THU0046 FRACTALKINE PROMOTES DIFFERENTIATION INTO OSTEOCLASTS FROM HUMAN PERIPHERAL BLOOD MONOCYTES
Authors: Sei Muraoka, Kaichi Kaneko, Natsuko Kusunoki, Shinichi Kawai, Toshihiro Nanki
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Fractalkine (FKN) also known as chemokine (C-X3-C motif) ligand 1 plays important roles in the pathogenesis of rheumatoid arthritis (RA). Clinical trials of monoclonal antibody against FKN for RA are currently in progress. Although FKN has been reported to be involved in the migration of osteoclast precursor cells, the direct effect of FKN on osteoclast differentiation is not clear. <h3>Objectives</h3> In this study, we aimed to clarify the effect of FKN on differentiation into osteoclasts from human peripheral blood monocytes. <h3>Methods</h3> CD14-positive monocytes were purified from peripheral blood obtained from healthy donors by magnetic beads. CD16-positive and CD16-negative peripheral blood monocytes were isolated from the CD14-positive monocytes. The purified peripheral blood monocytes were incubated with M-CSF + RANKL with or without FKN for 1 week. The cells were stained for tartrate-resistant acid phosphatase (TRAP). TRAP-positive multinucleated (three or more nuclei) cells were counted as osteoclasts. The cells were seeded onto plates coated with calcium phosphate thin films, and the resorption lacunae were examined. Next, CD14-positive monocytes were incubated with GM-CSF + IL-4 with or without FKN for 1 week to differentiate into dendritic cells. The surface markers of these cells were analyzed by flow cytometry. In addition, the monocyte-derived dendritic cells were further incubated with M-CSF + RANKL with or without FKN. Then the cells were stained for TRAP. The research procedure has been approved by the ethics committee of Toho University School of Medicine (Approval number: 27060). <h3>Results</h3> CD16-negative peripheral blood monocytes differentiated into osteoclasts by incubation with M-CSF + RANKL. The osteoclast differentiation was enhanced by additional stimulation with FKN in a concentration-dependent manner. In addition, calcium resorption was also enhanced by addition of FKN. On the other hand, CD16-positive monocytes treated with M-CSF + RANKL did not differentiate into osteoclasts with or without FKN. CD14-positive monocytes differentiated into dendritic cells by stimulation with GM-CSF + IL-4. Expression of CD14 was decreased and CD1a expression was increased on the monocyte-derived dendritic cells. CD16-negative monocyte-derived dendritic cells differentiated into osteoclasts by further stimulation with M-CSF + RANKL. By co-stimulation with FKN, the osteoclast differentiation from CD16-negative monocyte-derived dendritic cells was also enhanced. <h3>Conclusion</h3> FKN promotes osteoclast differentiation from human peripheral blood CD16-negative monocytes and also from CD16-negative monocyte-derived dendritic cells. FKN might contribute bone destruction in the affected joints of RA as well as inflammatory cell accumulation into the synovial tissue. <h3>References</h3> [1] Tanaka Y, Takeuchi T, Umehara H, Nanki T, et al. Safety, pharmacokinetics, and efficacy of E6011, an antifractalkine monoclonal antibody, in a first-in-patient phase 1/2 study on rheumatoid arthritis. Mod Rheumatol. 2018; 28: 58. [2] Nanki T, Imai T, Kawai S. Fractalkine/CX3CL1 in rheumatoid arthritis. Mod Rheumatol. 2017; 27: 392. [3] Nanki T, et al. Inhibition of fractalkine ameliorates murine collagen-induced arthritis. J Immunol. 2004; 173: 7010. [4] Nanki T, et al. Migration of CX3CR1-positive T cells producing type 1 cytokines and cytotoxic molecules into the synovium of patients with rheumatoid arthritis. Arthritis Rheum. 2002; 46: 2878. <h3>Disclosure of Interests</h3> Sei Muraoka Grant/research support from: Novartis, Speakers bureau: Pfizer, Chugai, Kaichi Kaneko: None declared, Natsuko Kusunoki: None declared, Shinichi Kawai Grant/research support from: Nippon Zoki, Chugai, Ono, Ayumi, Hisamitu, Eisai, Japan Tobacco, Nippon Kayaku, Daiichi Sankyo, Astellas, Yutoku, and Mitsubishi Tanabe, Consultant for: Santen, Japan Tobacco, Speakers bureau: Ayumi, Chugai, Ono, Astellas, Pfizer, Celltrion, Toshihiro Nanki Grant/research support from: Chugai, Eisai, Takeda, Teijin, Eli Lilly, Bristol-Myers, AbbVie, Ono, Novartis, Asahikasei, Mitsubishi-Tanabe, Astellas, Ayumi, Pfizer, Daiichi Sankyo, Shionogi, Sanofi, Nippon Kayaku, Yutoku, Actelion, UCB, Bayer, Nihon Pharmaceutical., Consultant for: UCB, Eisai, Chugai, Ono, Gilead., Speakers bureau: Mitsubishi-Tanabe, Chugai, Eisai, Takeda, Astellas, Janssen, Eli Lilly, Ayumi, Pfizer, Asahikasei, Sanofi, Daiichi Sankyo, Otsuka, AbbVie, Ono, Teijin, Nippon Kayaku, UCB.