Interleukin‐23 Regulates Inflammatory Osteoclastogenesis via Activation of CLEC5A(+) Osteoclast Precursors.

Objective: To investigate the role of interleukin‐23 (IL‐23) in pathologic bone remodeling in inflammatory arthritis. Methods: In this study we investigated the role of IL‐23 in osteoclast differentiation and activation using in vivo gene transfer techniques in wild‐type and myeloid DNAX‐activation protein 12–associating lectin‐1 (MDL‐1)–deficient mice, and by performing in vitro and in vivo osteoclastogenesis assays using spectral flow cytometry, micro–computed tomography analysis, Western blotting, and immunoprecipitation. Results: Herein, we show that IL‐23 induces the expansion of a myeloid osteoclast precursor population and supports osteoclastogenesis and bone resorption in inflammatory arthritis. Genetic ablation of C‐type lectin domain family member 5A, also known as MDL‐1, prevents the induction of osteoclast precursors by IL‐23 that is associated with bone destruction, as commonly observed in inflammatory arthritis. Moreover, osteoclasts derived from the bone marrow of MDL‐1–deficient mice showed impaired osteoclastogenesis, and MDL‐1−/− mice had increased bone mineral density. Conclusion: Our data show that IL‐23 signaling regulates the availability of osteoclast precursors in inflammatory arthritis that could be effectively targeted for the treatment of inflammatory bone loss in inflammatory arthritis. [ABSTRACT FROM AUTHOR]