Fig. 7. Examination of key cell types in Mmp13^–/– endochondral bones. (A,B) TRAP (red) stained 1-week-old wild-type and Mmp13^–/– tibial epiphyses shows no difference in the osteoclast population (red staining) in the trabecular bone (TB) and endostea (E) of wild-type and Mmp13^–/– mice. (C,D) Formation of the bone marrow cavity and mineralization were analyzed by Van Kossa stain on newborn wild-type and Mmp13^–/– metatarsals. Mineralized tissue (brown staining) is present in endosteum (E) surrounding the bone marrow cavity, and in the surrounding trabecular bone (TB) in both wild-type and Mmp13^–/– bones. (E,F) PECAM-immunostained 1-week-old tibia showing vessels (brown staining) in the trabecular bone (TB). There is no overt difference in localization or morphology of blood vessels in Mmp13^–/– mice compared with wild type. Scale bars: 200 µm in A,B; 100 µm in C-F.