B-cell KO mice display decreased baseline BMD and increase bone resorption, concurrent with decreased BM OPG concentrations. (A) BMD was determined by DXA in μMT/μMT B-cell KO mice (□) and age-matched WT controls (▪) at the total body, spine, and femurs. (B) Longitudinal (top) and cross-sectional (bottom) μCT reconstructions of distal femurs from WT and μMT/μMT B-cell KO mice. (C) Elevated biochemical indices of bone resorption (CTx) were observed in B-cell KO mice. (D) Decreased OPG production was detected in μMT/μMT B-cell KO BM compared with equivalent amounts of WT BM. Mean ± SD of 8 mice per group; *P < .05. (E) Real-time RT-PCR quantitation of OPG mRNA expression in 3 independent WT and B-cell KO mice. *P < .01. (F) B-cell reconstitution of μMT/μMT B-cell KO rescues BMD (*P < .01 versus WT) and (G) OPG production (*P < .05 versus WT). Mice were reconstituted at 4 weeks of age and BMD and RT-PCR studies preformed at 12 weeks of age.