MiR-1a-3p/Fcgr4-dependent osteoclast activation regulates pathological bone loss

Osteoporosis is a systemic metabolic disease characterized by disrupted homeostasis between osteoclast-mediated bone resorption and osteoblast-mediated bone formation. Accumulating evidence indicates that chronic systemic pathological states can exert sustained effects on osteo-immune homeostasis. However, how these disturbances promote immune-mediated osteoclast dysregulation remains unclear.

Candidate miRNAs targeting Fcgr4 were identified using bioinformatic prediction tools, and the direct interaction between miR-1a-3p and Fcgr4 was validated by dual-luciferase reporter assay. RAW264.7 cells were transfected with miR-1a-3p mimics or inhibitors to assess the effects of miR-1a-3p on osteoclast, which was evaluated by tartrate-resistant acid phosphatase (TRAP) staining, RT-qPCR, and Western blotting. miR-1a-3p expression was further analyzed in human osteoporosis cohorts and animal models of bone loss. Furthermore, to investigate whether systemic psychological stress-a chronic pathological state with sustained immunoregulatory consequences-regulates this axis, a chronic unpredictable mild stress (CUMS) model was established to examine stress-associated regulation of this axis. miR-1a-3p expression were detected by qRT-PCR, and FcγRIV-SYK-NFATc1 pathway activation was assessed by immunofluorescence staining, qRT-PCR, and Western blot.

We identified Fcgr4 as a direct target of miR-1a-3p and found that miR-1a-3p overexpression significantly suppressed osteoclast activity by inhibiting Fcgr4-dependent signaling. Consistent with this regulatory relationship, miR-1a-3p expression was significantly reduced in both human osteoporosis cohorts and animal models of bone loss. In the CUMS model, decreased miR-1a-3p expression was accompanied by increased Fcgr4 expression, activation of the FcγRIV-SYK-NFATc1 signaling pathway, enhanced osteoclast activity, and osteoporotic bone loss.

These findings support a role for the miR-1a-3p-Fcgr4 axis in linking systemic pathological changes to immune-mediated osteoclast dysregulation, providing a mechanistic framework for pathological bone loss and a basis for understanding immune-bone interactions in chronic systemic diseases.