Cell cycle-dependent expression of potassium channels and cell proliferation in rat mesenchymal stem cells from bone marrow

Objective : Recently, our team has demonstrated that voltage-gated delayed rectifier K + current (IK DR ) and Ca 2+ -activated K + current (I KCa ) are present in rat bone marrow-derived mesenchymal stem cells; however, little is known of their physiological roles. The present study was designed to investigate whether functional expression of IK DR and I KCa would change with cell cycle progression, and whether they could regulate proliferation in undifferentiated rat mesenchymal stem cells (MSCs). Materials and Methods : Membrane potentials and ionic currents were recorded using whole-cell patch clamp technique, cell cycling was analysed by flow cytometry, cell proliferation was assayed with DNA incorpora- tion method and the related genes were down-regulated by RNA interference (RNAi) and examined using RT-PCR. Results : It was found that membrane potential hyperpolarized, and cell size increased during the cell cycle. In addition, IK DR decreased, while I KCa increased during progress from G 1 to S phase. RT-PCR revealed that the mRNA levels of Kv1.2 and Kv2.1 (likely responsible for IK DR ) reduced, whereas the mRNA level of KCa3.1 (responsible for intermediate-conductance I KCa ) increased with the cell cycle progression. Down-regulation of Kv1.2, Kv2.1 or KCa3.1 with the specific RNAi, targeted to correspond- ing gene inhibited proliferation of rat MSCs. Conclusion : These results demonstrate that membrane potential, IK DR and I KCa channels change with cell cycle progression and corresponding alteration of gene expression. IK DR and intermediate-conductance I KCa play an important role in maintaining membrane potential and they participate in modulation of proliferation in rat MSCs.