β-Glucan modulates trained immunity to inhibit osteoclast differentiation via NOD2/RIPK2 signaling pathway.

OBJECTIVE: This study investigated how β-glucan (BG)-induced trained immunity (TI) regulates osteoclast-driven bone resorption, with emphasis on the pivotal signaling axis governing this anti-resorptive memory.

METHODS: Bone marrow-derived macrophages (BMMs) were primed with BG for 24 h and subsequently challenged with LPS to establish a TI model, validated by cytokine secretion profiling (IL-1β, IL-6, TNF-α). Osteoclastogenesis was induced by M-CSF/RANKL and assessed via TRAP staining, F-actin ring formation, immunofluorescence for CTSK/MMP-9, and bone resorption assays. Histological evaluation (H&E and TRAP staining) and micro-CT analysis were performed to assess alveolar bone remodeling in a murine periodontitis model. Transcriptomic profiling and functional validation using genetic/pharmacological perturbations identified critical signaling pathways.

RESULTS: BG induced robust TI in macrophages under osteoclastogenic stimuli. Trained BMMs maintained long-term suppression of LPS-driven osteoclast reactivation. Systemic BG preconditioning preserved alveolar bone architecture in vivo. Complete abolition of BG's anti-osteoclastic effects by NOD2/RIPK2 blockade validated the mechanism.

CONCLUSION: BG establishes innate immune memory through NOD2/RIPK2 signaling to counter pathological osteoclast activation, positioning TI modulation as a translational strategy against inflammatory bone loss.