title: Functional integration of electrically active cardiac derivatives from genetically engineered human embryonic stem cells with quiescent recipient ventricular cardiomyocytes: insights into the development of cell-based pacemakers.
abstract: BACKGROUND
  Human embryonic stem cells (hESCs) derived from blastocysts can propagate indefinitely in culture while maintaining pluripotency, including the ability to differentiate into cardiomyocytes (CMs); therefore, hESCs may provide an unlimited source of human CMs for cell-based therapies. Although CMs can be derived from hESCs ex vivo, it remains uncertain whether a functional syncytium can be formed between donor and recipient cells after engraftment.
  
  
  RESULTS
  Using a combination of electrophysiological and imaging techniques, here we demonstrate that electrically active, donor CMs derived from hESCs that had been stably genetically engineered by a recombinant lentivirus can functionally integrate with otherwise-quiescent, recipient, ventricular CMs to induce rhythmic electrical and contractile activities in vitro. The integrated syncytium was responsive to the beta-adrenergic agonist isoproterenol as well as to other pharmacological agents such as lidocaine and ZD7288. Similarly, a functional hESC-derived pacemaker could be implanted in the left ventricle in vivo. Detailed optical mapping of the epicardial surface of guinea pig hearts transplanted with hESC-derived CMs confirmed the successful spread of membrane depolarization from the site of injection to the surrounding myocardium.
  
  
  CONCLUSIONS
  We conclude that electrically active, hESC-derived CMs are capable of actively pacing quiescent, recipient, ventricular CMs in vitro and ventricular myocardium in vivo. Our results may lead to an alternative or a supplemental method for correcting defects in cardiac impulse generation, such as cell-based pacemakers.
authors.affiliation: Department of Medicine, Johns Hopkins University, Baltimore, Md 21205, USA.
authors.forename: Tian
authors.initials: T
authors.lastname: Xue
authors.forename: Hee Cheol
authors.initials: HC
authors.lastname: Cho
authors.forename: Fadi G
authors.initials: FG
authors.lastname: Akar
authors.forename: Suk-Ying
authors.initials: SY
authors.lastname: Tsang
authors.forename: Steven P
authors.initials: SP
authors.lastname: Jones
authors.forename: Eduardo
authors.initials: E
authors.lastname: Marbán
authors.forename: Gordon F
authors.initials: GF
authors.lastname: Tomaselli
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Li
mesh_terms: D000200:Action Potentials; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002454:Cell Differentiation; D002459:Cell Fusion; D002478:Cells, Cultured / Q000166:cytology / Q000502:physiology; D003673:Defective Viruses / Q000235:genetics / Q000502:physiology; D004594:Electrophysiology; D005260:Female; D017930:Genes, Reporter; D005822:Genetic Vectors / Q000494:pharmacology*; D015726:Giant Cells / Q000166:cytology / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D006168:Guinea Pigs; D015497:HIV-1 / Q000235:genetics / Q000502:physiology; D006321:Heart / Q000502:physiology; D006329:Heart Conduction System / Q000166:cytology / Q000502:physiology; D006352:Heart Ventricles / Q000166:cytology; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008012:Lidocaine / Q000494:pharmacology; D051379:Mice; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000187:drug effects / Q000502:physiology / Q000637:transplantation; D009924:Organ Culture Techniques; D010496:Pericardium / Q000502:physiology; D039904:Pluripotent Stem Cells / Q000166:cytology* / Q000502:physiology; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D014161:Transduction, Genetic
chemical_list: D000318:Adrenergic beta-Agonists; D011743:Pyrimidines; C082246:ICI D2788; D049452:Green Fluorescent Proteins; D008012:Lidocaine; D007545:Isoproterenol