Roles and Molecular Mechanisms of Serum Exosomal miRNA-223 and miRNA-132 in Juvenile Idiopathic Arthritis

The pathogenesis of juvenile idiopathic arthritis (JIA) has not yet been clarified and is closely related to persistent overactivation of the JAK/STAT signaling pathway. MicroRNA (miRNA)-223 (miR-223) and miRNA-132 (miR-132) might be involved in the development of JIA. However, the mechanism underlying the pathogenesis of JIA is unclear. In this study, we investigated the roles and molecular mechanisms of serum exosomal miR-223 and miR-132 in JIA.  Methods: Patients with systemic JIA were selected as the systemic group (sJIA), patients with polyarticular JIA and oligoarticular JIA were selected as the articular group (aJIA), and healthy children who underwent physical examinations at the same time were selected as the normal control group (NC). Exosomes were extracted from the serum, and the purified exosomes were subjected to electron microscopy to observe their particle morphology. The particle size distribution and concentration of the exosomes were detected by an N30E particle size analyzer. The expression levels of miR-223 and miR-132 in exosomes were quantitatively detected by the SYBR green method. The protein levels of STAT3 and SOCS3 were detected by Western blot.

The expression level of miR-223 in serum exosomes of the sJIA group was significantly higher than in the aJIA group and the NC group (4.04±0.34 vs. 1.52±0.30, 0.88±0.17), and the difference was statistically significant (P<0.001). However, the expression level of miR-132 in serum exosomes of the sJIA group was significantly lower than in the aJIA group and the NC group (0.09±0.01 vs. 0.17±0.02, 0.94±0.08), and the difference was statistically significant (P<0.001). The expression levels of serum interleukin (IL)-6, IL-8, and IL-10 in the sJIA group were significantly higher than those in the aJIA group and the NC group; the difference was statistically significant (P<0.001). The IL-17 expression in the sJIA group and aJIA group was significantly greater than the expression levels in the NC groups (P<0.001). The expression level of miR-223 in exosomes was positively correlated with the expression levels of the clinical inflammatory factors IL-6, IL-8, IL-10, and IL-17 (P<0.001). However, the expression level of miR-132 in exosomes was negatively correlated with the expression levels of clinical inflammatory factors of IL-6, IL-8, IL-10, and IL-17 (P<0.001). The expression level of SOCS3 protein in both the sJIA and aJIA groups was significantly higher than in the NC group (0.25±0.05 and 0.21±0.03 vs. 0.10±0.02, respectively), and the difference was statistically significant (P<0.05). Regrettably, there was no significant difference yet in the expression level of STAT3 in the three groups (P>0.05).

miR-223 and miR-132 may be two potential new markers of JIA, providing new ideas for diagnostic tests and therapeutic interventions. But larger studies are needed to confirm these findings and assess their generalizability across diverse populations. miR-223 may promote inflammation in JIA patients by enhancing the JAK/STAT signaling pathway, while miR-132 may reduce inflammation in JIA patients by inhibiting the JAK/STAT signaling pathway. Its inhibitory effect may be closely related to SOCS3 through the JAK/STAT signaling pathway.