Increased trabecular bone in the subepiphyseal region and normal TRAP⁺ osteoclast numbers in femurs of 2-week-old Csf1^op/Csf1op; TgCS5/+ mice. (A-F) Images of sections of the subepiphyseal regions of the distal femurs from wild-type (A,D), Csf1^op/Csf1op (B,E), and Csf1op/Csf1op; TgCS5/+ mice (C,F), stained for TRAP and counterstained with hematoxylin, show the larger amount of unresorbed trabecular bone and smaller bone marrow cavity of the femurs of Csf1^op/Csf1op; TgCS5/+ mice compared with those of wild-type mice. (D-F) Regions circled by the dashed blue lines delineate hypertrophic chondrocyte regions. (G-I) Illustration of images in panels D-F shows bone marrow (BM) cavity, trabecular bone (TB), hypertrophic region (HR) of cartilage, proliferative region (PR) of cartilage, and osteoclasts as the red outline of the trabecular bone. Asterisks in HR indicate concentration of CSF-1-expressing cells visualized in CSF-1-promoter-first intron driven lac Z (TgZ) transgenic mice³²  and shown in the insert to G. (J-O) High magnification images of regions of yellow (J-L) and blue (M-O) boxed areas in panels D-F, showing the TRAP⁺ osteoclasts in the regions of trabecular bone (J-L) and periosteum (M-O) in wild-type (J,M), Csf1^op/Csf1op (K,N), and Csf1op/Csf1op; TgCS5/+ mice (L,O). TRAP⁺ osteoclasts (arrows) are stained red. CB indicates cortical bone; bar is 1 mm in panels A-C and 50 μm in panels D-O.