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Abstract

Introduction

Protocol

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References

Medicine

Myocardial Infarction in Neonatal Mice, A Model of Cardiac Regeneration

Published: May 24th, 2016

DOI:

10.3791/54100

1Department of Physiology and Pharmacology, Western University

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 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.

Myocardial infarction (MI) is a leading cause of death worldwide, and remains responsible for about one third of heart failure cases1. While the advent of percutaneous intervention and continuous optimization of the use of thrombolytics has increased reperfusion following MI, cardiomyocyte death and loss of contractile myocardium nevertheless occurs. There also remain large numbers of "no-option" patients who are not candidates for or do not see benefit from these interventions. These patients continue to experience disabling ischemia leading to scar formation and deleterious ventricular remodeling as a mechanism of infarct healing. This process ult....

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Breeding pairs of C57BL/6 and CD-1 IG-S mice were purchased from Charles River. Animals used in this study were handled in accordance with the guidelines of the Canadian Council on Animal Care, and study protocols were approved by the Animal Use Subcommittee at Western University, London, Canada.

1. Animal Care

  1. After birthing is complete and pups have been initially breast-fed by their mother for a few hr, place them in a different cage with a CD-1 foster mother. CD-1 mothers displ.......

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The myocardial infarction procedure at P1 can be completed in 10 - 15 min and has a mortality rate of 7.8% (5 out of 64 pups). After surgery, mice recover from hypothermic anesthesia within the next 5 - 20 min (time of recovery depends on body temperature reached during anesthesia and speed of surgeon). When using P7 pups (for comparison with a non-regenerative myocardium), a longer period of cooling is required to reach torpor. P7 pups are much larger and have more difficulty recovering .......

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The surgical LAD ligation demonstrated herein is a reliable method to produce MI in neonatal mice. This model provides researchers with a reproducible model with which to study mammalian heart regeneration. Visualization of the coronary vasculature is a key component of this method, ensuring correct suture placement and thus guaranteeing reproducibility. While adult mice do not possess poikilothermic capabilities, the body temperature and metabolic rate of neonatal mice is closely associated with ambient temperature. Fur.......

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This study was supported by an operating grant from the Canadian Institutes of Health Research (CIHR) to Q.F. (grant #MOP-119600).

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Name Company Catalog Number Comments
8-0 Nylon Suture Microsurgery Instruments 8-0 Nylon
11-0 Nylon Suture Shanghai Pudong Medical Products Co Ltd H1101
Fine Scissors Fine Science Tools 14058-09
Small forceps Fine Science Tools 11063-07
Micro Needle Holder Fine Science Tools 12060-02
Zeiss Opmi 6s/S3 Microscope Zeiss 300002
Isoflurane Baxter CA2L9100
Isoflurane Chamber Made in Feng laboratory
Bead Sterilizer Fine Science Tools 18000-45
2,3,5-Triphenyltetraolium chloride (TTC) Sigma T8877
Stereomicroscope SteREO Discovery. V8 Zeiss 435400
AxioVision 8.0 Zeiss
Axiocam Icc5 Zeiss 426554
Heat pad Sunbeam  731A0-CN
Sterile Gloves VWR 414004-430
Gauze Sponges Ducare 90212
Ice

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