Inhibition of DNM1L and mitochondrial fission attenuates inflammatory response in fibroblast-like synoviocytes of rheumatoid arthritis.

Mitochondrial fission and fusion are important for mitochondrial function, and dynamin 1-like protein (DNM1L) is a key regulator of mitochondrial fission. We investigated the effect of mitochondrial fission on mitochondrial function and inflammation in fibroblast-like synoviocytes (FLSs) during rheumatoid arthritis (RA). DNM1L expression was determined in synovial tissues (STs) from RA and non-RA patients. FLSs were isolated from STs and treated with a DNM1L inhibitor (mdivi-1, mitochondrial division inhibitor 1) or transfected with DNM1L-specific siRNA. Mitochondrial morphology, DNM1L expression, cell viability, mitochondrial membrane potential, reactive oxygen species (ROS), apoptosis, inflammatory cytokine expression and autophagy were examined. The impact of mdivi-1 treatment on development and severity of collagen-induced arthritis (CIA) was determined in mice. Up-regulated DNM1L expression was associated with reduced mitochondrial length in STs from patients with RA and increased RA severity. Inhibition of DNM1L in FLSs triggered mitochondrial depolarization, mitochondrial elongation, decreased cell viability, production of ROS, IL-8 and COX-2, and increased apoptosis. DNM1L deficiency inhibited IL-1ß-mediated AKT/IKK activation, NF-κBp65 nuclear translocation and LC3B-related autophagy, but enhanced NFKBIA expression. Treatment of CIA mice with mdivi-1 decreased disease severity by modulating inflammatory cytokine and ROS production. Our major results are that up-regulated DNM1L and mitochondrial fission promoted survival, LC3B-related autophagy and ROS production in FLSs, factors that lead to inflammation by regulating AKT/IKK/NFKBIA/NF-κB signalling. Thus, inhibition of DNM1L may be a new strategy for treatment of RA.

Silencing lncRNA HOTAIR declines synovial inflammation and synoviocyte proliferation and promotes synoviocyte apoptosis in osteoarthritis rats by inhibiting Wnt/ß-catenin signaling pathway.

Osteoarthritis (OA) is a degenerative injury of the articular cartilage and reactive hyperplasia of the articular rim and subchondral bone. Due to its poor prognosis, this study is to research the influences of lncRNA HOTAIR on synovial inflammation and synoviocyte apoptosis and proliferation in OA rats by regulating the Wnt/ß-catenin pathway. Rat OA model was constructed by means of cruciate ligament resection, and the successfully modeled rats were injected with sh-HOTAIR, or Wnt/ß-catenin pathway activator (LiCl), and synoviocytes were transfected with sh-HOTAIR or LiCl for investigation of the influences of HOTAIR and Wnt/ß-catenin pathway on synoviocytes proliferation and apoptosis. ELISA and RT-qPCR were used to detect the levels of IL-1ß, IL-6 and TNF-α in serum, synovial tissue and synoviocytes in rats, respectively. The protein levels of bax, bcl-2, wnt1 and ß-catenin in synovial tissue and synoviocytes were tested by Western blot analysis. Highly expressed HOTAIR existed in synovial tissue and synoviocytes of rats. There were declining arthritis index, inflammation, synoviocytes proliferation, cycle progression and promoted synoviocytes apoptosis by silencing HOTAIR and inhibited Wnt/ß-catenin pathway. Down-regulation of HOTAIR could reverse the effect of LiCl on progression of OA rats. There was strained activation of Wnt/ß-catenin pathway via declining HOTAIR. This study suggests that silencing lncRNA HOTAIR and inhibited Wnt/ß-catenin pathway decline synovial inflammation and synoviocyte proliferation and promote apoptosis in OA rats.

Proliferation of rheumatoid arthritis fibroblast-like synoviocytes is enhanced by IL-17-mediated autophagy through STAT3 activation.

Fibroblast-like synoviocytes (FLSs), with their tumor-like proliferation, play an important role in rheumatoid arthritis (RA), and interleukin-17 (IL-17) participates in RA pathology by affecting FLSs. The aims of this study were to investigate the effects of IL-17 on the proliferation and autophagy of FLSs and the role of signal transducer and activator of transcription-3 (STAT3) in RA. FLSs were treated with IL-17 at different concentrations (0, 1, 10, and 20 ng/mL); then, autophagy was assayed with western blotting, immunofluorescence, and transmission electron microscopy. The effects of IL-17 on FLSs proliferation were measured with the Cell Counting Kit-8 assay and flow cytometry to analyze cell cycle distribution, and proliferating cell nuclear antigen (PCNA) was detected by western blotting. The autophagy inhibitors, 3-methyladenine (3-MA) and chloroquine (CQ), were used to determine the effect of autophagy on proliferation in IL-17-treated FLSs. Finally, the STAT3 inhibitor STA21 was used to examine the relationship between STAT3 and autophagy in IL-17-treated FLSs. Our results showed that IL-17 positively affected autophagy and proliferation in FLSs. Inhibition of autophagy suppressed the IL-17-mediated proliferation of FLSs. Additionally, suppression of STAT3 activation decreased autophagy in IL-17-treated FLSs. Our findings showed that IL-17 promoted the tumor-like proliferation of FLSs by upregulating autophagy via STAT3 activation.

Morphological evidence of telocytes in human synovium.

A new cell type named telocyte (i.e. cell with distinctive prolongations called telopodes) has recently been identified in the stroma of various organs in humans. However, no study has yet reported the existence of telocytes in the synovial membrane of diarthrodial joints. This work was therefore undertaken to search for telocytes in the normal human synovium using transmission electron microscopy, immunohistochemistry and immunofluorescence. Ultrastructural analyses demonstrated the presence of numerous spindle-shaped telocytes in the whole synovial sublining layer. Synovial telocytes exhibited very long and thin moniliform telopodes and were particularly concentrated at the boundary between the lining and sublining layers and around blood vessels. Light microscopy confirmed the presence of CD34-positive telocytes in the aforementioned locations. Moreover, synovial telocytes coexpressed CD34 and platelet-derived growth factor receptor α. Double immunostaining further allowed to unequivocally differentiate synovial telocytes (CD34-positive/CD31-negative) from vascular endothelial cells (CD34-positive/CD31-positive). The in vitro examination of fibroblast-like synoviocyte primary cultures revealed the coexistence of different cell types, including CD34-positive telocytes projecting typical moniliform telopodes. In conclusion, our work provides the first evidence that telocytes do exist in the human synovium and lays the groundwork for future studies on synovial telocytes in a variety of degenerative and destructive joint diseases.

Flexor Tendon Sheath Engineering Using Decellularized Porcine Pericardium.

BACKGROUND: The flexor tendon sheath is an ideal target for tissue engineering because it is difficult to reconstruct by conventional surgical methods. The authors hypothesized that decellularized porcine pericardium can be used as a scaffold for engineering a biologically active tendon sheath. METHODS: The authors' protocol removed cellular material from the pericardium and preserved the structural architecture in addition to the collagen and glycosaminoglycan content. The scaffold was successfully reseeded with human sheath synoviocytes and human adipose-derived stem cells. Cells were evaluated for 8 weeks after reseeding. RESULTS: The reseeded construct demonstrated continuous production of hyaluronic acid, the main component of synovial fluid. After being seeded on the membrane, adipose-derived stem cells demonstrated down-regulation of collagen I and III and up-regulation of hyaluronan synthase 2. CONCLUSION: The results indicate that decellularized porcine pericardium may be a potential scaffold for engineering a biologically active human tendon sheath.