Circ_0024085 and circ_0000339 as potential biomarkers for the diagnosis of ankylosing spondylitis

Objective This study aimed to identify novel circular RNA (circRNA) biomarkers in peripheral blood mononuclear cells (PBMCs) for the diagnosis of ankylosing spondylitis (AS) and to explore their potential pathogenic mechanisms.Methods High-throughput circRNA sequencing was performed on PBMCs from 3 AS patients and 3 healthy controls. Differentially expressed circRNAs were validated by RT-qPCR in an independent cohort (64 AS patients and 24 healthy individuals). Diagnostic performance was evaluated via ROC curve analysis. Correlations between circRNA expression and clinical inflammatory markers were assessed. Bioinformatics analysis was employed to predict target miRNAs and enriched signaling pathways.Results A total of 53 circRNAs were differentially expressed in AS PBMCs. Among these, circ_0024085 and circ_0000339 were significantly upregulated in AS (41.6-fold and 27.0-fold, p < 0.05), and demonstrated good diagnostic performance (AUC = 0.815 for the combination). The expression of Circ_0024085 was inversely correlated with erythrocyte sedimentation rate (ESR, p = 0.005) and monocyte count (p = 0.027). Bioinformatic analysis indicated that the target miRNAs of circ_0024085 were significantly enriched in the IL‑4/IL‑13 signaling pathway, while those of circ_0000339 were enriched in the SEMA4D signaling pathway.Conclusion Our findings identify circ_0024085 and circ_0000339 as potential diagnostic biomarkers for AS. With bioinformatics predictions indicating that Circ_0024085 may exert an anti-inflammatory effect via M2 macrophage polarization, whereas circ_0000339 might contribute to bone damage through SEMA4D signaling.