Background Monocytes play an important role in autoimmune disease including rheumatoid arthritis (RA) or systemic sclerosis (SSc). Monocytes are the first immune cells which migrate from blood to the site of inflammation leading to tissue destruction due to enhanced proinflammatory cytokines secretion. It has been shown that abnormalities in microRNA (miRNA) expression are related to inflammatory cytokines production by T and B cells in several rheumatic diseases, however miRNAs have never been fully analysed in monocytes population. The aim of this study was to evaluate a global miRNAs profiling of monocytes from RA and SSc patients which are predicted to target proinflammatory genes.

Materials and methods Total RNAs from CD14+ monocytes of 12 RA, 10 SSc patients and 10 HC were isolated. Thirty-two samples were barcoded using Small-RNA-Library-Set, pooled and sequenced on Illumina HiSeq 2000 platform. Expression of circulating miRNA-5196 was also measured in sera of 12 RA patients before and after 6 month TNF-α therapy and correlated (Spearman analysis) with disease activity score (DAS) 28.

Results Based on next generation sequencing (NGS) we received 10 million reads from each sample. Following computational analysis we selected 14 specific miRNA candidates which are predicted to target inflammatory mediators out of 188 and 171 significantly changed miRNAs in monocytes of RA and SSc patients, respectively. Interestingly, miRNA-10–5p (targeting IRAK4) was 3.1-fold increased in SSc compared to RA (p<0.001) and 7.8-fold (p<0.001) upregulated compared to HC monocytes. Additional validation of miRNA candidates using qPCR and correlation with clinical data will be performed. Furthermore, the level of circulating miRNA-5196 was significantly elevated (p<0.001, 4.7-fold) in RA compared to HC sera. There was a positive correlation between delta DAS28 following 6 months therapy and delta miRNA-5196 expression (p=0.03).

Conclusions Our results identify new miRNA candidates which are predicated to regulate inflammatory genes in RA and SSc monocytes whereas miRNA-10–5p could be used as a biomarker exclusively characterising SSc. Also circulating miRNA-5196 can be used as a good predictor of anti-TNF-α treatment in RA patients.

Supported by 2015/16/S/NZ6/00041 from National Science Centre, Poland and EMBO ST Fellowship.