Research Article

Exploring the miRNA-126 and IL-21 Regulatory Pathway in Rheumatoid Arthritis Patients

Abstract

Background: Rheumatoid arthritis (RA) is a chronic autoimmune disease driven by a network of pro-inflammatory cytokines and epigenetic regulators that together sustain synovial inflammation and joint damage. Interleukin-21 (IL-21), produced mainly by T follicular helper and Th17 cells, has been implicated in the activation of synovial fibroblasts, osteoclastogenesis and autoantibody production, while microRNA-126 (miRNA-126) has emerged as a regulator of immune cell signalling with reported, though inconsistent, alterations in RA synovial tissue. Whether circulating levels of these two molecules move together in RA patients has not been well characterised. Objective: To measure serum IL-21 concentration and relative miRNA-126 expression in RA patients compared with healthy controls, to evaluate their association with rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibody status, to test the correlation between the two markers, and to assess their individual diagnostic performance. Method: Fifty RA patients recruited from teaching hospitals and outpatient clinics in Najaf, Iraq, and forty age- and sex-comparable healthy controls were enrolled. RF was assessed by latex agglutination and anti-CCP antibody by ELISA. Serum IL-21 was measured by sandwich ELISA. Total RNA was extracted from serum and reverse-transcribed, and miRNA-126 relative expression was determined by one-step RT-qPCR using U6 as the reference gene and the 2∧-ΔΔCt method. Results: RA patients had significantly higher serum IL-21 (178.2 ± 42.4 ng/L versus 126.6 ± 14.0 ng/L, p <0.001) and miRNA-126 fold-change (2.62 ± 1.19 versus 1.07 ± 0.37, p <0.001) than controls. RF and anti-CCP were positive in 82.0% and 92.0% of RA patients, respectively, and in none of the controls. miRNA-126 and IL-21 correlated strongly in RA patients (Pearson r = 0.936, p <0.001) but not in controls (r = -0.02, p = 0.88). Receiver operating characteristic analysis showed excellent discrimination for both markers (miRNA-126: AUC 0.961; IL-21: AUC 0.965). Conclusion: Circulating miRNA-126 and IL-21 are jointly elevated in RA and tightly correlated in patients but not in healthy individuals, consistent with a disease-specific coupling between this microRNA and its putative downstream cytokine target. Both markers show strong individual diagnostic accuracy and merit further evaluation as combined, minimally invasive biomarkers of RA.

Authors affiliation:

Ahmed Abdulridha Ameen Shlash (ORCID): Department of Medical Laboratory Techniques, College of Health and Medical Technologies/Kufa, Al Furat Al Awsat Technical University, Kufa, Iraq.

How To Cite: A.A.A. Shlash. Exploring the miRNA-126 and IL-21 Regulatory Pathway in Rheumatoid Arthritis Patients. Current Research in Health Sciences, 4(2):13–19, 2026. https://doi.org/10.58613/crhs422