MSU at concentrations up to 1 mg 106 cells for 72 hours of culture did not modify the incorporation of propidium iodide by OBs, and an average of 80% PI negative http://www.selleckchem.com/products/z-vad-fmk.html OBs was rou tinely obtained in control conditions, as well as in the presence of MSU. In contrast, the prolif eration rate of MSU treated OBs dose dependently decreased from 0. 1 to 1 mg MSU 106 cells. The significant threshold reduction was observed at 0. 3 mg MSU, with a plateau of reduction attained at 0. 8 mg MSU. The respective proliferation rates were re duced from 30% to 55% of the Inhibitors,Modulators,Libraries OB proliferation rate in control conditions. Thus, although MSU microcrystals at the concentrations tested did not modify the viability of Inhibitors,Modulators,Libraries OBs, they significantly decreased the proliferation of OBs and could, in parallel, affect other functions.

MSU alters OB functions Mineralization MSU present in the culture medium of human OBs affects parameters implicated in bone mineralization, such as alkaline phosphatase activity and osteocalcin content. To assess the mineralization function of OBs in the presence of MSU or vehicle in vitro, OB Inhibitors,Modulators,Libraries cultures were stained with alizarin red S, a marker of matrix calcium that allows a quantitative evaluation of mineralization. OBs incubated with MSU showed a reduced ARS staining of the newly calcified matrix. The quantities of ARS in cultures of MSU activated OBs were dose dependently de creased by 1. 6 and 2. 1 fold compared with those ob served in vehicle treated OBs. Moreover, the addition of MSU suppressed in a time dependent manner the expression of the mRNA of procollagen 1, a typical bone matrix constituent, with a sixfold decrease at 48 hours in the presence of 1 mg MSU.

These data indicate that MSU affects the formation of certain matrix components and in fine bone matrix mineralization. MMP activity Bone matrix degradation depends, among other factors, on enzymes such as matrix metalloproteinases Inhibitors,Modulators,Libraries that are known to be implicated in pathophysiological processes. Although bone matrix degradation is re lated mainly to osteoclasts, OBs can also be involved Inhibitors,Modulators,Libraries in bone resorption through selleck kinase inhibitor their production of several MMPs. The activity of generic MMPs, as evaluated in supernatants of OBs cultured with MSU, was increased by 120% over that of unstimulated cells. These results indicate that MSU stimulated OBs may be directly implicated in matrix degradation of bone with MSU deposits. Phagocytosis of MSU by OBs is tightly regulated Signaling pathways affected by MSU These data document profound effects of MSU on the behavior of OBs. These data indicate that the pathways regulating OB functions are likely to be affected by the presence of MSU.