Correlation Between miRNA-326 Expression and Serum IL-17 Levels in Iraqi Patients with Rheumatoid Arthritis: A Case-Control Study

Abstract

Background: Rheumatoid arthritis (RA) is a chronic systemic autoimmune condition driven by synovial inflammation and arthritic destruction. MicroRNA-326 (miR-326) regulates Th17 cell differentiation, the major source of IL-17, a key pro-inflammatory cytokine in RA pathogenesis. Objectives: The study aims to measure the expression level of miRNA-326 and serum IL-17 in RA patients and healthy controls, analyze the correlation between miRNA-326 expressions with that of serum IL 17 levels, as well as evaluate diagnostic value by ROC curve analysis. Methods: A case-control study (October 2025–February 2026) that include fifty patients who confirmed as RA along with forty healthy subjects ages matched [44,34] from five different hospitals in Najaf/Iraq. The expression of miRNA-326 was evaluated by one-step RT-qPCR (using U6 snRNA as a reference gene and the 2⁻ΔΔCt method). Sandwich ELISA was used to quantify IL-17. RF was determined by latex agglutination and anti-CCP by qualitative ELISA. Statistical analyses were performed using the Mann–Whitney U test, Spearman's correlation and bootstrap ROC analysis. Results: miRNA-326 was significantly downregulated in RA patients (mean fold change 0.596 ± 0.387) versus controls (1.265 ± 0.864; p < 0.0001). Serum IL-17 was significantly elevated in RA patients (64.89 ± 6.73 ng/L) versus controls (49.64 ± 4.79 ng/L; p < 0.0001). A strong negative correlation was observed between miRNA-326 and IL-17 in RA patients (Spearman r = −0.672, p < 0.0001). ROC analysis yielded AUC values of 0.944 (95% CI: 0.885–0.991) for IL-17 (sensitivity 84.0%, specificity 100.0%; cut-off ≥ 60.50 ng/L) and 0.777 (95% CI: 0.671–0.869) for miRNA-326 (sensitivity 88.0%, specificity 57.5%; cut-off ≤ 1.041). RF positivity was 82% (41/50) and anti-CCP positivity was 94% (47/50). Conclusion: miRNA-326 is significantly downregulated while IL-17 is markedly elevated in RA, with a strong negative correlation between them. Both biomarkers demonstrate meaningful diagnostic value, supporting the involvement of the miRNA-326/Th17/IL-17 regulatory axis in RA pathogenesis in RA pathogenesis.