AnnexinA1-Dectin 1 axis is a key regulator of osteoclastogenesis underlying irradiation induced bone loss in male mice

The molecular mechanisms linking immune cell signaling to osteoclastogenesis remain incompletely defined. Here, we identify an Annexin A1 (AnxA1)-Dectin-1 axis as a key driver of osteoclast differentiation. Dectin-1 (CLEC7A), a myeloid C-type lectin receptor best known for β-glucan recognition, is shown to bind the endogenous ligand AnxA1 on pre-osteoclasts, thereby promoting their maturation. In Dectin-1 deficient mice, reduced osteoclast numbers resulted in increased bone volume, whereas β-glucan-induced Dectin-1 activation enhanced osteoclastogenesis. Within the bone marrow niche, AnxA1 was abundantly expressed on B220+ B cells, and γ-irradiation markedly increased its surface translocation both in vitro and in vivo. γ-irradiated B220+ B cells exhibited strong Dectin-1 binding capacity and robustly stimulated osteoclast differentiation in a Dectin-1-dependent manner. These findings establish the AnxA1-Dectin-1 interaction as a critical immune-skeletal communication pathway, revealing a mechanism by which radiation exposed immune cells can accelerate bone resorption. Targeting this axis offers a potential strategy to mitigate radiation-induced bone degradation and preserve skeletal homeostasis.