Background Synovial hypertrophy and synovitis could be seen in both rheumatoid arthritis (RA) and inflammatory osteoarthritis (OA) as a consequence of deregulated pro-inflammatory cytokine production. Abnormal local microribonucleic acids (miRNAs) production that regulate the inflammatory milieu in the synovial joints has been reported in several studies. Due to their stability miRNAs are widely explored as potential diagnostic biomarkers for both diseases as well as for disease activity and treatment response.
Objectives The objective of our study was to evaluate the role of expression levels of miR-223 in the synovial fluid (SF) of RA and OA patients as diagnostic biomarker in the clinical practice.
Methods Total RNA including miRNAs was isolated from SF of 48 RA, 16 OA and 11 healthy controls (HCs) by using RNeasy Protect Cell Mini kit (according to manufacturer's protocol). Reverse transcription was performed in order to synthesize cDNA by using miScript II RT kit. Expression of miR-223 was analyzed by relative quantitation method 2^–(ΔΔCq). As reference control for normalization RNU6B gene was used. Data were analyzed by SPSS. The results were compared to HCs as well as between the two disease groups.
Results In SF miR-223 was overexpressed in 79.17% of the RA (p=1.64 x 10–3) and in 62.50% of OA patients (p=0.885) when compared to HCs. SF miR-223 levels were upregulated in 77.08% of the RA when compared to OA patients (p=6.2x10–3). In order to evaluate the diagnostic accuracy of miR-223 expression levels in SF to distinguish patients with RA or OA from HCs as well as between the two diagnostic groups receiver operating characteristic (ROC) curve analysis was constructed using RQ values. Expression levels of miR-223 in SF could discriminate RA patients from HCs with high diagnostic accuracy since area under the curve (AUC) was 0.841 (95 CI: 0.724–0.958; p=4.6x10–4) with 87.5% sensitivity and 72.7% specificity. ROC curve analysis showed that OA patients could not be well distinguished from HCs (AUC =0.631; 95 CI: 0.417–0.845) probably due to the small sample size but SF miR-223 levels could be used to discriminate OA from RA with the following AUC =0.693 (95% CI: 0,493–0.893) and with 68.8% sensitivity and 66.7% specificity.
Conclusions SF miR-223 level could serve as potential diagnostic biomarker for RA as it could distinguish RA from both HCs as well as inflammatory OA. Larger sets are needed to confirm the diagnostic accuracy of miR-223 in RA.
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Acknowledgement Acknowledgement: The study was supported by Grant 14-D/2012 funded by MU-Sofia.
Disclosure of Interest None declared