Background Micro-ribonucleic acids (microRNAs) comprise a class of non-coding small microRNA that regulates gene expression on posttranscriptional level. Altered expression profile of certain microRNAs has been found in the peripheral blood (PB), synovial fluid (SF) and synovial fibroblasts of rheumatoid arthritis (RA) patients. The use of microRNAs as biomarkers for RA in the clinical practice is based on correlation between their expression levels and scores for disease activity and progression. We found that altered expression of certain microRNAs in SF of RA patients correlate with the ultrasound scores for active synovitis.
Materials and methods 46 RA patients according to the 1987 ACR criteria were included in the study. Before an arthrocentesis we performed ultrasound assessment and scoring of the joint inflammation by using both grey scale and power Doppler technic for defining the synovial thickening and degree of vascularisation. MicroRNA-155 and -146a expression levels in paired PB and SF samples were investigated through PCR (SYBR Green technology) and compared to healthy controls (HCs).
Results SF in 80,43% and in 69,55% (p < 0.05, T-test) of RA patients showed overexpression of microRNA-155 and microRNA-146a, respectively, when compared to the HCs. There was a good correlation of microRNA-155 expression level and the ultrasound score for active synovitis grade ≥ 2 (Spearman’s correlation coefficient 0.313, p < 0.016) and for microRNA-146a (Spearman’s correlation coefficient 0.241, p < 0.066). The levels of microRNA-155 and -146a correlated with the presence of erosions (Spearman’s correlation coefficient 0.373, p < 0.004 and 0.318, p < 0.014, respectively) and the imaging score (Spearman’s correlation coefficient 0.412, p < 0.001 and 0.341, p < 0.008, respectively).
Conclusion The laboratory and imaging data showed correlation between the expression levels of the chosen microRNAs with the active joint inflammation and destruction. Differences could be explained by the different disease stage and progression characterised by higher erosion score and tendency to lesser synovial thickened and vascularisation as well as by the possibility of different expression levels of microRNA though the disease course. Further analysis with higher number of patients is needed to confirm if these microRNAs could be used in the clinical practice as local biomarkers for both disease activity and progression.
Acknowledgement The study was supported by Grant 55/2013 funded by Medical University – Sofia, Bulgaria