Fig. (1) ATP-induced calcium deposition in monolayer culture of osteoarthritis chondrocytes and meniscal cells derived from the same patients. Fig. (1A), meniscal cells and chondrocytes induced calcification measured by uptake of ⁴⁵Ca (n=3). Fig. (1B), cells were cultured in chondrogenesis and osteogenesis media and treated with extracellular ATP (n=5). Alizarin red staining was quantified (1B) to measure the absorbance correlated to calcium deposition after visualized (1C) using light microscopy.