ORIGINAL ARTICLE

Cell Research (2006): 949-960
© 2006 IBCB, SIBS, CAS All rights reserved 1001-0602/06 $ 30.00
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5-Azacytidine induces changes in electrophysiological properties of human mesenchymal stem cells

Bartosz Balana, Cecilia Nicoletti, Ihor Zahanich, Eva M Graf, Torsten Christ, Sabine Boxberger,Ursula Ravens

Correspondence: Ursula Ravens Tel: +49 351 4586300; Fax: +49 351 4586315; E-mail: ravens@rcs.urz.tu-dresden.de Received, 5 August 2006; revised, 17 October 2006; accepted, 14 November 2006

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Previously, mouse bone marrow-derived stem cells (MSC) treated with the unspecific DNA methyltransferase inhibitor 5-azacytidine were reported to differentiate into cardiomyocytes. The aim of the present study was to investigate the efficiency of a similar differentiation strategy in human mononuclear cells obtained from healthy bone marrow donors. After 1¨C3 passages, cultures were exposed for 24 h to 5-azacytidine (3 ¦ÌM) followed by 6 weeks of further culture. Drug treatment did not induce expression of myogenic marker MyoD or cardiac markers Nkx2.5 and GATA-4 and did not yield beating cells during follow-up. In patch clamp experiments, approximately 10-15% of treated and untreated cells exhibited L-type Ca2+ currents. Almost all cells showed outwardly rectifying K+ currents of rapid or slow activation kinetics. Mean current amplitude at +60 mV doubled after 6 weeks of treatment compared with time-matched controls. Membrane capacitance of treated cells was significantly larger than in controls 2 weeks after treatment and remained high after 6 weeks. Expression levels of mRNAs for the K+ channels Kv1.1, Kv1.5, Kv2.1, Kv4.3 and KCNMA1 and for the Ca2+ channel Cav1.2 were not affected by 5-azacytidine. Treatment with potassium channel blockers tetraethylammonium and clofilium at concentrations shown previously to inhibit rapid or slowly activating K+ currents of hMSC inhibited proliferation of these cells. Our results suggest that despite the absence of differentiation of hMSC into cardiomyocytes, treatment with 5-azacytidine caused profound changes in current density.

Cell Research (2006) 16:949-960. doi: 10.1038/sj.cr.7310116; published online 12 December 2006

Keywords: human mesenchymal stem cells, 5-azacytidine, cardiac differentiation, outward K+ currents