Abstract
Human bone marrow-derived mesenchymal stem cells (hMSCs) have the potential to differentiate into several types of cells. In these processes, intracellular Ca (Cai)plays important roles for the cellular functions. Recently, we have found that hMSCs demonstrate spontaneous Cai oscillations without agonist stimulations, which result primarily from the release of Ca from intracellular stores via InsP3 receptors. The precise mechanisms for its generation are not clear. In this study, we investigated the underlying mechanisms of spontaneous Cai oscillation using by conforcal Ca imaging. By the application of blockers for P2Y receptor (PPADS) and P2Y1 receptor (A3P5PS and BzATP), Cai oscillations were completely blocked. The application of hexokinase, an ATP scavenger, completely blocked Cai oscillations, suggested that ATP stimulates P2Y1 receptors to produce InsP3. To confirm this, we directly measured ATP in the supernatant by luciferin-luciferase assay and found the increase of ATP in the medium with hMSCs, indicating the existence of an autocrine purinergic signaling loop. Cai oscillations were completely blocked by connexin blockers but not Cl channel blockers. From these results, we conclude that spontaneous Cai oscillations are generated by an ATP autocrine signaling in hMSCs, which is composed primarily by hemi-gap-junction channels, P2Y1 receptors, PLC-β and InsP3 induced Ca release. [Jpn J Physiol 55 Suppl:S125 (2005)]
