Dual effect of IL‐7/IL‐7R signalling on the osteoimmunological system: a potential therapeutic target for rheumatoid arthritis.

The IL‐7/IL‐7R pathway plays a vital role in the immune system, especially in the inflammatory response. Monocytes/macrophages (osteoclast precursors) have been recently recognized as important participants in the osteoclastogenesis of rheumatoid arthritis (RA) patients. Here, we aimed to investigate the therapeutic potential of IL‐7/IL‐7R pathway in RA and to determine whether it could restrain osteoclastogenic functions and therefore ameliorate RA. Firstly, collagen‐induced arthritis (CIA) mice were administered with IL‐7Rα‐target antibodies to assess their therapeutic effect on arthritis. We found that blockade of the IL‐7/IL‐7R pathway protected CIA mice from bone destruction in addition to inducing inflammatory remission, by altering the RANKL/RANK/OPG ratio and consequently decreasing osteoclast formation. To explore the effect and mechanism of this pathway, bone marrow cells were induced to osteoclasts and treated with IL‐7, a STAT5 inhibitor or supernatants from T cells. The results showed that the IL‐7/IL‐7R pathway played a direct inhibitory role in osteoclast differentiation via STAT5 signalling pathway in a RANKL‐induced manner. We applied flow cytometry to analyse the effect of IL‐7 on T‐cell RANKL expression and found that IL‐7/IL‐7R pathway had an indirect role in the osteoclast differentiation process by enhancing the RANKL expression on T cells. In conclusion, the IL‐7/IL‐7R pathway exhibited a dual effect on osteoclastogenesis of CIA mice by interacting with osteoimmunology processes and could be a novel therapeutic target for autoimmune diseases such as RA. [ABSTRACT FROM AUTHOR]