Figure 1.

Normal and osteopetrotic tibial bones from wild-type and RANK^−/− mice. The upper panels are H&E-stained longitudinal sections of tibiae from 4-weeks-old mice showing a normal growth plate and underlying metaphyseal trabecular bone and bone marrow from a wild-type mouse (left panel) and a thickened growth plate and unremodeled osteopetrotic bone (yellow arrow) filling the medullary cavity from a RANK^−/− mouse (right panel). The lower panels are TRAP-stained sections of the bone beneath the growth plate showing TRAP-positive (red, arrow) osteoclasts in the wild-type tibia and absence of osteoclasts and TRAP staining in the RANK^−/− tibia.