CIRCULATING EXOSOMAL MIRNAS AS BIOMARKERS FOR SUBCLINICAL INFLAMMATION IN SERONEGATIVE RHEUMATOID ARTHRITIS

Background: Seronegative rheumatoid arthritis (RA) lacks conventional autoantibodies, making early diagnosis and inflammation monitoring challenging. Exosomal microRNAs (miRNAs) have emerged as promising biomarkers due to their stability and role in immune regulation. Objective: To investigate the expression profiles of circulating exosomal miRNAs in seronegative RA patients and identify molecular signatures associated with subclinical inflammation. Methods: This cross-sectional study was conducted over eight months in Lahore, Pakistan. Ninety-six patients with seronegative RA were enrolled based on 2010 ACR/EULAR criteria. Plasma-derived exosomes were isolated and validated using nanoparticle tracking analysis and Western blotting. miRNAs (miR-146a, miR-155, miR-21, miR-223, miR-125b) were quantified using qRT-PCR. Subclinical inflammation was assessed through high-resolution musculoskeletal ultrasound and biochemical markers (CRP, ESR). Statistical analyses included t-tests, ANOVA, and Pearson correlations (p < 0.05 considered significant). Results: miR-155 (3.16 ± 1.04), miR-223 (2.72 ± 0.88), and miR-146a (2.41 ± 0.92) showed significantly elevated expression levels. Strong positive correlations were observed between miRNA levels and PD ultrasound scores (miR-155: r = 0.63, p < 0.001; miR-223: r = 0.59, p < 0.001). CRP-stratified analysis revealed significantly higher miRNA expression in patients with elevated CRP (>5 mg/L). Conclusion: Circulating exosomal miRNAs, particularly miR-155, miR-223, and miR-146a, may serve as sensitive biomarkers for detecting subclinical inflammation in seronegative RA. These findings support their potential utility in enhancing early diagnosis and personalized disease monitoring.