Figure 4.

TNF injection decreases bone marrow stromal cell-derived factor-1 levels and increases blood osteoclast precursor frequency. Wild-type mice (3/group) were given subcutaneous injections of murine TNF (0.5 μg/injection, 4 times/day) or PBS for 3 days and were sacrificed 2 hours after the last injection on the fourth day. (a) The circulating CD11b⁺/Gr-1^-/lo osteoclast precursor frequency was determined by fluorescence-activated cell sorting analysis. (b) Stromal cell-derived factor 1 (SDF-1) levels in the bone marrow were measured by ELISA. (c) Expression of SDF-1 mRNA in bone marrow was determined by real-time RT-PCR. Data are the mean ± standard error of the mean of three pairs of mice receiving TNF or PBS injection. *P < 0.05 versus blood or PBS-treated mice.