However, high doses of ATP can lead to an increase in matrix #metalloproteinase 13 (MMP-13) activity and extracellular inorganic pyrophosphate (ePPi) accumulation, which can lead to undesirable effects such as #mineralization of articular cartilage. Therefore, the purpose of this study is to identify the mechanism of ATP-mediated #catabolism and to determine a therapeutic dose range to maximize the #anabolic effect.