HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 2006-0388v1 25/11/2712    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints/Permissions Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Yanagi, K. Articles by Yamashita, J. K. Search for Related Content PubMed PubMed Citation Articles by Yanagi, K. Articles by Yamashita, J. K.

EMBRYONIC STEM CELLS

Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels and T-Type Calcium Channels Confer Automaticity of Embryonic Stem Cell-Derived Cardiomyocytes

^aLaboratory of Stem Cell Differentiation, Stem Cell Research Center, Institute for Frontier Medical Sciences, Kyoto University, Kyoto, Japan;
^bFirst Department of Surgery, University of Toyama Graduate School of Medicine, Toyama, Japan;
^cDepartment of Physiology, Faculty of Medicine, Jichi Medical University, Tochigi, Japan;
^dDepartment of Physiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan;
^ePRESTO, Japan Science and Technology Agency, Tokyo, Japan

Key Words. In vitro differentiation • Embryonic stem cells • Stroma cells • Stem/progenitor cells • Differentiation • Tissue regeneration

Correspondence: Jun K. Yamashita, M.D., Ph.D., Laboratory of Stem Cell Differentiation, Stem Cell Research Center, Institute for Frontier Medical Sciences, Kyoto University, 53 Shogoin Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan. Telephone: +81-75-751-3853; Fax: +81-75-751-4824; e-mail: juny{at}frontier.kyoto-u.ac.jp

Received June 26, 2006; accepted for publication July 22, 2007.
First published online in STEM CELLS EXPRESS   July 26, 2007.



Regeneration of cardiac pacemakers is an important target of cardiac regeneration. Previously, we developed a novel embryonic stem (ES) cell differentiation system that could trace cardiovascular differentiation processes at the cellular level. In the present study, we examine expressions and functions of ion channels in ES cell-derived cardiomyocytes during their differentiation and identify ion channels that confer their automaticity. ES cell-derived Flk1⁺ mesoderm cells give rise to spontaneously beating cardiomyocytes on OP9 stroma cells. Spontaneously beating colonies observed at day 9.5 of Flk1⁺ cell culture (Flk-d9.5) were significantly decreased at Flk-d23.5. Expressions of ion channels in pacemaker cells hyperpolarization-activated cyclic nucleotide-gated (HCN)1 and -4 and voltage-gated calcium channel (Cav)3.1 and -3.2 were significantly decreased in purified cardiomyocytes at Flk-d23.5 compared with at Flk-d9.5, whereas expression of an atrial and ventricular ion channel, inward rectifier potassium channel (Kir)2.1, did not change. Blockade of HCNs and Cav ion channels significantly inhibited beating rates of cardiomyocyte colonies. Electrophysiological studies demonstrated that spontaneously beating cardiomyocytes at Flk-d9.5 showed almost similar features to those of the native mouse sinoatrial node except for relatively deep maximal diastolic potential and faster maximal upstroke velocity. Although 60% of myocytes at Flk-d23.5 revealed almost the same properties as those at Flk-d9.5, 40% of myocytes showed loss of HCN and decreased Cav3 currents and ceased spontaneous beating, with no remarkable increase of Kir2.1. Thus, HCN and Cav3 ion channels should be responsible for the maintenance of automaticity in ES cell-derived cardiomyocytes. Controlled regulation of these ion channels should be required to generate complete biological pacemakers.

Disclosure of potential conflicts of interest is found at the end of this article.