Background Overexpression of the components of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway are key factors of the pathogenic mechanisms underlying systematic juvenile idiopathic arthritis (SJIA).

Objectives The present study aimed to investigate the association between microRNA (miR)-19a, miR-21 and the JAK/STAT signaling pathway.

Methods A total of 20 patients with SJIA were included in the study, and peripheral blood mononuclear cells (PBMCs) from 20 normal controls were also collected.RNAiso was used to extract total RNA, and the RNA was then reverse transcribed into cDNA. Primers were designedto detect the mRNA of miR-19a and miR-21, and U6 was set as the internal parameter. In addition, the mRNA of STAT3, suppressor of cytokine signaling 3 (SOCS3), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) was detected, and β-actin was set as the internal parameter. Reverse transcription-quantitative polymerase chain reaction was performed to detect the expression levels of these proteins in patients with SJIA and control subjects, and non-parametric tests were used to analyze the statistical differences in 2-ΔΔCq between the two groups.

Results The expression levels of miR-19a and miR-21 were significantly lower in the SJIA group compared with the control group (P<0.05). SOCS3, TNF-α and STAT3 were shown to be the target genes of miR-19a and miR-21, as determined by Targetscan. The expression levels of STAT3, SOCS3,TNF-α and IL-6 mRNA were significantly higher compared with those of the control group (P<0.05).

Conclusions In the PBMCs of the patients with SJIA, miR-19a and miR-21 expression levels were lower compared with those of the control group, and the JAK/STAT signaling pathway was activated, which indicated that miR-19a and miR-21 may participate in the activation ofthe JAK/STAT signaling pathway.

Disclosure of Interest None declared