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a Department of Medicine, University of Hong Kong, Hong Kong, China;
b Departments of Medicine and
c Cellular and
d Molecular Medicine and Institute for Cell Engineering, Johns Hopkins University, Baltimore, Maryland, USA
Key Words. Embryonic stem cells • Electrophysiology • Pluripotency • Ion channels
Correspondence: Ronald Li, Ph.D., Johns Hopkins University, 720 Rutland Avenue, Ross 1165, Baltimore, Maryland 21205, USA. Telephone: 410-614-0035; Fax: 410-502-2802; e-mail: ronaldli{at}jhmi.edu; and Hung-Fat Tse, M.D., University of Hong Kong, Cardiology Division, Queen Mary Hospital, Pokfulam, Hong Kong. e-mail: hftse{at}hkucc.hku.hk
Pluripotent embryonic stem cells (ESCs) possess promising potential for cell-based therapies, but their electrophysiological properties have not been characterized. Here we describe the presence of ionic currents in mouse (m) and human (h) ESCs and their physiological function. In mESCs, tetraethylammonium (TEA)–sensitive depolarization-activated delayed rectifier K+ currents (IKDR) (8.6 ± 0.9 pA/pF at +40 mV; IC50 = 1.2 ± 0.3 mM), which contained components sensitive to 4-aminopyridine (4-AP) (IC50 = 0.5 ± 0.1 mM) and 100 nM Ca2+-activated K+ current (IKCa) blocker iberiotoxin (IBTX),were detected in 52.3% of undifferentiated cells.IKDR was similarly present in hESCs (~100%) but with an approximately sixfold higher current density (47.5 ± 7.9 pA/pF at +40 mV). When assayed by bromodeoxyurindine incorporation, application of TEA, 4-AP, or IBTX significantly reduced the proliferation of mESCs and hESCs in a dose-dependent manner (p < .05). A hyperpolarization-activated inward current (Ih) (–2.2 ± 0.4 pA/pF at –120 mV) was detected in 23% of mESCs but not hESCs. Neither Nav nor Cav currents were detected in mESCs and hESCs. Microarray and reverse transcription–polymerase chain reaction analyses identified several candidate genes for the ionic currents discovered. Collectively, our results indicate that pluripotent ESCs functionally express several specialized ion channels and further highlight similarities and differences between the two species. Practical considerations for the therapeutic use of ESCs are discussed.
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