Histophotomicrographs of slides stained with OPN antibodies using immunohistochemistry.

OPN staining intensity were more pronounced in TLR4-/- mice than in WT mice on postoperative days 4 and 7. Typical large, rounded osteoblasts were recognized on the surface of the newly-formed bone in both groups on day 14. On day 28, less OPN positive staining was detected in both WT and TLR4^−/− mice. (scale bar: 100 µm; bolded black arrows: defect margin; LB: lamellar bone; WB: woven bone; OPN(+): OPN positive stains; OB: osteoblasts).