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The present study aimed at characterizing the phenotype and functions of adherent synovial fluid (SF) cells derived from rheumatoid arthritis (RA), comparing with fibroblast-like synoviocytes (FLS) derived from RA synovial tissue (ST). Adherent SF-derived cells were spindle-shaped from passages 1-6 under light microscopy. The cell surface marker profile in SF-derived cells from passage 1-6 was similar to that of ST-derived FLS. Levels of MMP-1 and MMP-3 were not significantly different between SF-derived cells and ST-derived FLS (p = 0.20 and p = 0.40, respectively). There was no significant difference in the optical density value between two cell types in the cell invasion assay (p = 0.10). SF-derived adherent cells have a fibroblast-like phenotype from very early culture passages and have the potential to produce MMPs with the invasive capacity to degrade cartilage, identical to ST-derived FLS. Therefore, these cells could substitute for ST-derived FLS in studying the pathogenesis of RA.

Abstract: Objectives: To investigate the effects of benzo[a]pyrene (B[a]P), a major toxic component of cigarette smoke, on the expression of Slug and to determine the effect of B[a]P/Slug on the invasive properties of rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS). Method: The expression of Slug was measured by real-time PCR following the stimulation of FLS with different concentrations of B[a]P or EGF. The phosphorylation of the key enzymes in the signaling pathway was analyzed by western blots. Inhibitors of PI3K/Akt/mTOR pathway were used to confirm the critical pathway for Slug expression. An in vitro cell invasion assay was performed using RA FLS treated with Slug cDNA, Slug small interference RNA, or control. Results: Slug expression increased significantly following treatment with B[a]P or EGF in a dose-dependent manner. The stimulation of FLS with B[a]P or EGF induced the phosphorylation of Akt kinase, but not in ERK, JNK and p38. The Slug mRNA expression induced by B[a]P and EGF decreased significantly following the treatment with PI3K/Akt/mTOR inhibitors. Slug overexpression using Slug cDNA upregulated the invasive function of FLS, and Slug depletion using siRNA showed the opposite effect compared with the control. In addition, the stimulation with B[a]P increased the invasive function of the control siRNA-treated FLS but not in the Slug siRNA-treated FLS. Conclusion: Our data showed that B[a]P regulates the invasive properties of RA FLS through Slug expression. This mechanism may provide a novel molecular link underlying the association between smoking and increased radiographic progression in RA. [Copyright &y& Elsevier]

The aim of this study is to investigate the effects of CIP2A (Cancerous inhibitor of protein phosphatase 2A) on the apoptosis of RA FLS. Proliferation and apoptotic activity of RA FLS following treatment with CIP2A siRNA or control siRNA were analyzed using MTT assays and Cell Death Detection kit. RA FLS was treated with CIP2A siRNA or control siRNA in 3-, 6-, and 9-day intervals for a Western blot analysis to determine C-Myc expression. To evaluate the signal transduction pathways engaged in apoptosis, caspase-3 activity, caspase-9 activity, PARP, and phosphorylation of the Akt kinase were analyzed by Western blot. Cell viability of RA FLS was significantly lower in the CIP2A siRNA-treated group compared with the control after 7 days ( p = 0.022). Apoptosis of RA FLS was significantly higher in the CIP2A siRNA-treated group compared with the control when incubated for 3, 6, and 9 days ( p = 0.029, p = 0.021, p = 0.043, respectively). C-Myc expression did not change with the different incubation periods. CIP2A siRNA-treated FLS expressed higher level of activated caspase-3, caspase-9, and PARP ( p = 0.014, p = 0.020, p = 0.021, respectively) and lower level of phosphorylated Akt ( p = 0.001) compared with those treated with the control siRNA. Our data show that CIP2A expression in RA FLS is an important mediator of dysfunctional apoptosis independent of c-Myc stabilization. Expression of CIP2A may contribute to apoptotic resistance of RA FLS through the activation of Akt and deactivation of caspase-3, caspase-9, and PARP. Inhibition of CIP2A may therefore constitute a novel, promising therapeutic target in RA. [ABSTRACT FROM AUTHOR]

Fibroblast-like synoviocytes (FLS) play an important role in the pathogenesis of rheumatoid arthritis. Raf kinase inhibitor protein (RKIP) negatively regulates the Raf/MEK/ERK and NF-κB pathway. The role of RKIP in rheumatoid FLS is unknown. The purpose of the present study was to investigate the function of RKIP in rheumatoid FLS. Rheumatoid FLS were transfected with either RKIP-expressing plasmids or RKIP small interfering RNA (siRNA). RKIP protein was detected in rheumatoid synovial tissue (ST) and FLS. RKIP overexpression significantly decreased IL-6 mRNA expression in TNF-α-stimulated rheumatoid FLS. RKIP overexpression also showed a decreased trend in IL-8, MMP-1, and MMP-3 mRNA expression in TNF-α-stimulated rheumatoid FLS. RKIP silencing resulted in significantly increased MMP-1 and MMP-3 mRNA expression in TNF-α-stimulated rheumatoid FLS. RKIP silencing also increased IL-6 and IL-8 mRNA expression in TNF-α-stimulated rheumatoid FLS, but this increase did not reach statistical significance. TNF-α-induced ERK and NF-κB activation was suppressed in FLS with RKIP overexpression. RKIP silencing resulted in a significantly higher invasion index in TNF-α-stimulated rheumatoid FLS compared to controls. These results suggest that RKIP might be a potential therapeutic target for rheumatoid arthritis. [ABSTRACT FROM AUTHOR]