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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 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.
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'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 40–80 mmHg11. In addition, this experiment did not rely on a ventilator, which could effectively avoid ventilator-associated technical manipulation and injury12.
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 (8–10 weeks, 20–25 g) were provided by the Animal Center of South Medical University.
1. Preoperative preparation
2. Induction of anesthesia and shaving
3. Surgery
4. Echocardiographic assessment of successful ligation and measurements
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...
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...
The authors have nothing to disclose.
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).
Name | Company | Catalog Number | Comments |
Absorbable suture (5-0) | Shandong Kang Lida Medical Products Co., Ltd | 5-0 | Ligation |
Animal ultrasound system VEVO2100 | Visual Sonic | VEVO2100 | Echocardiography |
Cold light illuminator | Olympus | ILD-2 | Light |
Heat pad- thermostatic surgical system (ALC-HTP-S1) | SHANGHAI ALCOTT BIOTECH CO | ALC-HTP-S1 | Heating |
Isoflurane | RWD life science | R510-22 | Inhalant anaesthesia |
Matrx VIP 3000 Isofurane Vaporizer | Midmark Corporation | VIP 3000 | Anesthetization |
Medical nylon suture (5-0) | Ningbo Medical Needle Co. | 5-0 | Close the skin |
Pentobarbital sodium salt | Merck | 25MG | Anesthetization |
Precision electronic balance | Denver Instrument | TB-114 | Weighing sensor |
Self-made spacer | 25-gauge needle | ||
Silk suture (5-0) | Yangzhou Yuankang Medical Devices Co., Ltd. | 5-0 | Ligation |
Small animal microsurgery equipment | Napox | MA-65 | Surgical instruments |
Transmission Gel | Guang Gong pai | 250ML | Echocardiography |
Veet hair removal cream | Reckitt Benchiser | RQ/B 33 Type 2 | Remove hair of mice |
Vertical automatic electrothermal pressure steam sterilizer | Hefei Huatai Medical Equipment Co. | LX-B50L | Auto clean the surgical instruments |
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