Bone resorption involves sequential stages of osteoclast precursor migration and differen-tiation of osteoclast precursors into multinucleated osteoclasts. Stromal cell derived factor (SDF)-1 is a chemotactic factor for osteoclast precursor migration. Matrix metalloproteinase (MMP)-9 is involved in migration of osteoclast precursors and activation of interleukin(IL)-1β. Alveolar bone destruction is a characteristic feature of periodontal disease. Treponema lecithinolyticum is a oral spirochete isolated from the periodontal lesions. The effect of lipopolysaccharide(LPS) from T. lecithinolyticum on expression of SDF-1 and MMP-9 was examined in cocultures of bone marrow cells and osteblasts derived from mouse calvariae.

T. lecithinolyticum LPS increased expression of MMP-9 in the coculture. Polymyxin B, an inhibitor of LPS, abolished the increase of MMP-9 mRNA expression by LPS. LPS did not increase the expression of SDF-1, IL-1β and tumor necrosis factor(TNF)-α mRNA in cocultures. Prostaglandin E₂(PGE₂) up-regulated the expression of MMP-9 and NS398, an inhibitor of PGE2 synthesis, down-regulated the induction of MMP-9 expression by T. lecithinolyticm LPS.

These results suggest that T. lecithinolytium LPS increases MMP-9 expression in bone cells via PGE₂ and that the induction of MMP-9 expression by T. lecithinolyticum LPS is involved in alveolar bone destruction of periodontitis patients by the increase of osteoclast precursor migration and the activation of bone resorption-inducing cytokine.