MicroRNA-20a suppresses RANKL-modulated osteoclastogenesis and prevents bone erosion in mice with rheumatoid arthritis through the TLR4/p38 pathway.

Abnormal osteoclast formation plays a significant part in rheumatoid arthritis (RA). As potent therapeutic biomarkers, microRNAs (miRNAs) have obtained increasing attention. Recently, treatment regimens regarding miRNAs have been implicated in skeletal diseases. The aim of this study is to assess the expression and function of miR-20a during osteoclast proliferation and differentiation and its correlation with bone erosion in RA mice. The expression of miR-20a was observed to be diminished in the ankle tissues of RA mice relative to that in normal controls evaluated by RT-qPCR. Hematoxylin and eosin staining, Safranin O-fast green staining, and tartrateresistant acid phosphatase staining were used to evaluate the effects of miR-20a on RA symptoms. The proliferation and differentiation of osteoclasts, and bone erosion were repressed by agomiR-20a injection. 3'UTR luciferase reporter assays were conducted to validate the putative binding between miR-20a and receptor activation of nuclear factor-κB ligand (RANKL). The protein expression and phosphorylation level of toll-like receptor4 (TLR4)/p38 pathway-related factors were detected by Western blot. miR-20a inhibited proliferation and differentiation potentials to osteoclasts partly through the TLR4/p38 pathway. The current work provides evidence that miR-20a hinders proliferation and differentiation of osteoclasts by targeting RANKL through the TLR4/p38 pathway.