Cytosolic free Ca2+ concentration exhibits a characteristic temporal pattern during in vitro cartilage differentiation: a possible regulatory role of calcineurin in Ca-signalling of chondrogenic cells.
310 - 323.
We measured changes of cytosolic Ca2+ concentration during chondrogenesis, which occurs in high-density cultures (HDC) of chondrifying chicken mesenchymal cells. A significant, transient elevation was detected in Fura-2-loaded cells on day 3 of culturing, when majority of chondrogenic cells of HDC become differentiated. This 140 nM peak of cytosolic Ca2+ concentration is a result of increased Ca-influx and is indispensable to proper chondrogenesis, because addition of 0.8mM EGTA to culture medium on day 2 or 3 significantly decreased the intracellular Ca2+ concentration abolishing the Ca2+-peak of day 3 and inhibited cartilage formation. Uncontrolled Ca2+ influx evoked by a Ca2+ ionophore exerted dual effects on chondrogenesis in a concentration-dependent manner; 0.1mg/L A23187 increased, whereas 5 mg/L A23187 almost totally blocked cartilage formation. Intracellular Ca-stores seemed not to have any significant participation in the regulation of changes of cytosolic Ca2+ concentration of chondrifying cells. Activity of Ca-calmodulin-dependent protein phosphatase, calcineurin responded to changes of intracellular Ca2+ concentration induced by EGTA or A23187 in a differentiation stage-dependent manner. Since inhibition of calcineurin with cyclosporine A eliminated the peak in the cytosolic Ca2+ concentration, an active regulatory role of calcineurin on Ca2+ influx of chondrifying cells can be supposed.
|Title:||Cytosolic free Ca2+ concentration exhibits a characteristic temporal pattern during in vitro cartilage differentiation: a possible regulatory role of calcineurin in Ca-signalling of chondrogenic cells.|
|Keywords:||Animals, Calcimycin, Calcineurin, Calcium, Calcium Signaling, Cartilage, Cell Differentiation, Cells, Cultured, Chick Embryo, Chondrocytes, Cytosol, Egtazic Acid, SOX9 Transcription Factor|
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