Ca(2+) oscillations regulated by Na(+)-Ca(2+) exchanger and plasma membrane Ca(2+) pump induce fluctuations of membrane currents and potentials in human mesenchymal stem cells.
Human bone marrow-derived mesenchymal stem cells (hMSCs) have the potential to differentiate into several types of cells. We have demonstrated spontaneous [Ca(2+)](i) oscillations in hMSCs without agonist stimulation, which result primarily from release of Ca(2+) from intracellular stores via InsP(3) receptors. In this study, we further investigated functions and contributions of Ca(2+) transporters on plasma membrane to generate [Ca(2+)](i) oscillations. In confocal Ca(2+) imaging experiments, spontaneous [Ca(2+)](i) oscillations were observed in 193 of 280 hMSCs. The oscillations did not sustain in the Ca(2+) free solution and were completely blocked by the application of 0.1mM La(3+). When plasma membrane Ca(2+) pumps (PMCAs) were blocked with blockers, carboxyeosin or caloxin, [Ca(2+)](i) oscillations were inhibited. Application of Ni(2+) or KBR7943 to block Na(+)-Ca(2+) exchanger (NCX) also inhibited [Ca(2+)](i) oscillations. Using RT-PCR, mRNAs were detected for PMCA type IV and NCX, but not PMCA type II. In the patch clamp experiments, Ca(2+) activated outward K(+) currents (I(KCa)) with a conductance of 170+/-21.6pS could be recorded. The amplitudes of I(KCa) and membrane potential (V(m)) periodically fluctuated liked to [Ca(2+)](i) oscillations. These results suggest that in undifferentiated hMSCs both Ca(2+) entry through plasma membrane and Ca(2+) extrusion via PMCAs and NCXs play important roles for [Ca(2+)](i) oscillations, which modulate the activities of I(KCa) to produce the fluctuation of V(m).
Kawano
Seiko
S
Department of Cardiovascular Diseases, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510, Japan. seiko.card@mri.tmd.ac.jp
Otsu
Keishi
K
Shoji
Satoshi
S
Yamagata
Kazuo
K
Hiraoka
Masayasu
M
D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D008564:Membrane Potentials; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D024681:Potassium Channels, Calcium-Activated; D019831:Sodium-Calcium Exchanger; D000252:Calcium-Transporting ATPases; D002118:Calcium