Dan Liu

Rheumatoid arthritis (RA) is a chronic inflammation mediated by autoimmune responses. MEG3, a kind of long noncoding RNA (lncRNA), participates in cell proliferation in cancer tissues. However, the correlation between MEG3 and RA is yet unclear. Therefore, to clarify how MEG3 works in RA, we performed a series of experiments using RA samples. We found that MEG3 was downregulated in the fibroblast‐like synoviocytes of RA patients (RA‐FLS), in comparison with healthy subjects. MEG3 was also down‐regulated evidently in lipopolysaccharide (LPS)‐treated chondrocyte. As part of our experiments, MEG3 was overexpressed in chondrocyte by transfection with lentivirus containing sequences encoding MEG3. In addition, in presence of LPS, reductions were identified not only in the cell proliferation, but also in the generation of interleukin‐23 (IL‐23), which, however were reversed in the lentivirus (containing MEG3‐encoding sequences)‐transfected chondrocytes. Up‐regulated MEG3 resulted in an increase the level of Ki67. Moreover, MEG3 was negatively correlated with miR‐141, and miR‐141 was up‐regulated in LPS‐treated chondrocyte. Inhibitory effects of MEG3 overexpression, mentioned above, were partially abolished by overexpressed miR‐141. Further, animal experiment also showed the inhibitory effect of MEG3 in overexpression on the AKT/mTOR signaling pathway. In‐vivo experiments also showed that cell proliferation was facilitated by MEG3 overexpression with inhibited inflammation. In summary, the protective role of MEG3 in RA was proved to be exerted by the increase in the rate of proliferation, which might correlate to the regulatory role of miR‐141 and AKT/mTOR signal pathway, suggesting that MEG3 holds great promise as a therapeutic strategy for RA.

We aimed to investigate the regulation of circular RNAs in lipopolysaccharide (LPS)-treated chondrocytes isolated from SD rat. In this study, we analyzed how circFADS2 was regulated in LPS-treated chondrocytes and isolates from Rheumatoid arthritis (RA) patients and found that circFADS2 and mTOR were highly expressed whereas miR-498 expression was significantly reduced. We then silenced circFADS2 in LPS-treated chondrocytes; this resulted in a declined expression of type II collagen, but an increase in the expression of MMP-13, COX-2, and IL-6. Overall, silencing circFADS2 caused a significant reduction in the proliferative rate of LPS-treated chondrocytes, increased apoptotic levels, miR-498 upregulation, and mTOR downregulation. Dual-luciferase reporter assay indicated that circFADS2 directly targeted miR-498. In contrast, miR-498 down-regulation affected circFADS2 silencing, promoting extracellular matrix (ECM) degradation and apoptosis. The 3' UTR of the mTOR gene is targeted by miR-498, and consequently, in cells transfected with miR-498, there was a significant reduction of mTOR expression at the protein and mRNA levels. Silencing mTOR had a similar effect to circFADS2 silencing on type II collagen, MMP-13, COX-2, and IL-6 expression, as well as cell proliferation and apoptosis. In conclusion, circFADS2 may affect LPS-induced chondrocytes properties by regulating the ECM catabolism, inflammation, and apoptosis in chondrocytes.