This work was supported by grants from the National Natural Science Foundation of China (81770271; to Y, Liao), the Joint Funds of the National Natural Science Foundation of China (U1908205; to Y, Liao), and the Municipal Planning Projects of Scientific Technology of Guangzhou (201804020083; to Dr Liao).

All procedures were carried out following the guidelines of the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH Publication No. 85-23, revised in 1996). C57BL/6J male mice (8&#8211;10 weeks, 20&#8211;25 g) were provided by the Animal Center of South Medical University.
1. Preoperative preparation
<ol>
	<li>Pinch off the tip of a 25 G needle with a needle holder and blunt it with a hard object like the holder.</li>
	<li>Pass a 5&#8211;0 absor...

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The authors have nothing to disclose.

There is still a vastly underexplored area in cardiac non-ischemic preconditioning. Based on our previous studies, we switched to using absorbable sutures to improve the myocardial hypertrophic preconditioning model.
In previous reports, many investigators used silk suture to constrict the aortic arch8,14,15. Silk suture was easily available and was often used for surgical wound suture, tissue ligatio...

Ischemic preconditioning is a phenomenon that induces brief non-lethal episodes of ischemia and reperfusion to the heart and has the capacity to dramatically reduce myocardial injury1. Given the obvious clinical implications of ischemic preconditioning, such as limiting myocardial infarct size2 and suppressing ventricular tachyarrhythmias after myocardial revascularization3, there have been lots of research to dissect the mechanisms underlying cardio-protective effects induced by preconditioning4,5. In contrast, other non-ischemic types of preconditioning have received relatively little attention. Cardiac hypertrophy may be blunted in patients with aortic stenosis undergoing aortic valve replacement6. Wherever the state of pathological myocardial hypertrophy exists, the principle of preconditioning is rarely reported.
In 1991, Rockman et al. firstly established a mouse model of left ventricular hypertrophy by transverse aortic constriction (TAC)7. By operating TAC twice in mice, we have previously proved that myocardial hypertrophic preconditioning (MHP) leads to transient hypertrophic stimulation in the heart thereby making the heart more resistant to sustained hypertrophic stress in the future8. The characteristics of the MHP model have been validated by ultrasound biomicroscope and hemodynamic assessment9. Key points in constructing the model was to perform thoracotomy three times, TAC for a week, debanding for a week, and secondary TAC for 6 weeks. However, debanding could cause bleeding, which made it difficult to be mastered by novices and difficult to be popularized. In addition, it is also a technical challenge to intubate mice. Improper intubation could cause tracheal injury, pneumothorax, and even death in mice. So, it is necessary and valuable to improve some procedures while constructing the MHP model.
To reduce the difficulty of the model and increase its success, we switched to absorbable sutures for the first TAC and monitored the model&#39;s success by measuring pressure gradient across the aortic constriction under echocardiography10. Based on our preliminary experiment, it would be difficult to induce sufficient myocardial hypertrophy in mice with too low-pressure gradient, while mice with too high-pressure gradient would develop acute heart failure or even die. The ideal pressure gradient for the model ranges from 40&#8211;80 mmHg11. In addition, this experiment did not rely on a ventilator, which could effectively avoid ventilator-associated technical manipulation and injury12.

<table>
	<tbody>
		<tr>
			<td>Absorbable suture (5-0)</td>
			<td>Shandong Kang Lida Medical Products Co., Ltd</td>
			<td>5-0</td>
			<td>Ligation</td>
		</tr>
		<tr>
			<td>Animal ultrasound system VEVO2100</td>
			<td>Visual Sonic</td>
			<td>VEVO2100</td>
			<td>Echocardiography</td>
		</tr>
		<tr>
			<td>Cold light illuminator</td>
			<td>Olympus</td>
			<td>ILD-2</td>
			<td>Light</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>Isoflurane</td>
			<td>RWD life science</td>
			<td>R510-22</td>
			<td>Inhalant anaesthesia</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>Close the skin</td>
		</tr>
		<tr>
			<td>Pentobarbital sodium salt</td>
			<td>Merck</td>
			<td>25MG</td>
			<td>Anesthetization</td>
		</tr>
		<tr>
			<td>Precision electronic balance</td>
			<td>Denver Instrument</td>
			<td>TB-114</td>
			<td>Weighing sensor</td>
		</tr>
		<tr>
			<td>Self-made spacer</td>
			<td></td>
			<td></td>
			<td>25-gauge needle</td>
		</tr>
		<tr>
			<td>Silk suture (5-0)</td>
			<td>Yangzhou Yuankang Medical Devices Co., Ltd.</td>
			<td>5-0</td>
			<td>Ligation</td>
		</tr>
		<tr>
			<td>Small animal microsurgery equipment</td>
			<td>Napox</td>
			<td>MA-65</td>
			<td>Surgical instruments</td>
		</tr>
		<tr>
			<td>Transmission Gel</td>
			<td>Guang Gong pai</td>
			<td>250ML</td>
			<td>Echocardiography</td>
		</tr>
		<tr>
			<td>Veet hair removal cream</td>
			<td>Reckitt Benchiser</td>
			<td>RQ/B 33 Type 2</td>
			<td>Remove hair of mice</td>
		</tr>
		<tr>
			<td>Vertical automatic electrothermal pressure steam sterilizer</td>
			<td>Hefei Huatai Medical Equipment Co.</td>
			<td>LX-B50L</td>
			<td>Auto clean the surgical instruments</td>
		</tr>
	</tbody>
</table>

operating transverse aortic constriction with absorbable suture to obtain transient myocardial hypertrophy

Based on twice transverse aortic constrictions (TACs) in mice, it is proved that myocardial hypertrophic preconditioning (MHP) could attenuate cardiomyocyte hypertrophy and slow down progression to heart failure. For novices, however, the MHP model is usually quite difficult to establish because of the technical obstacles in ventilator operation, opening the chest repeatedly, and bleeding caused by debanding. To facilitate this model, to increase the surgical success rate and to reduce the incidence of bleeding, we switched to absorbable sutures for the first TAC combing with a ventilator-free technique. Using a 2-week absorbable suture, we demonstrated that this procedure could cause significant myocardial hypertrophy in 2 weeks; and 4 weeks after surgery, myocardial hypertrophy was almost completely regressed to the baseline. Using this protocol, the operators could master the MHP model easily with a lower operation mortality.

In this study, we randomly divided 45 mice into three groups, the sham, the silk suture group, and the absorbable suture group (the number of each group on D0 (baseline), D14, and D28 after TAC was 15, 10, and 5, respectively). On D7, D14, D21, and D28 after the surgery, the constricted peak velocity was determined by echocardiography. We found that the blood flow velocity at the constriction was still greater than 3,000 mm/s in the second week after TAC even though an absorbable suture had been used to constrict the aor...

Watch this Scientific Journal Video about Operating Transverse Aortic Constriction with Absorbable Suture to Obtain Transient Myocardial Hypertrophy at JoVE.com

Operating Transverse Aortic Constriction with Absorbable Suture to Obtain Transient Myocardial Hypertrophy

This protocol presents an improved method to obtain transient myocardial hypertrophy with absorbable suture, simulating left ventricular hypertrophy decrease after removing pressure overload. It could be valuable for the studies on myocardial hypertrophic preconditioning.

Based on twice transverse aortic constrictions (TACs) in mice, it is proved that myocardial hypertrophic preconditioning (MHP) could attenuate ...

This protocol presents an improved method to obtain transient myocardial hypertrophy, using absorbable sutures, which stimulates left ventricular hypertrophy decrease after removing pressure overload. Using this protocol, researchers can easily mastered the model with a lower operation mortality. Demonstrating the procedure will be Xiaoxia Huang, a technician from my laboratory.Begin by pinching off the tip of a 25 gauge needle with a needle holder and blunting it. Then, pass a 5/0 absorbable suture through this needle and curve the blunt needle to a 90 degree angle using the holder. Pinch off the tip of another 25 gauge needle, then curve it to a 120 degree angle and smoothen the tip with a holder to be used as a spacer in the ligation step.Prepare sterilized surgical instruments, including one ophthalmic scissors, one micro scissors, two microsurgical elbow tweezers, one needle holder, and one micro needle holder. To begin the surgery, confirm complete anesthesia of the mouse with the pedal withdrawal reflex. Keep the mouse in the supine position by fixing the incisors with a suture and fixing the limbs with adhesive tape.Remove the hair from the neck and disinfect the area with iodine and 75%alcohol. Start the surgery by making an incision over 10 millimeters at the midline position between the suprasternal notch and chest. Then separate the skin and the superficial fascia.Make an incision in the first intercostal space as close as possible to the sternum and bluntly penetrate to open this space with elbow tweezers. Gently separate the parenchyma and the thymus until the transverse aortic arch is visible. Pass a 5/0 absorbable suture under the aortic arch between the brachiocephalic artery and the left common carotid artery with a latch needle.Place the previously prepared spacer on the transverse aorta and make a double knot on the spacer with the suture. Gently, but quickly remove the spacer and cut the ends of the suture. Close the first intercostal space and skin using 5/0 nylon sutures.Disinfect the skin again with 75%alcohol. Seven days after surgery, place the mouse in the supine position, maintaining it at 37 degrees Celsius, and tape its limbs to the electrode. Remove chest hair and apply ultrasonic coupling agent to the mouse's chest.Then access TAC with a 30 megahertz probe. Tilt the platform to the far left. Keep the probe in the vertical position and lower it on the chest along the right parasternal line.Adjust the X and Y-axis under B-mode until the aortic arch and constriction are clearly visible. Using Doppler mode, measure the peak velocity, dimensions, and contractility of the left ventricle. Select the mice with a velocity of more than 3000 millimeters per second as the TAC group.Using a 30 megahertz probe, assess the left ventricular dimensions and contractility. Reset the platform to the horizontal position, keeping the probe at 30 degrees counterclockwise to the left parasternal line. Obtain a short axis view of the heart by manipulating the X and Y-axis in B-mode.Then, press M-mode to show the indicator line and acquire images with Cine Store and Frame Store for later measurement of the LV chamber dimension, fractional shortening, and LV wall thickness. Pulsed-wave Doppler imaging performed after 14 days of TAC showed that the blood flow velocity at the constriction was greater than 3000 millimeters per second even though an absorbable suture had been used to constrict the aortic arch. The pressure gradient of blood flow after 14 days of TAC was maintained above 40 millimeters of mercury.Interestingly, there was no constriction in the fourth week after surgery, indicating that the absorbable suture had been completely absorbed. The left ventricular parameters in the silk suture group and the absorbable suture group on days zero, 14, and 28 after TAC, on M-mode imaging, are shown here. On day 14 after TAC, the left ventricular posterior wall thickness at end-diastole increased, while the left ventricular internal diameter at end-diastole slightly decreased.The ejection fraction of the left ventricle was unaffected by the use of absorbable sutures. The heart weight to body weight ratio comparison of the silk suture group, absorbable suture group, and the sham group is shown here. Histological slices of the heart showed that cardiomyocytes significantly enlarged from day 14 to day 28 in the silk suture group, but mostly regressed on day 28 in the absorbable suture group.When attempting this protocol, it is most important to not damage the parental pleura to avoid pneumothorax. Make sure to blunt the tip of the needle as much as possible and perform the procedure gently. There are many potential application for this method, such as establishing the model of myocardial hypertrophy preconditioning, exploring the mechanism of hypertrophy regression, and investigating the time of left ventricular reversible remodeling.

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6.1K visualizações.  Southern Medical University. This protocol presents an improved method to obtain transient myocardial hypertrophy, using absorbable sutures, which stimulates left ventricular hypertrophy decrease after removing pressure overload. Using this protocol, researchers can easily mastered the model with a lower operation mortality. Demonstrating the procedure will be Xiaoxia Huang, a technician from my laboratory.Begin by pinching off the tip of a 25 gauge needle with a needle holder and blunting it. Then, pass a 5/0 abs...