MiR-92a inhibits fibroblast-like synoviocyte proliferation and migration in rheumatoid arthritis by targeting AKT2.

Growing data have indicated that the miR-17-92 cluster is implicated in inflammatory response and rheumatoid arthritis (RA). This study was aimed to investigate the effects of miR-92a on the proliferation and migration of rheumatoid arthritis fibroblast-like synoviocytes (RA-FLSs). Our results showed that miR-92a was significantly down-regulated in RA synovial tissue and RA-FLSs, whereas the protein level of AKT2 is increased. Restoration of miR-92a suppressed the proliferation and migration of RA-FLSs. Down-regulation of miR-92a promotes proliferation and migration of normal human FLSs. Dual luciferase reporter gene assay showed that miR-92a could specifically bind with the 30UTR of AKT2 and significantly repressed the luciferase activity. Down-regulation or up-regulation of miR-92a significantly increased or decreased the protein and phosphorylation levels of AKT2. siRNA-mediated down-regulation of AKT2 significantly prevented cell proliferation and migration of RA-FLSs, which were similar to the effects induced by overexpression of miR-92a. Moreover, AKT2 overexpression rescued miR-92a-mediated suppressive effect on proliferation and migration of RA-FLS. Thus, miR-92a could inhibit the proliferation and migration of RA-FLSs through regulation of AKT2 expression.

TNF­α increases inflammatory factor expression in synovial fibroblasts through the toll­like receptor­3­mediated ERK/AKT signaling pathway in a mouse model of rheumatoid arthritis.

Osteoarthritis is a type of joint disease that may lead to other joint diseases. Previous research has demonstrated that tumor necrosis factor (TNF)­α is associated with osteoarthritis activity and pathology. The possible mechanisms of the TNF­α­mediated signaling pathway have not been clearly elaborated in synovial fibroblasts. The present study aimed to investigate the potential mechanisms of TNF­α in a mouse model of iodoacetate­induced osteoarthritis. Reverse transcription­quantitative polymerase chain reaction, ELISA, western blotting and immunohistochemistry were performed to evaluate the role of TNF­α in the progression of osteoarthritis. The results revealed that the serum levels of TNF­α, interleukin (IL)­1ß, IL­4 and IL­6 were significantly upregulated in a mouse model of iodoacetate­induced osteoarthritis compared with healthy mice (P<0.01). TNF­α, IL­1ß, IL­4 and IL­6 mRNA and protein levels were also significantly upregulated in synovial fibroblasts in the experimental mice (P<0.01). It was demonstrated that TNF­α increased pro­inflammation factors matrix metalloproteinase (MMP)­3, MMP­9, nuclear factor (NF)­κB and receptor activator of NF­κB ligand (RANKL) in synovial fibroblasts. It was also observed that the toll­like receptor (TLR)­3 was significantly upregulated and extracellular signal­regulated kinase (ERK) and protein kinase B (AKT) were significantly downregulated in synovial fibroblasts in osteoarthritis mice (P<0.01). An in vitro assay demonstrated that TNF­α inhibitor decreased mRNA and protein levels of IL­1ß, IL­4 and IL­6 in synovial fibroblasts. The knockdown of TLR­3 abolished the TNF­α upregulated mRNA and protein levels of IL­1ß, IL­4 and IL­6 in synovial fibroblasts. In addition, the knockdown of TLR­3 also reversed TNF­α­upregulated ERK and AKT expression in synovial fibroblasts. In vivo assays demonstrated that TNF­α inhibitor significantly decreased the deposition of IL­1ß, IL­4 and IL­6 as well as bone destruction and significantly increased the body weight and osteoarthritis score for osteoarthritic mice (P<0.01). TNF­α inhibitor decreased TLR­3 and significantly increased the expression and phosphorylation of ERK and AKT in articular cartilage (P<0.01). In conclusion the results of the present study indicate that TNF­α serves an essential role in synovial fibroblasts in osteoarthritis, suggesting that inhibition of TNF­α may decrease inflammation via the TLR­3­mediated ERK/AKT signaling pathway in a mouse model of monosodium iodoacetate­induced osteoarthritis.

Overexpressed miR-145 inhibits osteoclastogenesis in RANKL-induced bone marrow-derived macrophages and ovariectomized mice by regulation of Smad3.

BACKGROUND: MicroRNAs (miRs) play an important role in osteoclastogenesis. However, no study has investigated the underlying molecular mechanisms of miR-145 in this process. The purpose of the present study was to investigate the role of miR-145 and its post-transcriptional mechanism in the progression of osteoclast differentiation. METHODS: Macrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor-kB ligand (RANKL) were used to induce osteoclastogenesis originated from bone marrow-derived macrophages (BMMs). Female C57BL/6J mice were divided into sham, OVX, OVX + NC-agomir and OVX + miR-145-agomir groups. Tartrate-resistant acid phosphatase (TRAP) staining was performed to identify osteoclasts in-vitro and in-vivo. The mRNA and protein levels in osteoclast and tibia were assayed by qRT-PCR and western blotting, respectively. RESULTS: miR-145 expression was inhibited in RANKL-induced osteoclastogenesis, whereas overexpression of miR-145 attenuated it. We further found that Smad3 is a direct target gene of miR-145 by binding with its 3'-UTR. Overexpression of miR-145 significantly suppressed Smad3 mRNA and protein expression. In-vivo, miR-145 agomir treatment inhibited osteoclast activity in OVX mice by inhibiting Smad3 expression. CONCLUSION: We provide the evidence that over-expression of miR-145 could inhibit osteoclast differentiation, at least partially, by decreasing Smad3 expression.