DKK1-neutralizing antibody stimulates osteoblastogenesis and reduces osteoclastogenesis in myelomatous bones. (A-D) Decalcified, sequential, myelomatous bone sections from control (A-B) and anti-DKK1–treated hosts (C,D) were stained for TRAP (A,C) and immunohistochemically stained for osteocalcin (B,D). Whereas in control bones TRAP-expressing osteoclasts covered the whole bone surface and no osteocalcin-expressing osteoblasts were detected, anti-DKK1 treatment resulted in marked reduction in number of osteoclasts and increased number of osteoblasts. OB indicates osteoblasts; OC, osteoclasts. (E-F) Numbers of multinucleated, TRAP-expressing osteoclasts and osteocalcin-expressing osteoblasts (E) and ratio of osteoblasts to osteoclasts in myelomatous bones (F). Data are expressed as mean ± SEM. Original magnification, 200×. Images were obtained using an Olympus BH2 microscope equipped with a 160 ×/0.17 numerical aperture objective (Olympus, Melville, NY). Images were acquired using a SPOT2 digital camera (Diagnostic Instruments, Sterling Heights, MI), and were processed using Adobe Photoshop version 10 (Adobe Systems, San Jose, CA).