Serum miR-214 as a novel biomarker for ankylosing spondylitis

Objective Serum microRNA (miR) in ankylosing spondylitis (AS) patients has been rarely identified. The objective of this study was to find AS-specific miR in sera of patients with AS. Methods Total RNAs were isolated from whole sera of patients with AS, patients with rheumatoid arthritis (RA), and healthy controls (HC) using miRNeasy Serum/Plasma Kit. The presence of miR was assayed using Agilent 2100 Bioanalyzer Small RNA assay. Each RNA sample was used for miR microarray. To verify microarray results, candidate circulating miRs were validated by quantitative polymerase chain reaction (qPCR) using samples from patients with AS (n = 65), patients with RA (n = 25), and HCs (n = 39). Cycle threshold values were converted to copy numbers by drawing a standard curve using a synthetic chemical standard. All clinical values were also evaluated at the time of miR isolation. Results A total of 887 miRs were screened for three groups. Lower expression of miR-214 in AS than in HC and RA was observed after normalization of raw data. Finally, lower expression of serum miR-214 was confirmed in AS after validation by qPCR. Correlation analysis showed that the level of miR-214 of AS was significantly associated with Ankylosing Spondylitis Disease Activity Score-C-reactive protein (r = 0.299, P = 0.02). However, other disease-specific variables showed no statistical significance: gender (P = 0.286), peripheral arthritis (P = 0.634), enthesitis (P = 0.464), dacylitis (P = 0.750), psoriasis (P = 0.552), inflammatory bowel disease (P = 0.369), human leukocyte antigen-B27 positivity (P = 0.473), use of non-steroidal anti-inflammatory drugs (P = 0.448), and use of tumor necrosis factor-blocker in the last 3 months (P = 0.505). Conclusion miR-214 may serve as a noninvasive biomarker for diagnosis of AS. In addition, expression level of miR-214 was associated with disease activity.