PROPAGATION OF INTERCELLULAR CA2+ WAVES IN MECHANICALLY STIMULATED ARTICULAR CHONDROCYTES

Intercellular Ca2+ signalling in primary cultures of articular chondro cytes was investigated with digital fluorescence ,ideo imaging, Mechan ical stimulation of a single cell induced a wave of increased Ca2+ tha t was communicated to surrounding cells, Intercellular Ca2+ spreading was inhibited by 18 alpha-glycyrrhetinic acid, demonstrating the invol vement of gap junctions in signal propagation, In the absence of extra cellular Ca2+ mechanical stimulation failed to induce Ca2+ responses a nd communicated Ca2+ waves, Under these conditions Ca2+ microinjection induced intercellular waves involving the cells immediately surroundi ng the stimulated one, Mechanical stress induced Ca2+ influx in the st imulated, but not in the adjacent cells, as assessed by the Mn2+ quenc hing technique. Cell treatment with thapsigargin failed to block mecha nically induced signal propagation, but significantly. reduced the num ber of cells involved in the communicated Ca2+ wave, Similar results w ere obtained with the phospholipase C inhibitor U73122, which is known to prevent InsP(3) generation, These results provide evidence that me chanical stimulation induces a cytosolic Ca2+ increase that may permea te gap junctions, thus acting as an intercellular messenger mediating cell-to-cell communication in articular chondrocytes.