G-CSF–induced mobilization is not mediated by osteoclasts. (A) TRAP staining in tibial spongiosa from mice treated with saline (Sal) or G-CSF for 2 (G2), 4 (G4), or 6 days, followed by 4 days of recovery (G10). Osteoclasts are stained in red. (B) Histomorphometry for osteoclast surface per bone surface (OcS/BS) and number of osteoclasts per bone perimeter (NOc/BPm) in the trabeculae of the proximal tibial secondary spongiosa from mice mobilized for 6 days with G-CSF. (C) qRT-PCR for cathepsin K mRNA in endosteal cells. *P < .05. (D-F) Effect of zoledronic acid and G-CSF treatment on osteoclast (D) and osteoblast (E) surface per bone surface in the trabeculae, mobilization of CFCs into blood (F) and spleen (G), and mobilization of competitive repopulating cells (H). In panels B, D, and E, each bar is mean ± SEM of 4 mice per group. In panels C and F through H, each symbol represents an individual mouse, and bars are the mean from one representative experiment of 2 independent experiments.