Figure 3. Integral steps in endochondral ossification are unperturbed during non-stabilized fracture repair in Mmp13^−/− mice.

(A) Overlay of SO stained sections with in situ hybridization for Col2 (red) indicate no difference in the early differentiation of chondrocytes in WT and Mmp13 ^−/− calluses at day 5. Overlay of SO stained sections with in situ hybridization for Col10 (yellow) shows a delay in hypertrophic chondrocyte removal in the Mmp13 ^−/− callus at day 14. Scale bar = 1 mm (B) Cellular analyses of WT and Mmp13 ^−/− calluses at day 14 show that blood vessels (PECAM) and osteoclasts (TRAP) are present in the Mmp13 ^−/− callus while aggrecan cleavage by MMPs (DIPEN epitope) is reduced in the Mmp13 ^−/− callus. Scale bar = 1 mm