Recombinant L-plastin induces osteoclast differentiation from RANKL-primed precursors. (A-C) RAW 264.7 cells were primed with RANKL (50 ng/ml) for 2 days and then cultured for an additional 2 days without RANKL treatment (negative control, NC), with RANKL (50 ng/ml, positive control, PC), with human recombinant L-plastin (rLPL) at different concentrations (5, 10, or 25 μg/ml) (A), or with human recombinant I-plastin-1 (rIPL), L-plastin (rLPL), T-plastin (rTPL), or control protein (rCP, an unrelated protein produced by the same process) (5-10 μg/ml), (B) and average osteoclast numbers were assessed. Data are means ± SEM., N = 3-11 independent experiments, ***P < .001 **P < .01, *P < .05 assessed by ANOVA and compared to NC by post hoc Bonferroni test. (C) Representative images of TRAP-stained osteoclast cultures formed in indicated conditions; 100-μm scale bar applies to all images.