Comparison of osteoarthritis meniscal cell-mediated and osteoarthritis chondrocyte-mediated calcium deposition. (a) ATP-induced calcium deposition in the monolayer cultures of osteoarthritis (OA) meniscal cells derived from four OA patients (OA-M) (see Table 3) was 60% greater than present in the monolayer cultures of OA hyaline articular chondrocytes (OA-C). The difference was statistically significant (*P < 0.05). (b) Calcium phosphocitrate (CaPC) inhibited ATP-induced calcium deposition in the monolayer cultures of OA meniscal cells in a dose-dependent manner (*P < 0.001). Count per minute (CPM) data were normalized against total protein levels.