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Zhang H, Patton HN, Wood GA, Yan P, Loew LM, Acker CD, Walcott GP, Rogers JM. Optical mapping of cardiac electromechanics in beating in vivo hearts. Biophys J 2023; 122:4207-4219. [PMID: 37775969 PMCID: PMC10645561 DOI: 10.1016/j.bpj.2023.09.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 08/31/2023] [Accepted: 09/26/2023] [Indexed: 10/01/2023] Open
Abstract
Optical mapping has been widely used in the study of cardiac electrophysiology in motion-arrested, ex vivo heart preparations. Recent developments in motion artifact mitigation techniques have made it possible to optically map beating ex vivo hearts, enabling the study of cardiac electromechanics using optical mapping. However, the ex vivo setting imposes limitations on optical mapping such as altered metabolic states, oversimplified mechanical loads, and the absence of neurohormonal regulation. In this study, we demonstrate optical electromechanical mapping in an in vivo heart preparation. Swine hearts were exposed via median sternotomy. Voltage-sensitive dye, either di-4-ANEQ(F)PTEA or di-5-ANEQ(F)PTEA, was injected into the left anterior descending artery. Fluorescence was excited by alternating green and amber light for excitation ratiometry. Cardiac motion during sinus and paced rhythm was tracked using a marker-based method. Motion tracking and excitation ratiometry successfully corrected most motion artifact in the membrane potential signal. Marker-based motion tracking also allowed simultaneous measurement of epicardial deformation. Reconstructed membrane potential and mechanical deformation measurements were validated using monophasic action potentials and sonomicrometry, respectively. Di-5-ANEQ(F)PTEA produced longer working time and higher signal/noise ratio than di-4-ANEQ(F)PTEA. In addition, we demonstrate potential applications of the new optical mapping system including electromechanical mapping during vagal nerve stimulation, fibrillation/defibrillation. and acute regional ischemia. In conclusion, although some technical limitations remain, optical mapping experiments that simultaneously image electrical and mechanical function can be conducted in beating, in vivo hearts.
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Affiliation(s)
- Hanyu Zhang
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | - Haley N Patton
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | - Garrett A Wood
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | - Ping Yan
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, Farmington, Connecticut
| | - Leslie M Loew
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, Farmington, Connecticut
| | - Corey D Acker
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, Farmington, Connecticut
| | - Gregory P Walcott
- Department of Medicine, Division of Cardiovascular Disease, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jack M Rogers
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama.
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2
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Djemai M, Cupelli M, Boutjdir M, Chahine M. Optical Mapping of Cardiomyocytes in Monolayer Derived from Induced Pluripotent Stem Cells. Cells 2023; 12:2168. [PMID: 37681899 PMCID: PMC10487143 DOI: 10.3390/cells12172168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 08/21/2023] [Accepted: 08/25/2023] [Indexed: 09/09/2023] Open
Abstract
Optical mapping is a powerful imaging technique widely adopted to measure membrane potential changes and intracellular Ca2+ variations in excitable tissues using voltage-sensitive dyes and Ca2+ indicators, respectively. This powerful tool has rapidly become indispensable in the field of cardiac electrophysiology for studying depolarization wave propagation, estimating the conduction velocity of electrical impulses, and measuring Ca2+ dynamics in cardiac cells and tissues. In addition, mapping these electrophysiological parameters is important for understanding cardiac arrhythmia mechanisms. In this review, we delve into the fundamentals of cardiac optical mapping technology and its applications when applied to hiPSC-derived cardiomyocytes and discuss related advantages and challenges. We also provide a detailed description of the processing and analysis of optical mapping data, which is a crucial step in the study of cardiac diseases and arrhythmia mechanisms for extracting and comparing relevant electrophysiological parameters.
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Affiliation(s)
- Mohammed Djemai
- CERVO Brain Research Center, Institut Universitaire en Santé Mentale de Québec, Quebec City, QC G1J 2G3, Canada
| | - Michael Cupelli
- Cardiovascular Research Program, VA New York Harbor Healthcare System, New York, NY 11209, USA
- Department of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Health Sciences University, New York, NY 11203, USA
| | - Mohamed Boutjdir
- Cardiovascular Research Program, VA New York Harbor Healthcare System, New York, NY 11209, USA
- Department of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Health Sciences University, New York, NY 11203, USA
- Department of Medicine, NYU School of Medicine, New York, NY 10016, USA
| | - Mohamed Chahine
- CERVO Brain Research Center, Institut Universitaire en Santé Mentale de Québec, Quebec City, QC G1J 2G3, Canada
- Department of Medicine, Faculty of Medicine, Université Laval, Quebec City, QC G1V 0A6, Canada
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3
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Swift LM, Kay MW, Ripplinger CM, Posnack NG. Stop the beat to see the rhythm: excitation-contraction uncoupling in cardiac research. Am J Physiol Heart Circ Physiol 2021; 321:H1005-H1013. [PMID: 34623183 DOI: 10.1152/ajpheart.00477.2021] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Optical mapping is an imaging technique that is extensively used in cardiovascular research, wherein parameter-sensitive fluorescent indicators are used to study the electrophysiology and excitation-contraction coupling of cardiac tissues. Despite many benefits of optical mapping, eliminating motion artifacts within the optical signals is a major challenge, as myocardial contraction interferes with the faithful acquisition of action potentials and intracellular calcium transients. As such, excitation-contraction uncoupling agents are frequently used to reduce signal distortion by suppressing contraction. When compared with other uncoupling agents, blebbistatin is the most frequently used, as it offers increased potency with minimal direct effects on cardiac electrophysiology. Nevertheless, blebbistatin may exert secondary effects on electrical activity, metabolism, and coronary flow, and the incorrect administration of blebbistatin to cardiac tissue can prove detrimental, resulting in erroneous interpretation of optical mapping results. In this "Getting It Right" perspective, we briefly review the literature regarding the use of blebbistatin in cardiac optical mapping experiments, highlight potential secondary effects of blebbistatin on cardiac electrical activity and metabolic demand, and conclude with the consensus of the authors on best practices for effectively using blebbistatin in optical mapping studies of cardiac tissue.
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Affiliation(s)
- Luther M Swift
- Children's National Heart Institute, Children's National Hospital, Washington, District of Columbia.,Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Hospital, Washington, District of Columbia
| | - Matthew W Kay
- Department of Biomedical Engineering, George Washington University, Washington, District of Columbia
| | | | - Nikki Gillum Posnack
- Children's National Heart Institute, Children's National Hospital, Washington, District of Columbia.,Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Hospital, Washington, District of Columbia.,Department of Pediatrics, George Washington University, Washington, District of Columbia.,Department of Pharmacology and Physiology, George Washington University, Washington, District of Columbia
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4
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Zhou Y, Ding M, Nagel G, Konrad KR, Gao S. Advances and prospects of rhodopsin-based optogenetics in plant research. PLANT PHYSIOLOGY 2021; 187:572-589. [PMID: 35237820 PMCID: PMC8491038 DOI: 10.1093/plphys/kiab338] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 07/05/2021] [Indexed: 05/20/2023]
Abstract
Microbial rhodopsins have advanced optogenetics since the discovery of channelrhodopsins almost two decades ago. During this time an abundance of microbial rhodopsins has been discovered, engineered, and improved for studies in neuroscience and other animal research fields. Optogenetic applications in plant research, however, lagged largely behind. Starting with light-regulated gene expression, optogenetics has slowly expanded into plant research. The recently established all-trans retinal production in plants now enables the use of many microbial opsins, bringing extra opportunities to plant research. In this review, we summarize the recent advances of rhodopsin-based plant optogenetics and provide a perspective for future use, combined with fluorescent sensors to monitor physiological parameters.
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Affiliation(s)
- Yang Zhou
- Institute of Physiology, Department of Neurophysiology, Biocenter, University of Wuerzburg, Wuerzburg 97070, Germany
| | - Meiqi Ding
- Institute for Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, Biocenter, University of Wuerzburg, Wuerzburg 97082, Germany
| | - Georg Nagel
- Institute of Physiology, Department of Neurophysiology, Biocenter, University of Wuerzburg, Wuerzburg 97070, Germany
| | - Kai R. Konrad
- Institute for Molecular Plant Physiology and Biophysics, Julius-von-Sachs-Institute, Biocenter, University of Wuerzburg, Wuerzburg 97082, Germany
| | - Shiqiang Gao
- Institute of Physiology, Department of Neurophysiology, Biocenter, University of Wuerzburg, Wuerzburg 97070, Germany
- Author for communication:
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5
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Ramlugun GS, Sands GB, Zhao J, LeGrice IJ, Smaill BH. A novel system for mapping regional electrical properties and characterizing arrhythmia in isolated intact rat atria. Am J Physiol Heart Circ Physiol 2021; 321:H412-H421. [PMID: 34213393 DOI: 10.1152/ajpheart.00185.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Detailed global maps of atrial electrical activity are needed to understand mechanisms of atrial rhythm disturbance in small animal models of heart disease. To date, optical mapping systems have not provided enough spatial resolution across sufficiently extensive regions of intact atrial preparations to achieve this goal. The aim of this study was to develop an integrated platform for quantifying regional electrical properties and analyzing reentrant arrhythmia in a biatrial preparation. Intact atria from 6/7-mo-old female spontaneously hypertensive rats (SHRs; n = 6) were isolated and secured in a constant flow superfusion chamber at 37°C. Optical mapping was performed with the membrane-voltage dye di-4-ANEPPS using LED excitation and a scientific complementary metal-oxide semiconductor (sCMOS) camera. Programmed stimulus trains were applied from right atrial (RA) and left atrial (LA) sites to assess rate-dependent electrical behavior and to induce atrial arrhythmia. Signal-to-noise ratio was improved by sequential processing steps that included spatial smoothing, temporal filtering, and, in stable rhythms, ensemble-averaging. Activation time, repolarization time, and action potential duration (APD) maps were constructed at high spatial resolution for a wide range of coupling intervals. These data were highly consistent within and between experiments. They confirmed preferential atrial conduction pathways and demonstrated distinct medial-to-lateral APD gradients. We also showed that reentrant arrhythmias induced in this preparation were explained by the spatial variation of these electrical properties. Our new methodology provides a robust means of 1) quantifying regional electrical properties in the intact rat atria at higher spatiotemporal resolution than previously reported, and 2) characterizing reentrant arrhythmia and analyzing mechanisms that give rise to it.NEW & NOTEWORTHY Despite wide-ranging optical mapping studies, detailed information on regional atrial electrical properties in small animal models of heart disease and how these contribute to reentrant arrhythmia remains limited. We have developed a novel experimental platform that enables both to be achieved in a geometrically intact isolated rat bi-atrial preparation.
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Affiliation(s)
- Girish S Ramlugun
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Gregory B Sands
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Jichao Zhao
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Ian J LeGrice
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.,Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Bruce H Smaill
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.,Department of Physiology, University of Auckland, Auckland, New Zealand
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6
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Filice D, Dhahri W, Solan JL, Lampe PD, Steele E, Milani N, Van Biber B, Zhu WZ, Valdman TS, Romagnuolo R, Otero-Cruz JD, Hauch KD, Kay MW, Sarvazyan N, Laflamme MA. Optical mapping of human embryonic stem cell-derived cardiomyocyte graft electrical activity in injured hearts. Stem Cell Res Ther 2020; 11:417. [PMID: 32988411 PMCID: PMC7523067 DOI: 10.1186/s13287-020-01919-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 08/13/2020] [Accepted: 09/01/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) show tremendous promise for cardiac regeneration, but the successful development of hESC-CM-based therapies requires improved tools to investigate their electrical behavior in recipient hearts. While optical voltage mapping is a powerful technique for studying myocardial electrical activity ex vivo, we have previously shown that intra-cardiac hESC-CM grafts are not labeled by conventional voltage-sensitive fluorescent dyes. We hypothesized that the water-soluble voltage-sensitive dye di-2-ANEPEQ would label engrafted hESC-CMs and thereby facilitate characterization of graft electrical function and integration. METHODS We developed and validated a novel optical voltage mapping strategy based on the simultaneous imaging of the calcium-sensitive fluorescent protein GCaMP3, a graft-autonomous reporter of graft activation, and optical action potentials (oAPs) derived from di-2-ANEPEQ, which labels both graft and host myocardium. Cardiomyocytes from three different GCaMP3+ hESC lines (H7, RUES2, or ESI-17) were transplanted into guinea pig models of subacute and chronic infarction, followed by optical mapping at 2 weeks post-transplantation. RESULTS Use of a water-soluble voltage-sensitive dye revealed pro-arrhythmic properties of GCaMP3+ hESC-CM grafts from all three lines including slow conduction velocity, incomplete host-graft coupling, and spatially heterogeneous patterns of activation that varied beat-to-beat. GCaMP3+ hESC-CMs from the RUES2 and ESI-17 lines both showed prolonged oAP durations both in vitro and in vivo. Although hESC-CMs partially remuscularize the injured hearts, histological evaluation revealed immature graft structure and impaired gap junction expression at this early timepoint. CONCLUSION Simultaneous imaging of GCaMP3 and di-2-ANEPEQ allowed us to acquire the first unambiguously graft-derived oAPs from hESC-CM-engrafted hearts and yielded critical insights into their arrhythmogenic potential and line-to-line variation.
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Affiliation(s)
- Dominic Filice
- Department of Bioengineering, University of Washington, Seattle, WA, 98195, USA
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Wahiba Dhahri
- McEwen Stem Cell Institute, University Health Network, 101 College Street, Rm 3-908, Toronto, ON, M5G 1L7, Canada
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, M5G 2N2, Canada
| | - Joell L Solan
- Fred Hutchinson Cancer Research Center, Seattle, WA, 98109, USA
| | - Paul D Lampe
- Fred Hutchinson Cancer Research Center, Seattle, WA, 98109, USA
| | - Erin Steele
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
- Department of Biology, University of Washington, Seattle, WA, 98195, USA
| | - Nikita Milani
- Department of Bioengineering, University of Washington, Seattle, WA, 98195, USA
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
| | - Benjamin Van Biber
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Wei-Zhong Zhu
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Tamilla Sadikov Valdman
- McEwen Stem Cell Institute, University Health Network, 101 College Street, Rm 3-908, Toronto, ON, M5G 1L7, Canada
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, M5G 2N2, Canada
| | - Rocco Romagnuolo
- McEwen Stem Cell Institute, University Health Network, 101 College Street, Rm 3-908, Toronto, ON, M5G 1L7, Canada
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, M5G 2N2, Canada
| | - José David Otero-Cruz
- Institute for Stem Cell & Regenerative Medicine, University of Washington, Seattle, WA, 98195, USA
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Kip D Hauch
- Department of Bioengineering, University of Washington, Seattle, WA, 98195, USA
| | - Matthew W Kay
- Department of Biomedical Engineering, G. Washington University, Washington, DC, 20052, USA
| | - Narine Sarvazyan
- Department of Pharmacology & Physiology, G. Washington University, Washington, DC, 20052, USA
| | - Michael A Laflamme
- McEwen Stem Cell Institute, University Health Network, 101 College Street, Rm 3-908, Toronto, ON, M5G 1L7, Canada.
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, M5G 2N2, Canada.
- Department of Laboratory Medicine & Pathobiology, University of Toronto, Toronto, ON, M5G 1L7, Canada.
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7
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Olejnickova V, Sedmera D. What is the optimal light source for optical mapping using voltage- and calcium-sensitive dyes? Physiol Res 2020; 69:599-607. [DOI: 10.33549/physiolres.934471] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Optical mapping is a fluorescence-based physiological method to image spreading of action potential in excitable tissues, such as the heart and central nervous system. Because of the requirements for high speed imaging in low light conditions, highly sensitive high-speed cameras together with an optical system with maximum photon efficiency are required. While the optimization of these two components is relatively straightforward, the choice of the perfect light source is less simple; depending on the other (usually fixed) components, various parameters may acquire different weight in decision-making process. Here we describe the rationale for building an optical mapping setup and consider the relative advantages and disadvantages of three different commonly available light sources: mercury vapor lamp (HBO), xenon lamp (XBO), and light emitting diode (LED). Using the same optical system (fluorescence macroscope) and high-speed camera (Ultima L), we have tested each of the sources for its ability to provide bright and even illumination of the field of view and measured its temporal fluctuations in intensity. Then we used each in the actual optical mapping experiment using isolated, perfused adult mouse heart or chick embryonic heart to determine the actual signal to noise ratio at various acquisition rates. While the LED sources have undergone significant improvements in the recent past, the other alternatives may still surpass them in some parameters, so they may not be the automatic number one choice for every application.
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Affiliation(s)
| | - D Sedmera
- Developmental Cardiology, Institute of Physiology, Prague, Czech Republic.
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8
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Shroff SN, Das SL, Tseng HA, Noueihed J, Fernandez F, White JA, Chen CS, Han X. Voltage Imaging of Cardiac Cells and Tissue Using the Genetically Encoded Voltage Sensor Archon1. iScience 2020; 23:100974. [PMID: 32299055 PMCID: PMC7160579 DOI: 10.1016/j.isci.2020.100974] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Revised: 02/21/2020] [Accepted: 03/05/2020] [Indexed: 01/19/2023] Open
Abstract
Precise measurement of action potentials (APs) is needed to observe electrical activity and cellular communication within cardiac tissue. Voltage-sensitive dyes (VSDs) are traditionally used to measure cardiac APs; however, they require acute chemical addition that prevents chronic imaging. Genetically encoded voltage indicators (GEVIs) enable long-term studies of APs without the need of chemical additions, but current GEVIs used in cardiac tissue exhibit poor kinetics and/or low signal to noise (SNR). Here, we demonstrate the use of Archon1, a recently developed GEVI, in hiPSC-derived cardiomyocytes (CMs). When expressed in CMs, Archon1 demonstrated fast kinetics comparable with patch-clamp electrophysiology and high SNR significantly greater than the VSD Di-8-ANEPPS. Additionally, Archon1 enabled monitoring of APs across multiple cells simultaneously in 3D cardiac tissues. These results highlight Archon1's capability to investigate the electrical activity of CMs in a variety of applications and its potential to probe functionally complex in vitro models, as well as in vivo systems.
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Affiliation(s)
- Sanaya N Shroff
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Shoshana L Das
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA; Harvard-MIT Program in Health Sciences and Technology, Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA
| | - Hua-An Tseng
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Jad Noueihed
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Fernando Fernandez
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - John A White
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Christopher S Chen
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA.
| | - Xue Han
- Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA.
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9
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O'Shea C, Pavlovic D, Rajpoot K, Winter J. Examination of the Effects of Conduction Slowing on the Upstroke of Optically Recorded Action Potentials. Front Physiol 2019; 10:1295. [PMID: 31681008 PMCID: PMC6798176 DOI: 10.3389/fphys.2019.01295] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 09/26/2019] [Indexed: 01/27/2023] Open
Abstract
Introduction The upstroke of optical action potentials (APs) recorded from intact hearts are generally recognized to be slower than those recorded with microelectrodes. This is thought to reflect spatial signal averaging within the volume of tissue that makes up the optical signal. However, to date, there has been no direct experimental study on the relationship between conduction velocity (CV) and optical AP upstroke morphology in the intact heart. Notably, it is known that sodium channel block and gap junction inhibition, which both slow CV, exert differential effects on the upstroke velocity of microelectrode-recorded APs. Whether such differences are evident in optical APs is not known. The present study sought to determine the relationship between tissue CV and optical AP upstroke velocity in intact mouse hearts. Materials and Methods Isolated, perfused mouse hearts were stained with the potentiometric dye Rh-237. Fluorescent signals were recorded from across the anterior surface of the left and right ventricles during constant pacing. Maximum rate of change in fluorescence (dF/dtmax) and tissue CV were assessed in control conditions, during an acute period of low-flow ischemia, and following perfusion of flecainide (1–3 μmol/L), a sodium channel blocker, or carbenoxolone (10–50 μmol/L), a gap junction inhibitor. Results During epicardial pacing, an anisotropic pattern was observed in both activation and dF/dtmax maps, with more rapid optical AP upstroke velocities orientated along the fastest conduction paths (and vice versa). Low-flow ischemia resulted in a time-dependent slowing of ventricular CV, which was accompanied by a concomitant reduction in optical AP upstroke velocity. All values returned to baseline on tissue reperfusion. Both flecainide and carbenoxolone were associated with a concentration-dependent reduction in CV and decrease in optical AP upstroke velocity, despite distinct mechanisms of action. Similar responses to carbenoxolone were observed for low- (156 μm pixel with) and high- (20 μm pixel width) magnification recordings. Comparison of data from all interventions revealed a linear relationship between CV and upstroke dF/dt. Conclusion In intact mouse hearts, slowing of optical AP upstroke velocity is directly proportional to the change in CV associated with low-flow ischemia, sodium channel block, and gap junction inhibition.
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Affiliation(s)
- Christopher O'Shea
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom.,EPSRC Centre for Doctoral Training in Physical Sciences for Health, University of Birmingham, Birmingham, United Kingdom
| | - Davor Pavlovic
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Kashif Rajpoot
- School of Computer Science, University of Birmingham, Birmingham, United Kingdom
| | - James Winter
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
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10
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Chang Z, Liu F, Wang L, Deng M, Zhou C, Sun Q, Chu J. Near-infrared dyes, nanomaterials and proteins. CHINESE CHEM LETT 2019. [DOI: 10.1016/j.cclet.2019.08.034] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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11
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Ferenczi EA, Tan X, Huang CLH. Principles of Optogenetic Methods and Their Application to Cardiac Experimental Systems. Front Physiol 2019; 10:1096. [PMID: 31572204 PMCID: PMC6749684 DOI: 10.3389/fphys.2019.01096] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 08/08/2019] [Indexed: 12/12/2022] Open
Abstract
Optogenetic techniques permit studies of excitable tissue through genetically expressed light-gated microbial channels or pumps permitting transmembrane ion movement. Light activation of these proteins modulates cellular excitability with millisecond precision. This review summarizes optogenetic approaches, using examples from neurobiological applications, and then explores their application in cardiac electrophysiology. We review the available opsins, including depolarizing and hyperpolarizing variants, as well as modulators of G-protein coupled intracellular signaling. We discuss the biophysical properties that determine the ability of microbial opsins to evoke reliable, precise stimulation or silencing of electrophysiological activity. We also review spectrally shifted variants offering possibilities for enhanced depth of tissue penetration, combinatorial stimulation for targeting different cell subpopulations, or all-optical read-in and read-out studies. Expression of the chosen optogenetic tool in the cardiac cell of interest then requires, at the single-cell level, introduction of opsin-encoding genes by viral transduction, or coupling "spark cells" to primary cardiomyocytes or a stem-cell derived counterpart. At the system-level, this requires construction of transgenic mice expressing ChR2 in their cardiomyocytes, or in vivo injection (myocardial or systemic) of adenoviral expression systems. Light delivery, by laser or LED, with widespread or multipoint illumination, although relatively straightforward in vitro may be technically challenged by cardiac motion and light-scattering in biological tissue. Physiological read outs from cardiac optogenetic stimulation include single cell patch clamp recordings, multi-unit microarray recordings from cell monolayers or slices, and electrical recordings from isolated Langendorff perfused hearts. Optical readouts of specific cellular events, including ion transients, voltage changes or activity in biochemical signaling cascades, using small detecting molecules or genetically encoded sensors now offer powerful opportunities for all-optical control and monitoring of cellular activity. Use of optogenetics has expanded in cardiac physiology, mainly using optically controlled depolarizing ion channels to control heart rate and for optogenetic defibrillation. ChR2-expressing cardiomyocytes show normal baseline and active excitable membrane and Ca2+ signaling properties and are sensitive even to ~1 ms light pulses. They have been employed in studies of the intrinsic cardiac adrenergic system and of cardiac arrhythmic properties.
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Affiliation(s)
- Emily A. Ferenczi
- Department of Neurology, Massachusetts General Hospital and Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States
| | - Xiaoqiu Tan
- Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Christopher L.-H. Huang
- Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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12
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O’Shea C, Holmes AP, Winter J, Correia J, Ou X, Dong R, He S, Kirchhof P, Fabritz L, Rajpoot K, Pavlovic D. Cardiac Optogenetics and Optical Mapping - Overcoming Spectral Congestion in All-Optical Cardiac Electrophysiology. Front Physiol 2019; 10:182. [PMID: 30899227 PMCID: PMC6416196 DOI: 10.3389/fphys.2019.00182] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 02/14/2019] [Indexed: 12/30/2022] Open
Abstract
Optogenetic control of the heart is an emergent technology that offers unparalleled spatio-temporal control of cardiac dynamics via light-sensitive ion pumps and channels (opsins). This fast-evolving technique holds broad scope in both clinical and basic research setting. Combination of optogenetics with optical mapping of voltage or calcium fluorescent probes facilitates 'all-optical' electrophysiology, allowing precise optogenetic actuation of cardiac tissue with high spatio-temporal resolution imaging of action potential and calcium transient morphology and conduction patterns. In this review, we provide a synopsis of optogenetics and discuss in detail its use and compatibility with optical interrogation of cardiac electrophysiology. We briefly discuss the benefits of all-optical cardiac control and electrophysiological interrogation compared to traditional techniques, and describe mechanisms, unique features and limitations of optically induced cardiac control. In particular, we focus on state-of-the-art setup design, challenges in light delivery and filtering, and compatibility of opsins with fluorescent reporters used in optical mapping. The interaction of cardiac tissue with light, and physical and computational approaches to overcome the 'spectral congestion' that arises from the combination of optogenetics and optical mapping are discussed. Finally, we summarize recent preclinical work applications of combined cardiac optogenetics and optical mapping approach.
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Affiliation(s)
- Christopher O’Shea
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
- School of Computer Science, University of Birmingham, Birmingham, United Kingdom
- EPSRC Centre for Doctoral Training in Physical Sciences for Health, School of Chemistry, University of Birmingham, Birmingham, United Kingdom
| | - Andrew P. Holmes
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
- Institute of Clinical Sciences, University of Birmingham, Birmingham, United Kingdom
| | - James Winter
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Joao Correia
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Xianhong Ou
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Ruirui Dong
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Shicheng He
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Paulus Kirchhof
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
- Department of Cardiology, UHB NHS Trust, Birmingham, United Kingdom
| | - Larissa Fabritz
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
- Department of Cardiology, UHB NHS Trust, Birmingham, United Kingdom
| | - Kashif Rajpoot
- School of Computer Science, University of Birmingham, Birmingham, United Kingdom
| | - Davor Pavlovic
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
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Zhang H, Iijima K, Huang J, Walcott GP, Rogers JM. Optical Mapping of Membrane Potential and Epicardial Deformation in Beating Hearts. Biophys J 2017; 111:438-451. [PMID: 27463145 DOI: 10.1016/j.bpj.2016.03.043] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 03/01/2016] [Accepted: 03/24/2016] [Indexed: 11/26/2022] Open
Abstract
Cardiac optical mapping uses potentiometric fluorescent dyes to image membrane potential (Vm). An important limitation of conventional optical mapping is that contraction is usually arrested pharmacologically to prevent motion artifacts from obscuring Vm signals. However, these agents may alter electrophysiology, and by abolishing contraction, also prevent optical mapping from being used to study coupling between electrical and mechanical function. Here, we present a method to simultaneously map Vm and epicardial contraction in the beating heart. Isolated perfused swine hearts were stained with di-4-ANEPPS and fiducial markers were glued to the epicardium for motion tracking. The heart was imaged at 750 Hz with a video camera. Fluorescence was excited with cyan or blue LEDs on alternating camera frames, thus providing a 375-Hz effective sampling rate. Marker tracking enabled the pixel(s) imaging any epicardial site within the marked region to be identified in each camera frame. Cyan- and blue-elicited fluorescence have different sensitivities to Vm, but other signal features, primarily motion artifacts, are common. Thus, taking the ratio of fluorescence emitted by a motion-tracked epicardial site in adjacent frames removes artifacts, leaving Vm (excitation ratiometry). Reconstructed Vm signals were validated by comparison to monophasic action potentials and to conventional optical mapping signals. Binocular imaging with additional video cameras enabled marker motion to be tracked in three dimensions. From these data, epicardial deformation during the cardiac cycle was quantified by computing finite strain fields. We show that the method can simultaneously map Vm and strain in a left-sided working heart preparation and can image changes in both electrical and mechanical function 5 min after the induction of regional ischemia. By allowing high-resolution optical mapping in the absence of electromechanical uncoupling agents, the method relieves a long-standing limitation of optical mapping and has potential to enhance new studies in coupled cardiac electromechanics.
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Affiliation(s)
- Hanyu Zhang
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | - Kenichi Iijima
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jian Huang
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Gregory P Walcott
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jack M Rogers
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama.
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14
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Zhang H, Reichert E, Cohen AE. Optical electrophysiology for probing function and pharmacology of voltage-gated ion channels. eLife 2016; 5. [PMID: 27215841 PMCID: PMC4907688 DOI: 10.7554/elife.15202] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 05/12/2016] [Indexed: 12/15/2022] Open
Abstract
Voltage-gated ion channels mediate electrical dynamics in excitable tissues and are an important class of drug targets. Channels can gate in sub-millisecond timescales, show complex manifolds of conformational states, and often show state-dependent pharmacology. Mechanistic studies of ion channels typically involve sophisticated voltage-clamp protocols applied through manual or automated electrophysiology. Here, we develop all-optical electrophysiology techniques to study activity-dependent modulation of ion channels, in a format compatible with high-throughput screening. Using optical electrophysiology, we recapitulate many voltage-clamp protocols and apply to Nav1.7, a channel implicated in pain. Optical measurements reveal that a sustained depolarization strongly potentiates the inhibitory effect of PF-04856264, a Nav1.7-specific blocker. In a pilot screen, we stratify a library of 320 FDA-approved compounds by binding mechanism and kinetics, and find close concordance with patch clamp measurements. Optical electrophysiology provides a favorable tradeoff between throughput and information content for studies of NaV channels, and possibly other voltage-gated channels. DOI:http://dx.doi.org/10.7554/eLife.15202.001 Ion channels are specialized proteins that span the cell membrane. When activated, these channels allow ions to pass through them, which can produce electrical spikes that carry information in nerve cells and regulate the beating of the heart. Researchers interested in understanding how ion channels behave often use a technique called patch clamp electrophysiology to measure the electrical current across the cell membrane. The technique can be used to probe if a specific drug can block an ion channel, but it is not well suited to screening lots of potential drugs because it is slow and expensive. A group of ion channels known as voltage-gated sodium channels play an important role in generating the electrical spikes in nerve cells. One subtype called NaV1.7 is involved in sensing pain and drugs that block NaV1.7 might be useable as painkillers, but only if they are specific to this channel. This is because there are many similar sodium channels that are important in other processes in the body. Zhang et al. have now developed a new light-based technique to measure how ion channels behave. The technique uses light to activate the channel and a fluorescent protein to report on the membrane’s voltage. Zhang et al. used the new technique to probe how sodium channels, in particular NaV1.7, interact with drugs. Mammalian cells grown in the lab were engineered to produce NaV1.7, a light-activated ion channel (called CheRiff), and a fluorescent reporter protein. A flash of blue light delivered to the cells activated CheRiff, which in turn activated NaV1.7. At the same time, the fluorescence of the reporter protein was used as a read-out of NaV1.7’s activity. Zhang et al. showed that they could reproduce many conventional electrophysiology measurements using their new light-based approach. Optical measurements were then used to screen 320 drugs to see whether they could block NaV1.7. The results of the screen corresponded closely with measurements made using conventional electrophysiology. These results demonstrate that the new optical technique is both fast and precise enough to be used in drug discovery. Further studies could now ask if this optical technique can also be used to study other ion channels, such as potassium channels and calcium channels. DOI:http://dx.doi.org/10.7554/eLife.15202.002
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Affiliation(s)
- Hongkang Zhang
- Departments of Chemistry and Chemical Biology and Physics, Harvard University, Cambridge, United States.,Howard Hughes Medical Institute, Harvard University, Cambridge, United States
| | - Elaine Reichert
- Departments of Chemistry and Chemical Biology and Physics, Harvard University, Cambridge, United States
| | - Adam E Cohen
- Departments of Chemistry and Chemical Biology and Physics, Harvard University, Cambridge, United States.,Howard Hughes Medical Institute, Harvard University, Cambridge, United States
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Jaimes R, Walton RD, Pasdois P, Bernus O, Efimov IR, Kay MW. A technical review of optical mapping of intracellular calcium within myocardial tissue. Am J Physiol Heart Circ Physiol 2016; 310:H1388-401. [PMID: 27016580 DOI: 10.1152/ajpheart.00665.2015] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 03/21/2016] [Indexed: 12/18/2022]
Abstract
Optical mapping of Ca(2+)-sensitive fluorescence probes has become an extremely useful approach and adopted by many cardiovascular research laboratories to study a spectrum of myocardial physiology and disease conditions. Optical mapping data are often displayed as detailed pseudocolor images, providing unique insight for interpreting mechanisms of ectopic activity, action potential and Ca(2+) transient alternans, tachycardia, and fibrillation. Ca(2+)-sensitive fluorescent probes and optical mapping systems continue to evolve in the ongoing effort to improve therapies that ease the growing worldwide burden of cardiovascular disease. In this technical review we provide an updated overview of conventional approaches for optical mapping of Cai (2+) within intact myocardium. In doing so, a brief history of Cai (2+) probes is provided, and nonratiometric and ratiometric Ca(2+) probes are discussed, including probes for imaging sarcoplasmic reticulum Ca(2+) and probes compatible with potentiometric dyes for dual optical mapping. Typical measurements derived from optical Cai (2+) signals are explained, and the analytics used to compute them are presented. Last, recent studies using Cai (2+) optical mapping to study arrhythmias, heart failure, and metabolic perturbations are summarized.
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Affiliation(s)
- Rafael Jaimes
- Department of Biomedical Engineering, The George Washington University. Washington, District of Columbia
| | - Richard D Walton
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; Institut National de la Santé et de la Recherche Médicale, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; and L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Philippe Pasdois
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; Institut National de la Santé et de la Recherche Médicale, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; and L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Olivier Bernus
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; Institut National de la Santé et de la Recherche Médicale, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; and L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Igor R Efimov
- Department of Biomedical Engineering, The George Washington University. Washington, District of Columbia; L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University. Washington, District of Columbia;
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Everett TH, Hulley GS, Lee KW, Chang R, Wilson EE, Olgin JE. The effects of remodeling with heart failure on mode of initiation of ventricular fibrillation and its spatiotemporal organization. J Interv Card Electrophysiol 2015; 43:205-15. [PMID: 26001644 DOI: 10.1007/s10840-015-0016-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 05/05/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE The effect of the heart failure substrate on the initiation of ventricular fibrillation (VF) and its resulting mechanism is not known. The objective of this study was to determine the effects of substrate on VF initiation and its spatiotemporal organization in the heart failure model. METHODS Optical action potentials were recorded from LV wedge preparations either from structurally normal hearts (control, n = 11) or from congestive heart failure (CHF; n = 7), at the epicardial surface, endocardial surface which included a papillary muscle, and a transmural cross section. Action potential duration (APD(80)) was determined, and VF was initiated. A fast Fourier transform was calculated, and the dominant frequency (DF) was determined. RESULTS The CHF group showed increased VF vulnerability (69 vs 26 %, p < 0.03), and every mapped surface showed an APD(80) gradient which included islands of higher APDs on the transmural surface (M cells) which was not observed in controls. VF in the CHF group was characterized by stable, discrete, high-DF areas that correlated to either foci or spiral waves located on the transmural surface at the site of the papillary muscle. Overall, the top 10 % of DFs correlated to an APD of 101 ms while the bottom 10 % of DFs correlated to an APD of 126 ms (p < 0.01). CONCLUSIONS In the CHF model, APD gradients correlated with an increased vulnerability to VF, and the highest stable DFs were located on the transmural surface which was not seen in controls. This indicates that the CHF substrate creates unique APD and DF characteristics.
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Affiliation(s)
- Thomas H Everett
- Krannert Institute of Cardiology, Indiana University School of Medicine, 1800 N. Capitol, Ste. E400E, Indianapolis, IN, 46202, USA,
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17
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Lau E, Kossidas K, Kim TY, Kunitomo Y, Ziv O, Zhen S, Taylor C, Schofield L, Yammine J, Liu G, Peng X, Qu Z, Koren G, Choi BR. Spatially Discordant Alternans and Arrhythmias in Tachypacing-Induced Cardiac Myopathy in Transgenic LQT1 Rabbits: The Importance of IKs and Ca2+ Cycling. PLoS One 2015; 10:e0122754. [PMID: 25970695 PMCID: PMC4430457 DOI: 10.1371/journal.pone.0122754] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 02/12/2015] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Remodeling of cardiac repolarizing currents, such as the downregulation of slowly activating K+ channels (IKs), could underlie ventricular fibrillation (VF) in heart failure (HF). We evaluated the role of Iks remodeling in VF susceptibility using a tachypacing HF model of transgenic rabbits with Long QT Type 1 (LQT1) syndrome. METHODS AND RESULTS LQT1 and littermate control (LMC) rabbits underwent three weeks of tachypacing to induce cardiac myopathy (TICM). In vivo telemetry demonstrated steepening of the QT/RR slope in LQT1 with TICM (LQT1-TICM; pre: 0.26±0.04, post: 0.52±0.01, P<0.05). In vivo electrophysiology showed that LQT1-TICM had higher incidence of VF than LMC-TICM (6 of 11 vs. 3 of 11, respectively). Optical mapping revealed larger APD dispersion (16±4 vs. 38±6 ms, p<0.05) and steep APD restitution in LQT1-TICM compared to LQT1-sham (0.53±0.12 vs. 1.17±0.13, p<0.05). LQT1-TICM developed spatially discordant alternans (DA), which caused conduction block and higher-frequency VF (15±1 Hz in LQT1-TICM vs. 13±1 Hz in LMC-TICM, p<0.05). Ca2+ DA was highly dynamic and preceded voltage DA in LQT1-TICM. Ryanodine abolished DA in 5 out of 8 LQT1-TICM rabbits, demonstrating the importance of Ca2+ in complex DA formation. Computer simulations suggested that HF remodeling caused Ca2+-driven alternans, which was further potentiated in LQT1-TICM due to the lack of IKs. CONCLUSIONS Compared with LMC-TICM, LQT1-TICM rabbits exhibit steepened APD restitution and complex DA modulated by Ca2+. Our results strongly support the contention that the downregulation of IKs in HF increases Ca2+ dependent alternans and thereby the risk of VF.
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Affiliation(s)
- Emily Lau
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Konstantinos Kossidas
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Tae Yun Kim
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Yukiko Kunitomo
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Ohad Ziv
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Song Zhen
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Chantel Taylor
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Lorraine Schofield
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Joe Yammine
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Gongxin Liu
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Xuwen Peng
- Department of Comparative Medicine, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Gideon Koren
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
| | - Bum-Rak Choi
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, Rhode Island, United States of America
- * E-mail:
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18
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Kim JJ, Yang L, Lin B, Zhu X, Sun B, Kaplan AD, Bett GCL, Rasmusson RL, London B, Salama G. Mechanism of automaticity in cardiomyocytes derived from human induced pluripotent stem cells. J Mol Cell Cardiol 2015; 81:81-93. [PMID: 25644533 PMCID: PMC4409767 DOI: 10.1016/j.yjmcc.2015.01.013] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 11/26/2014] [Accepted: 01/15/2015] [Indexed: 10/24/2022]
Abstract
BACKGROUND AND OBJECTIVES The creation of cardiomyocytes derived from human induced pluripotent stem cells (hiPS-CMs) has spawned broad excitement borne out of the prospects to diagnose and treat cardiovascular diseases based on personalized medicine. A common feature of hiPS-CMs is their spontaneous contractions but the mechanism(s) remain uncertain. METHODS Intrinsic activity was investigated by the voltage-clamp technique, optical mapping of action potentials (APs) and intracellular Ca(2+) (Cai) transients (CaiT) at subcellular-resolution and pharmacological interventions. RESULTS The frequency of spontaneous CaiT (sCaiT) in monolayers of hiPS-CMs was not altered by ivabradine, an inhibitor of the pacemaker current, If despite high levels of HCN transcripts (1-4). HiPS-CMs had negligible If and IK1 (inwardly-rectifying K(+)-current) and a minimum diastolic potential of -59.1±3.3mV (n=18). APs upstrokes were preceded by a depolarizing-foot coincident with a rise of Cai. Subcellular Cai wavelets varied in amplitude, propagated and died-off; larger Cai-waves triggered cellular sCaTs and APs. SCaiTs increased in frequency with [Ca(2+)]out (0.05-to-1.8mM), isoproterenol (1μM) or caffeine (100μM) (n≥5, p<0.05). HiPS-CMs became quiescent with ryanodine receptor stabilizers (K201=2μM); tetracaine; Na-Ca exchange (NCX) inhibition (SEA0400=2μM); higher [K(+)]out (5→8mM), and thiol-reducing agents but could still be electrically stimulated to elicit CaiTs. Cell-cell coupling of hiPS-CM in monolayers was evident from connexin-43 expression and CaiT propagation. SCaiTs from an ensemble of dispersed hiPS-CMs were out-of-phase but became synchronous through the outgrowth of inter-connecting microtubules. CONCLUSIONS Automaticity in hiPS-CMs originates from a Ca(2+)-clock mechanism involving Ca(2+) cycling across the sarcoplasmic reticulum linked to NCX to trigger APs.
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Affiliation(s)
- Jong J Kim
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261, USA; Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Lei Yang
- Department of Developmental Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Bo Lin
- Department of Developmental Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Xiaodong Zhu
- University of Iowa, Carver College of Medicine, Division of Cardiovascular Medicine, Iowa City, IA 52242, USA
| | - Bin Sun
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Aaron D Kaplan
- Center for Cellular and Systems Electrophysiology, University at Buffalo, State University of New York, Buffalo, NY 14214, USA
| | - Glenna C L Bett
- Center for Cellular and Systems Electrophysiology, University at Buffalo, State University of New York, Buffalo, NY 14214, USA; Departments of Physiology and Biophysics, University at Buffalo, State University of New York, Buffalo, NY 14214, USA; Departments of Gynecology-Obstetrics, University at Buffalo, State University of New York, Buffalo, NY 14214, USA
| | - Randall L Rasmusson
- Center for Cellular and Systems Electrophysiology, University at Buffalo, State University of New York, Buffalo, NY 14214, USA; Departments of Physiology and Biophysics, University at Buffalo, State University of New York, Buffalo, NY 14214, USA
| | - Barry London
- University of Iowa, Carver College of Medicine, Division of Cardiovascular Medicine, Iowa City, IA 52242, USA
| | - Guy Salama
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261, USA; Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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Fisher JAN, Salzberg BM. Two-Photon Excitation of Fluorescent Voltage-Sensitive Dyes: Monitoring Membrane Potential in the Infrared. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 859:427-53. [PMID: 26238063 DOI: 10.1007/978-3-319-17641-3_17] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Functional imaging microscopy based on voltage-sensitive dyes (VSDs) has proven effective for revealing spatio-temporal patterns of activity in vivo and in vitro. Microscopy based on two-photon excitation of fluorescent VSDs offers the possibility of recording sub-millisecond membrane potential changes on micron length scales in cells that lie upwards of one millimeter below the brain's surface. Here we describe progress in monitoring membrane voltage using two-photon excitation (TPE) of VSD fluorescence, and detail an application of this emerging technology in which action potentials were recorded in single trials from individual mammalian nerve terminals in situ. Prospects for, and limitations of this method are reviewed.
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20
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Optical mapping of optogenetically shaped cardiac action potentials. Sci Rep 2014; 4:6125. [PMID: 25135113 PMCID: PMC4137261 DOI: 10.1038/srep06125] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 07/30/2014] [Indexed: 12/19/2022] Open
Abstract
Light-mediated silencing and stimulation of cardiac excitability, an important complement to electrical stimulation, promises important discoveries and therapies. To date, cardiac optogenetics has been studied with patch-clamp, multielectrode arrays, video microscopy, and an all-optical system measuring calcium transients. The future lies in achieving simultaneous optical acquisition of excitability signals and optogenetic control, both with high spatio-temporal resolution. Here, we make progress by combining optical mapping of action potentials with concurrent activation of channelrhodopsin-2 (ChR2) or halorhodopsin (eNpHR3.0), via an all-optical system applied to monolayers of neonatal rat ventricular myocytes (NRVM). Additionally, we explore the capability of ChR2 and eNpHR3.0 to shape action-potential waveforms, potentially aiding the study of short/long QT syndromes that result from abnormal changes in action potential duration (APD). These results show the promise of an all-optical system to acquire action potentials with precise temporal optogenetics control, achieving a long-sought flexibility beyond the means of conventional electrical stimulation.
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Abstract
In the past decade, optical mapping provided crucial mechanistic insight into electromechanical function and the mechanism of ventricular fibrillation. Therefore, to date, optical mapping dominates experimental cardiac electrophysiology. The first cardiac measurements involving optics were done in the early 1900s using the fast cinematograph that later evolved into methods for high-resolution activation and repolarization mapping and stimulation of specific cardiac cell types. The field of "optocardiography," therefore, emerged as the use of light for recording or interfering with cardiac physiology. In this review, we discuss how optocardiography developed into the dominant research technique in experimental cardiology. Furthermore, we envision how optocardiographic methods can be used in clinical cardiology.
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Patti J, Isacoff EY. Measuring membrane voltage with fluorescent proteins. Cold Spring Harb Protoc 2013; 2013:606-13. [PMID: 23818671 DOI: 10.1101/pdb.top075804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Measuring signal transduction in large numbers of cells with high spatial and temporal resolution is fundamental to studying information processing in the nervous system. DNA-encoded sensors have an advantage in that they can be introduced into an organism noninvasively and targeted to specific brain regions, cell types, or subcellular compartments. A variety of chimeric proteins that report transmembrane voltage have been developed. The prototype sensor, FlaSh, is a green fluorescent protein fused to a voltage-sensitive K(+) channel, where voltage-dependent rearrangements in the channel induce changes in the protein's fluorescence. Subsequent sensors have refined this basic design using a monomeric voltage-sensing phosphatase domain from Ciona intestinalis and pairs of fluorescent proteins to produce a larger fluorescent signal. These sensors and their uses are discussed here.
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Ronzhina M, Cmiel V, Janoušek O, Kolářová J, Nováková M, Babula P, Provazník I. Application of the optical method in experimental cardiology: action potential and intracellular calcium concentration measurement. Physiol Res 2012; 62:125-37. [PMID: 23234419 DOI: 10.33549/physiolres.932369] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
It has been shown that, in addition to conventional contact electrode techniques, optical methods using fluorescent dyes can be successfully used for cardiac signal measurement. In this review, the physical and technical fundamentals of the method are described, as well as the properties of the most common systems for measuring action potentials and intracellular calcium concentration. Special attention is paid to summarizing limitations and trends in developing this method.
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Affiliation(s)
- M Ronzhina
- Department of Biomedical Engineering, Faculty of Electrical Engineering and Communication, Brno University of Technology, Brno, Czech Republic.
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Abstract
Cardiac optical mapping has proven to be a powerful technology for studying cardiovascular function and disease. The development and scientific impact of this methodology are well-documented. Because of its relevance in cardiac research, this imaging technology advances at a rapid pace. Here, we review technological and scientific developments during the past several years and look toward the future. First, we explore key components of a modern optical mapping set-up, focusing on: (1) new camera technologies; (2) powerful light-emitting-diodes (from ultraviolet to red) for illumination; (3) improved optical filter technology; (4) new synthetic and optogenetic fluorescent probes; (5) optical mapping with motion and contraction; (6) new multiparametric optical mapping techniques; and (7) photon scattering effects in thick tissue preparations. We then look at recent optical mapping studies in single cells, cardiomyocyte monolayers, atria, and whole hearts. Finally, we briefly look into the possible future roles of optical mapping in the development of regenerative cardiac research, cardiac cell therapies, and molecular genetic advances.
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Affiliation(s)
- Todd J Herron
- Department of Internal Medicine, Cardiovascular Research Center, University of Michigan, 2800 Plymouth Road, Ann Arbor, MI 48109-2800, USA
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25
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Lang D, Sulkin M, Lou Q, Efimov IR. Optical mapping of action potentials and calcium transients in the mouse heart. J Vis Exp 2011:3275. [PMID: 21946907 PMCID: PMC3230201 DOI: 10.3791/3275] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The mouse heart is a popular model for cardiovascular studies due to the existence of low cost technology for genetic engineering in this species. Cardiovascular physiological phenotyping of the mouse heart can be easily done using fluorescence imaging employing various probes for transmembrane potential (Vm), calcium transients (CaT), and other parameters. Excitation-contraction coupling is characterized by action potential and intracellular calcium dynamics; therefore, it is critically important to map both Vm and CaT simultaneously from the same location on the heart1-4. Simultaneous optical mapping from Langendorff perfused mouse hearts has the potential to elucidate mechanisms underlying heart failure, arrhythmias, metabolic disease, and other heart diseases. Visualization of activation, conduction velocity, action potential duration, and other parameters at a myriad of sites cannot be achieved from cellular level investigation but is well solved by optical mapping1,5,6. In this paper we present the instrumentation setup and experimental conditions for simultaneous optical mapping of Vm and CaT in mouse hearts with high spatio-temporal resolution using state-of-the-art CMOS imaging technology. Consistent optical recordings obtained with this method illustrate that simultaneous optical mapping of Langendorff perfused mouse hearts is both feasible and reliable.
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Affiliation(s)
- Di Lang
- Department of Biomedical Engineering, Washington University in St. Louis, USA
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Salama G, Akar FG. Deciphering Arrhythmia Mechanisms - Tools of the Trade. Card Electrophysiol Clin 2011; 3:11-21. [PMID: 21572551 PMCID: PMC3093299 DOI: 10.1016/j.ccep.2010.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Pathophysiological remodeling of cardiac function occurs at multiple levels, spanning the spectrum from molecular and sub-cellular changes to those occurring at the organ-system levels. Of key importance to arrhythmias are changes in electrophysiological and calcium handling properties at the tissue level. In this review, we discuss how high-resolution optical action potential and calcium transient imaging has advanced our understanding of basic arrhythmia mechanisms associated with multiple cardiovascular disorders, including the long QT syndrome, heart failure, and ischemia-reperfusion injury. We focus on the role of repolarization gradients (section 1) and calcium mediated triggers (section 2) in the initiation and maintenance of complex arrhythmias in these settings.
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Affiliation(s)
- Guy Salama
- University of Pittsburgh, The Cardiovascular Institute, Pittsburgh, PA, 15261
| | - Fadi G. Akar
- Mount Sinai School of Medicine, New York, NY 10029, Tel: 212-241-9251; FAX: 212-241-4080
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Chen G, Yang X, Kerchner LJ, Salama NR, Alber S, Shusterman V, London B, Salama G. WITHDRAWN: Sex-differences in sodium/calcium exchange expression is a determinant of the arrhythmia phenotype in pre-pubertal rabbit hearts with Long QT type 2. Heart Rhythm 2010:S1547-5271(10)01438-4. [PMID: 21193060 PMCID: PMC3163039 DOI: 10.1016/j.hrthm.2010.12.040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2010] [Accepted: 12/23/2010] [Indexed: 11/26/2022]
Abstract
This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
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Affiliation(s)
- Guojun Chen
- Cardiovascular Institute, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Xiaoyan Yang
- Cardiovascular Institute, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Laurie J. Kerchner
- Cardiovascular Institute, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Naomi R. Salama
- Cardiovascular Institute, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Sean Alber
- Center for Biological Imaging, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Vladimir Shusterman
- Cardiovascular Institute, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Barry London
- Cardiovascular Institute, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
| | - Guy Salama
- Cardiovascular Institute, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261
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28
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Bruegmann T, Malan D, Hesse M, Beiert T, Fuegemann CJ, Fleischmann BK, Sasse P. Optogenetic control of heart muscle in vitro and in vivo. Nat Methods 2010; 7:897-900. [PMID: 20881965 DOI: 10.1038/nmeth.1512] [Citation(s) in RCA: 319] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Accepted: 08/30/2010] [Indexed: 11/09/2022]
Abstract
Electrical stimulation is the standard technique for exploring electrical behavior of heart muscle, but this approach has considerable technical limitations. Here we report expression of the light-activated cation channel channelrhodopsin-2 for light-induced stimulation of heart muscle in vitro and in mice. This method enabled precise localized stimulation and constant prolonged depolarization of cardiomyocytes and cardiac tissue resulting in alterations of pacemaking, Ca(2+) homeostasis, electrical coupling and arrhythmogenic spontaneous extrabeats.
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Affiliation(s)
- Tobias Bruegmann
- Institute of Physiology I, Life and Brain Center, University of Bonn, Bonn, Germany
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29
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Walton RD, Benoist D, Hyatt CJ, Gilbert SH, White E, Bernus O. Dual excitation wavelength epifluorescence imaging of transmural electrophysiological properties in intact hearts. Heart Rhythm 2010; 7:1843-9. [PMID: 20816869 DOI: 10.1016/j.hrthm.2010.08.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Accepted: 08/23/2010] [Indexed: 10/19/2022]
Abstract
BACKGROUND Epifluorescence imaging using voltage-sensitive dyes has provided unique insights into cardiac electrical activity and arrhythmias. However, conventional dyes use blue-green excitation light, which has limited depth penetration. OBJECTIVE The aim of this study was to demonstrate that combining a short and a long excitation wavelength using near-infrared (NIR) dyes allows for epifluorescence imaging of transmural electrophysiological properties in intact hearts. METHODS Epifluorescence imaging was performed in rat hearts (N = 11) using DI-4-ANEPPS and the NIR dye DI-4-ANBDQBS. Activation and action potential duration (APD) patterns were investigated at 2 excitation wavelengths (530 and 660 nm) after epicardial stimulation at various cycle lengths (160 to 70 ms). RESULTS Optical action potential upstrokes acquired with 660-nm excitation of DI-4-ANBDQBS were significantly longer than upstrokes obtained with 530-nm excitation of DI-4-ANEPPS (P < .001). Comparison of activation maps showed counterclockwise rotation of isochrones consistent with a transmural rotation of myofibers. Pronounced APD modulation by the activation sequence was observed at both excitation wavelengths. Significantly prolonged APDs (P = .016) and steeper APD restitution curves were found with DI-4-ANBDQBS (660-nm excitation) when compared with DI-4-ANEPPS (530-nm excitation). Dual excitation wavelength experiments using solely DI-4-ANBDQBS yielded similar results. Monophasic action potential recordings showed prolonged APD and steeper APD restitution curves in the endocardium, indicating that 660-nm excitation provides a significant endocardial contribution to the signal. Three-dimensional computer simulations confirmed our findings. CONCLUSION Dual excitation wavelength epifluorescence allows detecting transmural heterogeneity in intact hearts. It therefore has the potential to become an important tool in experimental cardiac electrophysiology.
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Affiliation(s)
- Richard D Walton
- Institute of Membrane and Systems Biology, Faculty of Biological Sciences, Multidisciplinary Cardiovascular Research Centre, University of Leeds, Leeds LS2 9JT, UK
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Nguyen DT, Ding C, Wilson E, Marcus GM, Olgin JE. Pirfenidone mitigates left ventricular fibrosis and dysfunction after myocardial infarction and reduces arrhythmias. Heart Rhythm 2010; 7:1438-45. [PMID: 20433946 DOI: 10.1016/j.hrthm.2010.04.030] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 04/23/2010] [Indexed: 11/18/2022]
Abstract
BACKGROUND Post-myocardial infarction (MI) complications include ventricular tachycardia (VT). Excessive non-MI fibrosis, involving the infarct border zone (IBZ) and beyond, is an important substrate for VT vulnerability. OBJECTIVE This study assessed whether the antifibrotic agent pirfenidone can mitigate fibrosis in remodeling and determined its effects on myocardial function and VT susceptibility in a rodent MI model. METHODS We studied 2 groups of rats undergoing MI 1 week prior to treatment: a control group (n = 15) treated with placebo and a pirfenidone group (n = 15). We performed serial echocardiograms, and after 4 weeks of treatment, we conducted electrophysiological and optical mapping studies as well as histology. RESULTS There was less decline in left ventricular (LV) ejection fraction for pirfenidone-treated rats, 8.6% versus 24.3% in controls (P <0.01). Pirfenidone rats also had lower rates of VT inducibility, 28.6% versus 73.3% in control rats (P <0.05). Furthermore, pirfenidone-treated rats had faster conduction velocities in their IBZs compared with controls, at all pacing cycle lengths (P <0.05). Rats treated with pirfenidone also had smaller infarct dense scar (8.9% of LV myocardium vs. 15.7% in controls, P <0.014), less total LV fibrosis (15% vs. 30% in controls, P <0.003), and less nonscar fibrosis (6.6% vs. 12.6% in controls, P <0.006). CONCLUSION Pirfenidone decreased total and nonscar fibrosis in a rat MI model, which correlated with decreased infarct scar, improved LV function, and decreased VT susceptibility. Directly targeting post-MI fibrotic substrates may have a role in limiting infarct-dense scar, improving LV function, and reducing VT vulnerability.
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Affiliation(s)
- Duy T Nguyen
- Cardiac Electrophysiology and Cardiovascular Research Institute, University of California, San Francisco, USA
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31
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Ding C, Gepstein L, Nguyen DT, Wilson E, Hulley G, Beaser A, Lee RJ, Olgin J. High-resolution optical mapping of ventricular tachycardia in rats with chronic myocardial infarction. Pacing Clin Electrophysiol 2010; 33:687-95. [PMID: 20180914 DOI: 10.1111/j.1540-8159.2010.02704.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Ventricular tachycardia (VT) is a common cause of mortality in post-myocardial infarction (MI) patients, even in the current era of coronary revascularization treatment. We report a reproducible VT model in rats with chronic MI induced by ischemia-reperfusion and describe its electrophysiological characteristics using high-resolution optical mapping. METHODS An MI was generated by left anterior descending coronary ligation (25 minutes) followed by reperfusion in 20 rats. Electrophysiology study and optical mapping were performed 5 weeks later using a Langendorff-perfused preparation and compared to normal rats. RESULTS The conduction velocity of the MI border zone was decreased to 53% of the normal areas remote from the infarct (0.37 +/- 0.16 m/sec vs 0.70 +/- 0.09 m/sec, P < 0.0001). The rate of VT inducibility in MI rats was significantly greater than in normal control rats (70% vs 0%, P = 0.00002). VT circuits involving the infarct area were identified with optical mapping in 83% MI rats. In addition, fixed and functional conduction block were observed in the infarct border zone. CONCLUSION This ischemia-reperfusion MI rat model is a reliable VT model, which simulates clinical revascularization treatment. High-resolution optical mapping in this model is useful to study the mechanism of VT and evaluate the effects of therapies.
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Affiliation(s)
- Chunhua Ding
- Cardiac Electrophysiology and Cardiovascular Research Institute, University of California, San Francisco, California 94143, USA
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32
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Ding C, Everett TH. Assessment of cardiac conduction: basic principles of optical mapping. Methods Mol Biol 2010; 660:239-252. [PMID: 20680823 DOI: 10.1007/978-1-60761-705-1_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Extracellular recordings acquired from electrodes placed on the surface of cardiac tissue have traditionally been used to study the electrophysiological properties of the tissue. While this technique has been used in several studies that have increased our understanding of cardiac arrhythmias and action potential propagation, there are several limitations that have prevented us from seeing a bigger picture of arrhythmia mechanisms. These limitations include the limited number of electrodes and unstable recordings. Optical mapping was developed to increase the temporal and spatial resolution over traditional electrode recordings and ultimately the accuracy of the data analysis. This technology involves using a voltage-sensitive dye that binds to the cell membrane. The fluorescence changes of the dye have a linear relationship to the action potential changes of the cell membrane. These fluorescent changes can then be detected by a photodiode array, a CCD camera or a CMOS camera. This will allow the recording of the action potential in hundreds to thousands of different sites simultaneously. Presented in this chapter are the materials and hardware needed along with step-by-step instructions on setup and techniques used in optical mapping for larger tissue preparations.
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Affiliation(s)
- Chunhua Ding
- Cardiac Electrophysiology Section of Cardiology, Department of Medicine, University of California, San Francisco, CA, USA
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Salama G, Hwang SM. Simultaneous optical mapping of intracellular free calcium and action potentials from Langendorff perfused hearts. ACTA ACUST UNITED AC 2009; Chapter 12:Unit 12.17. [PMID: 19575468 DOI: 10.1002/0471142956.cy1217s49] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The cardiac action potential (AP) controls the rise and fall of intracellular free Ca2+ (Ca(i)), and thus the amplitude and kinetics of force generation. Besides excitation-contraction coupling, the reverse process where Ca(i) influences the AP through Ca(i)-dependent ionic currents has been implicated as the mechanism underlying QT alternans and cardiac arrhythmias in heart failure, ischemia/reperfusion, cardiac myopathy, myocardial infarction, congenital and drug-induced long QT syndrome, and ventricular fibrillation. The development of dual optical mapping at high spatial and temporal resolution provides a powerful tool to investigate the role of Ca(i) anomalies in eliciting cardiac arrhythmias. This unit describes experimental protocols to map APs and Ca(i) transients from perfused hearts by labeling the heart with two fluorescent dyes, one to measure transmembrane potential (Vm), the other Ca(i) transients. High spatial and temporal resolution is achieved by selecting Vm and Ca(i) probes with the same excitation but different emission wavelengths, to avoid cross-talk and mechanical components.
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Affiliation(s)
- Guy Salama
- University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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34
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Holcomb MR, Woods MC, Uzelac I, Wikswo JP, Gilligan JM, Sidorov VY. The potential of dual camera systems for multimodal imaging of cardiac electrophysiology and metabolism. Exp Biol Med (Maywood) 2009; 234:1355-73. [PMID: 19657065 DOI: 10.3181/0902-rm-47] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Fluorescence imaging has become a common modality in cardiac electrodynamics. A single fluorescent parameter is typically measured. Given the growing emphasis on simultaneous imaging of more than one cardiac variable, we present an analysis of the potential of dual camera imaging, using as an example our straightforward dual camera system that allows simultaneous measurement of two dynamic quantities from the same region of the heart. The advantages of our system over others include an optional software camera calibration routine that eliminates the need for precise camera alignment. The system allows for rapid setup, dichroic image separation, dual-rate imaging, and high spatial resolution, and it is generally applicable to any two-camera measurement. This type of imaging system offers the potential for recording simultaneously not only transmembrane potential and intracellular calcium, two frequently measured quantities, but also other signals more directly related to myocardial metabolism, such as [K(+)](e), NADH, and reactive oxygen species, leading to the possibility of correlative multimodal cardiac imaging. We provide a compilation of dye and camera information critical to the design of dual camera systems and experiments.
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Affiliation(s)
- Mark R Holcomb
- Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235-1807, USA
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35
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Ruangkittisakul A, Okada Y, Oku Y, Koshiya N, Ballanyi K. Fluorescence imaging of active respiratory networks. Respir Physiol Neurobiol 2009; 168:26-38. [DOI: 10.1016/j.resp.2009.02.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 02/11/2009] [Accepted: 02/20/2009] [Indexed: 11/17/2022]
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Demchenko AP, Yesylevskyy SO. Nanoscopic description of biomembrane electrostatics: results of molecular dynamics simulations and fluorescence probing. Chem Phys Lipids 2009; 160:63-84. [PMID: 19481071 DOI: 10.1016/j.chemphyslip.2009.05.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2009] [Revised: 05/18/2009] [Accepted: 05/19/2009] [Indexed: 12/21/2022]
Abstract
Electrostatic fields generated on and inside biological membranes are recognized to play a fundamental role in key processes of cell functioning. Their understanding requires an adequate description on the level of elementary charges and the reconstruction of electrostatic potentials by integration over all elementary interactions. Out of all the available research tools, only molecular dynamics simulations are capable of this, extending from the atomic to the mesoscopic level of description on the required time and space scale. A complementary approach is that offered by molecular probe methods, with the application of electrochromic dyes. Highly sensitive to intermolecular interactions, they generate integrated signals arising from electric fields produced by elementary charges at the sites of their location. This review is an attempt to provide a critical analysis of these two approaches and their present and potential applications. The results obtained by both methods are consistent in that they both show an extremely complex profile of the electric field in the membrane. The nanoscopic view, with two-dimensional averaging over the bilayer plane and formal separation of the electrostatic potential into surface (Psi(s)), dipole (Psi(d)) and transmembrane (Psi(t)) potentials, is constructive in the analysis of different functional properties of membranes.
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Affiliation(s)
- Alexander P Demchenko
- A.V. Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Leontovicha St. 9, Kiev 01601, Ukraine.
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Fenton FH, Cherry EM, Kornreich BG. Termination of equine atrial fibrillation by quinidine: an optical mapping study. J Vet Cardiol 2008; 10:87-103. [PMID: 19036667 DOI: 10.1016/j.jvc.2008.10.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 09/30/2008] [Accepted: 10/08/2008] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To perform the first optical mapping studies of equine atrium to assess the spatiotemporal dynamics of atrial fibrillation (AF) and of its termination by quinidine. ANIMALS Intact, perfused atrial preparations obtained from four horses with normal cardiovascular examinations. MATERIALS AND METHODS AF was induced by a rapid pacing protocol with or without acetylcholine perfusion, and optical mapping was used to determine spatial dominant frequency distributions, electrical activity maps, and single-pixel optical signals. Following induction of AF, quinidine gluconate was perfused into the preparation and these parameters were monitored during quinidine-induced termination of AF. RESULTS Equine AF develops in the context of spatial gradients in action potential duration (APD) and diastolic interval (DI) that produce alternans, conduction block, and Wenckebach conduction in different regions at fast pacing rates. Quinidine terminates AF and prevents subsequent reinduction by reducing the maximal frequency and increasing frequency homogeneity. CONCLUSIONS Heterogeneity of APD and DI promote alternans and conduction block at fast pacing rates in the equine atrium, predisposing to the development of AF. Quinidine terminates AF by reducing maximum frequency and increasing frequency homogeneity. Our results are consistent with the hypothesis that quinidine increases effective refractory period, thereby decreasing frequency.
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Affiliation(s)
- Flavio H Fenton
- Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853, USA
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Yan P, Xie A, Wei M, Loew LM. Amino(oligo)thiophene-based environmentally sensitive biomembrane chromophores. J Org Chem 2008; 73:6587-94. [PMID: 18665648 DOI: 10.1021/jo800852h] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
There is a growing need for cellular imaging with fluorescent probes that emit at longer wavelengths to minimize the effects of absorption, autofluorescence, and scattering from biological tissue. In this paper a series of new environmentally sensitive hemicyanine dyes featuring amino(oligo)thiophene donors have been synthesized via aldol condensation between a 4-methylpyridinium salt and various amino(oligo)thiophene carboxaldehydes, which were, in turn, obtained from amination of bromo(oligo)thiophene carboxaldehyde. Side chains on these fluorophores impart a strong affinity for biological membranes. Compared with benzene analogues, these thiophene fluorophores show significant red shift in the absorption and emission spectra, offering compact red and near-infrared emitting fluorophores. More importantly, both the fluorescence quantum yields and the emission peaks are very sensitive to various environmental factors such as solvent polarity or viscosity, membrane potential, and membrane composition. These chromophores also exhibit strong nonlinear optical properties, including two-photon fluorescence and second harmonic generation, which are themselves environmentally sensitive. The combination of long wavelength fluorescence and nonlinear optical properties make these chromophores very suitable for applications that require sensing or imaging deep inside tissues.
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Affiliation(s)
- Ping Yan
- Richard D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut 06030, USA
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40
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Johnson JR, Fu N, Arunkumar E, Leevy WM, Gammon ST, Piwnica-Worms D, Smith BD. Squaraine rotaxanes: superior substitutes for Cy-5 in molecular probes for near-infrared fluorescence cell imaging. Angew Chem Int Ed Engl 2007; 46:5528-31. [PMID: 17585399 PMCID: PMC2854038 DOI: 10.1002/anie.200701491] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- James R Johnson
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
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41
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Patrick MJ, Ernst LA, Waggoner AS, Thai D, Tai D, Salama G. Enhanced aqueous solubility of long wavelength voltage-sensitive dyes by covalent attachment of polyethylene glycol. Org Biomol Chem 2007; 5:3347-53. [PMID: 17912389 PMCID: PMC3021457 DOI: 10.1039/b711438a] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Long wavelength voltage-sensitive dyes (VSDs) called Pittsburgh (PGH) dyes were recently synthesized by coupling various heterocyclic groups to a styryl-thiophene intermediate forming extended, partially rigid chromophores. Unlike most styryl VSDs, dyes with a sulfonic acid anchor directly attached to the chromophore showed no solvatochromic absorption shifts. The limited water solubility of many long wavelength VSDs requires the use of surfactants to transport the dye through physiological saline solutions and effectively label biological membranes. Here, we tested the chemical substitution of the sulfonic acid moiety with polyethyleneglycol (PEG) chains, ranging from MW 750 to 5000, to overcome the poor solubility of VSDs while retaining their properties as VSDs. The chemical synthesis of PGH dyes and their PEG derivatives are described. The PEG derivatives were soluble in aqueous solutions (>1 mM) and still reported membrane potential changes. In frog and mouse hearts, the voltage sensitivity (DeltaF/F per action potential) and spectral properties of PEG dyes were the same as the sulfonated analogues. Thus, the solubility of VSDs can be considerably improved with small polyethyleneglycol chains and can provide an effective approach to improve staining of excitable tissues and optical recordings of membrane potential.
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Affiliation(s)
- Michael J Patrick
- Molecular Biosensor & Imaging Center, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA.
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Matiukas A, Mitrea BG, Qin M, Pertsov AM, Shvedko AG, Warren MD, Zaitsev AV, Wuskell JP, Wei MD, Watras J, Loew LM. Near-infrared voltage-sensitive fluorescent dyes optimized for optical mapping in blood-perfused myocardium. Heart Rhythm 2007; 4:1441-51. [PMID: 17954405 DOI: 10.1016/j.hrthm.2007.07.012] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Accepted: 07/06/2007] [Indexed: 10/23/2022]
Abstract
BACKGROUND Styryl voltage-sensitive dyes (e.g., di-4-ANEPPS) have been used successfully for optical mapping in cardiac cells and tissues. However, their utility for probing electrical activity deep inside the myocardial wall and in blood-perfused myocardium has been limited because of light scattering and high absorption by endogenous chromophores and hemoglobin at blue-green excitation wavelengths. OBJECTIVE The purpose of this study was to characterize two new styryl dyes--di-4-ANBDQPQ (JPW-6003) and di-4-ANBDQBS (JPW-6033)--optimized for blood-perfused tissue and intramural optical mapping. METHODS Voltage-dependent spectra were recorded in a model lipid bilayer. Optical mapping experiments were conducted in four species (mouse, rat, guinea pig, and pig). Hearts were Langendorff perfused using Tyrode's solution and blood (pig). Dyes were loaded via bolus injection into perfusate. Transillumination experiments were conducted in isolated coronary-perfused pig right ventricular wall preparations. RESULTS The optimal excitation wavelength in cardiac tissues (650 nm) was >70 nm beyond the absorption maximum of hemoglobin. Voltage sensitivity of both dyes was approximately 10% to 20%. Signal decay half-life due to dye internalization was 80 to 210 minutes, which is 5 to 7 times slower than for di-4-ANEPPS. In transillumination mode, DeltaF/F was as high as 20%. In blood-perfused tissues, DeltaF/F reached 5.5% (1.8 times higher than for di-4-ANEPPS). CONCLUSION We have synthesized and characterized two new near-infrared dyes with excitation/emission wavelengths shifted >100 nm to the red. They provide both high voltage sensitivity and 5 to 7 times slower internalization rate compared to conventional dyes. The dyes are optimized for deeper tissue probing and optical mapping of blood-perfused tissue, but they also can be used for conventional applications.
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Affiliation(s)
- Arvydas Matiukas
- Department of Pharmacology, State University of New York, Upstate Medical University, Syracuse, New York 13210, USA
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Johnson J, Fu N, Arunkumar E, Leevy W, Gammon S, Piwnica-Worms D, Smith B. Squaraine Rotaxanes: Superior Substitutes for Cy-5 in Molecular Probes for Near-Infrared Fluorescence Cell Imaging. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200701491] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
Congenital long QT syndrome is a rare inherited condition characterized by prolongation of action potential duration (APD) in cardiac myocytes, prolongation of the QT interval on the surface electrocardiogram (ECG), and an increased risk of syncope and sudden death due to ventricular tachyarrhythmias. Mutations of cardiac ion channel genes that affect repolarization cause the majority of the congenital cases. Despite detailed characterizations of the mutated ion channels at the molecular level, a complete understanding of the mechanisms by which individual mutations may lead to arrhythmias and sudden death requires study of the intact heart and its modulation by the autonomic nervous system. Here, we will review studies of molecularly engineered mice with mutations in the genes (a) known to cause long QT syndrome in humans and (b) specific to cardiac repolarization in the mouse. Our goal is to provide the reader with a comprehensive overview of mouse models with long QT syndrome and to emphasize the advantages and limitations of these models.
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Affiliation(s)
- Guy Salama
- Cardiovascular Institute, University of Pittsburgh Medical Center, Scaife S-572, 200 Lothrop Street, Pittsburgh, PA 15213, USA
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Hwang SM, Choi BR, Salama G. Monte Carlo simulation of 3D mapping of cardiac electrical activity with spinning slit confocal optics. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2006; 2006:1093-1097. [PMID: 17946022 DOI: 10.1109/iembs.2006.259837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Optical techniques used to map transmembrane potential and intracellular Ca2+ activities of intact hearts are restricted to the surface and cannot resolve activity in deeper layers due to the lack of depth resolution. The recent development of spinning slit confocal optics offers advantages of depth resolution as well as high-speed confocal imaging which are necessary for millisecond-scale, depth-resolved mapping of membrane potential and/or intracellular Ca2+ concentration. Here, we show simulated confocal optics derived from confocal slits on a high-speed spinning disk using Monte Carlo method with a numerical heart tissue model and find that depth-resolved optical mapping is feasible down to around 800 microm below the surface using 670-nm excitation light. The numerical model shows that (1) a minimum slit separation, which is found to be a function of depth of the focal plane and the numerical aperture of the objective lens, for minimum background noise exists and (2) narrower slit widths result in slightly greater depth resolution but has a negative impact in significantly lower overall fluorescence intensity. An experimental test of this optics has been performed by imaging two overlapping layers of fluorescent beads and the result confirms the expected depth resolution in non-scattering medium. These results will be able to serve as a benchmark on how a 3D-imaging system can be expected to perform and what kind of theoretical depth-resolution can be expected from it.
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MESH Headings
- Action Potentials/physiology
- Body Surface Potential Mapping/instrumentation
- Body Surface Potential Mapping/methods
- Computer Simulation
- Equipment Design
- Equipment Failure Analysis
- Heart Conduction System/physiology
- Image Interpretation, Computer-Assisted/instrumentation
- Image Interpretation, Computer-Assisted/methods
- Imaging, Three-Dimensional/instrumentation
- Imaging, Three-Dimensional/methods
- Microscopy, Confocal/instrumentation
- Microscopy, Confocal/methods
- Microscopy, Fluorescence/instrumentation
- Microscopy, Fluorescence/methods
- Models, Cardiovascular
- Models, Statistical
- Molecular Probe Techniques/instrumentation
- Monte Carlo Method
- Optics and Photonics/instrumentation
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Affiliation(s)
- Seong-min Hwang
- Department of Cell Biology & Physiology, School of Medicine, University of Pittsburgh, 3500 Terrace Street, Pittsburgh, PA 15261, USA.
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