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

Abstract

Objective: Recently, our team has demonstrated that voltage-gated delayed rectifier K+ current (IKDR) and Ca2+-activated K+ current (IKCa) 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 IKCa 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 IKCa increased during progress from G1 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 IKCa) 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 IKCa channels change with cell cycle progression and corresponding alteration of gene expression. IK DR and intermediate-conductance IKCa play an important role in maintaining membrane potential and they participate in modulation of proliferation in rat MSCs. © 2007 The Authors.