An Intact Pericardium Ischemic Rodent Model

Summary

This protocol outlines the steps for inducing myocardial infarction in mice while preserving the pericardium and its contents.

Abstract

This protocol has shown that the pericardium and its contents play an essential anti-fibrotic role in the ischemic rodent model (coronary ligation to induce myocardial injury). The majority of pre-clinical myocardial infarction models require the disruption of pericardial integrity with loss of the homeostatic cellular milieu. However, recently a methodology has been developed by us to induce myocardial infarction, which minimizes pericardial damage and retains the heart's resident immune cell population. An improved cardiac functional recovery in mice with an intact pericardial space following coronary ligation has been observed. This method provides an opportunity to study inflammatory responses in the pericardial space following myocardial infarction. Further development of the labeling techniques can be combined with this model to understand the fate and function of pericardial immune cells in regulating the inflammatory mechanisms that drive remodeling in the heart, including fibrosis.

Introduction

To this day, cardiovascular disease (CVD) is recognized as the leading cause of death globally, resulting in a significant financial burden and reduction in patient quality of life¹. Coronary artery disease (CAD) is a sub-type of CVD and plays an essential role in the development of myocardial infarction (MI), which is a chief contributor to mortality. By definition, MI results from irreversible injury to the myocardial tissue due to prolonged conditions of ischemia and hypoxia. Myocardial tissue lacks regeneration capacity, so injuries are permanent and result in the replacement of heart muscle with a fibrotic scar that can be initially protec....

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Protocol

Male and female C57BL/6J mice between 8-14 weeks of age were used for these experiments. This protocol has received ethical approval from the Animal Care Committee at the University of Calgary and follows all animal care guidelines.

1. Mouse preparation and surgery

1. Sterilize surgical tools (via bead sterilizer or autoclave).
2. Weigh mouse for presurgical weight and analgesic dose.
3. Place the mouse in an induction box with 4% isoflurane and 800 mL/min of oxygen. Confirm the anesthetic plane by pinching the toes and observing the animal for lack of reflex.
4. Inject analgesic subcutaneously (0.1 mg/kg of Bu....

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Results

This modified coronary ligation model has been optimized to achieve reproducibility and animal survival. However, due to the significant injury induced in the heart, some expected intra-operative and post-operative mortality are associated with the procedure. The standard mortality is typically higher in males (~25-35%) than in females (~ 10-15%).

Successful induction of an MI with the modified coronary ligation should be evident by changes in the heart's functional parameters and structur.......

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Discussion

Inducing an MI in a closed pericardium in rodents is unique and can have potentially significant applications. The procedure relies heavily on the surgeon's familiarity with the rodent model and rodent cardiac anatomy. Success is also dependent on the care given during three critical steps: intercostal muscle incision and rib retraction (Steps 1.11-1.13), creating the infarct (Step 1.17 ), and animal recovery (Steps 1.22-1.24).

The thoracotomy must be done diligently to avoid puncturing or.......

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Materials

Name	Company	Catalog Number	Comments
Steri-350 Bead Sterilizer	Inotech	NC9449759
10% Formalin	Millipore Sigma	HT501128-4L
40 µm Cell strainer	VWR	CA21008-949	Falcon, 352340
70 µm Cell strainer	VWR	CA21008-952	Falcon, 352350
ACK Lysis Buffer	Thermo Fisher	A1049201
BD Insyte-W Catheter Needle 24 G X 3/4"	CDMV Inc	108778
Betadine (10% povidone-iodine topical solution)	CDMV Inc	104826
Blunt Forceps	Fine Science Tools	FST 11000-12
BNP Ophthalmic Ointment	CDMV Inc	17909
Castroviejo Needle Driver	Fine Science Tools	FST 12061-01
Centrifuge 5810R	Eppendorf	22625101
Collagenase I	Millipore Sigma	SCR103
Collagenase XI	Millipore Sigma	C7657
Covidien 5-0 Polysorb Suture - CV-11 taper needle	Medtronic Canada	GL-890
Covidien 5-0 Polysorb Suture - PC-13 cutting needle	Medtronic Canada	SL-1659
Curved Blunt Forceps	Fine Science Tools	FST 11009-13
Dako Mounting Medium	Agilen	CS70330-2
DNase I	Millipore Sigma	11284932001
Ethanol, 100%	Millipore Sigma	MFCD00003568
Ethicon 8-0 Ethilon Suture - BV-130-4 taper needle	Johnson & Johnson Inc.	2815G
Fiber-Optic Light	Nikon	2208502
Fine Forceps	Fine Science Tools	FST 11150-10
Fluoresbrite® YG Carboxylate Microspheres 1.00 µm	Polysciences, Inc.	15702
Geiger Thermal Cautery Unit	World Precision Instruments	501293	Model 150-ST
Hyaluronidase	Millipore Sigma	H4272
Isofluorane Vaporizer	Harvard Apparatus	75-0951
Isoflurane USP, 250 mL	CDMV Inc	108737
Magnetic Fixator Retraction System	Fine Science Tools	18200-20
MX550D- 40 MHz probe	Fujifilm- Visual Sonics
Needle Driver	Fine Science Tools	FST 12002-12
PE-10 Tubing	Braintree Scienctific, Inc.	PE10 50 FT
Scissors	Fine Science Tools	FST 14184-09
SMZ-1B Stereo Microscope	Nikon	SMZ1-PS
VentElite Small Animal Ventilator	Harvard Apparatus	55-7040
Vetergesic (10 mL, 0.3mg/mL buprenorphine))	CDMV Inc	124918	controlled drug
Vevo 2100 Software	Fujifilm-Visual Sonics