Background/Purpose: Infiltration of the synovium by mononuclear cells, including monocytes, is one of the main features of RA. 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 and overall RA development. It has been shown that abnormalities in miRNA expression are related to inflammatory molecules production by mononuclear cells, however miRNAs have never been fully analysed in monocytes population. The aim of this study was to explore global miRNA and transcriptomic profiling of monocytes from RA patients to predict which aberrantly expressed miRNA can negatively modulate inflammatory molecules.

Methods: Total RNAs from CD14+ monocytes of 12 RA and 10 healthy control (HC) were isolated. The samples were barcoded using Small-RNA-Library-Set for miRNA and simultaneously for RNA-Seq transcriptomic profiling using Illumina HiSeq 2000 platform. Hierarchical clustering was performed to select upregulated miRNAs and significantly downregulated transcripts which are predicted to be the putative target gene of miRNAs. Following computational analysis, selected miRNAs-mRNA candidates were validated using qPCR. Finally, the miRNA candidate was correlated (using Spearman analysis) with clinical parameters including DAS28.

Results: Using 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 significantly changed miRNAs in RA monocytes vs HC. Based on the highest scoring in terms of negative correlation (r= -0.97, p=1.7e-07, FDR=0.04) and the number of seed regions of miRNA (n=5) binding with the 3’UTR of mRNA, we selected miRNA-146b-3p and its target gene anti-inflammatory retinoic acid receptor alpha (RARA) transcript. In addition, miRNA-146b-3p was 1.12-fold upregulated (p=0.02) compared to HC monocytes. Similarly to NGS studies, qPCR analysis confirmed significantly increased expression of miRNA-146b-3p in RA vs HC monocytes (3.2-fold, p=0.01) and negative correlation between miRNA-146b-3p and RARA expression (r= -0.39, p=0.031). In addition, both NGS and qPCR analyses demonstrated negative correlation between miRNA-146b-3p expression and DAS28 score (r= -0.75, p=0.009 and r= -0.62, p=0.034, respectively).

Conclusion: We have identified a new miRNA candidate miRNA-146b-3p which is predicated to negatively regulate anti-inflammatory RARA transcript that may elucidate an increased inflammatory phenotype of RA monocytes.

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

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/global-mirna-expression-and-transcriptomic-profiling-of-monocytes-from-ra-patients/