FIG. 2.

Periosteum and bone marrow/endosteum give rise to osteoblasts/osteocytes during bone graft healing. (Left) Schematic representations of Rosa 26 (blue) or wildtype bone grafts transplanted in the cortex of wildtype host tibias. Longitudinal sections through the mouse tibia stained with TC (middle) and adjacent sections stained with X-gal (right) at 14 days after bone grafting. X-gal-positive osteoblasts and osteocytes (arrow) are found at the intact periosteal surface (A-C), at the intact endosteal surface (D-F), within the marrow cavity (G-I), and at both periosteal and endosteal surfaces in positive controls (J-M), but not in negative controls (N-U). X-gal-positive osteoclasts express β-galactosidase ubiquitously (K, L, T, and U, arrowheads). Dotted orange lines delimit the bone graft. High magnifications correspond to boxed areas. Scale bars: B, E, H, K, O, and S = 1 mm; C, F, I, L, M, P, Q, and T = 100 μm; U = 20 μm.