Immunological Mechanisms of Osteoporosis and Bone Health

Bone health is maintained through a tightly regulated balance between bone formation by osteoblasts and bone resorption by osteoclasts. Immune cells and their secreted mediators are now recognised as central regulators of this process, giving rise to the field of osteoimmunology. Key cytokines such as receptor activator of nuclear factor κB ligand (RANKL), tumour necrosis factor-α (TNF-α) and interleukins interact with bone cells to influence differentiation, activity and survival. Adaptive immune cells—including T-helper subsets, regulatory T cells and B lymphocytes—modulate osteoclastogenesis either directly via cell–cell contact or indirectly through cytokine networks. Innate immune cells, such as macrophages and neutrophils, contribute to both steady-state remodelling and inflammation-driven bone loss. Oxidative stress and non-coding RNAs add further layers of regulation by affecting transcription factors and signalling pathways. Emerging data on chromatin remodelling and local drug-delivery systems underscore the therapeutic potential of targeting immune–bone cross-talk. Understanding these immunological mechanisms offers routes to prevent fractures, improve healing and address the global burden of osteoporosis.

Research from Nature Portfolio

Recent studies have elucidated the role of a chromatin remodeller, BRD9, in osteoclast differentiation. Loss of BRD9 in myeloid progenitors unleashes osteoclastogenesis by dampening interferon-β signalling, thereby accelerating bone resorption. Mechanistic work revealed that BRD9 forms a complex with FOXP1 to activate Stat1 transcription and sustain interferon-β production. Pharmacological inhibition of BRD9 enhanced osteoclast commitment, while local delivery of BRD9 modulators in a silk fibroin hydrogel mitigated drug-induced osteonecrosis and acute bone loss in experimental models. These findings position chromatin remodelling as a novel checkpoint in immune-driven bone remodelling and offer a blueprint for targeted therapies in inflammatory bone disorders.

Immunological Mechanisms of Osteoporosis and Bone Health publication trend

The graph below shows the total number of articles in immunological mechanisms of osteoporosis and bone health across all publications each year (not limited to Nature Index journals).

Technical terms

Osteoclast: A bone-resorbing cell derived from myeloid lineage that degrades mineralised bone matrix.

RANKL: Receptor activator of nuclear factor κB ligand; a cytokine essential for osteoclast differentiation and activation.

OPG: Osteoprotegerin; a decoy receptor that binds RANKL to inhibit osteoclastogenesis.

Osteoclastogenesis: The process of differentiation and activation of osteoclasts from precursor cells.

Chromatin remodelling: Dynamic modification of chromatin structure that regulates gene expression.

MicroRNA: Small non-coding RNA molecules that regulate gene expression post-transcriptionally.

References

1. BRD9-mediated chromatin remodeling suppresses osteoclastogenesis through negative feedback mechanism. Nature Communications (2023).
2. Interaction between bone and immune cells: Implications for postmenopausal osteoporosis. Seminars in Cell and Developmental Biology (2021).
3. The Role of Inflammatory Cytokines, the RANKL/OPG Axis, and the Immunoskeletal Interface in Physiological Bone Turnover and Osteoporosis. Scientifica (2013).
4. Oxidative Stress and Inflammation in Osteoporosis: Molecular Mechanisms Involved and the Relationship with microRNAs. International Journal of Molecular Sciences (2023).
5. Immunoporosis: Role of Innate Immune Cells in Osteoporosis. Frontiers in Immunology (2021).
6. Macrophage-Osteoclast Associations: Origin, Polarization, and Subgroups. Frontiers in Immunology (2021).