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Dual-Dye Optical Mapping of Hearts from RyR2R2474S Knock-In Mice of Catecholaminergic Polymorphic Ventricular Tachycardia
* These authors contributed equally
In This Article
Summary
This protocol introduces dual-dye optical mapping of mouse hearts obtained from wild-type and knock-in animals affected by catecholaminergic polymorphic ventricular tachycardia, including electrophysiological measurements of transmembrane voltage and intracellular Ca2+ transients with high temporal and spatial resolution.
Abstract
The pro-arrhythmic cardiac disorder catecholaminergic polymorphic ventricular tachycardia (CPVT) manifests as polymorphic ventricular tachycardia episodes following physical activity, stress, or catecholamine challenge, which can deteriorate into potentially fatal ventricular fibrillation. The mouse heart is a widespread species for modeling inherited cardiac arrhythmic diseases, including CPVT. Simultaneous optical mapping of transmembrane potential (Vm) and calcium transients (CaT) from Langendorff-perfused mouse hearts has the potential to elucidate mechanisms underlying arrhythmogenesis. Compared with the cellular level investigation, the optical mapping technique can test some electrophysiological parameters, such as the determination of activation, conduction velocity, action potential duration, and CaT duration. This paper presents the instrumentation setup and experimental procedure for high-throughput optical mapping of CaT and Vm in murine wild-type and heterozygous RyR2-R2474S/+ hearts, combined with programmed electrical pacing before and during the isoproterenol challenge. This approach has demonstrated a feasible and reliable method for mechanistically studying CPVT disease in an ex vivo mouse heart preparation.
Introduction
Inherited cardiac disorder catecholaminergic polymorphic ventricular tachycardia (CPVT) manifests as polymorphic ventricular tachycardia (PVT) episodes following physical activity, stress, or catecholamine challenge, which can deteriorate into potentially fatal ventricular fibrillation1,2,3,4. Recent evidence following its first report as a clinical syndrome in 1995 implicated mutations in seven genes, all involved in sarcoplasmic reticular (SR) store Ca2+ release in this condition: the most frequently reported RYR2 encod....
Protocol
Male 10 to 14-week-old wild-type mice or RyR2-R2474S/+ mice (C57BL/6 background) weighing 20-25 g are used for the experiments. All procedures have been approved by the animal care and use committee of Southwest Medical University, Sichuan, China (approval NO:20160930) in conformity with the national guidelines under which the institution operates.
1. Preparation
- Stock solutions
- Blebbistatin stock solution: Add 1 mL of 100% dimethyl sulfoxide (DMSO) in the original flask containing 2.924 mg of (-) blebbistatin powder to reach a concentration of 10 mM.
- Voltage indicator RH237 ....
Results
Optical mapping has been a popular approach in studying complex cardiac arrhythmias in the past decade. The optical mapping setup consists of an EMCCD camera, giving a sampling rate of up to 1,000 Hz and a spatial resolution of 74 x 74 µm for each pixel. It enables a rather high signal-noise ratio during signal sampling (Figure 1). Once the Langendorff-perfused heart reaches a stable state and the dye loading finishes, the heart is placed in the homoeothermic chamber under the illuminat.......
Discussion
Based on our experience, the keys to a successful dual-dye optical mapping of a mouse heart include a well-prepared solution and heart, dye loading, achieving the best signal-to-noise ratio, and reducing the motion artifact.
Preparation of solution
Krebs solution is essential for a successful heart experiment. MgCl2 and CaCl2 stock solutions (1 mol/L) are prepared in advance considering their water absorption and added to the Krebs solution after al.......
Disclosures
None of the authors has any conflicts of interest to declare.
Acknowledgements
This study is supported by the National Natural Science Foundation of China (81700308 to XO and 31871181 to ML, and 82270334 to XT), Sichuan Province Science and Technology Support Program (CN) (2021YJ0206 to XO, 23ZYZYTS0433, and 2022YFS0607 to XT, and 2022NSFSC1602 to TC) and State Key Laboratory for Chemistry and Molecular Engineering of Medicinal Resources (Guangxi Normal University) (CMEMR2017-B08 to XO), MRC (G10031871181 to ML02647, G1002082, ML), BHF (PG/14/80/31106, PG/16/67/32340, PG/12/21/29473, PG/11/59/29004 ML), BHF CRE at Oxford (ML) grants.
....Materials
| Name | Company | Catalog Number | Comments |
| 0.2 μm syringe filter | Medical equipment factory of Shanghai Medical Instruments Co., Ltd., Shanghai, China | N/A | To filter solution |
| 15 mL centrifuge tube | Guangzhou Jet Bio-Filtration Co., Ltd. China | CFT011150 | |
| 1 mL Pasteur pipette | Beijing Labgic Technology Co., Ltd. China | 00900026 | |
| 1 mL Syringe | B. Braun Medical Inc. | YZB/GER-5474-2014 | |
| 200 μL PCR tube | Sangon Biotech Co., Ltd. Shanghai. China | F611541-0010 | Aliquote the stock solutions to avoid repeated freezing and thawing |
| 50 mL centrifuge tube | Guangzhou Jet Bio-Filtration Co., Ltd. China | CFT011500 | Store Tyrode's solution at 4 °C for follow-up heart isolation |
| 585/40 nm filter | Chroma Technology | N/A | Filter for calcium signal |
| 630 nm long-pass filter | Chroma Technology | G15604AJ | Filter for voltage signal |
| Avertin (2,2,2-tribromoethanol) | Sigma-Aldrich Poole, Dorset, United Kingdom | T48402-100G | To minimize suffering and pain reflex |
| Blebbistatin | Tocris Bioscience, Minneapolis, MN, United States | SLBV5564 | Excitation-contraction uncoupler to eliminate motion artifact during mapping |
| CaCl2 | Sigma-Aldrich, St. Louis, MO, United States | SLBK1794V | For Tyrode's solution |
| Custom-made thermostatic bath | MappingLab, United Kingdom | TBC-2.1 | To keep temperature of perfusion solution |
| Dimethyl sulfoxide (DMSO) | Sigma-Aldrich | (RNBT7442) | Solvent for dyes |
| Dumont forceps | Medical equipment factory of Shanghai Medical Instruments Co.,Ltd.,Shanghai, China | YAF030 | |
| ElectroMap software | University of Birmingham | N/A | Quantification of electrical parameters |
| EMCCD camera | Evolve 512 Delta, Photometrics, Tucson, AZ, United States | A18G150001 | Acquire images for optical signals |
| ET525/36 sputter coated filter | Chroma Technology | 319106 | Excitation filter |
| Glucose | Sigma-Aldrich, St. Louis, MO, United States | SLBT4811V | For Tyrode's solution |
| Heparin Sodium | Chengdu Haitong Pharmaceutical Co., Ltd., Chengdu, China | (H51021209) | To prevent blood clots in the coronary artery |
| Iris forceps | Medical equipment factory of Shanghai Medical Instruments Co.,Ltd.,Shanghai, China | YAA010 | |
| Isoproterenol | MedChemExpress, Carlsbad, CA, United States | HY-B0468/CS-2582 | |
| KCl | Sigma-Aldrich, St. Louis, MO, United States | SLBS5003 | For Tyrode's solution |
| MacroLED | Cairn Research, Faversham, United Kingdom | 7355/7356 | The excitation light of fluorescence probes |
| MacroLED light source | Cairn Research, Faversham, United Kingdom | 7352 | Control the LEDs |
| Mayo scissors | Medical equipment factory of Shanghai Medical Instruments Co.,Ltd.,Shanghai, China | YBC010 | |
| MetaMorph | Molecular Devices | N/A | Optical signals sampling |
| MgCl2 | Sigma-Aldrich, St. Louis, MO, United States | BCBS6841V | For Tyrode's solution |
| MICRO3-1401 | Cambridge Electronic Design limited, United Kingdom | M5337 | Connect the electrical stimulator and Spike2 software |
| MyoPacer EP field stimulator | Ion Optix Co, Milton, MA, United States | S006152 | Electric stimulator |
| NaCl | Sigma-Aldrich, St. Louis, MO, United States | SLBS2340V | For Tyrode's solution |
| NaH2PO4 | Sigma-Aldrich, St. Louis, MO, United States | BCBW9042 | For Tyrode's solution |
| NaHCO3 | Sigma-Aldrich, St. Louis, MO, United States | SLBX3605 | For Tyrode's solution |
| NeuroLog System | Digitimer | NL905-229 | For ECG amplifier |
| OmapScope5 | MappingLab, United Kingdom | N/A | Calcium alternans and arrhythmia analysis |
| Ophthalmic scissors | Huaian Teshen Medical Instruments Co., Ltd., Jiang Su, China | T4-3904 | |
| OptoSplit | Cairn Research, Faversham, United Kingdom | 6970 | Split the emission light for detecting Ca2+ and Vm simultaneously |
| Peristalic pump | Longer Precision Pump Co., Ltd., Baoding, China, | BT100-2J | To pump the solution |
| Petri dish | BIOFIL | TCD010060 | |
| Pluronic F127 | Invitrogen, Carlsbad, CA, United States | 1899021 | To enhance the loading with Rhod2AM |
| RH237 | Thermo Fisher Scientifific, Waltham, MA, United States | 1971387 | Voltage-sensitive dye |
| Rhod-2 AM | Invitrogen, Carlsbad, CA, United States | 1890519 | Calcium indicator |
| Silica gel tube | Longer Precision Pump Co., Ltd., Baoding, China, | 96402-16 | Connect with the peristaltic pump |
| Silk suture | Yuankang Medical Instrument Co., Ltd.,Yangzhou, China | 20172650032 | To fix the aorta |
| Spike2 | Cambridge Electronic Design limited, United Kingdom | N/A | To record and analyze ECG data |
| Stimulation electrode | MappingLab, United Kingdom | SE1600-35-2020 | |
| T510lpxr | Chroma Technology | 312461 | For light source |
| T565lpxr | Chroma Technology | 321343 | For light source |
References
- Priori, S. G., Chen, S. R. Inherited dysfunction of sarcoplasmic reticulum Ca2+ handling and arrhythmogenesis. Circulation Research. 108 (7), 871-883 (2011).
- Goddard, C. A., et al.
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