ATP-Induced Ca²⁺ Signaling in Human Chondrons Cultured in 3-Dimensional Gels

Cell-cell communication allows for the coordination of biological functions. In this study, we found that chondrons increase their intracellular calcium concentration ([Ca²⁺]_ic) upon stimulation by ATP at a 10μM concentration in resting and stimulated cells. Digital fluorescence microscopy was used to determine the [Ca²⁺]_ic in resting and stimulated cells. Inhibition of signal propagation by the purinoceptor blocker, suramin, showed that ATP activates P2Y₂ purinoceptors. We also found that chondrons signaled in a calcium-free medium showing that bound intracellular calcium is used in signal propagation. This study is the first to illustrate that chondrons in 3-D gels respond to the extracellular messenger molecule ATP by increasing their intracellular calcium concentration.