Synovial Fibroblasts Of Patients Research Articles

Mechanism of Nrf2/miR338-3p/TRAP-1 pathway involved in hyperactivation of synovial fibroblasts in patients with osteoarthritis

Our previous study has confirmed that miR338-3p/TRAP-1 axis was involved in regulation of hyperactivation in human synovial fibroblasts (HFLS) of patients with osteoarthritis (OA). Here, we aim to further investigate the underlying causes of the abnormal activation miR338-3p/TRAP-1 at the molecular level. Our results showed that the decrease of NF-E2-related factor 2(Nrf2) was the direct cause of downregulation of miR338-3p and upregulation of TRAP-1 protein expression in HFLS of OA patients. Furthermore, we also found that the phosphorylation and nuclear entry of Nrf2 protein were significantly reduced in HFLS of OA patients than that of normal individuals, and both of them were positively correlated with miR338-3p levels. Bioinformatics analysis, luciferase assay, and CHIP experiment together indicated that Nrf2 could positively regulate the transcription of miR338-3p by binding to the Transcription Factor Binding Sites (TFBS) on its promoter. It was confirmed by in vitro assays that oltipraz (agonists of Nrf2) treatment effectively inhibited the hyperactivation of HFLS induced by TGF-β1, and the effects of oltipraz could be reversed by the exogenous TRAP-1. In short, our research has revealed for the first time that Nrf2/miR338-3p/TRAP-1 pathway was involved in hyperactivation of HFLS in OA patients, Nrf2 has the potential to be used as therapy and new drug target of OA.

MRNA vaccine against fibroblast activation protein ameliorates murine models of inflammatory arthritis.

Synovial fibroblasts in patients with rheumatoid arthritis (RA) contribute substantially to the perpetuation of synovitis and invasion to cartilage and bone, and are potential therapeutic targets. Fibroblast activation protein (FAP) is highly expressed by RA synovial fibroblasts and the expression is relatively specific. We tested whether FAP can serve as a molecular target to modulate synovial fibroblasts for therapy in experimental arthritis. mRNA encoding consensus FAP (cFAP) was encapsulated in lipid nanoparticles (LNP) and was injected intramuscularly as vaccine prior to induction of collagen-induced arthritis (CIA) and collagen antibody induced arthritis (CAIA) in mice. Development of CIA and CAIA was assessed clinically and by histology. cFAP mRNA-LNP vaccine provoked immune response to cFAP and mouse FAP (mFAP); prevented onset of CIA in 40% of mice and significantly reduced the severity of arthritis. In CAIA, cFAP mRNA-LNP did not prevent onset of arthritis but significantly reduced the severity of arthritis. cFAP mRNA-LNP vaccine was able to provoke immune response to mFAP and suppress inflammatory arthritis.

Differential inflammation-mediated function of prokineticin 2 in the synovial fibroblasts of patients with rheumatoid arthritis compared with osteoarthritis

Prokineticin 2 (PK2) is a secreted protein involved in several pathological and physiological processes, including the regulation of inflammation, sickness behaviors, and circadian rhythms. Recently, it was reported that PK2 is associated with the pathogenesis of collagen-induced arthritis in mice. However, the role of PK2 in the pathogenesis of rheumatoid arthritis (RA) or osteoarthritis (OA) remains unknown. In this study, we collected synovial tissue, plasma, synovial fluid, and synovial fibroblasts (SF) from RA and OA patients to analyze the function of PK2 using immunohistochemistry, enzyme-linked immunosorbent assays, and tissue superfusion studies. PK2 and its receptors prokineticin receptor (PKR) 1 and 2 were expressed in RA and OA synovial tissues. PKR1 expression was downregulated in RA synovial tissue compared with OA synovial tissue. The PK2 concentration was higher in RA synovial fluid than in OA synovial fluid but similar between RA and OA plasma. PK2 suppressed the production of IL-6 from TNFα-prestimulated OA-SF, and this effect was attenuated in TNFα-prestimulated RA-SF. This phenomenon was accompanied by the upregulation of PKR1 in OA-SF. This study provides a new model to explain some aspects underlying the chronicity of inflammation in RA.

Implication of HYBID (Hyaluronan-Binding Protein Involved in Hyaluronan Depolymerization) in Hyaluronan Degradation by Synovial Fibroblasts in Patients with Knee Osteoarthritis

Cell migration-inducing hyaluronidase 1 (CEMIP), also known as hyaluronan (HA)-binding protein involved in HA depolymerization (HYBID), plays a role in HA degradation. CEMIP2, also known as transmembrane protein 2 (TMEM2), possessing a sequence similarity with HYBID, is reported as a hyaluronidase in mice. However, the expression of these molecules in osteoarthritic synovium and their involvement in HA degradation in synovial fluid (SF) from patients with knee osteoarthritis remain elusive. This study examined their expression in synovial tissue and the relationship with molecular weight of HA in SF in knee osteoarthritis patients. Quantification of mRNA demonstrated that HYBID expression is significantly (5.5-fold) higher in osteoarthritic synovium than in normal control synovium, whereas TMEM2 expression level is similar between the two groups. By immunohistochemistry, HYBID was localized mainly to CD68-negative and fibroblast-specific protein 1-positive synovial lining cells and sublining fibroblasts in osteoarthritic synovium. The mRNA expression levels of HYBID, but not TMEM2, in osteoarthritic synovium positively correlated with distribution of lower-molecular-weight HA with below 1000 kDa in SF. HA-degrading activity in osteoarthritic synovial fibroblasts was abrogated by siRNA-mediated knockdown of HYBID. Among the 12 factors examined, IL-6 significantly up-regulated the HYBID expression and HA-degrading activity in osteoarthritic synovial fibroblasts. These data suggest that HYBID overexpressed by IL-6-stimulated synovial fibroblasts is implicated in HA degradation in osteoarthritic synovium.

MiR-155 promotes fibroblast-like synoviocyte proliferation and inflammatory cytokine secretion in rheumatoid arthritis by targeting FOXO3a.

The present study aimed to explore the expression and effects of microRNA (miR)-155 in synovial fibroblasts of patients with rheumatoid arthritis (RA). A total of 89 synovial tissues from RA patients and 49 control synovial tissues were collected, and the levels of miR-155 were measured by reverse transcription quantitative-PCR and western blotting. Fibroblast-like synoviocytes (FLS) were isolated from synovial tissues from the control group and were used to evaluate the roles of miR-155 and forkhead box protein O3a (FOXO3a). MTT assay was used to measure the proliferation of FLS. The expression of miR-155 in RA synovial tissues was significantly higher than that in the control group, but the expression of FOXO3a was significantly lower. In RA synovial tissues, miR-155 expression was negatively correlated with FOXO3a expression, but was positively correlated with the release of inflammatory cytokines interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α). A dual-luciferase reporter system showed that miR-155 inhibited the expression of FOXO3a in FLS cells. miR-155 also promoted secretion of the inflammatory cytokines IL-1β, IL-6 and TNF-α by FLS and proliferation of these cells by targeting FOXO3a.

Cilostazol add-on therapy for celecoxib synergistically inhibits proinflammatory cytokines by activating IL-10 and SOCS3 in the synovial fibroblasts of patients with rheumatoid arthritis.

Cilostazol (an inhibitor of phosphodiesterase type III) has potent anti-inflammatory effects, and celecoxib (a COX-2 specific inhibitor) has been reported to improve the unsatisfactory profile of NSAIDs. This study investigated the synergistic anti-arthritic potential of a multitarget-based cotreatment, in which cilostazol was used as an add-on therapy for celecoxib, using the synovial fibroblasts of RA patients (RASFs). Increased COX-2 protein expression and PGE2 synthesis by LPS (1μg/ml) were significantly and synergistically attenuated by cotreatment with 3μM cilostazol and 30μM celecoxib, whereas monotherapy with either cilostazol or celecoxib showed little effects. IL-10 mRNA levels in LPS-treated RASFs were moderately increased by pretreating cilostazol (1-10μM) or celecoxib (10-50μM) monotherapy, but 3μM of cilostazol add-on for 30μM celecoxib treatment synergistically increased IL-10 mRNA levels and IL-10 release to culture media. Cilostazol and celecoxib cotreatment similarly showed synergistic increase in SOCS3 mRNA levels. Accordingly, LPS-induced increases in IL-1β and IL-6 mRNA and TNF-α release were significantly and synergistically diminished by cilostazol and celecoxib cotreatment. Moreover, synovial cell proliferation was significantly suppressed by cotreatment. Summarizing, cotreatment with cilostazol and celecoxib exhibited a synergistic increase in IL-10 production and SOCS3 expressions, thereby resulted in synergistic decreases in IL-1β mRNA, IL-6 mRNA expression and TNF-α synthesis in association with synergistic decreases in COX-2 and PGE2 protein expression in the RA synovial fibroblasts. In conclusion, these observations suggest low concentrations of cilostazol and celecoxib cotreatment may ensure a synergistic anti-arthritic potential.

Estrogen-Mediated MicroRNA-101-3p Expression Represses Hyaluronan Synthase 2 in Synovial Fibroblasts From Idiopathic Condylar Resorption Patients

Idiopathic condylar resorption (ICR) is an aggressive form of osteoarthritis that is frequently observed in adolescent female patients. We hypothesized that an estrogen-mediated pathway may contribute to ICR development. An enzyme-linked immunosorbent assay was used to detect the levels of estradiol (E2) and hyaluronan in synovial fluid. Immunohistochemistry, real-time polymerase chain reaction, and Western blotting were used to detect the expression of microRNAs (miRNAs) and related genes after transfection of miRNA-101-3p mimics, inhibitor, or short interfering RNA into synovial fibroblasts.Dual-luciferase activity was determined to identify the direct effect of miRNA-101-3p on hyaluronan synthase 2 (HAS2). Linear regression analysis, the nonparametric Mann-Whitney U test, the Student t test, and 1-way analysis of variance were carried out to analyze the results of each group. The relationship between hyaluronan and E2 was negatively correlated in synovial fluid (Pearson r=-0.3179, P=.0230). Among the screened miRNAs, miRNA-101-3p was the most overexpressed in ICR. E2 mostly upregulated the expression of miRNA-101-3p at a dose of 10nmol/L 12hours after transfection in synovial fibroblasts of patients with ICR. However, E2 induction of miRNA-101-3p expression was significantly repressed by estrogen receptor α interference (P = 0.0286).The dual-luciferase assay showed that miRNA-101-3p regulated the expression of HAS2 by directly targeting its 3' untranslated region. We speculate that E2 regulates HAS2 expression by targeting miRNA-101-3p in synovial fibroblasts of patients with ICR. Thus, the E2-miRNA-101-3p-HAS2 pathway might play an important role in the pathogenesis of ICR.

Estradiol and proinflammatory cytokines stimulate ISG20 expression in synovial fibroblasts of patients with osteoarthritis.

Interferon stimulated gene 20-kDa (ISG20) has been implicated in the pathology of osteoarthritis (OA) and it has been separately found to be responsive to estrogen stimulation. OA disproportionately affects women, and especially older women, suggesting some role of reproductive hormones in its pathology. The current study characterized the expression of ISG20 following stimulation with estradiol (E2) and proinflammatory cytokines in OA synovial fibroblasts (OASFs). E2 and the proinflammatory cytokines interleukin-6 (IL-6), lipopolysaccharide (LPS), and tumor necrosis factor α (TNF-α) were used to stimulate OASFs in vitro. The expression of ISG20 before and after stimulation was detected using quantitative real-time polymerase chain reaction (RT-qPCR) and Western blotting. E2 and proinflammatory cytokine (IL-6, LPS and TNF-α) stimulation significantly induced the expression of ISG20 both at the messenger RNA (mRNA) and protein level. Moreover, the induction was time- and dose-dependent. Small interfering RNA (siRNA) was transfected into OASFs, and expression of the inflammatory factors interleukin-1α (IL-1α), IL-6, and interleukin-10 (IL-10) was detected using RT-qPCR. Silencing ISG20 with siRNA inhibited the expression of IL-1α, IL-6, and IL-10. Thus, expression of ISG20 was regulated by estradiol and proinflammatory factors, while ISG20 in turn regulated the expression of other inflammatory factors. These data support the contention that ISG20 plays a role in the inflammatory process of OA.

Platelet-rich plasma promotes the migration and invasion of synovial fibroblasts in patients with rheumatoid arthritis

Platelet-rich plasma (PRP) is blood plasma that has been enriched with platelets, and the number of platelets is correlated with rheumatoid activity. PRP is a concentrated source of autologous platelets, and contains several different growth factors and cytokines, including platelet‑derived growth factor, transforming growth factor‑β and insulin‑like growth factor‑1, which stimulate healing of bone and soft tissue. Rheumatoid arthritis (RA) is characterized by synovial hyperplasia, cell activation, articular inflammation and invasion of the synovium into the adjacent bone and cartilage. The adhesion of fibroblast‑like synoviocytes (FLSs) onto the extracellular matrix (ECM), migration and invasion are important for the erosion and destruction of the articular cartilage of patients with RA. The aim of the present study was to investigate the effects of PRP on the adhesion, migration and invasion of RA‑FLSs. Scratch and Transwell migration assays determined that PRP at a concentration of 2 and 5% significantly enhanced the migration ability of RA‑FLSs. Treatment of RA‑FLSs with 2and 5% PRP promoted the adhesion and invasion of the cells. Additionally, the immunofluorescence assay revealed that PRP induced a decrease in the number of centrally located stress fibers and led to an increase in the formation of filopodia and lamellipodia in the detectable leading edge protrusions in RA‑FLSs. In addition, reverse transcription‑quantitative polymerase chain reaction and western blot analysis determined that PRP upregulated the protein and mRNA expression levels of matrix metalloproteinase‑1 (MMP‑1). In conclusion, the promotion of RA‑FLS cell migration, invasion and adhesion on the ECM by PRP may be modulated through the upregulation of MMP‑1 expression and the induction of actin cytoskeletal reorganization.

DKK1 expression by synovial fibroblasts in very early rheumatoid arthritis associates with lymphocyte adhesion in an in vitro flow co-culture system.

BackgroundSynovial fibroblasts play a key role in joint destruction and regulation of the inflammatory infiltrate in established rheumatoid arthritis (RA). The mechanisms by which this occurs in the earliest stages of RA are largely unknown. We investigated the role of Dickkopf-related protein 1 (DKK1) produced by synovial fibroblasts of patients with very early rheumatoid arthritis (VeRA).MethodsFibroblasts were isolated from the disease-modifying anti-rheumatic drug–naive Birmingham early arthritis cohort of patients with new onset of clinically apparent arthritis and inflammatory symptoms of ≤12 weeks’ duration, who at follow-up had either resolving arthritis or RA. Endothelial fibroblast co-cultures were formed using porous filters, and lymphocyte adhesion to co-cultures was assessed using phase-contrast microscopy. DKK1 gene expression and secretion were quantified by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.ResultsSynovial fibroblasts from patients with VeRA expressed significantly higher levels of DKK1 messenger RNA than those from patients with resolving arthritis. A similar trend was observed for DKK1 protein secretion. In co-culture constructs, more DKK1 tended to be secreted in co-cultures incorporating fibroblasts from VeRA than in co-cultures from non-inflamed joints and resolving arthritis. DKK1 secretion during co-culture positively correlated with lymphocyte adhesion.ConclusionsAlterations in DKK1 could be involved in the pathogenesis and perpetuation of the inflammatory response in the earliest clinically apparent stages of RA.

Dickkopf‑related protein 1 induces angiogenesis by upregulating vascular endothelial growth factor in the synovial fibroblasts of patients with temporomandibular joint disorders.

Angiogenesis has an important role in the progression of temporomandibular joint disorders (TMD). The aim of the present study was to explore the association between dickkopf-related protein 1 (DKK-1) and angiogenesis in TMD. The expression levels of DKK-1 and vascular endothelial growth factor (VEGF) were quantified by an ELISA assay of the synovial fluid from patients with TMD. The correlation between DKK-1 and VEGF was analyzed by Pearson correlation test. Synovial fibroblasts were isolated from patients with TMD and were subsequently treated with recombinant human DKK-1, anti-DKK-1 antibody, hypoxia inducible factor-1α (HIF-1α), or small interfering RNA (siRNA). The expression levels of DKK-1, HIF-1α, and VEGF were subsequently quantified. The present study also investigated the effects of DKK-1 on the migration of human umbilical vein endothelial cells (HUVEC). Increased expression levels of DKK-1 were concordant with increased expression levels of VEGF in the synovial fluid from patients with TMD. In the synovial fibroblasts, DKK-1 increased the expression levels of VEGF, and promoted HIF-1α nuclear localization. In addition, DKK-1 induced HUVEC migration, and HIF-1α siRNA inhibited DKK-1-induced cell migration. The results of the present study indicate that DKK-1 is associated with angiogenesis in the synovial fluid of patients with TMD. Furthermore, HIF-1α may be associated with DKK-1-induced HUVEC activation.

FRI0355 Microarray Analysis of Early and Late RA Human Synovial Fibroblasts Reveals A Unique Gene Expression Pattern in Early Disease

BackgroundHuman synovial fibroblasts are implicated in rheumatoid arthritis (RA) pathogenesis at two levels: they promote cartilage and bone destruction and contribute to persistent joint inflammation. Significant damage to RA joints...

THU0097 Neurogenic Inflammation in Rheumatoid Arthritis : Possible Role of Neuropeptides on Synovial Vanilloid Receptors

BackgroundNeurogenic inflammation is caused by neuropeptides, like substance P (SP) and calcitonin gene related peptide (CGRP), which are released by peripheral neurons and induce inflammatory signals. SP and CGRP act...

SP0161 SCID MICE: Models for arthritis and systemic diseases

Regardless of the type of chronic inflammatory immune-system driven disease, the majority of animal models are more or less distant to the respective disease entity in humans and frequently too...

The role of nucleotide-binding oligomerization domain 2 (Nod2) in initiation of rheumatoid arthritis. (68.7)

Abstract The etiology of several inflammatory diseases such as rheumatoid arthritis (RA) remains unknown. Some studies including data from our group, report that the receptor NOD2, a member of NLR family, is overexpressed in synovial fibroblasts of patients with RA. Since NOD2 activation might contribute to the initiation and perpetuation of chronic destructive inflammation in RA, we decided to investigate the role of this receptor in arthritis. Initially, WT and NOD2-/- mice were immunized with mBSA, and arthritis was induced by an i.a. injection of mBSA. Our data shows that knockout NOD2 mice did not develop arthritis, as evidenced by the low number of infiltrating cells into the articular cavity, and that transfer of wild type neutrophils into NOD2-/- mice did not restored the inflammatory status. Additionally, to assess if synovial fluid of RA patients could activate NOD2 in vitro, HEK293-Luciferase-NF-κB cells were transfected with a plasmid encoding the NOD2 receptor, 24 hours later these cells were stimulated with MDP or synovial fluid in different concentrations, osteoarthritis synovial fluid were used as control. Luciferase activity was measured 8 hours after stimulation. We observed that stimulation of NOD2 transfected cells with synovial fluid from RA patients leads to increased luciferase activity, suggesting the NF-κB activation dependent of NOD2 signaling in HEK293 cells. Together, these results suggest that NOD2 receptor has an important role in the pathogenesis of RA.

Cartilage Destruction in Granulomatosis with Polyangiitis (Wegener's Granulomatosis) Is Mediated by Human Fibroblasts after Transplantation into Immunodeficient Mice

A key feature of granulomatosis with polyangiitis (GPA; or Wegener's granulomatosis) is the granulomatous inflammation of the upper respiratory tract, which leads to the subsequent destruction of adjacent tissues. The aim of our work was to study the histopathological and cellular components of tissue destruction of human GPA tissue transplanted into immunodeficient mice. Biopsy specimens from patients with active GPA (n = 10) or sinusitis (controls, n = 6) were s.c. co-implanted with healthy allogeneic human nasal cartilage into immunodeficient pfp/rag2(-/-) mice. Transplants were examined for their destructive capability of the allografted human cartilage. In addition, nasal fibroblasts from patients with GPA (n = 8) and control healthy nasal fibroblasts (n = 5) were cultured, and cell proliferation and apoptosis were quantified. mRNA and protein levels of matrix metalloproteinases and cytokines were evaluated at baseline and after proinflammatory stimulation. GPA implants showed massive destruction of the co-implanted human cartilage, whereas cartilage destruction was only marginal in control samples. Destruction was mediated by human fibroblasts and could be inhibited by corticoid treatment. The up-regulated production of matrix metalloproteinases 1, 3, and 13 and cytokines IL-6 and IL-8 was found in vivo and in vitro. Although proliferation of isolated fibroblasts was comparable between GPA and controls, GPA samples showed a significant delay of apoptosis. The destruction of nasal cartilage in GPA is mainly mediated by fibroblasts that can be blocked by corticosteroids, and this tissue destruction is not dependent on the influx of leukocytes.

Chemerin induces CCL2 and TLR4 in synovial fibroblasts of patients with rheumatoid arthritis and osteoarthritis

IntroductionChemerin stimulates migration of leukocytes to sites of inflammation and also increases inflammatory signaling in chondrocytes suggesting a function of chemerin in joint inflammation. Synovial fibroblasts (SF) are critically involved in synovitis and subsequent cartilage destruction. Here, we analyzed whether synovial fibroblasts express chemerin and its receptor CMKLR1. Further, the role of chemerin in synovial fibroblast chemotaxis, proliferation, insulin response and release of inflammatory proteins was studied. MethodsSynovial tissue sections were labeled with chemerin antibody and chemerin was measured in synovial fluid by ELISA. Chemerin mRNA and protein as well as CMKLR1 expression were determined in SFs from patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Effects of chemerin on cytokines, chemokines and matrix metalloproteinases (MMP), and on proliferation, migration and insulin signaling were analyzed appropriately. ResultsSFs expressed CMKLR1 and chemerin mRNA, and chemerin protein was found in cell supernatants of synovial fibroblasts. Immunohistochemistry detected chemerin in synovial tissue predominantly localized within the lining layer. Chemerin was present in synovial fluids of RA, OA and psoriatic arthritis patients in similar concentrations. Chemerin neither increased IL-6 levels nor MMP-2 or −9 activity in SFs. Also, it did not act as a chemoattractant for these cells. With respect to intracellular signaling, neither basal nor insulin-mediated phosphorylation of Akt was affected. However, chemerin significantly increased TLR4 mRNA and synthesis of CCL2 in SFs while CCL4 and −5 were not altered. Cell proliferation of SFs, however, was modestly reduced by chemerin. ConclusionsThese data show that human SFs express both chemerin and its receptor. As chemerin enhanced expression of TLR4 and induced release of CCL2 in SFs, a role of this protein in innate immune system-associated joint inflammation is proposed.

Mechanisms and clinical relevance of TRAIL-triggered responses in the synovial fibroblasts of patients with rheumatoid arthritis

Results of studies in mice suggest a protective role for TRAIL in arthritis. The aim of this study was to investigate the role of TRAIL in patients with rheumatoid arthritis (RA). In the present study, we compared RA fibroblast-like synoviocytes (FLS) that were resistant or sensitive to TRAIL-induced apoptosis and the expression of TRAIL receptors in these cells, and also investigated the clinical features of the patients from whom the FLS were derived. Furthermore, we evaluated the levels of TRAIL and its soluble decoy receptor osteoprotegerin (OPG) in patients with RA, patients with osteoarthritis (OA), and patients with spondylarthritis (SpA). Sensitivity to TRAIL-induced apoptosis varied in FLS from different patients, and the severity of disease in patients with RA was inversely correlated with the susceptibility of their FLS to TRAIL-induced apoptosis. TRAIL-sensitive cells expressed significantly lower levels of TRAILR-1, and silencing of TRAILR-1 increased TRAIL-induced apoptosis in RA FLS. TRAIL levels were elevated in the arthritic joints of patients with established RA, and TRAIL levels in the synovial fluid of these patients were elevated compared with levels in the synovial fluid of patients with OA or SpA. At baseline, a low OPG-to-TRAIL ratio in the sera of patients with early RA was associated with a better evolution of disease activity, but high serum levels of TRAIL at followup were associated with joint damage. These findings suggest that TRAIL has a dual role in RA, and that the resistance of RA FLS to TRAIL-induced apoptosis is associated with a disease-promoting activity of TRAIL in RA.

Pectenotoxin-2 induces G1 arrest of the cell cycle in synovial fibroblasts of patients with rheumatoid arthritis

Rheumatoid arthritis (RA), a chronic inflammatory disease, is characterized by hyperplasia of the synovial fibroblasts, due in part to increased cell growth. This study investigated the mechanisms underlying the anti-proliferative action of pectenotoxin-2 (PTX-2), isolated from marine sponges, in synovial fibroblasts obtained from RA patients. PTX-2 concentration-dependently inhibited the growth of synovial fibroblasts, arresting them in the G1 phase of their cell cycle. The G1 arrest was correlated with down-regulation of cyclin D1 and cyclin-dependent kinase (Cdk) 6, with a concomitant up-regulation of the tumor suppressor, p53, and the Cdk inhibitor, p21 (WAF1/CIP1). Following PTX-2 treatment of synovial fibroblasts, an increased binding of p21 with Cdk2 and Cdk6 was paralleled by a significant decrease in retinoblastoma protein (pRB) phosphorylation and in the protein levels of E2F transcription factors. Thus, PTX-2 might help identify new therapeutic agents against RA-mediated hyperplasia of synovial fibroblasts.

IL-15 Induced an Increased SDF-1 Expression in the Synovial Fibroblasts of Patients with Rheumatoid Arthritis

IL-15 Induced an Increased SDF-1 Expression in the Synovial Fibroblasts of Patients with Rheumatoid Arthritis