CD97 deficiency enhanced TNFα induced osteoclastogenesis in vivo. WT and CD97 KO female mice were injected over calvaria with PBS or TNF (0.75 μg) daily for 4 days. A) Representative micrographs of TRAP-stained histological sections of calvaria. B) Percentage of TRAP(+) osteoclast surface per bone volume. C-I Total RNA from calvaria of WT and CD97 KO mice was extracted. mRNA expression was expressed as fold change compared to control group. C) RANKL, D) OPG, E) RANKL/OPG mRNA ratio, F) IL-1α, G) CCL2, H) CCL3, and I) IL-6 mRNA expression in calvaria by real-time PCR. Experiments were performed at least three times and the pooled data are shown. Values represent mean±SEM. *, Significant effect of CD97 KO mice; #, Significant effect of rmTNFα treatment, p<0.05.