Article
Change in osteoclast differentiation and activity by visfatin and rheumatoid arthritis synovial fibroblasts
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Authors
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Jana Fuchs
- Campus Kerckhoff, Justus Liebig University Giessen, Department of Rheumatology and Clinical Immunology, Bad Nauheim
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Mona Arnold
- Campus Kerckhoff, Justus Liebig University Giessen, Department of Rheumatology and Clinical Immunology, Bad Nauheim
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Klaus Frommer
- Campus Kerckhoff, Justus Liebig University Giessen, Department of Rheumatology and Clinical Immunology, Bad Nauheim
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Iris Aykara
- Campus Kerckhoff, Justus Liebig University Giessen, Department of Rheumatology and Clinical Immunology, Bad Nauheim
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Teresa Laibe
- Campus Kerckhoff, Justus Liebig University Giessen, Department of Rheumatology and Clinical Immunology, Bad Nauheim
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Stefan Rehart
- Agaplesion Markus Hospital, Department of Orthopaedics and Trauma Surgery, Frankfurt
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Ulf Müller-Ladner
- Campus Kerckhoff, Justus Liebig University Giessen, Department of Rheumatology and Clinical Immunology, Bad Nauheim
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Elena Neumann
- Campus Kerckhoff, Justus Liebig University Giessen, Department of Rheumatology and Clinical Immunology, Bad Nauheim
| Published: | August 31, 2022 |
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Outline
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Introduction: Osteoclasts are the most important mediators of bone erosion in rheumatoid arthritis (RA) with a major influence on disease prognosis. Additionally, RA synovial fibroblasts (RASF) contribute significantly to joint destruction. RASF affect osteoclastogenesis, e.g. by producing pro-osteoclastogenic factors such as IL-6 and RANKL. In contrast, visfatin inhibits osteoclast differentiation but promotes the release of inflammatory factors such as IL-6. In this study, the effect of RASF with/without activation by IL-1 and visfatin on osteoclastogenesis was evaluated.
Methods: PBMCs were isolated from blood from healthy donors and RA patients. After addition of M-CSF, RANKL and TGF-β, osteoclastogenesis was initiated. RASF-conditioned medium (CM) was obtained from a 90% confluent RASF culture after 48 h. A comparison was made between differentiating PBMCs in monoculture, in culture with CM (10%, 20%, 30%) and in direct co-culture with RASF with/without IL-1 (0.05 ng/ml) or visfatin (25 ng/ml). Two weeks after PBMC-isolation, cells were stained using TRAP and IL-6 was measured in supernatants collected on the same day. Depending on the variability, 3-6 pictures per well were used for quantification of nuclei (2, 3-5, 6-10, >11).
Results: IL-6 production increased non-linearly with increasing proportion of CM added to both healthy (e.g. CM-IL-1: 20% p=0.0429, 30% p=0.0007; n=5) and RA PBMC (CM-IL-1: 20% p=0.0156, 30% p=0.0004; n=6) compared to controls in all settings. IL-6-production increased in all settings with IL-1 (e.g. co-culture 2.4-fold) and visfatin (e.g. CM-visfatin: 10%=5.3-fold, 20%=6.4-fold, 30%=4.7-fold) compared to unstimulated control. Baseline IL-6-concentrations were higher in RA osteoclasts compared to healthy donors in all settings and further increased by IL-1 or visfatin (e.g. CM-visfatin 10%=2.1-fold, 20%=3.0-fold, 30%=2.7-fold). During osteoclastogenesis, CM-10% led to a decrease in the number of 2 (only IL-1/unstimulated), 3-5 and 6-10 nucleated osteoclasts in all settings in healthy and RA donors (n=4 each).
Conclusion: Compared to unstimulated controls, IL-6-levels were increased by IL-1 and visfatin in all settings in monoculture and co-coculture. Baseline IL-6-levels were higher in osteoclast cultures of RA patients compared to healthy donors. A decrease in osteoclastogenesis was observed specifically by addition of low amounts of RASF-CM showing that direct cell contact is not required to promote osteoclastogenesis.
