Elevated cytokines in osteoporotic blood correlate with immune microenvironment shifts and dysregulated circRNA...

Osteoporosis (OP) pathogenesis is inextricably linked to immune microenvironment dysregulation. However, the sex-specific immunoregulatory disparities between senile osteoporosis (SOP) and postmenopausal osteoporosis (PMOP) remain incompletely elucidated.

In this study, we integrated multi-cohort bulk transcriptomics, single-cell RNA sequencing (scRNA-seq), and independent clinical validations to systematically decipher the distinct immune landscapes and circular RNA (circRNA) regulatory axes underlying SOP and PMOP.

Bulk transcriptomic analysis revealed pervasive cytokine activation in OP, and such activation may be linked to divergent gene signatures between cohorts. Notably, LAG3 and TBX21 emerged as core cytokine-related hub genes across datasets. Immune deconvolution demonstrated sexually dimorphic microenvironment remodeling: male SOP patients exhibited a significant decrease in CD4⁺ T cells alongside expanded NK and CD8⁺ T cells, whereas female PMOP patients were primarily characterized by an increased proportion of monocytes. Furthermore, we constructed an immune-targeted competitive endogenous RNA (ceRNA) regulatory network and identified three core circRNAs (hsa-KMT5B_0001, hsa-TMEM55A_0001, and hsa-TNFRSF21_0001) as potential upstream regulators of these immune shifts. Subsequent scRNA-seq analysis of bone marrow mononuclear cells validated the peripheral immune imbalances and overexpressed the heightened expression of key cytokine genes predominantly to dendritic cells and monocytes. Finally, quantitative RT-PCR and flow cytometry in an independent clinical cohort further validated the upregulation of the target transcripts and the specific expansion of NK cells in SOP.

This study unveils the sex-divergent immune-associated mechanisms underlying OP and delineates three novel circRNA-cytokine networks. These findings provide a theoretical basis and candidate molecular targets for the development of stratified, sex-specific clinical interventions for OP.