IL-34 accelerates MM-induced osteolysis in mice. (A) Transmission radiographs of the skull of mice IV injected with MM cells (MOPC315.BM^Control or MOPC315.BM^Il34KD) at day 45 postinjection, compared with age-matched healthy controls. Red circles refer to regions with severe bone lesions. (B) Quantitation of cortical bone thickness (centimeters), bone densities (milligrams per centimeter-cubed), and mineral volumes (milligrams) of regions described in panel A. (C) Transmission radiographs of the fifth and sixth lumbar vertebrae of mice described in panel A. (D) Quantitation of bone densities (milligrams per centimeter-cubed) and mineral volumes (milligrams) of regions described in panel C. (E) Transmission radiographs of femurs of mice described in panel A. (F) Quantitation of bone densities (milligrams per centimeter-cubed) and mineral volumes (milligrams) of regions described in panel E. Blue bars, cortical structures; red bars, trabecular structures. (G) Measurement of serum Ca²⁺ levels in mice described in panel A at the indicated days after injection. Data are mean ± SEM; *P < .05.