Injection of LPS from P. gingivalis (P.g.) and the TLR2 agonist Pam2 above skull bones stimulates osteoclast formation, expression of osteoclastic and osteoclastogenic genes, and bone loss in skull bones from 5-week-old mice.
A and B, LPS P. gingivalis and Pam2 enhanced the number of tartrate-resistant acid phosphatase-positive, multinucleated osteoclasts (TRAP+MuOCL); the left panel of B shows a parietal bone 6 days after injection of vehicle, and the right panel of B shows osteoclasts in parietal bones 6 days after injection of LPS P. gingivalis. C–G, injection of LPS P. gingivalis or Pam2 increased the mRNA expression of c-fos, Nfatc1, Acp5, Ctsk, and Tnfsf11 after 3 days in skull bones from wild type (wt) but not from Tlr2-deficient mice. H, injection of LPS P. gingivalis or Pam2 resulted in bone loss after 6 days in skull bones from wild type but not in Tlr2-deficient mice. Images shown are representative of seven images per group. **, p < 0.01; ***, p < 0.001 compared with unstimulated controls (A and C–G). Data are the means of six-seven observations, and S.E. is given as vertical bars.