Fundamental study of osteoclast chemotaxis toward chemoattractants expressed in periodontitis

Background and Objective Periodontitis is a chronic inflammatory disease that leads to bone resorption by osteoclasts ( OC s). Several factors contribute to the differentiation of OC s from hematopoietic precursors. Cellular chemotactic factors are expressed in periodontitis tissue, but the effects of these chemoattractants on OC s are not well understood. Here we examined the effects of chemoattractants produced in inflamed periodontal tissue on OC chemotaxis. Material and Methods Rat bone‐marrow OC s were cultured in OC culture medium for 3 or 6 d. Using EZ ‐ TAXIS can™, the chemotactic response of these OCs to several chemoattractants [monocyte chemotactic protein‐1; macrophage inflammatory protein 1α; regulated on activation, normal T ‐cell expressed and secreted; stromal cell‐derived factor‐1α; and complement activation product 5a ( C 5a)] was measured. In addition, we measured the effect of C 5a‐specific inhibitors on chemotactic responses toward C 5a. The recorded chemotactic responses were quantitatively analysed using Image J software. Results Chemoattractants associated with periodontal disease significantly increased the chemotactic activity of differentiated rat OC s in a concentration‐dependent manner, with C 5a inducing the highest chemotactic activity of OC s cultured for 3 or 6 d. The C 5a‐specific inhibitor significantly inhibited chemotaxis toward C 5a in a concentration‐dependent manner. Conclusion We suggest that C 5a plays an important role in pathologic bone resorption in periodontal disease by stimulating the chemotaxis of OC s. Therefore, C 5a is a potential target for the treatment of periodontal disease.