and the tidal volume to 300 &#181;L. 
		&#8203;NOTE: It is unnecessary to use positive end-expiratory pressure mode.</li>
		<li>Pull out the tongue slightly with tweezers, lift the mandible with a tongue depressor to expose the glottis, and perform intra-tracheal intubation by inserting a 22 G cannula into the glottis.</li>
		<li>Switch on the mini ventilator and connect the tracheal cannula to the ventilator. The phenomenon of thoracic undulation becoming equal to the ventilator frequency indicates successful intubation. Fix the cannula with tape to prevent slipping during the operation.</li>
	</ol>
	</li>
</ol>
2. Permanent ligation of the right coronary artery
<ol>
	<li>Connect the electrocardiography (ECG) electrodes (see Table of Materials) to the mouse limbs correctly and record the ECG. 
	NOTE: One of the II, III, or AVF lead is selected as a monitoring lead; Lead III is more appropriate.</li>
	<li>Open the chest.
	<ol>
		<li>Make a 1 cm long incision in the skin parallel to the third right rib with ophthalmic scissors. Determine the third intercostal again and ensure adequate space according to the sternum angle. 
		NOTE: The direction of the skin incision is made from the sternum angle to the right anterior axillary line.</li>
		<li>Separate and cut the pectoralis major and pectoralis minor muscles with scissors and micro forceps above the third intercostal space. After that, bluntly separate the intercostal muscle with elbow forceps to expose the surgical field. 
		NOTE: Only a small part of pectoral muscles needs to be cut, and then a blunt separation is recommended to expose the heart.</li>
		<li>Incise the pericardium. Lift the right atrium with sterile cotton and ligate the RCA with a sterile 8-0&#160;nylon thread with a ligation range of 3-5 mm. After ligating the RCA, the monitoring ECG (lead III) shows ST-segment elevation.&#160; 
		NOTE: Because the mouse RCA is invisible, its anatomic location must be carefully confirmed. The myocardium of the RV is much thinner than that of the LV. Therefore, it is difficult to grasp the depth of the inserted needle. It is easy to induce sinus bradycardia and atrioventricular block if the depth of the inserted needle is too deep and the ligation range is too large.</li>
	</ol>
	</li>
	<li>Remove the sterile cotton and&#160;suture muscles and skin with a sterile 5-0 nylon thread to close the intercostal incision.&#160;Disinfect the skin again with 75% alcohol and&#160;single-house the mouse&#160;after surgery. 
	NOTE: The well-sutured muscle is important for avoiding aerothorax. A sterile drainage tube is placed in the chest cavity until the completion of chest closing, and then the chest cavity is evacuated by an injection syringe connecting the drainage tube. 
	NOTE: After surgery, mice are placed on a heating&#160;pad. Analgesics such as buprenorphine (0.1 mg/kg body weight, subcutaneously injection) are required to reduce the animals&#39; pain after the surgery. The expected complications are sinus bradycardia and atrioventricular block, and the mortality rate post-surgery is 10-20%.</li>
</ol>
3. Echocardiographic assessment of the RV function after surgery
NOTE: For echocardiography, use an MS400D probe with a center frequency of 30 MHz, connected to a high-resolution ultrasound imaging system (see Table of Materials). The echocardiography examination is performed 4 weeks after surgery.
<ol>
	<li>Anesthetize the mouse with 3% isoflurane via inhalation.</li>
	<li>Place the mouse in the supine position on an ultrasonic platform for animal fixation and ultrasonic operation. Tape its claws to the electrode to obtain an ECG recording through a system attached to the ultrasonic machine.</li>
	<li>Monitor heart rate through ECG and maintain it between 450-550 beats/min by adjusting the anesthetic concentration between 1.5% and 3%.</li>
	<li>Remove the hair from the mouse&#39;s chest with a depilatory cream and apply ultrasound gel to the skin of the chest.</li>
	<li>Set the platform to the horizontal position. Orient the transducer parallel to the left leg and obtain the left ventricular long-axis image. Rotate the probe 90&#176; clockwise to obtain the LV short-axis view. Press the Cine store button to save the images. 
	NOTE: The upper-left of the platform is tilted at the lowest point. The LV short-axis rotation angle of the transducer is maintained while the transducer is oriented toward the right shoulder of the mouse.</li>
	<li>Move down the transducer vertically, maintaining its position over the upper abdomen and below the mouse&#39;s diaphragm under B-mode. Adjust the platform position slightly by rotating its x- and y-axes until the RV, right atrium (RA), left atrium (LA), and LV are clearly seen on the screen. Save apical four-chamber images by pressing the Cine store or Frame store button. 
	NOTE: B-mode is used to show the two-dimension (2D) view of the heart.</li>
	<li>Press M-mode; after the 2x indicator line appears, locate the indicator line at the tricuspid valve orifice to obtain the movement of the tricuspid annular plane. Press the Cine store or Frame store button to save data and images. 
	NOTE: M-mode means motion mode, which reveals the motion of the heart or vessel in a curve form.</li>
	<li>Press Measure button to enter measurement mode. Click on Area measurement button to zone into RV and LV. Calculate the area of RV and LV to obtain the area ratio of RV to LV.
	<ol>
		<li>Click on Timeline button and make two baselines to define the movement range of the tricuspid annular plane during the systolic and diastolic periods. Click on Distance button and measure the distance between two baselines to obtain tricuspid annular plane systolic excursion (TAPSE).</li>
	</ol>
	</li>
	<li>Tilt the left side of the platform at the lowest point. Keep the probe at a 30&#176; angle to the horizontal axis along the right anterior axillary line. Rotate the x- and y-axes of the platform to display the RV.
	<ol>
		<li>Press M-mode button and locate the indicator line at the septum&#39;s hyperechoic point to obtain the M-mode image of the RV interface. Press Cine store button to save the picture.</li>
	</ol>
	</li>
	<li>Open the M-mode image of the RV interface, press Measure button to enter measurement mode. Measure the RV inner distance at the end of diastole (RVIDd), RV ejection fraction (RVEF), and RV fraction shortening (RVFS) using the in-built measurement tool of the echocardiographic system.</li>
	<li>Stop administering isoflurane and place the mouse on the heating pad for 3-5 min until it regains consciousness. After that, return the mouse to its cage with 12 h light/dark cycle.</li>
</ol>
4. Invasive measurements of RV hemodynamic
NOTE: RV hemodynamic is assessed through right heart catheterization 4 weeks after RVI. A 1.0 F catheter together with a monitoring system is applied.
<ol>
	<li>Anesthetize the mouse with an intraperitoneal injection of 50 mg/kg of sodium pentobarbital (see Table of Materials).</li>
	<li>After confirming the disappearance of the pedal withdrawal reflex, keep the mouse in the supine position and immobilize it with adhesive tape.</li>
	<li>Shave the chest hair from the sternal angle to the xiphoid. Disinfect the operating area with 75% alcohol.</li>
	<li>Perform tracheal intubation and set the parameter of the animal ventilator as described in steps 1.5.2-1.5.3.</li>
	<li>Make a 1 cm bilateral incision on the skin above the xiphoid process and transect the diaphragm and rib with ophthalmic scissors to expose the heart.</li>
	<li>Puncture the right ventricular free wall with a 32 G needle. Remove the needle and press the wound with cotton to stanch bleeding.</li>
	<li>Insert the tip of the catheter into the right ventricle through the puncture site and push the catheter forward slowly. Adjust the position of the tip to obtain a typical RV pressure waveform shown on a monitor and recording system. 
	NOTE: Right jugular vein is also an appropriate route for hemodynamic measurement.</li>
	<li>After 10 min of stabilization, record the data of RV systolic blood pressure (RVSBP), RV end-diastolic pressure (RVEDP), and RV dP/dt. Click on Select button to select cardiac cycles for calculation and then click on Analyze button to calculate the mean values of the selected cycles.</li>
	<li>Remove the catheter after completion of recording and then place it inside normal saline solution.</li>
	<li>Euthanize the mouse with an intraperitoneal injection of overdose pentobarbital sodium (150 mg/kg) and then sacrifice it by cervical dislocation.</li>
	<li>Collect the heart and tibia for histological analysis.</li>
</ol>
5. Coronary vascular cast using a vascular casting agent
<ol>
	<li>Heparinize the mouse with an intraperitoneal injection of 200 IU/mL of heparin sodium at 2000 IU/kg (see Table of Materials).</li>
	<li>Anesthetize the mouse with an intraperitoneal injection of 50 mg/kg of sodium pentobarbital.</li>
	<li>Place the animal supine on the pad and intubate for artificial ventilation following steps 1.5.2-1.5.3.</li>
	<li>Open the chest with surgical scissors as described in step 4.5 and expose the heart.</li>
	<li>Make a 3 mm notch with ophthalmic scissors on the right atria and perfuse the heart with 5 mL of normal saline through the cardiac apex with an injector.</li>
	<li>Block the blood from the aorta with an aortic clamp and perfuse 0.1 mL of nitroglycerin (1 mg/mL) through the cardiac apex with an injector to dilate the coronary artery.</li>
	<li>Prepare the cast reagent by mixing the ingredients in the kit according to the manufacturer&#39;s instructions (see Table of Materials). 
	NOTE: It is recommended to prepare the cast reagent and perfusion with normal saline and nitroglycerin simultaneously to prevent microvascular closure.</li>
	<li>Perfuse the heart with 1 mL of cast reagent through the cardiac apex and wait for 2-3 h.</li>
	<li>Erode the heart with 50% sodium hydroxide for 2-3 days and remove the muscle tissue or connective tissue by rinsing with normal saline.</li>
	<li>Take pictures under a camera. 
	CAUTION: The cast reagent is harmful to the eyes, skin, and respiratory tract. Sodium hydroxide is corrosive. Wearing protective gloves, goggles, and a lab coat is required. The cast reagent must be prepared in a fume hood.</li>
</ol>

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The authors have nothing to disclose.

Sicard and colleagues from France first reported a mouse model of RVI in 2019, which described the surgical process and focused on the interaction between LV and RV after RVI9. However, to date, no study has reported using this model for further studies. A more detailed procedure would be helpful for researchers to use the mouse model of RVI for investigation. In contrast to the report by Sicard et al.9, we provided step-by-step information for model generation and strategy...

The right ventricle (RV), long thought to be a simple tube connected to the pulmonary artery, has been wrongfully neglected for many years1. However, there has been an increasing interest in RV function recently since it plays an essential role in hemodynamic disorders2,3 and may serve as an independent risk predictor of cardiovascular disease4,5,6,7. RV diseases include RV infarction (RVI), pulmonary artery hypertension, and valvular disease8. In contrast to the immense interest in pulmonary artery hypertension, RVI has remained neglected7,9.
RVI, usually accompanied by inferior-posterior myocardial infarction10,11, is caused by right coronary artery (RCA) occlusion. According to clinical investigations, severe RVI likely induces hemodynamic disturbances and arrhythmias, such as hypotension, bradycardia, and atrioventricular block, associated with higher hospital morbidity and mortality12,13,14. RV function could recover spontaneously to a certain extent even in the absence of reperfusion15,16. Several morphological and functional differences exist between the left ventricle (LV) and RV17. RV is believed to be more resistant to ischemia than LV8, partially due to the more extensive collateral circulation formation after RVI. Clarifying the differences between LV infarction (LVI) and RVI and identifying the underlying mechanisms would provide new therapeutic targets for cardiac regeneration and ischemic heart failure. However, owing to the difficulty associated with&#160;RVI mouse model generation, basic research on RVI is mainly limited.
A large animal model of RVI has been generated by ligating RCA in swine18, which is easier to operate because of the visible RCA. Compared with the large animal model, the mouse model has the following advantages: more accessibility in gene manipulation, lower economic cost, and shorter experimental period19,20. Although a mouse RVI model focusing on the influence of RVI on LV function was reported previously, the detailed steps of the procedure, the difficulties and key points of operation, and the model characteristics such as hemodynamic changes were not fully introduced9,21.
This article provides detailed surgical procedures for generating a mouse model of RVI. Moreover, this model was characterized by echocardiographic measurement, invasive hemodynamic evaluation, and histological analysis. Furthermore, a coronary vasculature cast was performed to observe the coronary arterial arrangement in RV. The technique introduced in this paper would help beginners to quickly grasp the generation of the mouse RVI model with acceptable operation mortality and reliable evaluation approaches. The mouse model of RVI would help research the mechanisms of right heart failure and seek new therapeutic targets of RV remodeling.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2,3,5-triphenyltetrazolium chloride</td>
			<td>Sigma</td>
			<td>T8877</td>
			<td>For TTC staining</td>
		</tr>
		<tr>
			<td>Animal Mini Ventilator</td>
			<td>Havard</td>
			<td>Type 845</td>
			<td>For artificial ventilation</td>
		</tr>
		<tr>
			<td>Animal ultrasound system VEVO2100</td>
			<td>Visual Sonic</td>
			<td>VEVO2100</td>
			<td>Measurement for Doppler flow velocity and AS plaque</td>
		</tr>
		<tr>
			<td>Batson&#8217;s #17 Anatomical Corrosion Kit</td>
			<td>Polyscience Inc</td>
			<td>7349</td>
			<td>For vasculature casting</td>
		</tr>
		<tr>
			<td>buprenorphine</td>
			<td>Isoreag</td>
			<td>1134630-70-8</td>
			<td>For reduce the pain of mice after surgery</td>
		</tr>
		<tr>
			<td>C57BL/6J mice + D29A1A2:D27</td>
			<td>Animal Center of South Medical University</td>
			<td>-</td>
			<td>For the generation of mouse RVI model</td>
		</tr>
		<tr>
			<td>Camera</td>
			<td>Sangnond</td>
			<td></td>
			<td>For taking photograph</td>
		</tr>
		<tr>
			<td>Cold light illuminator</td>
			<td>Olympus</td>
			<td>ILD-2</td>
			<td>Light for operation</td>
		</tr>
		<tr>
			<td>electrocardiograph</td>
			<td>ADI Instrument</td>
			<td>ADAS1000</td>
			<td>For recording electrocardiogram</td>
		</tr>
		<tr>
			<td>hair removal cream</td>
			<td>Reckitt Benchiser</td>
			<td>RQ/B 33 Type 2</td>
			<td>Remove mouse hair</td>
		</tr>
		<tr>
			<td>Heat pad- thermostatic surgical system (ALC-HTP-S1)</td>
			<td>SHANGHAI ALCOTT BIOTECH CO</td>
			<td>ALC-HTP-S1</td>
			<td>Heating</td>
		</tr>
		<tr>
			<td>Hematoxylin-eosin dye</td>
			<td>Leagene</td>
			<td>DH0003</td>
			<td>Hematoxylin-eosin staining</td>
		</tr>
		<tr>
			<td>Heparin sodium salt</td>
			<td>Macklin</td>
			<td>H837056</td>
			<td>For heparization</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>RWD life science</td>
			<td>R510-22</td>
			<td>Inhalant anaesthesia</td>
		</tr>
		<tr>
			<td>Lab made spatula</td>
			<td></td>
			<td></td>
			<td>Work as a laryngoscope</td>
		</tr>
		<tr>
			<td>Lab made tracheal cannula</td>
			<td></td>
			<td></td>
			<td>For intubation</td>
		</tr>
		<tr>
			<td>Matrx VIP 3000 Isofurane Vaporizer</td>
			<td>Midmark Corporation</td>
			<td>VIP 3000</td>
			<td>Anesthetization</td>
		</tr>
		<tr>
			<td>Medical nylon suture (5-0)</td>
			<td>Ningbo Medical Needle Co.</td>
			<td>5-0</td>
			<td>For chest close</td>
		</tr>
		<tr>
			<td>Microsurgical elbow tweezers</td>
			<td>RWD life science</td>
			<td>F11021-11</td>
			<td>For surgery</td>
		</tr>
		<tr>
			<td>Microsurgical scissors</td>
			<td>NAPOX</td>
			<td>MB-54-1</td>
			<td>For arteriotomy</td>
		</tr>
		<tr>
			<td>Millar Catheter</td>
			<td>AD Instruments, Shanghai</td>
			<td>1.0F</td>
			<td>Measurement of pressure gradient</td>
		</tr>
		<tr>
			<td>MS400D ultrasonic probe</td>
			<td>Visual Sonic</td>
			<td>MS400D</td>
			<td>Measurement for Doppler flow velocity and AS plaque</td>
		</tr>
		<tr>
			<td>needle forceps</td>
			<td>Visual Sonic</td>
			<td>F31006-12</td>
			<td>For surgery</td>
		</tr>
		<tr>
			<td>nitroglycerin</td>
			<td>BEIJING YIMIN MEDICINE Co</td>
			<td></td>
			<td>For dilating coronary artery</td>
		</tr>
		<tr>
			<td>Ophthalmic scissors</td>
			<td>RWD life science</td>
			<td>S11022-14</td>
			<td>For surgery</td>
		</tr>
		<tr>
			<td>Pentobarbital sodium salt</td>
			<td>Merck</td>
			<td>25MG</td>
			<td>Anesthetization</td>
		</tr>
		<tr>
			<td>PowerLab Multi-Directional Physiological Recording System</td>
			<td>AD Instruments, Shanghai</td>
			<td>4/35</td>
			<td>Pressure recording</td>
		</tr>
		<tr>
			<td>Precision electronic balance</td>
			<td>Denver Instrument</td>
			<td>TB-114</td>
			<td>Weighing scale</td>
		</tr>
		<tr>
			<td>Silk suture (8-0)</td>
			<td>Ningbo Medical Needle Co.</td>
			<td>6-0</td>
			<td>coronary artery ligation</td>
		</tr>
		<tr>
			<td>Small animal microsurgery equipment</td>
			<td>Napox</td>
			<td>MA-65</td>
			<td>Surgical instruments</td>
		</tr>
		<tr>
			<td>tissue forceps</td>
			<td>Visual Sonic</td>
			<td>F-12007-10</td>
			<td>For surgery</td>
		</tr>
		<tr>
			<td>tissue scissor</td>
			<td>Visual Sonic</td>
			<td>S13052-12</td>
			<td>Open chest for hemodynamic measurement</td>
		</tr>
		<tr>
			<td>Transmission Gel</td>
			<td>Guang Gong pai</td>
			<td>250ML</td>
			<td>preparation for Echocardiography measurement</td>
		</tr>
		<tr>
			<td>Vascular Clamps</td>
			<td>Visual Sonic</td>
			<td>R31005-06</td>
			<td>For blocking blood from aorta</td>
		</tr>
	</tbody>
</table>

generation and characterization of right ventricular myocardial infarction induced by permanent ligation of the right coronary artery in mice

Right ventricular infarction (RVI) is a common presentation in clinical practice. Severe RVI can lead to fatal hemodynamic dysfunction and arrhythmia. In contrast to the extensively used mouse myocardial infarction (MI) model generated by left coronary artery ligation, the RVI mouse model is rarely employed due to the difficulty associated with model generation. Research on the mechanisms and treatment of RVI-induced RV remodeling and dysfunction requires animal models to mimic the pathophysiology of RVI in patients. This study introduces a feasible procedure for RVI model generation in C57BL/6J mice. Further, this model was characterized based on the following: infarct size evaluation at 24 h after MI, assessment of cardiac remodeling and function with echocardiography, RV hemodynamics assessment, and histology of the infarct zone at 4 weeks after RVI. In addition, a coronary vasculature cast was performed to observe the coronary arterial arrangement in RV. This mouse model of RVI would facilitate the research on mechanisms of right heart failure and seek new therapeutic targets of RV remodeling.

In this study, mice were randomly assigned to the RVI (n = 11) or sham operation (n = 11) group. The coronary cast in 2 normal mouse hearts is shown in Figure 1A. In response to RCA ligation, ST-segment elevation was seen in lead III of the ECG (Figure 1B). Moreover, 2,3,5-triphenyl tetrazolium chloride (TTC) staining showed that the infarct area accounts for 45% of the RV free wall at 24 h postoperatively (Figure 1C,D</stro...

Watch this Scientific Journal Video about Generation and Characterization of Right Ventricular Myocardial Infarction Induced by Permanent Ligation of the Right Coronary Artery in Mice at JoVE.com

Generation and Characterization of Right Ventricular Myocardial Infarction Induced by Permanent Ligation of the Right Coronary Artery in Mice

There are several differences between the right and left ventricles. However, the pathophysiology of right ventricular infarction (RVI) has not been clarified. In the present protocol, a reproducible method for RVI mouse model generation is introduced, which may provide a means to explain the mechanism of RVI.

Right ventricular infarction (RVI) is a common presentation in clinical practice. Severe RVI can lead to fatal hemodynamic dysfunction and arrhythmia. In ...

generation-characterization-right-ventricular-myocardial-infarction

Research

JoVE Journal

Medicine

2.9K Views.  The First Clinical College of Dalian Medical University. There are several differences between the right and left ventricles. However, the pathophysiology of right ventricular infarction (RVI) has not been clarified. In the present protocol, a reproducible method for RVI mouse model generation is introduced, which may provide a means to explain the mechanism of RVI. 

Video: Generation and Characterization of Right Ventricular Myocardial Infarction Induced by Permanent Ligation of the Right Coronary Artery 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 ...

The Application Of Permanent Middle Cerebral Artery Ligation in the Mouse

Focal cerebral ischemia is among the most common type of stroke seen in patients. Due to the clinical significance there has been a prolonged effort to develop suitable animal models to study the events that unfold during ischemic insult. These techniques include transient or permanent, focal or global ischemia models using many different animal models, with the most common being rodents.
The permanent MCA ligation method which is also referred as pMCAo in the literature is used extensively as a focal ischemia model in rodents 1-6. This method was originally described for rats by Tamura et al. in 1981 7. In this protocol a craniotomy was used to access the MCA and the proximal regions were occluded by electrocoagulation. The infarcts involve mostly cortical and sometimes striatal regions depending on the location of the occlusion. This technique is now well established and used in many laboratories 8-13. Early use of this technique led to the definition and description of &#x201C;infarct core&#x201D; and &#x201C;penumbra&#x201D; 14-16, and it is often used to evaluate potential neuroprotective compounds 10, 12, 13, 17. Although the initial studies were performed in rats, permanent MCA ligation has been used successfully in mice with slight modifications 18-20 .
This model yields reproducible infarcts and increased post-survival rates. Approximately 80% of the ischemic strokes in humans happen in the MCA area 21 and thus this is a very relevant model for stroke studies. Currently, there is a paucity of effective treatments available to stroke patients, and thus there is a need for good models to test potential pharmacological compounds and evaluate physiological outcomes. This method can also be used for studying intracellular hypoxia response mechanisms in vivo. 
Here, we present the MCA ligation surgery in a C57/BL6 mouse. We describe the pre-surgical preparation, MCA ligation surgery and 2,3,5 Triphenyltetrazolium chloride (TTC) staining for quantification of infarct volumes.

Middle cerebral artery (MCA) ligation is a technique to study focal cerebral ischemia in animal models. In this method, the middle cerebral artery is exposed by craniotomy and ligated by cauterization. This method gives highly reproducible infarct volumes and increased post-operative survival rates compared to other methods available.

Focal cerebral ischemia is among the most common type of stroke seen in patients. Due to the clinical significance there has been a prolonged effort to ...

Modified Technique for Coronary Artery Ligation in Mice

Myocardial infarction (MI) is one of the most important causes of mortality in humans1-3. In order to improve morbidity and mortality in patients with MI we need better knowledge about pathophysiology of myocardial ischemia. This knowledge may be valuable to define new therapeutic targets for innovative cardiovascular therapies4. Experimental MI model in mice is an increasingly popular small-animal model in preclinical research in which MI is induced by means of permanent or temporary ligation of left coronary artery (LCA)5. In this video, we describe the step-by-step method of how to induce experimental MI in mice.
The animal is first anesthetized with 2% isoflurane. The unconscious mouse is then intubated and connected to a ventilator for artificial ventilation. The left chest is shaved and 1.5 cm incision along mid-axillary line is made in the skin. The left pectoralis major muscle is bluntly dissociated until the ribs are exposed. The muscle layers are pulled aside and fixed with an eyelid-retractor. After these preparations, left thoracotomy is performed between the third and fourth ribs in order to visualize the anterior surface of the heart and left lung. The proximal segment of LCA artery is then ligated with a 7-0 ethilon suture which typically induces an infarct size ~40% of left ventricle. At the end, the chest is closed and the animals receive postoperative analgesia (Temgesic, 0.3 mg/50 ml, ip). The animals are kept in a warm cage until spontaneous recovery.

The surgical procedure used to induce experimental myocardial infarction in mice begins with left thoracotomy between the third and the fourth ribs in order to visualize the anterior surface of the heart and left lung. The left coronary artery is ligated, the chest is closed and the mouse is allowed to recover spontaneously.

Myocardial infarction (MI) is one of the most important causes of mortality in humans1-3. In order to improve morbidity and mortality in patients with MI ...

Echocardiographic Assessment of the Right Heart in Mice

Transgenic and toxic models of pulmonary arterial hypertension (PAH) are widely used to study the pathophysiology of PAH and to investigate potential therapies. Given the expense and time involved in creating animal models of disease, it is critical that researchers have tools to accurately assess phenotypic expression of disease. Right ventricular dysfunction is the major manifestation of pulmonary hypertension. Echocardiography is the mainstay of the noninvasive assessment of right ventricular function in rodent models and has the advantage of clear translation to humans in whom the same tool is used. Published echocardiography protocols in murine models of PAH are lacking.
In this article, we describe a protocol for assessing RV and pulmonary vascular function in a mouse model of PAH with a dominant negative BMPRII mutation; however, this protocol is applicable to any diseases affecting the pulmonary vasculature or right heart. We provide a detailed description of animal preparation, image acquisition and hemodynamic calculation of stroke volume, cardiac output and an estimate of pulmonary artery pressure.

This article provides a protocol for the echocardiographic assessment of right ventricular size and pulmonary hypertension in mice. Applications include phenotype determination and serial assessment in transgenic and toxin-induced mouse models of cardiomyopathy and pulmonary vascular disease.

Transgenic and toxic models of pulmonary arterial hypertension (PAH) are widely used to study the pathophysiology of PAH and to investigate potential ...

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, ...

Permanent Ligation of the Left Anterior Descending Coronary Artery in Mice: A Model of Post-myocardial Infarction Remodelling and Heart Failure

Heart failure is a syndrome in which the heart fails to pump blood at a rate commensurate with cellular oxygen requirements at rest or during stress. It is characterized by fluid retention, shortness of breath, and fatigue, in particular on exertion. Heart failure is a growing public health problem, the leading cause of hospitalization, and a major cause of mortality. Ischemic heart disease is the main cause of heart failure.
Ventricular remodelling refers to changes in structure, size, and shape of the left ventricle. This architectural remodelling of the left ventricle is induced by injury (e.g., myocardial infarction), by pressure overload (e.g., systemic arterial hypertension or aortic stenosis), or by volume overload. Since ventricular remodelling affects wall stress, it has a profound impact on cardiac function and on the development of heart failure. A model of permanent ligation of the left anterior descending coronary artery in mice is used to investigate ventricular remodelling and cardiac function post-myocardial infarction. This model is fundamentally different in terms of objectives and pathophysiological relevance compared to the model of transient ligation of the left anterior descending coronary artery. In this latter model of ischemia/reperfusion injury, the initial extent of the infarct may be modulated by factors that affect myocardial salvage following reperfusion. In contrast, the infarct area at 24 hr after permanent ligation of the left anterior descending coronary artery is fixed. Cardiac function in this model will be affected by 1) the process of infarct expansion, infarct healing, and scar formation; and 2) the concomitant development of left ventricular dilatation, cardiac hypertrophy, and ventricular remodelling.
Besides the model of permanent ligation of the left anterior descending coronary artery, the technique of invasive hemodynamic measurements in mice is presented in detail.

Heart failure is the leading cause of hospitalization and a major cause of mortality. A model of permanent ligation of the left anterior descending coronary artery in mice is applied to investigate ventricular remodelling and cardiac dysfunction post-myocardial infarction. The technique of invasive hemodynamic measurements in mice is presented.

Heart failure is a syndrome in which the heart fails to pump blood at a rate commensurate with cellular oxygen requirements at rest or during stress. It ...

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 ...

Echocardiographic Measurement of Right Ventricular Diastolic Parameters in Mouse

Diastolic dysfunction is a prominent feature of right ventricular (RV) remodeling associated with conditions of pressure overload. However, the RV diastolic function is rarely quantified in experimental studies. This might be due to technical difficulties in the visualization of the RV in the apical four-chamber view in rodents. Here we describe two positions facilitating the visualization of the apical four-chamber view in mice to assess the RV diastolic function.
The apical four-chamber view is enabled by tilting the mouse fixation platform to the left and caudally (LeCa) or to the right and cranially (RiCr). Both positions provide images of comparable quality. The results of the RV diastolic function obtained from two positions are not significantly different. Both positions are comparably easy to perform. This protocol can be incorporated into published protocols and enables detailed investigations of the RV function.

Here we describe and compare two positions for obtaining the apical four-chamber view in mice. These positions enable the quantification of the right ventricular function, provide comparable results, and can be used interchangeably.

Diastolic dysfunction is a prominent feature of right ventricular (RV) remodeling associated with conditions of pressure overload. However, the RV ...

A Pulmonary Trunk Banding Model of Pressure Overload Induced Right Ventricular Hypertrophy and Failure

Right ventricular (RV) failure induced by sustained pressure overload is a major contributor to morbidity and mortality in several cardiopulmonary disorders. Reliable and reproducible animal models of RV failure are therefore warranted in order to investigate disease mechanisms and effects of potential therapeutic strategies. Banding of the pulmonary trunk is a common method to induce isolated RV hypertrophy but in general, previously described models have not succeeded in creating a stable model of RV hypertrophy and failure.
We present a rat model of pressure overload induced RV hypertrophy caused by pulmonary trunk banding (PTB) that enables different phenotypes of RV hypertrophy with and without RV failure. We use a modified ligating clip applier to compress a titanium clip around the pulmonary trunk to a pre-set inner diameter. We use different clip diameters to induce different stages of disease progression from mild RV hypertrophy to decompensated RV failure.
RV hypertrophy develops consistently in rats subjected to the PTB procedure and depending on the diameter of the applied banding clip, we can accurately reproduce different disease severities ranging from compensated hypertrophy to severe decompensated RV failure with extra-cardiac manifestations.
The presented PTB model is a valid and robust model of pressure overload induced RV hypertrophy and failure that has several advantages to other banding models including high reproducibility and the possibility of inducing severe and decompensated RV failure.

We present a surgical method to induce right ventricular hypertrophy and failure in rats.

Right ventricular (RV) failure induced by sustained pressure overload is a major contributor to morbidity and mortality in several cardiopulmonary ...

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 ...