Objective. MicroRNAs (miRNAs) play important roles in many biological processes and recent studies have provided growing evidences that miRNA dysregulation might play important roles in the pathogenesis of rheumatoid arthritis (RA). The aim of this study was to investigate the contribution of miRNAs to altered gene expressions in RA.
Methods. To investigate whether the differential expression of miRNA in RA could account for the altered expression of certain genes, we compared the different expressions of miRNAs and mRNAs in rheumatoid synovial fluid monocytes with that of normal peripheral blood (PB) monocytes by using a gene expression oligonucleotide microarray and a microRNA microarray.
Results. Comparative analysis of the mRNA profiles showed significant different expressions of 430 genes in RA synovial monocytes, of which 303 (70%) were upregulated and 127 (30%) were downregulated, as compared with that of normal PB monocytes. Out of differentially expressed 13 miRNAs, 9 miRNAs were upregulated and 4 miRNAs were downregulated in the RA synovial monocytes. A total of 62 genes were predicted as target genes of the 13 differentially expressed miRNAs in the RA synovial monocytes. Among the 62 miRNA-targeted genes, a few genes such as GSTM1, VIPR1, PADI4, CDA, IL21R, CCL5, IL7R, STAT4, HTRA1 and IL18BP have been reported to be associated with RA.
Conclusion. In the present study, we observed that several miRNAs are differentially expressed in RA synovial monocytes, and we suggest that these different expressions of miRNAs may regulate the expression of several genes associated with the pathogenesis of RA.

Keywords: MicroRNA, Rheumatoid arthritis, Microarray