Altered expression of miR-155 in peripheral blood mononuclear cells of rheumatoid arthritis patients

Objective ① To Screen for the miRNAs differently expressed in the peripheral blood mono-nuclear cells (PBMCs) of rheumatoid arthritis (RA) by microarray experiments. ② To further evaluate the expression of miR-155 in PBMCs of RA. ③ To determine the relevance between the expression of miR-155 and clinical as well as laboratory features. ④ To test whether inflammatory mediators can induce miR-155 expression in PBMCs of RA. Methods ① Total RNA was isolated from peripheral blood mononuclear cells obtained from 5 patients of RA and 5 normal controls. Expression profiling of miRNAs was performed in a microarray analysis. ② MiR-155 was identified for further study by stem-loop real-time RT-PCR based on SYBR-Green. PBMC from 26 patients of RA and 23 normal controls were collected. ③ Association between miR-155 and the clinical and laboratory features of RA was evaluated. ④ Induction of miR-155 following stimulation with TNF-α, IFN-γ and LPS of cultures of RA PBMCs was examined by real-time RT-PCR. Statistical analysis was done with student's t test, paired t test, and ANOVA, Spearman correlation. Results ① Expression profiling of miRNAs revealed significant differential expression of 14 miRNAs, of which signal intensity changed over two times. MiR-155 was up-regulated in PBMCs of RA than in normal controls (t=9.218, P=0.001).② The expression level of miR-155 had a positive correlation with serum CRP level (r=0.57, P=0.002). ③ Expression of miR-155 was markedly up-regulated in PBMCs of RA after stimulated with TNF-α, IFN-γ and LPS, especially with TNF-α. Conclusions The expression of miR-155 is induced by stimulating with TNF-α, IFN-γ and LPS. MiR-155 may be a regulator in RA pathogenesis. Further studies are required to elucidate the function of miR-155. Key words: Arthritis, Rheumatoid; Monocytes; miR-155