Left Coronary Artery Ligation: A Surgical Murine Model of Myocardial Infarction

Summary

Presented here is a surgical procedure for permanent ligation of the left coronary artery in mice. This model can be used to investigate the pathophysiology and associated inflammatory response after myocardial infarction.

Abstract

Ischemic heart disease and subsequent myocardial infarction (MI) is one of the leading causes of mortality in the United States and around the world. In order to explore the pathophysiological changes after myocardial infarction and design future treatments, research models of MI are required. Permanent ligation of the left coronary artery (LCA) in mice is a popular model to investigate cardiac function and ventricular remodeling post MI. Here we describe a less invasive, reliable, and reproducible surgical murine MI model by permanent ligation of the LCA. Our surgical model comprises of an easily reversible general anesthesia, endotracheal intubation that does not require a tracheotomy, and a thoracotomy. Electrocardiography and troponin measurement should be performed to ensure MI. Echocardiography at day 28 after MI will discern heart function and heart failure parameters. The degree of cardiac fibrosis can be evaluated by Masson's trichrome staining and cardiac MRI. This MI model is useful for studying the pathophysiological and immunological alterations after MI.

Introduction

Cardiovascular disease is a major public health concern that claims 17.9 million lives each year, accounting for 31 percent of global mortality¹. The most prevalent type of cardiovascular anomaly is coronary heart disease, and myocardial infarction (MI) is one of the major manifestations of coronary heart disease². MI is usually caused by thrombotic occlusion of a coronary artery due to the rupture of a vulnerable plaque³. The resulting ischemia causes profound ionic and metabolic changes in the affected myocardium, as well as a rapid decrease in systolic function. MI results in the death of cardi....

Protocol

The present study protocol was reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) of the University of Pittsburgh. Eight (sham n = 4 and MI n = 4) 1-year-old female C57BL/6J mice weighing 24-30 g were used for these experiments. Approximately 100% and at least 80% of mice survived in the first 24 h and 28 days, respectively.

1. Preparation and endotracheal intubation of the mice

1. Preheat a bead sterilizer (see Table of Materials) to 250 °C and place autoclaved surgical instruments in it for a few minutes.
2. Anesthetize the mouse in an induction chamber w....

Results

Figure 1 demonstrates the representative active ECG and respiration signals during the echocardiographic evaluation of sham (Figure 1A) and MI (Figure 1B) mice. Verification of active ECG and respiration signals are important before acquiring the echocardiographic data. Figure 2 shows echocardiographic measurement of cardiac functional parameters following 28 days after LCA ligation.

Discussion

The murine model of MI is gaining popularity in cardiovascular research laboratories, and this study describes a reproducible and clinically relevant MI model. This protocol improves the LCA ligation process in several ways. To begin with, the use of injectable pre-operative anesthetics such as xylazine/ketamine or sodium pentobarbital^14,15 is avoided. Only isoflurane anesthesia was used, which helps enhance animal survival rates (>80% survival 28 days after .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
22 G catheter needle	Exel INT	26741	Thoracentesis
24 G catheter needle	Exel INT	26746	Endotracheal intubation
4-0 nylon suture	Covetrus	29263	Suturing of muscles and skin
8-0 nylon suture	S&T	3192	Ligation of LAD
Anesthetic Vaporizers	Vet equip	VE-6047	Anesthetic support
Animal physiology monitor	Fujifilm	VEVO 3100	Monitor heart rate,respiration rate and body temperature
Betadine solution	PBS animal health	11205	Antispetic
Buprenorphine	Covetrus	55175	Analgesic
Disecting microscope	OMANO	OM2300S-V7	Binocular
Electric razor	Wahl	79300-1001M	Shaving
Electrode gel	Parker Laboratories	W60698L	Electrically conductive gel
Ethanol	Decon Laboratories	22-032-601	Disinfectant
Forceps	FST	11065-07	Stainless Steel
Gauze	Curity	CAR-6339-PK	Sterile
Heat lamp	Satco	S4998	Post surgery care
Heating pad	Kent scientific	Surgi-M	Temperature control
Hot Bead sterilizer	Germinator 500	11503	Sterilization of surgical instrument
Isoflurane	Covetrus	29405	Anesthesia
Masson’s trichrome staining kit	Thermoscientific	87019	Measurement of cardiac Fibrosis
Micro Needle Holder	FST	12500-12	Stainless Steel
Micro scissors	FST	15000-02	Stainless Steel
Ophthalmic ointment	Dechra	Puralube Vet	Sterile occular lubricant
Scanning Gel	Parker Laboratories	Aquasonic 100	Aqueous ultrasound transmission gel
Scissors	FST	14060-11	Stainless Steel
Small Animal Laryngoscope	Penn-Century	Model LS-2-M	Illuminating the oropharynx
Small animal ventilator	Harvard apparatus	557058	Ventilator support
Surgical light	Cole parmer	41723	Illuminator Width (in): 7
Vevo 3100 preclinical imaging platform	Fujifilm	VEVO 3100	Echocardiography
VevoLAB software	Fujifilm	VevoLAB 3.2.6	Echocardiography data analysis