Large-conductance Ca(2+)-activated potassium and ether-a-go-go potassium channels regulate proliferation of human mesenchymal stem cells

Abstract

BACKGROUND: Bone marrow-derived mesenchymal stem cells (MSCs) are a promising cell source for regenerative medicine; however, cellular physiology is not fully understood in human MSCs. The present study was to explore the potential role of the dominant functional ion channels, large-conductance Ca2+-activated potassium (BKCa) channel, ether-à-go-go potassium (hEAG1) channel, and sodium channel, in regulating proliferation of human MSCs using whole-cell patch clamp and cell proliferation assay approaches. RESULTS: We found that the BKCa channel blocker paxilline (1 μM) almost fully inhibited BKCa current (from 6.76±0.99 pA/pF of control, to 0.02±0.09 pA/pF at +100 mV, n=5, P<0.05) in human MSCs. The hEAG1 channel blocker astemizole (0.5 μM) significantly reduced hEAG1 current from 4.28±1.86 pA/pF to 1.40±1.13 pA/pF at +50 mV, n=6, P<0.05). The MTT experiment showed that paxilline at 0.3, 1.0, and 3.0 μM reduced cell proliferation to 97.2, 84.4, and 48.7% of control, respectively, and astemizole at 0.3, 0.5, and 1 μM decreased cell proliferation to 96.5, 80.5, and 45.8%, respectively. However, the sodium channel blocker tetrodotoxin (1 μM, fully blocked sodium current) had no effect on proliferation in human MSCs. 3H-thymidine incorporation assay demonstrated that both paxilline and astemizole reduced DNA synthesis rate in a concentration-dependent manner. Flowcytometry analysis displayed that inhibition of BKCa channel with 1 μM paxilline or hEAG1 channel with 0.5 μM astemizole accumulated cells at G0/G1 phase (from control 68.9% to 80.5% for paxilline; to 79.2% for astemizole). CONCLUSION: Our results demonstrate that BKCa and hEAG1 channels, but not sodium channel, participate in the regulation of cell proliferation by promoting G0/G1 cells into cell cycling progression.