Proliferation Of Synoviocytes In Rheumatoid Arthritis Research Articles

Up-regulation of miR-365 promotes the apoptosis and restrains proliferation of synoviocytes through downregulation of IGF1 and the inactivation of the PI3K/AKT/mTOR pathway in mice with rheumatoid arthritis

BackgroundThere is growing evidence of the ability of microRNAs (miRs) in rheumatoid arthritis (RA), thus our objective was to discuss the impact of miR-365 on the apoptosis and proliferation of synoviocytes in mice with RA by targeting IGF1 and mediating the PI3K/AKT/mTOR pathway. MethodsRA model mice was induced by type II collagen and freund’s adjuvant. The successfully modeled mice were injected with normal saline, miR-365 mimics, miR-365 inhibitors or their controls. TUNEL assay was adopted to detect apoptosis in synovial tissues, and expression of IL-1β and IL-6 in serum and synovial tissues was measured by ELISA and RT-qPCR. Mouse synoviocytes were isolated and cultured in vitro and identified by experiments. Cells were transfected with miR-365 mimics, IGF1 siRNA, or their controls to verify the role of miR-365 and IGF1 in cell vitality, proliferation and apoptosis of synoviocytes. ResultsUpregulation of miR-365 increased the number of TUNEL positive cells, depressed arthritis index, X-ray imaging score, and the expression of IL-1β and IL-6. High expression of miR-365 and low expression of IGF1 restrained the proliferation and facilitated apoptosis of synoviocytes. MiR-365 inhibited the expression of IGF1 and inhibited the activation of the PI3K/AKT/mTOR pathway. ConclusionOur study presents that up-regulation of miR-365 drives on apoptosis and restrains proliferation of synoviocytes in RA through downregulation of IGF1 and the inhibition of the PI3K/AKT/mTOR pathway. Thus, miR-365 may be a potential candidate for treatment of RA.

Inhibition of smoothened decreases proliferation of synoviocytes in rheumatoid arthritis.

Fibroblast-like synoviocytes (FLSs) contribute to synovial hyperplasia in rheumatoid arthritis (RA). Smoothened (Smo) is a key component of sonic hedgehog (Shh) signaling and contributes to tumor cell proliferation. The objective of this study was to investigate the role of Smo in RA synoviocyte proliferation. FLSs were isolated from RA synovium. Shh signaling was studied using a Smo antagonist (GDC-0449) and small interfering RNA (siRNA) targeting the Smo gene in FLSs. Cell proliferation was quantified by using kit-8 assay and cell cycle distribution and apoptosis were evaluated by flow cytometry. Cell cycle-related genes and proteins were detected by real-time PCR and western blot. FLSs treated with GDC-0449 or Smo-siRNA showed significantly decreased proliferation compared to controls (P < 0.05). Incubation with GDC-0449 or transfection with Smo-siRNA resulted in a significant increase of G1 phase cells compared to controls (P < 0.05). Cell cycle arrest was validated by the significant increase in cyclin D1 and E1 mRNA expression, decrease in cyclin-dependent kinase p21 mRNA expression in Smo-siRNA transfected cells (P < 0.05). Protein expression of cyclin D1 was also downregulated after Smo gene knockdown (P < 0.05). The results suggest that Shh signaling plays an important role in RA-FLSs proliferation in a Smo-dependent manner and may contribute to synovial hyperplasia. Targeting Shh signaling may help control joint damage in patients with RA.

High mobility group box 1 induces synoviocyte proliferation in rheumatoid arthritis by activating the signal transducer and activator transcription signal pathway

Recently, it was discovered that high mobility group box chromosomal protein 1 (HMGB1) acts as a potent pro-inflammatory cytokine that is released into the extracellular milieu. Signal transducer and activator of transcription (STAT) proteins play an important role in cytokine signaling. Some investigators have reported preferential activation of STAT1, and others have reported preferential activation of STAT3 in response to endogenous interleukin-6 (IL-6) in patients with rheumatoid arthritis. Here, we show that expression of the HMGB1 protein is increased in the articular tissues of collagen-induced arthritis (CIA) rats, especially in cytoplasm and extracellular, following synoviocyte proliferation and STAT1 activation. In vitro, recombined human HMGB1 induced RSC-364 cell proliferation, activated STAT1 phosphorylation, increased the expression of cyclin D1 and CDK4 protein, and decreased the expression of p21 protein. In summary, our study suggests that HMGB1 plays an important role of cytokine in the pathogenesis of RA, which possibly induces synovial cell proliferation by activating the STAT1 signal pathway.

Epigenetics and autoimmunity

Advances in genetics, such as sequencing of the human genome, have contributed to identification of susceptible genetic patterns in autoimmune diseases (AID). However, genetics is only one aspect of the diseases that does not reflect the influence of environment, sex or aging. Epigenetics, the control of gene packaging and expression independent of alterations in the DNA sequence, is providing new directions linking genetics and environmental factors. Recent findings have contributed to our understanding of how epigenetic modifications could influence AID development, showing differences between AID patients and healthy controls but also showing how one disease differs from another. With regards to epigenetic abnormalities, DNA methylation and histone modifications could be affected leading to large spatial and temporal changes in gene regulation. Other epigenetic processes, such as the influence of the ionic milieu around chromatin and DNA supercoiling stresses may be suspected also. The newly described role of microRNAs in control of gene expression is important by promoting or suppressing autoreactivity in AID. As a consequence control of cellular processes is affected becoming conducive, for example, to the development of autoreactive lymphocytes in systemic lupus erythematosus, synoviocyte proliferation in rheumatoid arthritis, or neural demyelination in multiple sclerosis. Application of epigenetics to AID is in its infancy and requires new hypotheses, techniques, tools, and collaborations between basic epigenetic researchers and autoimmune researchers in order to improve our comprehension of AID. From this will arise new therapeutics, means for early intervention, and perhaps prevention.

Taurine chloramine inhibits proliferation of rheumatoid arthritis synoviocytes by triggering a p53-dependent pathway

Taurine chloramine (Tau-Cl), originating from activated neutrophils, possesses antiinflammatory activities. Fibroblast-like synoviocytes (FLS) participate in the chronic synovitis and synovial membrane hyperplasia that are characteristic pathological features of rheumatoid arthritis (RA). The present study was conducted to investigate the mechanism of the Tau-Cl effect on the proliferation of these cells in culture. FLS were stimulated in vitro with platelet derived growth factor (PDGF) alone or together with Tau-Cl. Cell proliferation was evaluated by counting the total and dividing cell numbers and by measurement of (3)H-thymidine incorporation. Expression of the key cell-cycle regulators was evaluated at the protein (Western blotting) and/or mRNA (RT-PCR) levels. Treatment of RA FLS with Tau-Cl (200-500 microM) resulted in an early nuclear accumulation of p53 tumor suppressor protein. Moreover, Tau-Cl inhibited PDGF-triggered cell proliferation (IC(50) value approximately 250-300 microM), accompanied by characteristic modulation of p53 transcriptional targets: down-regulation of proliferating cell nuclear antigen (PCNA) and survivin, and concomitant up-regulation of p21 mitotic inhibitor. We propose that Tau-Cl inhibits proliferation of RA FLS by triggering a p53-dependent cell-cycle arrest and conclude that this compound suppresses pathways in FLS that are known to contribute to the pathology of RA.

Deflazacort modulates the fibrinolytic pattern and reduces uPA-dependent chemioinvasion and proliferation in rheumatoid arthritis synoviocytes

Extracellular fibrinolysis, controlled by the cell-associated fibrinolytic system (urokinase plasminogen activator, uPA; uPA receptor, uPAR; plasminogen activator inhibitor type-1, PAI-1), is involved in cartilage damage generation and in rheumatoid arthritis (RA) synovitis. Since steroids reduce the rate of radiological progression of RA, we planned to evaluate in healthy and RA synoviocytes the effects of the steroid deflazacort on uPA, uPAR and PAI-1 expression, and subsequent phenotypic modifications in terms of uPA/uPAR-dependent invasion and proliferation. uPA, uPAR and PAI-1 levels were studied by ELISA, RT-PCR (uPAR) and zymography (uPA) in synoviocytes from four RA patients and four healthy controls. Chemoinvasion was assessed by the Boyden chamber invasion assay, using Matrigel as the invasion substrate. Proliferation was evaluated by cell counting. Both invasion and proliferation were measured upon treatment with deflazacort 5 muM with or without parallel stimulation with uPA 500 ng/ml or in the presence of monoclonal anti-uPA and anti-uPAR antibodies. Invasion and proliferation of RA synoviocytes require a proper functional balance of the fibrinolytic system. Both deflazacort and monoclonal antibodies against uPA and uPAR reduced expression and activity of the system, thus inhibiting invasion and proliferation. In RA synoviocytes, deflazacort induced higher PAI-1 and lower uPA and uPAR levels, as well as a decrease in uPA enzymatic activity. The levels of uPAR mRNA were concomitantly reduced, as was uPA-induced chemoinvasion. All these effects were also shown in controls, though to a lesser extent. Deflazacort might control RA synovial proliferation and invasion by differential modulation of single members of the fibrinolytic system.

Developmental considerations of sperm protein 17 gene expression in rheumatoid arthritis synoviocytes.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by proliferative synovial tissue. We used mRNA differential display and library subtraction to compare mRNA expression in RA and osteoarthritis (OA) synoviocytes. We initially compared the mRNA expression patterns in 1 female RA and 1 OA synovia and found a differentially expressed 350 bp transcript in the RA synoviocytes which was, by sequence analysis, 100% homologous to sperm protein 17 (Sp17). Moreover, the Sp17 transcript was found differentially expressed in a RA synovial library that was subtracted with an OA synovial library. Using specific primers for full length Sp17, a 1.1 kb transcript was amplified from the synoviocytes of 7 additional female RA patients, sequenced and found to 100% homologous to Sp17. Thus, we found the unexpected expression of Sp17, a thought to be gamete-specific protein, in the synoviocytes of 8/8 female RA patients in contrast to control OA synoviocytes. Interestingly, Sp17's structural relationship with cell-binding and recognition proteins, suggests that Sp17 may function in cell-cell recognition and signaling in the RA synoviocyte. Further, Sp17 could have a significant regulatory role in RA synoviocyte gene transcription and/or signal transduction. Thus, Sp17 could have an important role in RA synoviocyte proliferation or defective apoptosis. Finally, the presence of Sp17 in synoviocytes has interesting developmental considerations.