Chemokines associated with periodontitis affect chemotactic activity of cultured osteoclasts

Methods: Rat osteoclasts were cultured using an osteoclast culture kit (Primary Cell Co., Ltd, Japan) for 3 or 6 days. The chemotactic responses of cultured osteoclasts were measured by EZ-TAXIScan (ECI, Inc. Japan) using MCP-1, MIP-1á, RANTES, SDF-1á and C5a as the cellular chemotactic factors. The recorded chemotactic responses were imported into Image J (National Institute of Health, USA), and analyzed quantitatively. We also examined the inhibitory effect of a C5a-specific antagonist (H-8135) on osteoclast chemotaxis. Osteoclasts were seeded on dentine slices and cultured for 14 days in medium containing C5a and H-8135. The areas of the resulting resorption pits on the dentine surfaces were measured.

Results: The chemokines associated with periodontal diseases significantly increased the chemotactic activity of differentiated rat osteoclasts in a concentration-dependent manner. C5a had the largest effect on the chemotactic activity of osteoclasts cultured for 3 and 6 days. H-8135 inhibited the C5a-induced increase in chemotactic activity of osteoclasts in a concentration-dependent manner. H-8135 also decreased the area of the resorption pits caused by osteoclasts on the dentine slices in a concentration-dependent manner.

Conclusion: C5a is suggested to play an important role in pathological bone resorption in periodontal diseases by stimulating the chemotaxis of osteoclasts. Specific inhibitors of C5a can be used as a new candidate inhibitory chemical for osteoclastic bone resorption.