Apical Resection Mouse Model to Study Early Mammalian Heart Regeneration

Summary

A step-by-step video protocol of apical resection is demonstrated in this study. Apical resection is a recently highlighted surgical approach in mammalian heart regeneration research. This study may promote the application of apical resection as a standard methodology in research into the mechanism underlying heart regeneration.

Abstract

Cardiovascular disease plagues the whole world due to intensive lifestyle changes. Heart regeneration holds great promise for repairing and restoring cardiomyocytes lost due to injury and disease. In contrast to the robust cardiac regeneration of certain lower vertebrates, adult mammalian hearts typically show minimal capacity for heart regeneration and repair. However, recent studies have sparked considerable scientific interest with the finding that, between postnatal day 1 to 7 (P1 to P7), the neonatal mouse heart retains significant regenerative potential after apical resection (i.e., surgical amputation and exposure of left ventricular apex). One major controversy over this finding might be due to the diverse surgery-related procedures used in efforts to replicate or expand upon this important finding. These instructions dynamically present the materials and methodology for apical resection in a mouse model. The salient steps of this rodent survival surgery involve hypothermia anesthesia, thoracotomy, surgical amputation of heart ventricular apex, and suture and recovery of mice. The approach described could expand the application of the apical resection mouse model for cardiovascular research.

Introduction

Prolonged human life span leads to various aging- and lifestyle-related diseases, including heart failure, a leading cause of mortality. However, without replacement of lost or dysfunctional cardiac muscle cells, current therapeutics can only transiently improve cardiac function^{1, 2}. Thus, it is necessary to discover and develop innovative strategies for cardiac regeneration and repair. The adult mammalian heart has limited regenerative potential. Studies from lower vertebrates, such as urodele amphibians and teleost fish, have provided unprecedented insights into the molecular and cellular mechanisms underlying heart regeneration^{3, 4}. Recently, ....

Protocol

All mouse experiments were approved by the Animal Care and Use Program at the National Institutes of Health (NIH) with protocol number H0083R3. The NHLBI IACUC approved the protocol without analgesics.

1. Hypothermia Anesthesia in Neonatal Mice

1. Sterilize sponges and surgical equipment in an autoclave before surgery. Prepare all the surgical materials and switch on a hot bead sterilizer 15-20 min in advance to reach 240°C to 270°C.
2. Transfer all C57BL/6 pups (age P1) from their nursing mother to a clean mouse cage with fresh bedding and nesting materials. Once the pups are taken into a surgery room, p....

Results

Mouse pups were euthanized 1, 2, and 21 days post-apical resection, and their hearts were collected for H&E and Masson's Trichrome stain. Blue color in Masson's Trichrome stain indicates the deposition of epicardial extracellular matrix⁵. With successful apical resection, a blood clot is effectively formed to seal the LV one day post-apical resection, as shown in Figure 1A. A gradual resorption of the blood clot and early cardiac fibrosis is observed, and replacement by myocardial tissue o.......

Discussion

Cardiac regeneration shows potential for the treatment and prevention of heart failure^{1, 2}. Animal models are indispensable and play a critical role in understanding how cardiac regeneration occurs^3-6. Many amphibians and fish regenerate heart tissue in response to injury, providing insight into our understanding of human cardiovascular disease^{13, 14}. In terms of evolution, however, the pathophysiology should be more conserved between a mouse model and humans. Heart regeneration in mammal.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Olsen-Hegar Needle Holders with Scissors, 1.5 mm	Fine Science Tools	12002-12
Vannas Spring Scissors - 2 mm Cutting Edge	Fine Science Tools	15000-03	Iridectomy scissors
Hot Bead Sterilizer	Fine Science Tools	18000-45
Iris Forceps, Straight, Serrated	Fine Science Tools	11064-07
Iris Forceps, Curved, Serrated	Fine Science Tools	11065-07
Shea Scissors - Curved/Blunt-Blunt/12cm	Fine Science Tools	14105-12
Round Handled Suture Tying Forceps, Straight	Fine Science Tools	18025-12
Round Handled Vannas Spring Scissors	Fine Science Tools	15400-12
Fine Hemostat	Fine Science Tools	13007-12
Magnifying Lamp	Luxolamp Corp	IM120
Heating lamp	Brandt Equipment llc	51152/3
6-0 Prolene sutures	Ethicon	8889H
Skin glue-Vetbond Tissue Adhesive	3M	1469
Sterile Cotton Tipped Applicators	Dynarex	4305
WEBCOL Alcohol Prep Pad	Covidien	6818	Medium 2 PLY, 200/BOX, Satured with 70% Isopropyl Alcohol
Curity All Purpose Sponges	Covidien	9024	Non-woven 4 PLY, 4"x4" (10.2cm×10.2cm)
Bench top protector sheet	KIMTECH SCIENCE	7546	18" x 19.5" (45.72cm x 49.53cm) x 50
0.9% Sodium Chloride, 250ml	Hospira Inc.	NDC 0409-6138-22
Betadine Solution Swabsticks	Purdue Products L.P.	NDC 67618-153-03
Autoclave	TOMY Digital Biology	SX-700	HIGH-PRESSURE STEAM STERILIZER
Slide scanner	HAMAMATSU	NanoZoomer 2.0-RS