title: Forced fusion of human ventricular scar cells with cardiomyocytes suppresses arrhythmogenicity in a co-culture model.
abstract: OBJECTIVE
  Fibrosis increases arrhythmogenicity in myocardial tissue by causing structural and functional disruptions in the cardiac syncytium. Forced fusion of fibroblastic cells with adjacent cardiomyocytes may theoretically resolve these disruptions. Therefore, the electrophysiological effects of such electrical and structural integration of fibroblastic cells into a cardiac syncytium were studied.
  
  
  RESULTS
  Human ventricular scar cells (hVSCs) were transduced with lentiviral vectors encoding enhanced green fluorescent protein alone (eGFP↑-hVSCs) or together with the fusogenic vesicular stomatitis virus G protein (VSV-G/eGFP↑-hVSCs) and subsequently co-cultured (1:4 ratio) with neonatal rat ventricular cardiomyocytes (NRVMs) in confluent monolayers yielding eGFP↑- and VSV-G/eGFP↑-co-cultures, respectively. Cellular fusion was induced by brief exposure to pH = 6.0 medium. Optical mapping experiments showed eGFP↑-co-cultures to be highly arrhythmogenic [43.3% early afterdepolarization (EAD) incidence vs. 7.7% in control NRVM cultures, P < 0.0001], with heterogeneous prolongation of action potential (AP) duration (APD). Fused VSV-G/eGFP↑-co-cultures displayed markedly lower EAD incidence (4.6%, P < 0.001) than unfused co-cultures, associated with decreases in APD, APD dispersion, and decay time of cytosolic Ca(2+) waves. Heterokaryons strongly expressed connexin43 (Cx43). Also, maximum diastolic potential in co-cultures was more negative after fusion, while heterokaryons exhibited diverse mixed NRVM/hVSC whole-cell current profiles, but consistently showed increased outward Kv currents compared with NRVMs or hVSCs. Inhibition of Kv channels by tetraethylammonium chloride abrogated the anti-arrhythmic effects of fusion in VSV-G/eGFP↑-co-cultures raising EAD incidence from 7.9 to 34.2% (P < 0.001).
  
  
  CONCLUSIONS
  Forced fusion of cultured hVSCs with NRVMs yields electrically functional heterokaryons and reduces arrhythmogenicity by preventing EADs, which is, at least partly, attributable to increased repolarization force.
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands.
authors.forename: Marc C
authors.initials: MC
authors.lastname: Engels
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands.
authors.forename: Saïd F A
authors.initials: SF
authors.lastname: Askar
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands.
authors.forename: Wanchana
authors.initials: W
authors.lastname: Jangsangthong
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands.
authors.forename: Brian O
authors.initials: BO
authors.lastname: Bingen
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands.
authors.forename: Iolanda
authors.initials: I
authors.lastname: Feola
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands.
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands.
authors.forename: Rupamanjari
authors.initials: R
authors.lastname: Majumder
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands Department of Cardiothoracic Surgery, Heart Lung Center Leiden, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Michel I M
authors.initials: MI
authors.lastname: Versteegh
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands Department of Cardiothoracic Surgery, Heart Lung Center Leiden, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Jerry
authors.initials: J
authors.lastname: Braun
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands Department of Cardiothoracic Surgery, Heart Lung Center Leiden, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: Robert J M
authors.initials: RJ
authors.lastname: Klautz
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands.
authors.forename: Dirk L
authors.initials: DL
authors.lastname: Ypey
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands.
authors.forename: Antoine A F
authors.initials: AA
authors.lastname: De Vries
authors.affiliation: Laboratory of Experimental Cardiology, Department of Cardiology, Heart Lung Center Leiden, Leiden University Medical Center, Albinusdreef 2, Leiden, RC 2300, The Netherlands D.A.Pijnappels@lumc.nl.
authors.forename: Daniël A
authors.initials: DA
authors.lastname: Pijnappels
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001145:Arrhythmias, Cardiac / Q000378:metabolism*; D002478:Cells, Cultured; D018920:Coculture Techniques; D006352:Heart Ventricles / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism*; D051381:Rats
chemical_list: D000889:Anti-Arrhythmia Agents
keywords: Cardiomyocytes; Cell culture; Early afterdepolarizations; Heterocellular fusion; Human ventricular scar cells