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 (IKDR) and Ca2+-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 IKDR 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 incorporation 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, IKDR 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 IKDR) 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 corresponding gene inhibited proliferation of rat MSCs. Conclusion: These results demonstrate that membrane potential, IKDR and I-KCa channels change with cell cycle progression and corresponding alteration of gene expression. IKDR and intermediate-conductance I-KCa play an important role in maintaining membrane potential and they participate in modulation of proliferation in rat MSCs.