Thus, MSU could remain intact inside OBs and deregulate specialized functions of OBs. To evaluate the fate of MSU in the presence of OBs, live confluent selleck chemicals Wortmannin primary human OBs were cultured with graded concentrations of MSU during 7 days. OBs that phagocytized MSU showed, after 48 hours of incubation, consistent morphologic changes, as studied with con focal microscopy. OBs dose dependently internalized MSU from 0. 1 to 1 mg 106 cells with an optimal effect at 0. 5 mg 106 cells, followed by a plateau. More than 90% of OBs had MSU internalized in large and fluid filled vacuoles, each containing a single microcrystal. Volume and shape of vacuoles depend on crystal size. Vacuoles were individualized with light microscopy after, at least, 24 hours of incuba tion. Numbers of vacuoles with MSU averaged 30 per OB.

Most of MSU were completely internalized in cells, but some crystals remained partially engulfed or along side the membrane. After 7 days of culture, phagocytosis of 0. 5 mg MSU 106 OBs was associated with unchanged vacuoles. These data suggest a pro longed process that could partly detoxify the cells by retaining Inhibitors,Modulators,Libraries MSU microcrystals in permanent phagosomes with a final noncapacity of OB to eliminate MSU containing vacuoles. MSU affects OB proliferation but not viability Because MSU can modulate cellular apoptosis and proliferation, the impact of MSU on OB sur vival and proliferation was evaluated before studying specialized OB functions. MSU at concentrations up to 1 mg 106 cells for 72 hours of culture did not modify Inhibitors,Modulators,Libraries the incorporation of propidium iodide by OBs, and an average of 80% PI negative 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 Inhibitors,Modulators,Libraries 0. 8 mg MSU. The respective proliferation rates were re duced from Inhibitors,Modulators,Libraries 30% to 55% of the OB proliferation rate in control conditions. Thus, although MSU microcrystals at the concentrations tested did not modify the viability of OBs, they significantly decreased the proliferation Inhibitors,Modulators,Libraries 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 cultures were stained with alizarin red S, a marker of matrix calcium Ixazomib Ki that allows a quantitative evaluation of mineralization. OBs incubated with MSU showed a reduced ARS staining of the newly calcified matrix.