The Sodium–Calcium Exchanger Controls the Membrane Potential of AFT024: A Mesenchymal Stem Cell Hematopoietic Niche Forming Line
Résumé
The aim of this study was to characterize the functional expression of sodium–calcium exchangers on AFT024 cell line, a murine model of mesenchymal stem/stromal cells (MSCs) supporting human primitive hematopoiesis. All current-clamp and voltage-clamp experiments were performed using the perforated patch whole-cell recording technique with amphotericin B. The membrane potential of −14 mV shifted to −35 mV when lowering the external sodium concentration to 0.33 mM and an increase of cytosolic calcium concentration was observed. KB-R7943, a selective blocker of cardiac sodium–calcium exchangers, also named NCX1, induced a hyperpolarization at physiological sodium concentration while it blocked the hyperpolarization observed at low sodium concentration. This demonstrates for the first time the presence of the sodium–calcium exchangers in AFT024 cells and provides initial evidence that the membrane potential of these stromal cells is maintained depolarized by this exchanger. Lowering external sodium concentration and KB-R7943 had no effect on the membrane potential of 2018 cells, a nonhematopoietic-supportive cell line. Since NCX1 is differentially expressed in AFT024 cells as compared with nonhematopoietic supportive cells with more restricted differentiation potential, this study suggests a potential role of this sodium–calcium exchanger, in the differentiation process or hematopoietic support of MSCs.