Name: dual-dye optical mapping of hearts from ryr2r2474s knock-in mice of catecholaminergic polymorphic ventricular tachycardia
Uploaded: 2023-12-22T12:20:00
Description: Watch this Scientific Journal Video about Dual-Dye Optical Mapping of Hearts from RyR2R2474S Knock-In Mice of Catecholaminergic Polymorphic Ventricular Tachycardia at JoVE.com

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.

Male 10&#160;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
<ol>
	<li>Stock solutions
	<ol>
		<li>Blebbistatin stock solution: Add 1 mL of 100% dimethyl sulfox...

<ol>
	<li>Priori, S. G., Chen, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inherited+dysfunction+of+sarcoplasmic+reticulum+Ca2++handling+and+arrhythmogenesis.">Inherited dysfunction of sarcoplasmic reticulum Ca2+ handling and arrhythmogenesis.</a> Circulation Research. 108 (7), 871-883 (2011).</li><li>Goddard, C. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiological+consequences+of+the+P2328S+mutation+in+the+ryanodine+receptor+(RyR2)+gene+in+genetically+modified+murine+hearts.">Physiological consequences of the P2328S mutation in the ryanodine receptor (RyR2) gene in genetically modified murine hearts.</a> Acta Physiologica. 194 (2), 123-140 (2008).</li><li>Sabir, I. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternans+in+genetically+modified+langendorff-perfused+murine+hearts+modeling+catecholaminergic+polymorphic+ventricular+tachycardia.">Alternans in genetically modified langendorff-perfused murine hearts modeling catecholaminergic polymorphic ventricular tachycardia.</a> Frontiers in Physiology. 1, 126 (2010).</li><li>Zhang, Y., Matthews, G. D., Lei, M., Huang, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abnormal+Ca2++homeostasis,+atrial+arrhythmogenesis,+and+sinus+node+dysfunction+in+murine+hearts+modeling+RyR2+modification.">Abnormal Ca2+ homeostasis, atrial arrhythmogenesis, and sinus node dysfunction in murine hearts modeling RyR2 modification.</a> Frontiers in Physiology. 4, 150 (2013).</li><li>Leenhardt, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Catecholaminergic+polymorphic+ventricular+tachycardia+in+children.+A+7-year+follow-up+of+21+patients.">Catecholaminergic polymorphic ventricular tachycardia in children. A 7-year follow-up of 21 patients.</a> Circulation. 91 (5), 1512-1519 (1995).</li><li>Priori, S. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mutations+in+the+cardiac+ryanodine+receptor+gene+(hRyR2)+underlie+catecholaminergic+polymorphic+ventricular+tachycardia.">Mutations in the cardiac ryanodine receptor gene (hRyR2) underlie catecholaminergic polymorphic ventricular tachycardia.</a> Circulation. 103 (2), 196-200 (2001).</li><li>Wehrens, X. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FKBP12.6+deficiency+and+defective+calcium+release+channel+(ryanodine+receptor)+function+linked+to+exercise-induced+sudden+cardiac+death.">FKBP12.6 deficiency and defective calcium release channel (ryanodine receptor) function linked to exercise-induced sudden cardiac death.</a> Cell. 113 (7), 829-840 (2003).</li><li>Novak, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+abnormalities+in+iPSC-derived+cardiomyocytes+generated+from+CPVT1+and+CPVT2+patients+carrying+ryanodine+or+calsequestrin+mutations.">Functional abnormalities in iPSC-derived cardiomyocytes generated from CPVT1 and CPVT2 patients carrying ryanodine or calsequestrin mutations.</a> Journal of Cellular and Molecular Medicine. 19 (8), 2006-2018 (2015).</li><li>Napolitano, C., Mazzanti, A., Bloise, R., Priori, S. G., Adam, M. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CACNA1C-related+disorders.">CACNA1C-related disorders.</a> GeneReviews. , (1993).</li><li>Makita, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+calmodulin+mutations+associated+with+congenital+arrhythmia+susceptibility.">Novel calmodulin mutations associated with congenital arrhythmia susceptibility.</a> Circulation. Cardiovascular Genetics. 7 (4), 466-474 (2014).</li><li>Gomez-Hurtado, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+CPVT-associated+calmodulin+mutation+in+CALM3+(CALM3-A103V)+activates+arrhythmogenic+Ca+waves+and+sparks.">Novel CPVT-associated calmodulin mutation in CALM3 (CALM3-A103V) activates arrhythmogenic Ca waves and sparks.</a> Circulation, Arrhythmia and Electrophysiology. 9 (8), (2016).</li><li>Wleklinski, M. J., Kannankeril, P. J., Knollmann, B. 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(148), e59663 (2019).</li><li>Choi, B. R., Salama, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+maps+of+optical+action+potentials+and+calcium+transients+in+guinea-pig+hearts:+mechanisms+underlying+concordant+alternans.">Simultaneous maps of optical action potentials and calcium transients in guinea-pig hearts: mechanisms underlying concordant alternans.</a> Journal of Physiology. 529, 171-188 (2000).</li><li>Rybashlykov, D., Brennan, J., Lin, Z., Efimov, I. 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(148), e59663 (2019).</li><li>He, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+dataset+of+dual+calcium+and+voltage+optical+mapping+in+healthy+and+hypertrophied+murine+hearts.">A dataset of dual calcium and voltage optical mapping in healthy and hypertrophied murine hearts.</a> Scientific Data. 8 (1), 314 (2021).</li><li>Lei, M., Huang, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+arrhythmogenesis:+a+tale+of+two+clocks.">Cardiac arrhythmogenesis: a tale of two clocks.</a> Cardiovascular Research. 116 (14), e205-e209 (2020).</li><li>Mal Baudot, ., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concomitant+genetic+ablation+of+L-type+Cav1.3+&#945;1D+and+T-type+Cav3.1+&#945;1G+Ca2++channels+disrupts+heart+automaticity.">Concomitant genetic ablation of L-type Cav1.3 &#945;1D and T-type Cav3.1 &#945;1G Ca2+ channels disrupts heart automaticity.</a> Scientific Reports. 10 (1), 18906 (2020).</li><li>Dai, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ZO-1+regulates+intercalated+disc+composition+and+atrioventricular+node+conduction.">ZO-1 regulates intercalated disc composition and atrioventricular node conduction.</a> Circulation Research. 127 (2), e28-e43 (2020).</li><li>Glukhov, A. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calsequestrin+2+deletion+causes+sinoatrial+node+dysfunction+and+atrial+arrhythmias+associated+with+altered+sarcoplasmic+reticulum+calcium+cycling+and+degenerative+fibrosis+within+the+mouse+atrial+pacemaker+complex1.">Calsequestrin 2 deletion causes sinoatrial node dysfunction and atrial arrhythmias associated with altered sarcoplasmic reticulum calcium cycling and degenerative fibrosis within the mouse atrial pacemaker complex1.</a> European Heart Journal. 36 (11), 686-697 (2015).</li><li>Torrente, A. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Burst+pacemaker+activity+of+the+sinoatrial+node+in+sodium-calcium+exchanger+knockout+mice.">Burst pacemaker activity of the sinoatrial node in sodium-calcium exchanger knockout mice.</a> Proceedings of the National Academy of Sciences of the United States of America. 112 (31), 9769-9774 (2015).</li><li>Yang, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ventricular+SK2+upregulation+following+angiotensin+II+challenge:+Modulation+by+p21-activated+kinase-1.">Ventricular SK2 upregulation following angiotensin II challenge: Modulation by p21-activated kinase-1.</a> Journal of Molecular and Cellular Cardiology. 164, 110-125 (2022).</li><li>Dong, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+protocol+for+dual+calcium-voltage+optical+mapping+in+murine+sinoatrial+preparation+with+optogenetic+pacing.">A protocol for dual calcium-voltage optical mapping in murine sinoatrial preparation with optogenetic pacing.</a> Frontiers in Physiology. 10, 954 (2019).</li><li>He, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+protocol+for+transverse+cardiac+slicing+and+optical+mapping+in+murine+heart.">A protocol for transverse cardiac slicing and optical mapping in murine heart.</a> Frontiers in Physiology. 10, 755 (2019).</li><li>Hoeker, G. 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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...

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 encoding ryanodine receptor 2 (RyR2) of Ca2+ release channels5,6, FKBP12.67, CASQ2 encoding cardiac calsequestrin8, TRDN encoding the junctional SR protein triadin9, and CALM19, CALM210, and CALM3 identically encoding calmodulin11,12. These genotypic patterns attribute the arrhythmic events to the unregulated pathological release of SR store Ca2+12.
Spontaneous Ca2+ release from SR can be detected as Ca2+ sparks or Ca2+ waves, which activates the Na+/Ca2+ exchanger (NCX). The exchanger of one Ca2+ for three Na+ generates an inward current, which speeds up the diastolic depolarization and drives the membrane voltage to the threshold of action potential (AP). In RyR2 knock-in mice, the increased activity of RyR2R4496C in the sinoatrial node (SAN) leads to an unanticipated decrease in SAN automaticity by Ca2+-dependent decrease of ICa,L and SR Ca2+ depletion during diastole, identifying subcellular pathophysiologic alterations contributing to the SAN dysfunction in CPVT patients13,14. Occurrence of the related cardiomyocyte cytosolic Ca2+ waves is more likely following increases in background cytosolic [Ca2+] following RyR sensitization by catecholamine, including isoproterenol (ISO), challenge.
Detailed kinetic changes in Ca2+ signaling following RyR2-mediated Ca2+ release in response to action potential (AP) activation that may be the cause of the observed ventricular arrhythmias in intact cardiac CPVT models remain to be determined for the full range of reported RyR2 genotypes12. This paper presents the instrumentation setup and experimental procedure for high-throughput mapping of Ca2+ signals and transmembrane potentials (Vm) in murine wild-type (WT) and heterozygous RyR2-R2474S/+ hearts, combined with programmed electrical pacing before and after isoproterenol challenge. This protocol provides a method for the mechanistic study of CPVT disease in isolated mouse hearts.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.2 &#956;m syringe filter</td>
			<td>Medical equipment factory of Shanghai Medical Instruments Co., Ltd., Shanghai, China</td>
			<td>N/A</td>
			<td>To filter solution</td>
		</tr>
		<tr>
			<td>15 mL centrifuge tube</td>
			<td>Guangzhou Jet Bio-Filtration Co., Ltd. China</td>
			<td>CFT011150</td>
			<td></td>
		</tr>
		<tr>
			<td>1 mL Pasteur pipette</td>
			<td>Beijing Labgic Technology Co., Ltd. China</td>
			<td>00900026</td>
			<td></td>
		</tr>
		<tr>
			<td>1 mL Syringe</td>
			<td>B. Braun Medical Inc.</td>
			<td>YZB/GER-5474-2014</td>
			<td></td>
		</tr>
		<tr>
			<td>200 &#956;L PCR tube</td>
			<td>Sangon Biotech Co., Ltd. Shanghai. China</td>
			<td>F611541-0010</td>
			<td>Aliquote the stock solutions&#160; to avoid repeated freezing and thawing</td>
		</tr>
		<tr>
			<td>50 mL centrifuge tube</td>
			<td>Guangzhou Jet Bio-Filtration Co., Ltd. China</td>
			<td>CFT011500</td>
			<td>Store Tyrode&#39;s solution at 4 &#176;C for follow-up heart isolation</td>
		</tr>
		<tr>
			<td>585/40 nm filter</td>
			<td>Chroma Technology</td>
			<td>N/A</td>
			<td>Filter for calcium signal</td>
		</tr>
		<tr>
			<td>630 nm long-pass filter</td>
			<td>Chroma Technology</td>
			<td>G15604AJ</td>
			<td>Filter for voltage signal</td>
		</tr>
		<tr>
			<td>Avertin (2,2,2-tribromoethanol)</td>
			<td>Sigma-Aldrich Poole, Dorset, United Kingdom</td>
			<td>T48402-100G</td>
			<td>To minimize suffering and pain reflex</td>
		</tr>
		<tr>
			<td>Blebbistatin</td>
			<td>Tocris Bioscience, Minneapolis, MN, United States</td>
			<td>SLBV5564</td>
			<td>Excitation-contraction uncoupler to&#160; eliminate motion artifact during mapping</td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Sigma-Aldrich, St. Louis, MO, United States</td>
			<td>SLBK1794V</td>
			<td>For Tyrode&#39;s solution</td>
		</tr>
		<tr>
			<td>Custom-made thermostatic bath</td>
			<td>MappingLab, United Kingdom</td>
			<td>TBC-2.1</td>
			<td>To keep temperature of perfusion solution</td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide (DMSO)</td>
			<td>Sigma-Aldrich</td>
			<td>(RNBT7442)</td>
			<td>Solvent for dyes</td>
		</tr>
		<tr>
			<td>Dumont forceps</td>
			<td>Medical equipment factory of Shanghai Medical Instruments Co.,Ltd.,Shanghai, China</td>
			<td>YAF030</td>
			<td></td>
		</tr>
		<tr>
			<td>ElectroMap software</td>
			<td>University of Birmingham</td>
			<td>N/A</td>
			<td>Quantification of electrical parameters</td>
		</tr>
		<tr>
			<td>EMCCD camera</td>
			<td>Evolve 512 Delta, Photometrics, Tucson, AZ, United States</td>
			<td>A18G150001</td>
			<td>Acquire images for optical signals</td>
		</tr>
		<tr>
			<td>ET525/36 sputter coated filter</td>
			<td>Chroma Technology</td>
			<td>319106</td>
			<td>Excitation filter</td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma-Aldrich, St. Louis, MO, United States</td>
			<td>SLBT4811V</td>
			<td>For Tyrode&#39;s solution</td>
		</tr>
		<tr>
			<td>Heparin Sodium</td>
			<td>Chengdu Haitong Pharmaceutical Co., Ltd., Chengdu, China</td>
			<td>(H51021209)</td>
			<td>To prevent blood clots in the coronary artery</td>
		</tr>
		<tr>
			<td>&#160;Iris forceps</td>
			<td>Medical equipment factory of Shanghai Medical Instruments Co.,Ltd.,Shanghai, China</td>
			<td>YAA010</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoproterenol</td>
			<td>MedChemExpress, Carlsbad, CA, United States</td>
			<td>HY-B0468/CS-2582</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma-Aldrich, St. Louis, MO, United States</td>
			<td>SLBS5003</td>
			<td>For Tyrode&#39;s solution</td>
		</tr>
		<tr>
			<td>MacroLED</td>
			<td>Cairn Research, Faversham, United Kingdom</td>
			<td>7355/7356</td>
			<td>The excitation light of fluorescence probes</td>
		</tr>
		<tr>
			<td>MacroLED light source</td>
			<td>Cairn Research, Faversham, United Kingdom</td>
			<td>7352</td>
			<td>Control the LEDs</td>
		</tr>
		<tr>
			<td>Mayo scissors</td>
			<td>Medical equipment factory of Shanghai Medical Instruments Co.,Ltd.,Shanghai, China</td>
			<td>YBC010</td>
			<td></td>
		</tr>
		<tr>
			<td>MetaMorph</td>
			<td>Molecular Devices</td>
			<td>N/A</td>
			<td>Optical signals sampling</td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Sigma-Aldrich, St. Louis, MO, United States</td>
			<td>BCBS6841V</td>
			<td>For Tyrode&#39;s solution</td>
		</tr>
		<tr>
			<td>MICRO3-1401</td>
			<td>Cambridge Electronic Design limited, United Kingdom</td>
			<td>M5337</td>
			<td>Connect the electrical stimulator and Spike2 software</td>
		</tr>
		<tr>
			<td>MyoPacer EP field stimulator</td>
			<td>Ion Optix Co, Milton, MA, United States</td>
			<td>S006152</td>
			<td>Electric stimulator</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma-Aldrich, St. Louis, MO, United States</td>
			<td>SLBS2340V</td>
			<td>For Tyrode&#39;s solution</td>
		</tr>
		<tr>
			<td>NaH2PO4&#160;</td>
			<td>Sigma-Aldrich, St. Louis, MO, United States</td>
			<td>BCBW9042</td>
			<td>For Tyrode&#39;s solution</td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Sigma-Aldrich, St. Louis, MO, United States</td>
			<td>SLBX3605</td>
			<td>For Tyrode&#39;s solution</td>
		</tr>
		<tr>
			<td>NeuroLog System</td>
			<td>Digitimer</td>
			<td>NL905-229</td>
			<td>For ECG amplifier</td>
		</tr>
		<tr>
			<td>OmapScope5</td>
			<td>MappingLab, United Kingdom</td>
			<td>N/A</td>
			<td>Calcium alternans and arrhythmia analysis</td>
		</tr>
		<tr>
			<td>Ophthalmic scissors</td>
			<td>Huaian Teshen Medical Instruments Co., Ltd., Jiang Su, China</td>
			<td>T4-3904</td>
			<td></td>
		</tr>
		<tr>
			<td>OptoSplit</td>
			<td>Cairn Research, Faversham, United Kingdom</td>
			<td>6970</td>
			<td>Split the emission light for detecting Ca2+ and Vm&#160; simultaneously</td>
		</tr>
		<tr>
			<td>Peristalic pump</td>
			<td>Longer Precision Pump Co., Ltd., Baoding, China,</td>
			<td>BT100-2J</td>
			<td>To pump the solution</td>
		</tr>
		<tr>
			<td>Petri dish</td>
			<td>BIOFIL</td>
			<td>TCD010060</td>
			<td></td>
		</tr>
		<tr>
			<td>Pluronic F127</td>
			<td>Invitrogen, Carlsbad, CA, United States</td>
			<td>1899021</td>
			<td>To enhance the loading with Rhod2AM</td>
		</tr>
		<tr>
			<td>RH237</td>
			<td>Thermo Fisher Scientifific, Waltham, MA, United States</td>
			<td>1971387</td>
			<td>Voltage-sensitive dye</td>
		</tr>
		<tr>
			<td>Rhod-2 AM</td>
			<td>Invitrogen, Carlsbad, CA, United States</td>
			<td>1890519</td>
			<td>Calcium indicator</td>
		</tr>
		<tr>
			<td>Silica gel tube</td>
			<td>Longer Precision Pump Co., Ltd., Baoding, China,</td>
			<td>96402-16</td>
			<td>Connect with the peristaltic pump</td>
		</tr>
		<tr>
			<td>Silk suture</td>
			<td>Yuankang Medical Instrument Co., Ltd.,Yangzhou, China</td>
			<td>20172650032</td>
			<td>To fix the aorta</td>
		</tr>
		<tr>
			<td>Spike2</td>
			<td>Cambridge Electronic Design limited, United Kingdom</td>
			<td>N/A</td>
			<td>To record and analyze ECG data</td>
		</tr>
		<tr>
			<td>Stimulation electrode</td>
			<td>MappingLab, United Kingdom</td>
			<td>SE1600-35-2020</td>
			<td></td>
		</tr>
		<tr>
			<td>T510lpxr</td>
			<td>Chroma Technology</td>
			<td>312461</td>
			<td>For light source</td>
		</tr>
		<tr>
			<td>T565lpxr</td>
			<td>Chroma Technology</td>
			<td>321343</td>
			<td>For light source</td>
		</tr>
	</tbody>
</table>

dual-dye optical mapping of hearts from ryr2r2474s knock-in mice of catecholaminergic polymorphic ventricular tachycardia

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.

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 &#181;m 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...

Watch this Scientific Journal Video about Dual-Dye Optical Mapping of Hearts from RyR2R2474S Knock-In Mice of Catecholaminergic Polymorphic Ventricular Tachycardia at JoVE.com

Dual-Dye Optical Mapping of Hearts from RyR2R2474S Knock-In Mice of Catecholaminergic Polymorphic Ventricular Tachycardia

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.

Dual-Dye Optical Mapping of Hearts from RyR2R2474S Knock-In Mice of Catecholaminergic Polymorphic Ventricular Tachycardia

The pro-arrhythmic cardiac disorder catecholaminergic polymorphic ventricular tachycardia (CPVT) manifests as polymorphic ventricular tachycardia episodes ...

This method will help us to reveal the electrophysiological properties and mechanisms of ventricular arrest smears associated with diseases such as catecholaminergic polymorphic ventricular tachycardia. Using this technique, we can obtain the membrane potential and intercellular calcium signals simultaneously under various programmed electrical pacing protocols, which is especially suitable for exploring the underlying mechanisms and dynamics of cardiac arrhythmic disease such as CPVT. To perform this experiment successfully, ensure to have a well perfused heart, proper dye loading, excitation-contraction uncoupling, and careful camera settings.To begin, set up the optical mapping system and turn on the camera for stable sampling temperature at minus 50 degrees Celsius. Place the harvested mouse heart into the cold CREB solution to slow metabolism and protect the heart. Remove the surrounding tissue of the aorta.Use a custom made cannulating needle to cannulate it, and fix it with a 4-0 silk suture. Now perfuse the heart with the Langendorff system at a constant speed of 3.5 to 4.0 milliliters per minute. Insert a small plastic tube into the left ventricle to release the congestion of solution in the chamber to avoid over preload and fix the plastic tube in the cannulating needle.Then place two leads into the perfusate in the bath and switch on the powers for the electrocardiogram amplifier box and electric stimulation controller. Next, initiate the referenced electrocardiogram or ECG software and continuously monitor the ECG. Perform the subsequent steps in the dark when the heart reaches a stable state condition.Perfuse the blebbistatin CREBs solution mixture constantly into the heart for 10 minutes to uncouple contraction from excitation and avoid contraction artifacts during filming. Then using a red flashlight, examine the heart to confirm the complete cessation of contractions. Perfuse the heart with Rhod-2 AM working solution for 15 minutes in the Langendorff perfusion system after uncoupling excitation contraction.Maintain oxygen supply during intracellular calcium dye loading. To prevent bubble formation from pluronic F-127, insert a bubble trap into the perfusion system. Dilute 10 microliters of RH 237 stock solution into 50 milliliters of perfusate and load for 10 minutes.Upon completing the dual dye loading, capture a sequence of photos. Confirm that voltage and calcium signals are adequate for analysis. Turn on the two LEDs for excitation lights and adjust their intensity to a proper range.Place the heart under the detection device, ensuring it is well illuminated by the two LEDs adjusting the light spot diameter to two centimeters. Set the working distance between the lens and the heart at 10 centimeters to achieve the desired sampling rate and spatial resolution. Open the signal sampling software to simultaneously control the camera and capture voltage and calcium signals.Start the MyoPacer Field Stimulator and set the pacing pattern to transistor transistor logic with two milliseconds of pacing duration per pulse. Set the initial intensity to 0.3 volts. Position a pair of platinum electrodes attached to the epicardial of the left ventricle apex.Apply 30 consecutive 10 hertz S1 stimuli to test the heart's diastolic voltage threshold using the ECG recording software. Gradually increase the voltage amplitude until one-to-one capture is achieved. Implement the S1-S1 protocol to measure calcium or action potential alternates and restitution properties.Pace the heart consecutively starting at a basic cycle length of 100 milliseconds. Decrease the cycle length by 10 milliseconds in each subsequent sequence until it reaches 50 milliseconds. Simultaneously initiate optical mapping prior to stimulation.To measure the ventricular effective refractory period using the S1-S2 stimulus protocol, start with an S1-S1 pacing cycle length of 100 milliseconds. Couple S2 at 60 milliseconds and decrease with a two millisecond step decrement until S2 fails to capture ectopic QRS complex. For arrhythmia induction, administer perpetual 50 hertz burst pacing and perform the same pacing episode after waiting for a two second interval of resting.Carefully monitor the electrocardiogram recordings during the continuous high frequency pacing period to promptly begin simultaneous optical mapping recordings when an interesting arrhythmic wave is generated. Proceed to capture images using the electron multiplying charge coupled device camera. In the image acquisition software, press Select Folder, and load images to begin the semi-automatic massive video data analysis process.Input the correct sampling parameters for the analysis. Manually set the image threshold and select the region of interest. Apply a three by three pixel Gaussian spatial filter, a Savitzky-Golay filter, and a top hat baseline correction.Then press Process Images to remove the baseline and calculate electrophysiological parameters like APD-80 and CATD-50. Set the initiation time of action potential duration at the peak and the terminal point at 80%repolarization for calculating APD-80. Similarly define the start time of calcium transient duration as the peak with the terminal point being 80%relaxation.Typical traces in heat maps of APD-80 and CATD-80 are shown. Isoproterenol shortens APD-80 and wild type and catecholaminergic polymorphic ventricular tachycardia or CPVT mice, but no difference was found after isoproterenol challenge. CATD-80 and CPVT mice was longer than in wild type after the isoproterenol challenge while there was no significance before treatment.According to the voltage signals, the wild type and CPVT hearts possessed the same conduction ability across the epicardium at baseline and after isoproterenol intervention. Heat maps demonstrated that CPVT mice have the same conduction ability as the wild-type mice before and after the isoproterenol challenge. Calcium amplitude alternates analysis showed that the calcium signals in wild-type hearts stayed stable at baseline during consecutive S1-S1 pacing at 14.29 and 16.67 hertz, while the CPVT hearts showed frequency dependent alternates.After the isoproterenol challenge, CPVT hearts exhibited frequency dependent alternates and calcium signal during S1-S1 pacing, while wild-type hearts were not influenced. Tachy arrhythmia analysis suggested that both wild type and CPVT hearts exhibit normal conduction during 50 hertz burst pacing at baseline. After profusion with isoproterenol, CPVT hearts showed high frequency rotors after 50 hertz burst pacing, while wild-type hearts maintained normal conduction.Following this procedure, adogen types and wild-type mice are used to illustrate the electro physiological and functional properties in these models or in the invention of pharmaceuticals. Optical mapping is a powerful tool for study cardiac arrhythmias, however it cannot be used clinically due to limitation in fluorescent dye under the excitation contraction uncoupling. With the development of fluorescent proper for different target molecule under the development of high revolution computation technology, the cardiac optic mapping technique is bound to achieve only applications.

Research

JoVE Journal

Biology

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