Background Micro-ribonucleic acids (miRNAs) are a class of small, non-coding RNAs that regulate the gene expression on posttranscriptional level. Abnormal miRNAs expression levels have been described in osteoarthritis (OA)patients – in synovial membrane, joint cartilage, chondrocytes, synovial fluid, peripheral blood. miRNAs control the chondrogenesis, osteoclastogenesis, cartilage homeostasis, catabolism and tissue repair. Recent studies have shown that miRNAs contribute to the development of OA through regulating the mechanotransduction or inflammation.
Objective The aim of our study was to comparethe systemic and local expression of certain miRNAsin OA patients and to establish a possible local dysregulation in their expression levels.
Materials and methods miRNAs expression levels were compared between matched peripheral blood (PB) and synovial fluid (SF) samples from 13 OA patients using quantitative real-time polymerase chain reaction (qPCR), SybrGreen technology. Relative changes of gene expression levels of miR-146a, miR-155, miR-223 and miR-193b were calculated by 2-∆∆Ct method and SPSS were used for statistical analysis. RNU6B gene was used as a reference control for normalisation.
Results We found difference in the expression levels of the chosen miRNAsbetween PB and SF inOA. miR-223 were downregulated in SF of all 13 (100%) patients when compared to PB (p < 0.05). Higher SF levels were found for miR-155 and miR-193b when compared to PB (53.85% and 76.92% of the patients, respectively). No statistical significant difference was observed between the systemic and local expression of miR-146a.
Conclusions Our results show that the differences between the systemic and local expression of certain microRNAs in OA could be used in the clinical practice as possible biomarkers for disease activity and severity. Larger sets and functional analysesare needed to establish if these miRNAs play crucial role in the disease pathogenesis and will reveal the potency of new therapeutic targets.