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Hennis K, Piantoni C, Biel M, Fenske S, Wahl-Schott C. Pacemaker Channels and the Chronotropic Response in Health and Disease. Circ Res 2024; 134:1348-1378. [PMID: 38723033 PMCID: PMC11081487 DOI: 10.1161/circresaha.123.323250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/13/2024]
Abstract
Loss or dysregulation of the normally precise control of heart rate via the autonomic nervous system plays a critical role during the development and progression of cardiovascular disease-including ischemic heart disease, heart failure, and arrhythmias. While the clinical significance of regulating changes in heart rate, known as the chronotropic effect, is undeniable, the mechanisms controlling these changes remain not fully understood. Heart rate acceleration and deceleration are mediated by increasing or decreasing the spontaneous firing rate of pacemaker cells in the sinoatrial node. During the transition from rest to activity, sympathetic neurons stimulate these cells by activating β-adrenergic receptors and increasing intracellular cyclic adenosine monophosphate. The same signal transduction pathway is targeted by positive chronotropic drugs such as norepinephrine and dobutamine, which are used in the treatment of cardiogenic shock and severe heart failure. The cyclic adenosine monophosphate-sensitive hyperpolarization-activated current (If) in pacemaker cells is passed by hyperpolarization-activated cyclic nucleotide-gated cation channels and is critical for generating the autonomous heartbeat. In addition, this current has been suggested to play a central role in the chronotropic effect. Recent studies demonstrate that cyclic adenosine monophosphate-dependent regulation of HCN4 (hyperpolarization-activated cyclic nucleotide-gated cation channel isoform 4) acts to stabilize the heart rate, particularly during rapid rate transitions induced by the autonomic nervous system. The mechanism is based on creating a balance between firing and recently discovered nonfiring pacemaker cells in the sinoatrial node. In this way, hyperpolarization-activated cyclic nucleotide-gated cation channels may protect the heart from sinoatrial node dysfunction, secondary arrhythmia of the atria, and potentially fatal tachyarrhythmia of the ventricles. Here, we review the latest findings on sinoatrial node automaticity and discuss the physiological and pathophysiological role of HCN pacemaker channels in the chronotropic response and beyond.
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Affiliation(s)
- Konstantin Hennis
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
| | - Chiara Piantoni
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
| | - Martin Biel
- Department of Pharmacy, Center for Drug Research (M.B., S.F.), Ludwig-Maximilians-Universität München, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Germany (M.B., S.F.)
| | - Stefanie Fenske
- Department of Pharmacy, Center for Drug Research (M.B., S.F.), Ludwig-Maximilians-Universität München, Germany
- German Centre for Cardiovascular Research (DZHK), Partner Site Munich Heart Alliance, Germany (M.B., S.F.)
| | - Christian Wahl-Schott
- Institute of Cardiovascular Physiology and Pathophysiology, Biomedical Center Munich, Walter Brendel Centre of Experimental Medicine, Faculty of Medicine (K.H., C.P., C.W.-S.), Ludwig-Maximilians-Universität München, Germany
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2
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Zhang ZH, Barajas-Martinez H, Jiang H, Huang CX, Antzelevitch C, Xia H, Hu D. Gene and stem cell therapy for inherited cardiac arrhythmias. Pharmacol Ther 2024; 256:108596. [PMID: 38301770 DOI: 10.1016/j.pharmthera.2024.108596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 12/11/2023] [Accepted: 01/13/2024] [Indexed: 02/03/2024]
Abstract
Inherited cardiac arrhythmias are a group of genetic diseases predisposing to sudden cardiac arrest, mainly resulting from variants in genes encoding cardiac ion channels or proteins involved in their regulation. Currently available therapeutic options (pharmacotherapy, ablative therapy and device-based therapy) can not preclude the occurrence of arrhythmia events and/or provide complete protection. With growing understanding of the genetic background and molecular mechanisms of inherited cardiac arrhythmias, advancing insight of stem cell technology, and development of vectors and delivery strategies, gene therapy and stem cell therapy may be promising approaches for treatment of inherited cardiac arrhythmias. Recent years have witnessed impressive progress in the basic science aspects and there is a clear and urgent need to be translated into the clinical management of arrhythmic events. In this review, we present a succinct overview of gene and cell therapy strategies, and summarize the current status of gene and cell therapy. Finally, we discuss future directions for implementation of gene and cell therapy in the therapy of inherited cardiac arrhythmias.
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Affiliation(s)
- Zhong-He Zhang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China
| | - Hector Barajas-Martinez
- Lankenau Institute for Medical Research, Lankenau Heart Institute, Wynnwood, PA, 19096, USA; Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Hong Jiang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China
| | - Cong-Xin Huang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China
| | - Charles Antzelevitch
- Lankenau Institute for Medical Research, Lankenau Heart Institute, Wynnwood, PA, 19096, USA; Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Hao Xia
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China.
| | - Dan Hu
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, 430060, PR China; Cardiovascular Research Institute, Wuhan University, Wuhan, 430060, PR China; Hubei Key Laboratory of Cardiology, Wuhan, 430060, PR China.
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3
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Liu CM, Chen YC, Hu YF. Harnessing cell reprogramming for cardiac biological pacing. J Biomed Sci 2023; 30:74. [PMID: 37633890 PMCID: PMC10463311 DOI: 10.1186/s12929-023-00970-y] [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: 05/06/2023] [Accepted: 08/22/2023] [Indexed: 08/28/2023] Open
Abstract
Electrical impulses from cardiac pacemaker cardiomyocytes initiate cardiac contraction and blood pumping and maintain life. Abnormal electrical impulses bring patients with low heart rates to cardiac arrest. The current therapy is to implant electronic devices to generate backup electricity. However, complications inherent to electronic devices remain unbearable suffering. Therefore, cardiac biological pacing has been developed as a hardware-free alternative. The approaches to generating biological pacing have evolved recently using cell reprogramming technology to generate pacemaker cardiomyocytes in-vivo or in-vitro. Different from conventional methods by electrical re-engineering, reprogramming-based biological pacing recapitulates various phenotypes of de novo pacemaker cardiomyocytes and is more physiological, efficient, and easy for clinical implementation. This article reviews the present state of the art in reprogramming-based biological pacing. We begin with the rationale for this new approach and review its advances in creating a biological pacemaker to treat bradyarrhythmia.
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Affiliation(s)
- Chih-Min Liu
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taipei, Taiwan
- Faculty of Medicine and Institute of Clinical Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Yi-Chun Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
- Institute of Biopharmaceutical Sciences, College of Pharmaceutical Sciences, National Yang Ming Chiao Tung University, Taipei, Taiwan
| | - Yu-Feng Hu
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taipei, Taiwan.
- Faculty of Medicine and Institute of Clinical Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan.
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
- Institute of Biopharmaceutical Sciences, College of Pharmaceutical Sciences, National Yang Ming Chiao Tung University, Taipei, Taiwan.
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4
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Henley T, Goudy J, Easterling M, Donley C, Wirka R, Bressan M. Local tissue mechanics control cardiac pacemaker cell embryonic patterning. Life Sci Alliance 2023; 6:e202201799. [PMID: 36973005 PMCID: PMC10043993 DOI: 10.26508/lsa.202201799] [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: 11/03/2022] [Revised: 03/13/2023] [Accepted: 03/15/2023] [Indexed: 03/29/2023] Open
Abstract
Cardiac pacemaker cells (CPCs) initiate the electric impulses that drive the rhythmic beating of the heart. CPCs reside in a heterogeneous, ECM-rich microenvironment termed the sinoatrial node (SAN). Surprisingly, little is known regarding the biochemical composition or mechanical properties of the SAN, and how the unique structural characteristics present in this region of the heart influence CPC function remains poorly understood. Here, we have identified that SAN development involves the construction of a "soft" macromolecular ECM that specifically encapsulates CPCs. In addition, we demonstrate that subjecting embryonic CPCs to substrate stiffnesses higher than those measured in vivo results in loss of coherent electrical oscillation and dysregulation of the HCN4 and NCX1 ion channels required for CPC automaticity. Collectively, these data indicate that local mechanics play a critical role in maintaining the embryonic CPC function while also quantitatively defining the range of material properties that are optimal for embryonic CPC maturation.
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Affiliation(s)
- Trevor Henley
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Julie Goudy
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Marietta Easterling
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Carrie Donley
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Robert Wirka
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Michael Bressan
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
- McAllister Heart Institute, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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Komosa ER, Wolfson DW, Bressan M, Cho HC, Ogle BM. Implementing Biological Pacemakers: Design Criteria for Successful. Circ Arrhythm Electrophysiol 2021; 14:e009957. [PMID: 34592837 PMCID: PMC8530973 DOI: 10.1161/circep.121.009957] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Each heartbeat that pumps blood throughout the body is initiated by an electrical impulse generated in the sinoatrial node (SAN). However, a number of disease conditions can hamper the ability of the SAN's pacemaker cells to generate consistent action potentials and maintain an orderly conduction path, leading to arrhythmias. For symptomatic patients, current treatments rely on implantation of an electronic pacing device. However, complications inherent to the indwelling hardware give pause to categorical use of device therapy for a subset of populations, including pediatric patients or those with temporary pacing needs. Cellular-based biological pacemakers, derived in vitro or in situ, could function as a therapeutic alternative to current electronic pacemakers. Understanding how biological pacemakers measure up to the SAN would facilitate defining and demonstrating its advantages over current treatments. In this review, we discuss recent approaches to creating biological pacemakers and delineate design criteria to guide future progress based on insights from basic biology of the SAN. We emphasize the need for long-term efficacy in vivo via maintenance of relevant proteins, source-sink balance, a niche reflective of the native SAN microenvironment, and chronotropic competence. With a focus on such criteria, combined with delivery methods tailored for disease indications, clinical implementation will be attainable.
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Affiliation(s)
- Elizabeth R Komosa
- Department of Biomedical Engineering (E.R.K., B.M.O.), University of Minnesota-Twin Cities, Minneapolis
- Stem Cell Institute (E.R.K., B.M.O.), University of Minnesota-Twin Cities, Minneapolis
| | - David W Wolfson
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (D.W.W., H.C.C.)
| | - Michael Bressan
- Department of Cell Biology and Physiology (M.B.), University of North Carolina-Chapel Hill
- McAllister Heart Institute (M.B.), University of North Carolina-Chapel Hill
| | - Hee Cheol Cho
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta (D.W.W., H.C.C.)
- Department of Pediatrics, Emory University, Atlanta, GA (H.C.C.)
| | - Brenda M Ogle
- Department of Biomedical Engineering (E.R.K., B.M.O.), University of Minnesota-Twin Cities, Minneapolis
- Stem Cell Institute (E.R.K., B.M.O.), University of Minnesota-Twin Cities, Minneapolis
- Department of Pediatrics (B.M.O), University of Minnesota-Twin Cities, Minneapolis
- Lillehei Heart Institute (B.M.O), University of Minnesota-Twin Cities, Minneapolis
- Institute for Engineering in Medicine (B.M.O), University of Minnesota-Twin Cities, Minneapolis
- Masonic Cancer Center (B.M.O), University of Minnesota-Twin Cities, Minneapolis
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6
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Naumova N, Iop L. Bioengineering the Cardiac Conduction System: Advances in Cellular, Gene, and Tissue Engineering for Heart Rhythm Regeneration. Front Bioeng Biotechnol 2021; 9:673477. [PMID: 34409019 PMCID: PMC8365186 DOI: 10.3389/fbioe.2021.673477] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Accepted: 06/24/2021] [Indexed: 01/01/2023] Open
Abstract
Heart rhythm disturbances caused by different etiologies may affect pediatric and adult patients with life-threatening consequences. When pharmacological therapy is ineffective in treating the disturbances, the implantation of electronic devices to control and/or restore normal heart pacing is a unique clinical management option. Although these artificial devices are life-saving, they display many limitations; not least, they do not have any capability to adapt to somatic growth or respond to neuroautonomic physiological changes. A biological pacemaker could offer a new clinical solution for restoring heart rhythms in the conditions of disorder in the cardiac conduction system. Several experimental approaches, such as cell-based, gene-based approaches, and the combination of both, for the generation of biological pacemakers are currently established and widely studied. Pacemaker bioengineering is also emerging as a technology to regenerate nodal tissues. This review analyzes and summarizes the strategies applied so far for the development of biological pacemakers, and discusses current translational challenges toward the first-in-human clinical application.
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Affiliation(s)
- Nataliia Naumova
- Department of Cardiac Thoracic Vascular Sciences and Public Health, University of Padua, Padua, Italy
| | - Laura Iop
- Department of Cardiac Thoracic Vascular Sciences and Public Health, University of Padua, Padua, Italy
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7
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Végh AMD, Verkerk AO, Cócera Ortega L, Wang J, Geerts D, Klerk M, Lodder K, Nobel R, Tijsen AJ, Devalla HD, Christoffels VM, Medina-Ramírez M, Smits AM, Tan HL, Wilders R, Goumans MJTH, Boink GJJ. Toward Biological Pacing by Cellular Delivery of Hcn2/SkM1. Front Physiol 2021; 11:588679. [PMID: 33488393 PMCID: PMC7815531 DOI: 10.3389/fphys.2020.588679] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 12/08/2020] [Indexed: 01/18/2023] Open
Abstract
Electronic pacemakers still face major shortcomings that are largely intrinsic to their hardware-based design. Radical improvements can potentially be generated by gene or cell therapy-based biological pacemakers. Our previous work identified adenoviral gene transfer of Hcn2 and SkM1, encoding a "funny current" and skeletal fast sodium current, respectively, as a potent combination to induce short-term biological pacing in dogs with atrioventricular block. To achieve long-term biological pacemaker activity, alternative delivery platforms need to be explored and optimized. The aim of the present study was therefore to investigate the functional delivery of Hcn2/SkM1 via human cardiomyocyte progenitor cells (CPCs). Nucleofection of Hcn2 and SkM1 in CPCs was optimized and gene transfer was determined for Hcn2 and SkM1 in vitro. The modified CPCs were analyzed using patch-clamp for validation and characterization of functional transgene expression. In addition, biophysical properties of Hcn2 and SkM1 were further investigated in lentivirally transduced CPCs by patch-clamp analysis. To compare both modification methods in vivo, CPCs were nucleofected or lentivirally transduced with GFP and injected in the left ventricle of male NOD-SCID mice. After 1 week, hearts were collected and analyzed for GFP expression and cell engraftment. Subsequent functional studies were carried out by computational modeling. Both nucleofection and lentiviral transduction of CPCs resulted in functional gene transfer of Hcn2 and SkM1 channels. However, lentiviral transduction was more efficient than nucleofection-mediated gene transfer and the virally transduced cells survived better in vivo. These data support future use of lentiviral transduction over nucleofection, concerning CPC-based cardiac gene delivery. Detailed patch-clamp studies revealed Hcn2 and Skm1 current kinetics within the range of previously reported values of other cell systems. Finally, computational modeling indicated that CPC-mediated delivery of Hcn2/SkM1 can generate stable pacemaker function in human ventricular myocytes. These modeling studies further illustrated that SkM1 plays an essential role in the final stage of diastolic depolarization, thereby enhancing biological pacemaker functioning delivered by Hcn2. Altogether these studies support further development of CPC-mediated delivery of Hcn2/SkM1 and functional testing in bradycardia models.
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Affiliation(s)
- Anna M D Végh
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands.,Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Arie O Verkerk
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands.,Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Lucía Cócera Ortega
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Jianan Wang
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Dirk Geerts
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Mischa Klerk
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Kirsten Lodder
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
| | - Ruby Nobel
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
| | - Anke J Tijsen
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Harsha D Devalla
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Vincent M Christoffels
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Max Medina-Ramírez
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Anke M Smits
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
| | - Hanno L Tan
- Department of Experimental Cardiology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands.,Netherlands Heart Institute, Utrecht, Netherlands
| | - Ronald Wilders
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
| | - Marie José T H Goumans
- Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, Netherlands
| | - Gerard J J Boink
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands.,Department of Clinical Cardiology, Heart Center, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
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8
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Ravindran D, Kok C, Farraha M, Selvakumar D, Clayton ZE, Kumar S, Chong J, Kizana E. Gene and Cell Therapy for Cardiac Arrhythmias. Clin Ther 2020; 42:1911-1922. [PMID: 32988632 DOI: 10.1016/j.clinthera.2020.09.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 08/19/2020] [Accepted: 09/01/2020] [Indexed: 12/21/2022]
Abstract
PURPOSE In the last decade, interest in gene therapy as a therapeutic technology has increased, largely driven by an exciting yet modest number of successful applications for monogenic diseases. Setbacks in the use of gene therapy for cardiac disease have motivated efforts to develop vectors with enhanced tropism for the heart and more efficient delivery methods. Although monogenic diseases are the logical target, cardiac arrhythmias represent a group of conditions amenable to gene therapy because of focal targets (biological pacemakers, nodal conduction, or stem cell-related arrhythmias) or bystander effects on cells not directly transduced because of electrical coupling. METHODS This review provides a contemporary narrative of the field of gene therapy for experimental cardiac arrhythmias, including those associated with stem cell transplant. Recent articles published in the English language and available through the PubMed database and other prominent literature are discussed. FINDINGS The promise of gene therapy has been realized for a handful of monogenic diseases and is actively being pursued for cardiac applications in preclinical models. With improved vectors, it is likely that cardiac disease will also benefit from this technology. Cardiac arrhythmias, whether inherited or acquired, are a group of conditions with a potentially lower threshold for phenotypic correction and as such hold unique potential as targets for cardiac gene therapy. IMPLICATIONS There has been a proliferation of research on the potential of gene therapy for cardiac arrhythmias. This body of investigation forms a strong basis on which further developments, particularly with viral vectors, are likely to help this technology progress along its translational trajectory.
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Affiliation(s)
- Dhanya Ravindran
- Centre for Heart Research, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia
| | - Cindy Kok
- Centre for Heart Research, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia
| | - Melad Farraha
- Centre for Heart Research, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia
| | - Dinesh Selvakumar
- Centre for Heart Research, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia; Department of Cardiology, Westmead Hospital, Westmead, New South Wales, Australia
| | - Zoe E Clayton
- Centre for Heart Research, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia
| | - Saurabh Kumar
- Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia; Department of Cardiology, Westmead Hospital, Westmead, New South Wales, Australia
| | - James Chong
- Centre for Heart Research, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia; Department of Cardiology, Westmead Hospital, Westmead, New South Wales, Australia
| | - Eddy Kizana
- Centre for Heart Research, The Westmead Institute for Medical Research, The University of Sydney, Sydney, New South Wales, Australia; Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia; Department of Cardiology, Westmead Hospital, Westmead, New South Wales, Australia.
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9
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Valiunas V, Cohen IS, Brink PR, Clausen C. A study of the outward background current conductance g K1, the pacemaker current conductance g f, and the gap junction conductance g j as determinants of biological pacing in single cells and in a two-cell syncytium using the dynamic clamp. Pflugers Arch 2020; 472:561-570. [PMID: 32415460 DOI: 10.1007/s00424-020-02378-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 03/31/2020] [Accepted: 04/02/2020] [Indexed: 12/21/2022]
Abstract
We previously demonstrated that a two-cell syncytium, composed of a ventricular myocyte and an mHCN2 expressing cell, recapitulated most properties of in vivo biological pacing induced by mHCN2-transfected hMSCs in the canine ventricle. Here, we use the two-cell syncytium, employing dynamic clamp, to study the roles of gf (pacemaker conductance), gK1 (background K+ conductance), and gj (intercellular coupling conductance) in biological pacing. We studied gf and gK1 in single HEK293 cells expressing cardiac sodium current channel Nav1.5 (SCN5A). At fixed gf, increasing gK1 hyperpolarized the cell and initiated pacing. As gK1 increased, rate increased, then decreased, finally ceasing at membrane potentials near EK. At fixed gK1, increasing gf depolarized the cell and initiated pacing. With increasing gf, rate increased reaching a plateau, then decreased, ceasing at a depolarized membrane potential. We studied gj via virtual coupling with two non-adjacent cells, a driver (HEK293 cell) in which gK1 and gf were injected without SCN5A and a follower (HEK293 cell), expressing SCN5A. At the chosen values of gK1 and gf oscillations initiated in the driver, when gj was increased synchronized pacing began, which then decreased by about 35% as gj approached 20 nS. Virtual uncoupling yielded similar insights into gj. We also studied subthreshold oscillations in physically and virtually coupled cells. When coupling was insufficient to induce pacing, passive spread of the oscillations occurred in the follower. These results show a non-monotonic relationship between gK1, gf, gj, and pacing. Further, oscillations can be generated by gK1 and gf in the absence of SCN5A.
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Affiliation(s)
- Virginijus Valiunas
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, 11794-8661, USA.
| | - Ira S Cohen
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, 11794-8661, USA
| | - Peter R Brink
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, 11794-8661, USA
| | - Chris Clausen
- Department of Physiology and Biophysics and the Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, 11794-8661, USA
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10
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Abstract
Cardiac pacemaking is a most fundamental cardiac function, thoroughly investigated for decades with a multiscale approach at organ, tissue, cell and molecular levels, to clarify the basic mechanisms underlying generation and control of cardiac rhythm. Understanding the processes involved in pacemaker activity is of paramount importance for a basic physiological knowledge, but also as a way to reveal details of pathological dysfunctions useful in the perspective of a therapeutic approach. Among the mechanisms involved in pacemaking, the "funny" (If) current has properties most specifically fitting the requirements for generation and control of repetitive activity, and has consequently received the most attention in studies of the pacemaker function. Present knowledge of the basic mechanisms of pacemaking and the properties of funny channels has led to important developments of clinical relevance. These include: (1) the successful development of heart rate-reducing agents, such as ivabradine, able to control cardiac rhythm and useful in the treatment of diseases such as coronary artery disease, heart failure and tachyarrhythmias; (2) the understanding of the genetic basis of disorders of cardiac rhythm caused by HCN channelopathies; (3) the design of strategies to implement biological pacemakers based on transfer of HCN channels or of stem cell-derived pacemaker cells expressing If, with the ultimate goal to replace electronic devices. In this review, I will give a brief historical account of the discovery of the funny current and the development of the concept of If-based pacemaking, in the context of a wider, more complex model of cardiac rhythmic function.
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Affiliation(s)
- Dario DiFrancesco
- Department of Biosciences, University of Milano, IBF-CNR University of Milano Unit, Milan, Italy
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Zhao H, Yang M, Wang F, Yang A, Zhao Q, Wang X, Tang Y, Wang T, Huang C. Overexpression of the medium‑conductance calcium‑activated potassium channel (SK4) and the HCN2 channel to generate a biological pacemaker. Mol Med Rep 2019; 20:3406-3414. [PMID: 31432175 DOI: 10.3892/mmr.2019.10591] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 07/25/2019] [Indexed: 11/06/2022] Open
Abstract
Ion channels serve important roles in the excitation‑contraction coupling of cardiac myocytes. Previous studies have shown that the overexpression or activation of intermediate‑conductance calcium‑activated potassium channel (SK4, encoded by KCNN4) in embryonic stem cell‑derived cardiomyocytes can significantly increase their automaticity. The mechanism underlying this effect is hypothesized to be associated with the activation of hyperpolarization‑activated cyclic nucleotide‑gated channel 2 (HCN2). The aim of the present study was to explore whether a biological pacemaker could be constructed by overexpressing SK4 alone or in combination with HCN2 in a rat model. Ad‑green fluorescent protein (GFP), Ad‑KCNN4 and Ad‑HCN2 recombinant adenoviruses were injected into the left ventricle of Sprague‑Dawley rat hearts. The rats were divided into a GFP group (n=10), an SK4 group (n=10), a HCN2 group (n=10) and an SK4 + HCN2 (SK4/HCN2) group (n=10). The isolated hearts were perfused at 5‑7 days following injection, and a complete heart block model was established. Compared with the GFP group, overexpressing SK4 alone did not significantly increase the heart rate after establishment of a complete heart block model [98.1±8.9 vs. 96.7±7.6 beats per min (BPM)], The heart rates in the SK4/HCN2 (139.9±21.9 BPM) and HCN2 groups (111.7±5.5 BPM) were significantly increased compared with the GFP and SK4 groups, and the heart rates in the SK4/HCN2 group were significantly increased compared with the SK4 or HCN2 groups. In the HCN2 (n=8) and the SK4/HCN2 (n=7) groups, the shape of the spontaneous ventricular rhythm was the same as the pacing‑induced ectopic rhythm in the transgenically altered site. By contrast, these rhythms were different in the SK4 (n=10) and GFP (n=10) groups. There were no significant differences in action potential duration alternans or ventricular arrhythmia inducibility between the four groups (all P>0.05). Western blotting, reverse transcription‑quantitative PCR and immunohistochemistry analyses showed that the expression levels of SK4 and HCN2 were significantly increased at the transgene site. Biological pacemaker activity could be successfully generated by co‑overexpression of SK4 and HCN2 without increasing the risk of ventricular arrhythmias. The overexpression of SK4 alone is insufficient to generate biological pacemaker activity. The present study provided evidence that SK4 and HCN2 combined could construct an ectopic pacemaker, laying the groundwork for the development of improved biological pacing mechanisms in the future.
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Affiliation(s)
- Hongyi Zhao
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
| | - Mei Yang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
| | - Fengyuan Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
| | - Ankang Yang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
| | - Qingyan Zhao
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
| | - Xi Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
| | - Yanhong Tang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
| | - Teng Wang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
| | - Congxin Huang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China
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Cardiomyocyte Progenitor Cells as a Functional Gene Delivery Vehicle for Long-Term Biological Pacing. Molecules 2019; 24:molecules24010181. [PMID: 30621310 PMCID: PMC6337610 DOI: 10.3390/molecules24010181] [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: 11/28/2018] [Revised: 12/28/2018] [Accepted: 12/31/2018] [Indexed: 01/16/2023] Open
Abstract
Sustained pacemaker function is a challenge in biological pacemaker engineering. Human cardiomyocyte progenitor cells (CMPCs) have exhibited extended survival in the heart after transplantation. We studied whether lentivirally transduced CMPCs that express the pacemaker current If (encoded by HCN4) can be used as functional gene delivery vehicle in biological pacing. Human CMPCs were isolated from fetal hearts using magnetic beads coated with Sca-1 antibody, cultured in nondifferentiating conditions, and transduced with a green fluorescent protein (GFP)- or HCN4-GFP-expressing lentivirus. A patch-clamp analysis showed a large hyperpolarization-activated, time-dependent inward current (−20 pA/pF at −140 mV, n = 14) with properties typical of If in HCN4-GFP-expressing CMPCs. Gap-junctional coupling between CMPCs and neonatal rat ventricular myocytes (NRVMs) was demonstrated by efficient dye transfer and changes in spontaneous beating activity. In organ explant cultures, the number of preparations showing spontaneous beating activity increased from 6.3% in CMPC/GFP-injected preparations to 68.2% in CMPC/HCN4-GFP-injected preparations (P < 0.05). Furthermore, in CMPC/HCN4-GFP-injected preparations, isoproterenol induced a significant reduction in cycle lengths from 648 ± 169 to 392 ± 71 ms (P < 0.05). In sum, CMPCs expressing HCN4-GFP functionally couple to NRVMs and induce physiologically controlled pacemaker activity and may therefore provide an attractive delivery platform for sustained pacemaker function.
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Choudhury M, Black N, Alghamdi A, D'Souza A, Wang R, Yanni J, Dobrzynski H, Kingston PA, Zhang H, Boyett MR, Morris GM. TBX18 overexpression enhances pacemaker function in a rat subsidiary atrial pacemaker model of sick sinus syndrome. J Physiol 2018; 596:6141-6155. [PMID: 30259525 PMCID: PMC6292813 DOI: 10.1113/jp276508] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 09/14/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The sinoatrial node (SAN) is the primary pacemaker of the heart. SAN dysfunction, or 'sick sinus syndrome', can cause excessively slow heart rates and pauses, leading to exercise limitation and syncope, currently treated by implantation of an electronic pacemaker. 'Biopacemaking' utilises gene therapy to restore pacemaker activity by manipulating gene expression. Overexpressing the HCN pacemaker ion channel has been widely used with limited success. We utilised bradycardic rat subsidiary atrial pacemaker tissue to evaluate alternative gene targets: the Na+ /Ca2+ exchanger NCX1, and the transcription factors TBX3 and TBX18 known to be involved in SAN embryonic development. TBX18 overexpression restored normal SAN function, as assessed by increased rate, improved heart rate stability and restoration of isoprenaline response. TBX3 and NCX1 were not effective in accelerating the rate of subsidiary atrial pacemaker tissue. Gene therapy targeting TBX18 could therefore have the potential to restore pacemaker function in human sick sinus syndrome obviating electronic pacemakers. ABSTRACT The sinoatrial node (SAN) is the primary pacemaker of the heart. Disease of the SAN, sick sinus syndrome, causes heart rate instability in the form of bradycardia and pauses, leading to exercise limitation and syncope. Biopacemaking aims to restore pacemaker activity by manipulating gene expression, and approaches utilising HCN channel overexpression have been widely used. We evaluated alternative gene targets for biopacemaking to restore normal SAN pacemaker physiology within bradycardic subsidiary atrial pacemaker (SAP) tissue, using the Na+ /Ca2+ exchanger NCX1, and the transcription factors TBX3 and TBX18. TBX18 expression in SAP tissue restored normal SAN function, as assessed by increased rate (SAN 267.5 ± 13.6 bpm, SAP 144.1 ± 8.6 bpm, SAP-TBX18 214.4 ± 14.4 bpm; P < 0.001), improved heart rate stability (standard deviation of RR intervals fell from 39.3 ± 7.2 ms to 6.9 ± 0.8 ms, P < 0.01; root mean square of successive differences of RR intervals fell from 41.7 ± 8.2 ms to 6.1 ± 1.2 ms, P < 0.01; standard deviation of points perpendicular to the line of identity of Poincaré plots (SD1) fell from 29.5 ± 5.8 ms to 7.9 ± 2.0 ms, P < 0.05) and restoration of isoprenaline response (increases in rates of SAN 65.5 ± 1.3%, SAP 28.4 ± 3.4% and SAP-TBX18 103.3 ± 10.2%; P < 0.001). These changes were driven by a TBX18-induced switch in the dominant HCN isoform in SAP tissue, with a significant upregulation of HCN2 (from 1.01 × 10-5 ± 2.2 × 10-6 to 2.8 × 10-5 ± 4.3 × 10-6 arbitrary units, P < 0.001). Biophysically detailed computer modelling incorporating isoform-specific HCN channel electrophysiology confirmed that the measured changes in HCN abundance could account for the observed changes in beating rates. TBX3 and NCX1 were not effective in accelerating the rate of SAP tissue.
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Affiliation(s)
- M. Choudhury
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - N. Black
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - A. Alghamdi
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - A. D'Souza
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - R. Wang
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - J. Yanni
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - H. Dobrzynski
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - P. A. Kingston
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - H. Zhang
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - M. R. Boyett
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
| | - G. M. Morris
- Institute of Cardiovascular SciencesUniversity of ManchesterManchesterUK
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Badu-Boateng C, Jennings R, Hammersley D. The therapeutic role of ivabradine in heart failure. Ther Adv Chronic Dis 2018; 9:199-207. [PMID: 30364460 DOI: 10.1177/2040622318784556] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 05/30/2018] [Indexed: 12/18/2022] Open
Abstract
Heart failure represents a major global cause of morbidity and mortality. Ivabradine is a selective funny current (If) inhibitor, which acts on the sinoatrial node, resulting in a reduction in heart rate. Ivabradine is currently licensed for use in patients with symptomatic heart failure with reduced ejection fraction and a heart rate persistently at least 70 beats per minute in spite of otherwise optimal prognostic heart failure pharmacotherapy. In this review article, we examine the mechanism of action of ivabradine, evaluate the clinical trials underpinning its application in heart failure and discuss its current recommended clinical use in this capacity.
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Affiliation(s)
| | - Robert Jennings
- Department of Medicine, Frimley Park Hospital, Frimley, Camberley, UK
| | - Daniel Hammersley
- Department of Cardiology, Kings College Hospital NHS Foundation Trust, Denmark Hill, London SE5 9RS, UK
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15
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Abstract
Electrogenesis in the heart begins in the sinoatrial node and proceeds down the conduction system to originate the heartbeat. Conduction system disorders lead to slow heart rates that are insufficient to support the circulation, necessitating implantation of electronic pacemakers. The typical electronic pacemaker consists of a subcutaneous generator and battery module attached to one or more endocardial leads. New leadless pacemakers can be implanted directly into the right ventricular apex, providing single-chamber pacing without a subcutaneous generator. Modern pacemakers are generally reliable, and their programmability provides options for different pacing modes tailored to specific clinical needs. Advances in device technology will probably include alternative energy sources and dual-chamber leadless pacing in the not-too-distant future. Although effective, current electronic devices have limitations related to lead or generator malfunction, lack of autonomic responsiveness, undesirable interactions with strong magnetic fields, and device-related infections. Biological pacemakers, generated by somatic gene transfer, cell fusion, or cell transplantation, provide an alternative to electronic devices. Somatic reprogramming strategies, which involve transfer of genes encoding transcription factors to transform working myocardium into a surrogate sinoatrial node, are furthest along in the translational pipeline. Even as electronic pacemakers become smaller and less invasive, biological pacemakers might expand the therapeutic armamentarium for conduction system disorders.
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Affiliation(s)
- Eugenio Cingolani
- Cedars-Sinai Heart Institute, 8700 Beverly Boulevard, Los Angeles, California 90048, USA
| | - Joshua I Goldhaber
- Cedars-Sinai Heart Institute, 8700 Beverly Boulevard, Los Angeles, California 90048, USA
| | - Eduardo Marbán
- Cedars-Sinai Heart Institute, 8700 Beverly Boulevard, Los Angeles, California 90048, USA
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16
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Zhao X, Gu T. Dysfunctional Hyperpolarization-Activated Cyclic Nucleotide-gated Ion Channels in Cardiac Diseases. Braz J Cardiovasc Surg 2017; 31:203-6. [PMID: 27556324 PMCID: PMC5062718 DOI: 10.5935/1678-9741.20160030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are reverse
voltage-dependent, and their activation depends on the hyperpolarization of the
membrane and may be directly or indirectly regulated by the cyclic adenosine
monophosphate (cAMP) or other signal-transduction cascades. The distribution,
quantity and activation states of HCN channels differ in tissues throughout the
body. Evidence exhibits that HCN channels play critical roles in the generation
and conduction of the electrical impulse and the physiopathological process of
some cardiac diseases. They may constitute promising drug targets in the
treatment of these cardiac diseases. Pharmacological treatment targeting HCN
channels is of benefit to these cardiac conditions.
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Affiliation(s)
- Xiaoqi Zhao
- Department of Cardiac Surgery ICU, First Affiliated Hospital, China Medical University, Shenyang, China
| | - Tianxiang Gu
- Department of Cardiac Surgery ICU, First Affiliated Hospital, China Medical University, Shenyang, China
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Motloch LJ, Larbig R, Darabi T, Reda S, Motloch KA, Wernly B, Lichtenauer M, Gebing T, Schwaiger A, Zagidullin N, Wolny M, Hoppe UC. Long-QT syndrome-associated caveolin-3 mutations differentially regulate the hyperpolarization-activated cyclic nucleotide gated channel 4. Physiol Int 2017. [DOI: 10.1556/2060.104.2017.2.6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Background
Caveolin-3 (cav-3) mutations are linked to the long-QT syndrome (LQTS) causing distinct clinical symptoms. Hyperpolarization-activated cyclic nucleotide channel 4 (HCN4) underlies the pacemaker current If. It associates with cav-3 and both form a macromolecular complex.
Methods
To examine the effects of human LQTS-associated cav-3 mutations on HCN4-channel function, HEK293-cells were cotransfected with HCN4 and wild-type (WT) cav-3 or a LQTS-associated cav-3 mutant (T78M, A85T, S141R, or F97C). HCN4 currents were recorded using the whole-cell patch-clamp technique.
Results
WT cav-3 significantly decreased HCN4 current density and shifted midpoint of activation into negative direction. HCN4 current properties were differentially modulated by LQTS-associated cav-3 mutations. When compared with WT cav-3, A85T, F97C, and T78M did not alter the specific effect of cav-3, but S141R significantly increased HCN4 current density. Compared with WT cav-3, no significant modifications of voltage dependence of steady-state activation curves were observed. However, while WT cav-3 alone had no significant effect on HCN4 current activation, all LQTS-associated cav-3 mutations significantly accelerated HCN4 activation kinetics.
Conclusions
Our results indicate that HCN4 channel function is modulated by cav-3. LQTS-associated mutations of cav-3 differentially influence pacemaker current properties indicating a pathophysiological role in clinical manifestations.
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Affiliation(s)
- LJ Motloch
- 1Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - R Larbig
- 2Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany
| | - T Darabi
- 1Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - S Reda
- 1Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - KA Motloch
- 3Research Program for Ophthalmology and Glaucoma Research, University Clinic of Ophthalmology and Optometry, Paracelsus Medical University/SALK, Salzburg, Austria
| | - B Wernly
- 1Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - M Lichtenauer
- 1Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - T Gebing
- 1Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - A Schwaiger
- 1Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - N Zagidullin
- 4Department of Internal Diseases, Bashkir State Medical University, Ufa, Russia
| | - M Wolny
- 1Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - UC Hoppe
- 1Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
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18
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Innovative pacing: Recent advances, emerging technologies, and future directions in cardiac pacing. Trends Cardiovasc Med 2016; 26:452-63. [PMID: 27017442 DOI: 10.1016/j.tcm.2016.02.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/15/2016] [Accepted: 02/17/2016] [Indexed: 11/20/2022]
Abstract
The field of cardiovascular medicine is rapidly evolving as advancements in technology and engineering provide clinicians new and exciting ways to care for an aging population. Cardiac pacing, in particular, has seen a series of game-changing technologies emerge in the past several years spurred by low-power electronics, high density batteries, improved catheter delivery systems and innovative software design. We look at several of these emerging pacemaker technologies, discussing the rationale, current state and future directions of these pioneering developments in electrophysiology.
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Boink GJ, Christoffels VM, Robinson RB, Tan HL. The past, present, and future of pacemaker therapies. Trends Cardiovasc Med 2015; 25:661-73. [DOI: 10.1016/j.tcm.2015.02.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 01/24/2015] [Accepted: 02/11/2015] [Indexed: 01/01/2023]
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Li N, Csepe TA, Hansen BJ, Dobrzynski H, Higgins RSD, Kilic A, Mohler PJ, Janssen PML, Rosen MR, Biesiadecki BJ, Fedorov VV. Molecular Mapping of Sinoatrial Node HCN Channel Expression in the Human Heart. Circ Arrhythm Electrophysiol 2015; 8:1219-27. [PMID: 26304511 DOI: 10.1161/circep.115.003070] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Accepted: 08/04/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND The hyperpolarization-activated current, If, plays an important role in sinoatrial node (SAN) pacemaking. Surprisingly, the distribution of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in human SAN has only been investigated at the mRNA level. Our aim was to define the expression pattern of HCN proteins in human SAN and different atrial regions. METHODS AND RESULTS Entire SAN complexes were isolated from failing (n=5) and nonfailing (n=9) human hearts cardioplegically arrested in the operating room. Three-dimensional intramural SAN structure was identified as the fibrotic compact region around the SAN artery with Connexin 43-negative pacemaker cardiomyocytes visualized in Masson's trichrome and immunostained cryosections. SAN protein was precisely isolated from the adjacent frozen SAN tissue blocks using a 16G biopsy needle. The purity of the SAN protein was confirmed by Connexin 43 immunoblot. All 3 HCN isoform proteins were detected in SAN. HCN1 was predominantly distributed in the human SAN with a 125.1±40.2 (n=12) expression ratio of SAN to right atrium. HCN2 and HCN4 expression levels were higher in SAN than in atria, with SAN to right atrium ratios of 6.1±0.9 and 4.6±0.6 (n=12), respectively. CONCLUSIONS This is the first study to conduct precise 3D molecular mapping of the human SAN by isolating pure pacemaker SAN tissue. All 3 cardiac HCN isoforms had higher expression in the SAN than in the atria. HCN1 was almost exclusively expressed in SAN, emphasizing its utility as a new specific molecular marker of the human SAN and as a potential target of specific treatments intended to modify sinus rhythm.
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Affiliation(s)
- Ning Li
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Thomas A Csepe
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Brian J Hansen
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Halina Dobrzynski
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Robert S D Higgins
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Ahmet Kilic
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Peter J Mohler
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Paul M L Janssen
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Michael R Rosen
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Brandon J Biesiadecki
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.)
| | - Vadim V Fedorov
- From the Department of Physiology & Cell Biology and Dorothy M. Davis Heart & Lung Research Institute (N.L., T.A.C., B.J.H., P.J.M., P.M.L.J., B.J.B., V.V.F.), Department of Surgery and Dorothy M. Davis Heart & Lung Research Institute (R.S.D.H., A.K.), The Ohio State University Wexner Medical Center, Columbus; Institute of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom (H.D.); and Departments of Pharmacology and Pediatrics, Columbia University, New York, NY (M.R.R.).
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Motloch LJ, Akar FG. Gene therapy to restore electrophysiological function in heart failure. Expert Opin Biol Ther 2015; 15:803-17. [PMID: 25865107 DOI: 10.1517/14712598.2015.1036734] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
INTRODUCTION Heart failure (HF) is a major public health epidemic and a leading cause of morbidity and mortality in the industrialized world. Existing treatments for patients with HF are often associated with pro-arrhythmic activity and risk of sudden cardiac death. Therefore, development of novel, effective and safe therapeutic options for HF patients is a critical area of unmet need. AREAS COVERED In this article, we review recent advances in the emerging field of cardiac gene therapy for the treatment of tachy- and bradyarrhythmias in HF. We provide an overview of gene-based approaches that modulate myocardial conduction, repolarization, calcium cycling and adrenergic signaling to restore heart rate and rhythm. EXPERT OPINION We highlight major advantages of gene therapy for arrhythmias, including the ability to selectively target specific cell populations and to limit the therapeutic effect to the region that requires modification. We illustrate how advances in our fundamental understanding of the molecular origins of arrhythmogenic disorders are allowing investigators to use targeted gene-based approaches to successfully correct abnormal excitability in the atria, ventricles and conduction system. Translation of various gene therapy approaches to humans may revolutionize our ability to combat lethal arrhythmias in HF patients.
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Affiliation(s)
- Lukas J Motloch
- The Cardiovascular Institute, Mount Sinai School of Medicine , One Gustave L. Levy Place, Box 1030, New York, NY 10029 , USA
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Chauveau S, Brink PR, Cohen IS. Stem cell-based biological pacemakers from proof of principle to therapy: a review. Cytotherapy 2014; 16:873-80. [PMID: 24831844 PMCID: PMC4051829 DOI: 10.1016/j.jcyt.2014.02.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 02/11/2014] [Accepted: 02/23/2014] [Indexed: 12/12/2022]
Abstract
Electronic pacemakers are the standard therapy for bradycardia-related symptoms but have shortcomings. Over the past 15 years, experimental evidence has demonstrated that gene and cell-based therapies can create a biological pacemaker. Recently, physiologically acceptable rates have been reported with an adenovirus-based approach. However, adenovirus-based protein expression does not last more than 4 weeks, which limits its clinical applicability. Cell-based platforms are potential candidates for longer expression. Currently there are two cell-based approaches being tested: (i) mesenchymal stem cells used as a suitcase for delivering pacemaker genes and (ii) pluripotent stem cells differentiated down a cardiac lineage with endogenous pacemaker activity. This review examines the current achievements in engineering a biological pacemaker, defines the patient population for whom this device would be useful and identifies the challenges still ahead before cell therapy can replace current electronic devices.
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Affiliation(s)
- Samuel Chauveau
- Department of Physiology and Biophysics, Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, USA
| | - Peter R Brink
- Department of Physiology and Biophysics, Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, USA
| | - Ira S Cohen
- Department of Physiology and Biophysics, Institute for Molecular Cardiology, Stony Brook University, Stony Brook, NY, USA.
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Scicchitano P, Cortese F, Ricci G, Carbonara S, Moncelli M, Iacoviello M, Cecere A, Gesualdo M, Zito A, Caldarola P, Scrutinio D, Lagioia R, Riccioni G, Ciccone MM. Ivabradine, coronary artery disease, and heart failure: beyond rhythm control. Drug Des Devel Ther 2014; 8:689-700. [PMID: 24940047 PMCID: PMC4051626 DOI: 10.2147/dddt.s60591] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Elevated heart rate could negatively influence cardiovascular risk in the general population. It can induce and promote the atherosclerotic process by means of several mechanisms involving endothelial shear stress and biochemical activities. Furthermore, elevated heart rate can directly increase heart ischemic conditions because of its skill in unbalancing demand/supply of oxygen and decreasing the diastolic period. Thus, many pharmacological treatments have been proposed in order to reduce heart rate and ameliorate the cardiovascular risk profile of individuals, especially those suffering from coronary artery diseases (CAD) and chronic heart failure (CHF). Ivabradine is the first pure heart rate reductive drug approved and currently used in humans, created in order to selectively reduce sinus node function and to overcome the many side effects of similar pharmacological tools (ie, β-blockers or calcium channel antagonists). The aim of our review is to evaluate the role and the safety of this molecule on CAD and CHF therapeutic strategies.
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Affiliation(s)
- Pietro Scicchitano
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
| | - Francesca Cortese
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
| | - Gabriella Ricci
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
| | - Santa Carbonara
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
| | - Michele Moncelli
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
| | - Massimo Iacoviello
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
| | - Annagrazia Cecere
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
| | - Michele Gesualdo
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
| | - Annapaola Zito
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
| | - Pasquale Caldarola
- Section of Cardiovascular Diseases, Policlinic, San Paolo Hospital, Bari, Italy
| | - Domenico Scrutinio
- Section of Cardiovascular Diseases, Fondazione Maugeri, Cassano Murge, Italy
| | - Rocco Lagioia
- Section of Cardiovascular Diseases, Fondazione Maugeri, Cassano Murge, Italy
| | - Graziano Riccioni
- Intensive Cardiology Care Unit, San Camillo de Lellis Hospital, Manfredonia, Foggia, Italy
| | - Marco Matteo Ciccone
- Section of Cardiovascular Diseases, Department of Emergency and Organ Transplantation, University of Bari, School of Medicine, Policlinico, Bari, Italy
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Kentish SJ, O'Donnell TA, Wittert GA, Page AJ. Diet-dependent modulation of gastro-oesphageal vagal afferent mechanosensitivity by endogenous nitric oxide. J Physiol 2014; 592:3287-301. [PMID: 24879868 DOI: 10.1113/jphysiol.2014.272674] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Neuronal nitric oxide (NO) plays an important role in gastric motor activity and modulates the mechanosensitivity of gastro-oesophageal vagal afferents. Effects of NO on food intake are dependent on feeding status. We sought to determine the effect of NO on gastro-oesophageal vagal afferent activity in the normally fed and food-restricted states and the second messenger pathways mediating these effects. Eight week old female C56BL/6 mice were fed ad libitum or food restricted for 14 h. An in vitro preparation was used to determine the functional effects of NO and the second messenger pathways involved. Expression of NO signal transduction molecules in vagal afferents was determined by reverse-transcription polymerase chain reaction (RT-PCR). Endogenous NO and the NO donor S-nitroso-N-acetylpenicillamine (SNAP) inhibited vagal mucosal afferent responses to tactile stimuli in mice fed ad libitum. After a 14 h fast endogenous NO and SNAP potentiated tension and mucosal afferent responses to mechanical stimulation. The excitatory effect of NO was blocked by the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor apocynin. After a 14 h fast expression of NADPH oxidase 2 (NOX2) mRNA in whole nodose ganglia was significantly reduced and the excitatory effect of NO on gastro-oesophageal vagal afferents was lost. Under fasting conditions the inhibitory effect of NO was blocked with the hyperpolarisation-activated cyclic nucleotide-gated (HCN) channel blocker ivabradine and mRNA expression of HCN3 in the nodose ganglia was elevated. In conclusion, the role of NO in the peripheral modulation of gastro-oesophageal vagal afferents is dynamic and dependent on feeding status.
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Affiliation(s)
- Stephen J Kentish
- Nerve-Gut Research Laboratory, Department of Medicine, University of Adelaide, Adelaide, Australia
| | - Tracey A O'Donnell
- Nerve-Gut Research Laboratory, Department of Medicine, University of Adelaide, Adelaide, Australia
| | - Gary A Wittert
- Nerve-Gut Research Laboratory, Department of Medicine, University of Adelaide, Adelaide, Australia
| | - Amanda J Page
- Nerve-Gut Research Laboratory, Department of Medicine, University of Adelaide, Adelaide, Australia Royal Adelaide Hospital, Adelaide, Australia
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Abstract
Efforts to use gene therapy to create a biological pacemaker as an adjunct or replacement of electronic pacemakers have been ongoing for about 15 years. For the past decade, most of these efforts have focused on the hyperpolarization-activated cyclic nucleotide gated-(HCN) gene family of channels alone or in combination with other genes. The HCN gene family is the molecular correlate of the cardiac pacemaker current, If. It is a suitable basis for a biological pacemaker because it generates a depolarizing inward current primarily during diastole and is directly regulated by cyclic adenosine monophosphate (cAMP), thereby incorporating autonomic responsiveness. However, biological pacemakers based either on native HCN channels or on mutated HCN channels designed to optimize biophysical characteristics have failed to attain the desired basal and maximal physiological heart rates in large animals. More recent work has explored dual gene therapy approaches, combining an HCN variant with another gene to reduce outward current, increase an additional inward current, or enhance cAMP synthesis. Several of these dual gene therapy approaches have demonstrated appropriate basal and maximal heart rates with little or no reliance on a backup electronic pacemaker during the period of study. Future research, besides examining the efficacy of other gene combinations, will need to consider the additional issues of safety and persistence of the viral vectors often used to deliver these genes to a specific cardiac region.
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Affiliation(s)
- Gerard J. J. Boink
- Heart Center, Department of Clinical & Experimental Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
- Netherlands Heart Institute, ICIN, Utrecht, the Netherlands
| | - Richard B. Robinson
- Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, New York, NY, USA
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The Anthropomorphic Mouse. J Cardiovasc Pharmacol 2014; 63:1-3. [DOI: 10.1097/fjc.0000000000000049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Morris GM, D'Souza A, Dobrzynski H, Lei M, Choudhury M, Billeter R, Kryukova Y, Robinson RB, Kingston PA, Boyett MR. Characterization of a right atrial subsidiary pacemaker and acceleration of the pacing rate by HCN over-expression. Cardiovasc Res 2013; 100:160-9. [DOI: 10.1093/cvr/cvt164] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Lu W, Yaoming N, Boli R, Jun C, Changhai Z, Yang Z, Zhiyuan S. mHCN4 genetically modified canine mesenchymal stem cells provide biological pacemaking function in complete dogs with atrioventricular block. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2013; 36:1138-49. [PMID: 23663261 DOI: 10.1111/pace.12154] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2013] [Revised: 03/01/2013] [Accepted: 03/06/2013] [Indexed: 01/13/2023]
Abstract
BACKGROUND The study was undertaken to assess the properties of mouse HCN4 (mHCN4)-modified canine mesenchymal stem cells (cMSCs) in dogs with experimentally induced complete atrioventricular (AV) block and electronic pacing. METHODS Complete AV block was induced in adult dogs who had undergone implantation of backup electronic pacemakers. cMSCs were transfected with mHCN4 genes. Evidence of successful IHCN4 expression was provided by patch-clamp detection. mHCN4-cMSCs or normal cMSCs were injected subepicardially into the left ventricular anterior wall of the dogs. Cardiac parameters were monitored for 6 weeks. Heart rate variability (HRV) was evaluated using quantitative Poincaré plots of R-RN against R-RN+1 intervals. cMSCs survival and expression of HCN4 in vivo were examined by histological studies and Western blot. RESULTS In 2 weeks, the maximum heart rate and the number of impulses generated from the injection sites were much higher in dogs injected with HCN4-modified MSCs than in control dogs. Basal heart rate increased in the HCN4 group and became fully stabilized by Week 4, evidenced by markedly reduced numbers of electronic pacemaker beats. At Week 2, HRV during exercise was significantly higher in HCN4 dogs than in controls as shown by descriptors of both instantaneous (SD1) and longer term (SD2) beat-to-beat deviations (P < 0.05). Hematoxylin-eosin staining and Western blot proved that cMSCs survive and express HCN4 protein in situ in heart of HCN4 dog. CONCLUSION Transplantation of mHCN4-modified cMSCs provided a stable biological pacemaking function that allowed an appropriate chronotropic response to physical exercise for up to 6 weeks.
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Affiliation(s)
- Wei Lu
- Department of Cardiology, Southwest Hospital, Third Military Medical University, Chongqing, China
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29
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Boink GJJ, Duan L, Nearing BD, Shlapakova IN, Sosunov EA, Anyukhovsky EP, Bobkov E, Kryukova Y, Ozgen N, Danilo P, Cohen IS, Verrier RL, Robinson RB, Rosen MR. HCN2/SkM1 gene transfer into canine left bundle branch induces stable, autonomically responsive biological pacing at physiological heart rates. J Am Coll Cardiol 2013; 61:1192-201. [PMID: 23395072 DOI: 10.1016/j.jacc.2012.12.031] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Revised: 12/07/2012] [Accepted: 12/18/2012] [Indexed: 11/30/2022]
Abstract
OBJECTIVES This study sought to test the hypothesis that hyperpolarization-activated cyclic nucleotide-gated (HCN)-based biological pacing might be improved significantly by hyperpolarizing the action potential (AP) threshold via coexpression of the skeletal muscle sodium channel 1 (SkM1). BACKGROUND Gene-based biological pacemakers display effective in vivo pacemaker function. However, approaches used to date have failed to manifest optimal pacemaker properties, defined as basal beating rates of 60 to 90 beats/min, a brisk autonomic response achieving maximal rates of 130 to 160 beats/min, and low to absent electronic backup pacing. METHODS We implanted adenoviral SkM1, HCN2, or HCN2/SkM1 constructs into left bundle branches (LBB) or left ventricular (LV) epicardium of atrioventricular-blocked dogs. RESULTS During stable peak gene expression on days 5 to 7, HCN2/SkM1 LBB-injected dogs showed highly stable in vivo pacemaker activity superior to SkM1 or HCN2 alone and superior to LV-implanted dogs with regard to beating rates (resting approximately 80 beats/min; maximum approximately 130 beats/min), no dependence on electronic backup pacing, and enhanced modulation of pacemaker function during circadian rhythm or epinephrine infusion. In vitro isolated LV of dogs overexpressing SkM1 manifested a significantly more negative AP threshold. CONCLUSIONS LBB-injected HCN2/SkM1 potentially provides a more clinically suitable biological pacemaker strategy than other reported constructs. This superiority is attributable to the more negative AP threshold and injection into the LBB.
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Affiliation(s)
- Gerard J J Boink
- Department of Pharmacology, Columbia University, New York, NY 10032, USA
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Direct conversion of quiescent cardiomyocytes to pacemaker cells by expression of Tbx18. Nat Biotechnol 2012; 31:54-62. [PMID: 23242162 DOI: 10.1038/nbt.2465] [Citation(s) in RCA: 230] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 11/28/2012] [Indexed: 01/09/2023]
Abstract
The heartbeat originates within the sinoatrial node (SAN), a small structure containing <10,000 genuine pacemaker cells. If the SAN fails, the ∼5 billion working cardiomyocytes downstream of it become quiescent, leading to circulatory collapse in the absence of electronic pacemaker therapy. Here we demonstrate conversion of rodent cardiomyocytes to SAN cells in vitro and in vivo by expression of Tbx18, a gene critical for early SAN specification. Within days of in vivo Tbx18 transduction, 9.2% of transduced, ventricular cardiomyocytes develop spontaneous electrical firing physiologically indistinguishable from that of SAN cells, along with morphological and epigenetic features characteristic of SAN cells. In vivo, focal Tbx18 gene transfer in the guinea-pig ventricle yields ectopic pacemaker activity, correcting a bradycardic disease phenotype. Myocytes transduced in vivo acquire the cardinal tapering morphology and physiological automaticity of native SAN pacemaker cells. The creation of induced SAN pacemaker (iSAN) cells opens new prospects for bioengineered pacemakers.
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Li RA. Gene- and cell-based bio-artificial pacemaker: what basic and translational lessons have we learned? Gene Ther 2012; 19:588-95. [PMID: 22673497 DOI: 10.1038/gt.2012.33] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Normal rhythms originate in the sino-atrial node, a specialized cardiac tissue consisting of only a few thousands of nodal pacemaker cells. Malfunction of pacemaker cells due to diseases or aging leads to rhythm generation disorders (for example, bradycardias and sick-sinus syndrome (SSS)), which often necessitate the implantation of electronic pacemakers. Although effective, electronic devices are associated with such shortcomings as limited battery life, permanent implantation of leads, lead dislodging, the lack of autonomic responses and so on. Here, various gene- and cell-based approaches, with a particular emphasis placed on the use of pluripotent stem cells and the hyperpolarization-activated cyclic nucleotide-gated-encoded pacemaker gene family, that have been pursued in the past decade to reconstruct bio-artificial pacemakers as alternatives will be discussed in relation to the basic biological insights and translational regenerative potential.
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Affiliation(s)
- R A Li
- Center of Cardiovascular Research, Mount Sinai School of Medicine, New York, NY 10029, USA.
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Boink GJJ, Nearing BD, Shlapakova IN, Duan L, Kryukova Y, Bobkov Y, Tan HL, Cohen IS, Danilo P, Robinson RB, Verrier RL, Rosen MR. Ca(2+)-stimulated adenylyl cyclase AC1 generates efficient biological pacing as single gene therapy and in combination with HCN2. Circulation 2012; 126:528-36. [PMID: 22753192 DOI: 10.1161/circulationaha.111.083584] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND Biological pacing performed solely via HCN2 gene transfer in vivo results in relatively slow idioventricular rates and only moderate autonomic responsiveness. We induced biological pacing using the Ca(2+)-stimulated adenylyl cyclase AC1 gene expressed alone or in combination with HCN2 and compared outcomes with those with single-gene HCN2 transfer. METHODS AND RESULTS We implanted adenoviral HCN2, AC1, or HCN2/AC1 constructs into the left bundle branches of atrioventricular-blocked dogs. During steady-state gene expression (days 5-7), differences between AC1, HCN2/AC1, and HCN2 alone were evident in basal beating rate, escape time, and dependence on electronic backup pacing. In HCN2, AC1, and HCN2/AC1, these parameters were as follows: basal beating rate: 50±1.5, 60±5.0, and 129±28.9 bpm (P<0.05 for HCN2/AC1 versus HCN2 or AC1 alone), respectively; escape time: 2.4±0.2, 1.3±0.2, and 1.1±.0.4 seconds (P<0.05 for AC1 and HCN2/AC1 versus HCN2); and percent electronic beats: 34±8%, 2±1%, and 6±2% (P<0.05 for AC1 and HCN2/AC1 versus HCN2). Instantaneous (SD1) and long-term (SD2) heart rate variability and circadian rhythm analyzed via 24-hour Holter recordings showed a shift toward greater sensitivity to parasympathetic modulation in animals injected with AC1 and a high degree of sympathetic modulation in animals injected with HCN2/AC1. CONCLUSION AC1 or HCN2/AC1 overexpression in left bundle branches provides highly efficient biological pacing and greater sensitivity to autonomic modulation than HCN2 alone.
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Affiliation(s)
- Gerard J J Boink
- Department of Pharmacology, Center for Molecular Therapeutics, Columbia University, New York, NY 10032, USA
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Rosen MR, Nargeot J, Salama G. The case for the funny current and the calcium clock. Heart Rhythm 2012; 9:616-8. [DOI: 10.1016/j.hrthm.2011.10.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Indexed: 01/01/2023]
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Karam CS, Akar FG. Genetic silencing of pacemaker cells: local intervention with global implications. J Am Heart Assoc 2012; 1:e001412. [PMID: 23130130 PMCID: PMC3487369 DOI: 10.1161/jaha.112.001412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Caline S Karam
- Cardiovascular Institute, Mount Sinai School of Medicine New York, NY
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Sosunov EA, Anyukhovsky EP. Differential effects of ivabradine and ryanodine on pacemaker activity in canine sinus node and purkinje fibers. J Cardiovasc Electrophysiol 2012; 23:650-5. [PMID: 22353259 DOI: 10.1111/j.1540-8167.2011.02285.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
INTRODUCTION It is generally accepted that at least 2 major mechanisms contribute to sinus node (SN) pacemaking: a membrane voltage (mainly I(f) ) clock and a calcium (Ca) clock (localized submembrane sarcoplasmic reticulum Ca(2+) release during late diastolic depolarization). The aim of this study was to compare the contributions of each mechanism to pacemaker activity in SN and Purkinje fibers (PFs) exhibiting normal or abnormal automaticity. METHODS AND RESULTS Conventional microelectrodes were used to record action potentials in isolated spontaneously beating canine SN and free running PF in control and in the presence of 0.1 μM isoproterenol. Ryanodine (0.1-3 μM) and ivabradine (3 μM) were used to inhibit sarcoplasmic reticulum Ca(2+) release or I(f), respectively. To induce automaticity at low membrane potentials, PFs were superfused with BaCl(2). In SN, ivabradine reduced the rate whereas ryanodine had no effect. Isoproterenol significantly accelerated automatic rate, which was decreased by ivabradine and ryanodine. In normally polarized PFs, ryanodine had no effects on the automatic rate in the absence or presence of isoproterenol, whereas ivabradine inhibited both control and isoproterenol-accelerated automaticity. In PF depolarized with BaCl(2), ivabradine decreased BaCl(2) -induced automatic rate while ryanodine had no effect. CONCLUSION In canine SN, I(f) contributes to both basal automaticity and β-adrenergic-induced rate acceleration while the ryanodine-inhibited Ca clock appears more involved in β-adrenergic regulation of pacemaker rate. In PF, normal automaticity depends mainly on I(f). Inhibition of basal potassium conductance results in high automatic rates at depolarized membrane potentials with SN-like responses to inhibition of membrane and Ca clocks.
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Affiliation(s)
- Eugene A Sosunov
- Department of Pharmacology, Center for Molecular Therapeutics, College of Physicians and Surgeons of Columbia University, New York, NY, USA
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37
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Abstract
The field of biological pacing is entering its second decade of active investigation. The inception of this area of study was serendipitous, deriving largely from observations made by several teams of investigators, whose common interest was to understand the mechanisms governing cardiac impulse initiation. Research directions taken have fallen under the broad headings of gene therapy and cell therapy, and biomaterials research has also begun to enter the field. In this Review, we revisit certain milestones achieved through the construction of a 'roadmap' in biological pacing. Whether the end result will be a clinically applicable biological pacemaker is still uncertain. However, promising constructs that achieve physiologically relevant heart rates and good autonomic responsiveness are now available, and proof of principle studies are giving way to translation to large-animal models in long-term studies. Provided that interest in the field continues, the next decade should see either biological pacemakers become a clinical reality or the improvement of electronic pacemakers to a point where the biological approach is no longer a viable alternative.
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Vicente-Steijn R, Passier R, Wisse LJ, Schalij MJ, Poelmann RE, Gittenberger-de Groot AC, Jongbloed MRM. Funny current channel HCN4 delineates the developing cardiac conduction system in chicken heart. Heart Rhythm 2011; 8:1254-63. [PMID: 21421080 DOI: 10.1016/j.hrthm.2011.03.043] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2010] [Accepted: 03/14/2011] [Indexed: 10/18/2022]
Abstract
BACKGROUND Hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) in the mouse is expressed in the developing cardiac conduction system (CCS). In the sinoatrial node (SAN), HCN4 is the predominant isoform responsible for the funny current. To date, no data are available on HCN4 expression during chicken CCS development. OBJECTIVE The purpose of this study was to provide the full-length sequence of Hcn4 and describe its expression pattern during development in relation to the CCS in the chicken embryo. METHODS Hcn4 RNA expression was studied by in situ hybridization in sequential chick developmental stages (HH11-HH35) and immunohistochemical staining was conducted for the myocardial protein cardiac troponin I and the cardiac transcription factor Nkx2.5. RESULTS We obtained the full-length sequence of Hcn4 in chick. Hcn4 expression was observed early in development in the primary heart tube. At later stages, expression became restricted to transitional zones flanked by working myocardium, comprising the sinus venosus myocardium where the SAN develops, the atrioventricular canal myocardium, the primary fold (a myocardial zone between the developing ventricles), and the developing outflow tract. Further in development, Hcn4 expression was restricted to the SAN, the atrioventricular node, the common bundle, the bundle branches, and the internodal and atrioventricular ring myocardium. CONCLUSION We have identified Hcn4 as a marker of the developing CCS in the chick. The primary heart tube expresses Hcn4, which is later restricted to the transitional zones and eventually the elements of the mature CCS. Furthermore, we hypothesize that expression patterns during development may delineate potential arrhythmogenic sites in the adult heart.
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Affiliation(s)
- Rebecca Vicente-Steijn
- Department of Anatomy & Embryology, Leiden University Medical Center, Leiden, The Netherlands
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Boink GJJ, Rosen MR. Regenerative therapies in electrophysiology and pacing: introducing the next steps. J Interv Card Electrophysiol 2010; 31:3-16. [PMID: 21161675 DOI: 10.1007/s10840-010-9529-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 11/04/2010] [Indexed: 12/27/2022]
Abstract
The morbidity and mortality of cardiac arrhythmias are major international health concerns. Drug and device therapies have made inroads but alternative approaches are still being sought. For example, gene and cell therapies have been explored for treatment of brady- and tachyarrhythmias, and proof of concept has been obtained for both biological pacing in the setting of heart block and gene therapy for ventricular tachycardias. This paper reviews the state of the art developments with regard to gene and cell therapies for cardiac arrhythmias and discusses next steps.
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Affiliation(s)
- Gerard J J Boink
- Heart Failure Research Center, Academic Medical Center, Amsterdam, Netherlands
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41
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Shlapakova IN, Nearing BD, Lau DH, Boink GJJ, Danilo P, Kryukova Y, Robinson RB, Cohen IS, Rosen MR, Verrier RL. Biological pacemakers in canines exhibit positive chronotropic response to emotional arousal. Heart Rhythm 2010; 7:1835-40. [PMID: 20708103 DOI: 10.1016/j.hrthm.2010.08.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Accepted: 08/06/2010] [Indexed: 11/30/2022]
Abstract
BACKGROUND Biological pacemakers based on the HCN2 channel isoform respond to beta-adrenergic and muscarinic stimulation, suggesting a capacity to respond to autonomic input. OBJECTIVE The purpose of this study was to investigate autonomic response to emotional arousal in canines implanted with murine HCN2-based biological pacemakers using gene therapy. METHODS An electronic pacemaker was implanted with its lead in the right ventricular apical endocardium (VVI 35 bpm). An adenoviral HCN2/GFP construct (Ad-HCN2, n = 7) or saline (control, n = 5) was injected into the left bundle branch on day 2 after radiofrequency ablation of the atrioventricular node to induce complete atrioventricular block. Emotional arousal was achieved by presenting food following an overnight fast. Autonomic control was evaluated with Poincaré plots of R-R(N) against R-R(N+1) intervals to characterize heart rate variability (HRV) and with continuous RR interval assessment via 24-hour ambulatory ECG. The 24-hour ECG and Poincaré plot shape were analyzed. RESULTS During day 1 after biological pacemaker implantation, Poincaré HRV parameters and RR intervals were unchanged with food presentation. However, on day 7, food presentation was accompanied by an increase in HRV (SD1, p < 0.07, and SD2, p < 0.05) and shortening of RR interval (P < .05) in dogs with Ad-HCN2 but not in controls. CONCLUSION This is the first demonstration that biological pacemakers are capable of responding to natural arousal stimuli to elicit appropriate chronotropic responses, a potential advantage over electronic pacemakers.
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Affiliation(s)
- Iryna N Shlapakova
- Columbia University College of Physicians and Surgeons, New York, New York, USA
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Xia S, Wang Y, Zhang Y, Deng SB, Du JL, Wang XC, She Q. Dynamic changes in HCN2, HCN4, KCNE1, and KCNE2 expression in ventricular cells from acute myocardial infarction rat hearts. Biochem Biophys Res Commun 2010; 395:330-5. [DOI: 10.1016/j.bbrc.2010.04.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2010] [Accepted: 04/01/2010] [Indexed: 11/29/2022]
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Abstract
Abstract: Pacemaking is a basic physiological process, and the cellular mechanisms involved in this function have always attracted the keen attention of investigators. The "funny" (I(f)) current, originally described in sinoatrial node myocytes as an inward current activated on hyperpolarization to the diastolic range of voltages, has properties suitable for generating repetitive activity and for modulating spontaneous rate. The degree of activation of the funny current determines, at the end of an action potential, the steepness of phase 4 depolarization; hence, the frequency of action potential firing. Because I(f) is controlled by intracellular cAMP and is thus activated and inhibited by beta-adrenergic and muscarinic M2 receptor stimulation, respectively, it represents a basic physiological mechanism mediating autonomic regulation of heart rate. Given the complexity of the cellular processes involved in rhythmic activity, an exact quantification of the extent to which I(f) and other mechanisms contribute to pacemaking is still a debated issue; nonetheless, a wealth of information collected since the current was first described more than 30 years ago clearly agrees to identify I(f) as a major player in both generation of spontaneous activity and rate control. I(f)- dependent pacemaking has recently advanced from a basic, physiologically relevant concept, as originally described, to a practical concept that has several potentially useful clinical applications and can be valuable in therapeutically relevant conditions. Typically, given their exclusive role in pacemaking, f-channels are ideal targets of drugs aiming to pharmacological control of cardiac rate. Molecules able to bind specifically to and block f-channels can thus be used as pharmacological tools for heart rate reduction with little or no adverse cardiovascular side effects. Indeed a selective f-channel inhibitor, ivabradine, is today commercially available as a tool in the treatment of stable chronic angina. Also, several loss-of-function mutations of HCN4 (hyperpolarization-activated, cyclic-nucleotide gated 4), the major constitutive subunit of f-channels in pacemaker cells, are known today to cause rhythm disturbances, such as for example inherited sinus bradycardia. Finally, gene- or cell-based methods for in situ delivery of f-channels to silent or defective cardiac muscle represent novel approaches for the development of biological pacemakers eventually able to replace electronic devices.
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Affiliation(s)
- Dario DiFrancesco
- University of Milano, Department of Biomolecular Sciences and Biotechnology, The PaceLab, via Celoria 26, 20133 Milano, Italy.
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Valiunas V, Kanaporis G, Valiuniene L, Gordon C, Wang HZ, Li L, Robinson RB, Rosen MR, Cohen IS, Brink PR. Coupling an HCN2-expressing cell to a myocyte creates a two-cell pacing unit. J Physiol 2009; 587:5211-26. [PMID: 19736302 DOI: 10.1113/jphysiol.2009.180505] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
We examined whether coupling of a ventricular myocyte to a non-myocyte cell expressing HCN2 could create a two-cell syncytium capable of generating sustained pacing. Three non-myocyte cell types were transfected with the mHCN2 gene and used as sources of mHCN2-induced currents. They were human mesenchymal stem cells and HEK293 cells, both of which express connexin43 (Cx43), and HeLa cells transfected with Cx43. Cell-cell coupling between heterologous pairs increased with time in co-culture, and hyperpolarization of the myocyte induced HCN2 currents, indicating current transfer from the mHCN2-expressing cell to the myocyte via gap junctions. The magnitude of the HCN2 currents recorded in myocytes increased with increasing junctional conductance. Once a critical level of electrical cell-cell coupling between myocytes and mHCN2 transfected cells was exceeded spontaneous action potentials were generated at frequencies of approximately 0.6 to 1.7 Hz (1.09 +/- 0.05 Hz). Addition of carbenoxolone (200 microM), a gap junction channel blocker, to the media stopped spontaneous activity in heterologous cell pairs. Carbenoxolone washout restored activity. Blockade of HCN2 currents by 100 microM 9-amino-1,2,3,4-tetrahydroacridine (THA) stopped spontaneous activity and subsequent washout restored it. Neither THA nor carbenoxolone affected electrically stimulated action potentials in isolated single myocytes. In summary, the inward current evoked in the genetically engineered (HCN2-expressing) cell was delivered to the cardiac myocyte via gap junctions and generated action potentials such that the cell pair could function as a pacemaker unit. This finding lays the groundwork for understanding cell-based biological pacemakers in vivo once an understanding of delivery and target cell geometry is defined.
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Affiliation(s)
- V Valiunas
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY 11794-8661, USA
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Abstract
Several hundred thousand electronic pacemakers are implanted in the US each year to treat abnormally slow heart rates. Biological pacemaker research strives to replace this hardware, and the associated monitoring and maintenance, by using gene or cell therapy to create a permanent and autonomically responsive pacemaker. While there are numerous technological hurdles to overcome before this is a therapeutic reality, one critical issue is determining the optimal channel gene to employ in creating a biological pacemaker. This review discusses the pros and cons of various model systems for characterizing and evaluating the function of candidate channel genes. It is argued that a sequential approach that combines in silico, in vitro and in vivo models is required.
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Abstract
Bradyarrhythmias are common and may be caused by sinus node dysfunction or conduction block. Many of these conditions can be treated by the implantation of electronic cardiac pacemakers that reduce mortality and morbidity in carefully selected patient groups. Implantable electronic pacemakers are small, sophisticated and reliable but not without complication and limitation. Efforts have been made to create a de novo sinus node using gene therapy, the so-called biopacemaker. This approach has potential as permanent cure for bradyarrythmias with greater physiological responsiveness than that provided by rate-responsive electronic pacemakers. This article reviews the current approaches to the problem and gives a perspective on the challenges remaining to bring the therapy to clinical practice.
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Affiliation(s)
- Gwilym M. Morris
- Cardiovascular Medicine, School of Medicine, University of Manchester, Manchester, UK,
| | - Mark R. Boyett
- Mark R. Boyett Cardiovascular Medicine, School of Medicine, University of Manchester, Manchester, UK
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Accili E. Putting the pacemaker channel through its paces to build a better biological pacemaker. J Physiol 2009; 587:1381-2. [PMID: 19336609 DOI: 10.1113/jphysiol.2009.170720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Eric Accili
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC, Canada.
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Joyner MJ, Nattel S. Fast and furious: new ways to think about, study and treat cardiac arrhythmias. J Physiol 2009; 587:1383-4. [PMID: 19336610 DOI: 10.1113/jphysiol.2009.170936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Michael J Joyner
- Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
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Current world literature. Curr Opin Organ Transplant 2009; 14:103-11. [PMID: 19337155 DOI: 10.1097/mot.0b013e328323ad31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Zhao X, Bucchi A, Oren RV, Kryukova Y, Dun W, Clancy CE, Robinson RB. In vitro characterization of HCN channel kinetics and frequency dependence in myocytes predicts biological pacemaker functionality. J Physiol 2009; 587:1513-25. [PMID: 19171659 DOI: 10.1113/jphysiol.2008.163444] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The pacemaker current, mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, contributes to the initiation and regulation of cardiac rhythm. Previous experiments creating HCN-based biological pacemakers in vivo found that an engineered HCN2/HCN1 chimeric channel (HCN212) resulted in significantly faster rates than HCN2, interrupted by 1-5 s pauses. To elucidate the mechanisms underlying the differences in HCN212 and HCN2 in vivo functionality as biological pacemakers, we studied newborn rat ventricular myocytes over-expressing either HCN2 or HCN212 channels. The HCN2- and HCN212-over-expressing myocytes manifest similar voltage dependence, current density and sensitivity to saturating cAMP concentrations, but HCN212 has faster activation/deactivation kinetics. Compared with HCN2, myocytes expressing HCN212 exhibit a faster spontaneous rate and greater incidence of irregular rhythms (i.e. periods of rapid spontaneous rate followed by pauses). To explore these rhythm differences further, we imposed consecutive pacing and found that activation kinetics of the two channels are slower at faster pacing frequencies. As a result, time-dependent HCN current flowing during diastole decreases for both constructs during a train of stimuli at a rapid frequency, with the effect more pronounced for HCN2. In addition, the slower deactivation kinetics of HCN2 contributes to more pronounced instantaneous current at a slower frequency. As a result of the frequency dependence of both instantaneous and time-dependent current, HCN2 exhibits more robust negative feedback than HCN212, contributing to the maintenance of a stable pacing rhythm. These results illustrate the benefit of screening HCN constructs in spontaneously active myocyte cultures and may provide the basis for future optimization of HCN-based biological pacemakers.
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Affiliation(s)
- Xin Zhao
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
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