IL-11 fails to stimulate osteoclastogenesis even when BMMs are primed with RANKL for 24 hours. (A) BMMs were pretreated with rM-CSF (10 ng/ml) or rM-CSF (10 ng/ml) and RANKL (100 ng/ml) for 24 hours and then cultured with rM-CSF (10 ng/ml) plus IL-11 (10 ng/ml) or RANKL (100 ng/ml) for 4 days in tissue culture dish. The cultures were then stained for TRAP activity. Each condition had three replicates (wells) and was repeated 4 times. A representative area of the culture from each condition is shown. (B) BMMS on bone slices were treated with the same conditions, but cultured for 9 days. Resorption pits were then visualized by SEM. Magnification by SEM was 200x. Each resorption assay had two replicates (bone slices). (C) Quantification of the bone resorption assays is shown, bars shown averaged ± S.E. *, p < 0.0001.