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Objective CXCL12γ is an alternative splicing isoform of CXCL12 with enhanced affinity for heparan sulfate (HS) proteoglycans. This study was undertaken to investigate the distribution and potential function of CXCL12γ in rheumatoid arthritis (RA) synovium and normal lymphoid tissue, where its immobilization to HS may be relevant in pathologic or homeostatic immune cell migration and activation. Methods Expression of CXCL12 or CXCL12γ was immunodetected in RA and normal synovium, lymphoid tissue, and cultured cells with anti–pan-CXCL12 or anti-CXCL12γ–specific monoclonal antibodies. CXCL12α and CXCL12γ messenger RNA expression was analyzed by quantitative reverse transcription–polymerase chain reaction. Binding of wild-type CXCL12 isoforms or their HS binding–defective mutants to monocyte-derived dendritic cells (DCs) was analyzed by flow cytometry. The effect of DC-bound CXCL12α and CXCL12γ on T cell activation was analyzed in DC/T cell allogeneic cultures. Results CXCL12γ expression was increased in RA compared to normal synovium and preferentially located in endothelia and DC-SIGN–positive cells. This distribution was also observed in lymphoid organs. Surface-bound CXCL12γ was detected in a fraction of freshly isolated DCs. Monocyte-derived DCs, but not monocytes, showed a high capacity to bind CXCL12γ in an HS-dependent manner. Surface-bound CXCL12α and CXCL12γ on monocyte-derived DCs were potent inhibitors of allogeneic T cell activation, in contrast to the T cell–stimulatory effects of soluble CXCL12 proteins. Conclusion CXCL12γ shows a specific and similar distribution in RA synovium and lymphoid tissue, consistent with its higher HS binding affinity. Presentation of CXCL12 to T cells on membrane HS in DCs can play a distinct regulatory role in T cell activation.

Objective Hypoxia is a prominent feature in rheumatoid arthritis (RA) synovium. However, its contribution to the pathogenesis of RA remains unclear. We undertook this study to systematically characterize the changes in gene expression induced by hypoxia in synovial fibroblasts. Methods We used microarray expression profiling in paired normoxic and hypoxic cultures of healthy synovial fibroblasts (HSFs) and RA synovial fibroblasts (RASFs). We used Student's paired t-test with Benjamini and Hochberg multiple testing correction to determine statistical significance. Validation of microarray data was performed by quantitative real-time reverse transcription–polymerase chain reaction analysis of selected genes. Biologic pathways differentially modulated by hypoxia in RASFs or HSFs were identified using unsupervised Ingenuity Pathways Analysis. Results Hypoxia induced significant changes in the expression of a large group of genes in both HSFs and RASFs. In RASFs, we observed a lower number of hypoxia-regulated genes and partial differences in their functional categories. The number of differentially expressed genes in RASFs compared with HSFs was significantly increased by hypoxia. Multiple gene sets involved in energy metabolism, intracellular signal transduction, angiogenesis, and immune and inflammatory pathways were significantly modified, the last in both proinflammatory and antiinflammatory directions. Conclusion These data demonstrate that hypoxia induces significant changes in gene expression in HSFs and RASFs and identify differences between RASF and HSF profiles. The hypoxia-induced gene expression program in synovial fibroblasts identifies new factors and pathways relevant to understanding their contribution to the pathogenesis of chronic arthritis.

Objective Hyperplasia of fibroblast-like synoviocytes (FLS) contributes to chronic inflammation and joint destruction in rheumatoid arthritis (RA). FLICE-inhibitory protein (FLIP) is an antiapoptotic protein that might prevent apoptotic elimination of FLS in response to death ligands such as tumor necrosis factor α (TNFα) or Fas ligand, which are present in RA synovium. Previous studies on FLIP expression by osteoarthritis (OA) and RA FLS have shown variable results, and the specific role of FLIP as an apoptosis inhibitor in these cells remains unclear. We undertook this study to investigate the expression and antiapoptotic function of FLIP in FLS. Methods We studied the expression of FLIP by immunohistochemistry and immunoblotting in synovial tissues or cultured FLS from RA and OA patients. FLS apoptosis was induced by an agonistic anti-Fas monoclonal antibody and FLS were then quantified. We studied the effects of cycloheximide (CHX), TNFα, and FLIP antisense oligonucleotide on FLIP expression and FLS apoptotic susceptibility. Results FLIPL was the isoform mainly expressed in lining synoviocytes and cultured FLS. Synovial tissues and cultured FLS from OA and RA tissues displayed similar patterns and levels of expression of FLIP. Fas-induced apoptosis was variable in different FLS lines, but differences between OA and RA groups were not detected. TNFα induced increases in FLIPL and FLIPS expression and protected RA FLS from apoptosis, while CHX induced the opposite effects. Down-regulation of FLIP by antisense oligonucleotide strongly sensitized RA FLS to Fas-mediated apoptosis. Conclusion Apoptosis susceptibility and FLIP expression are similar in OA and RA FLS. Down-regulation of FLIP sensitizes RA FLS to Fas-mediated apoptosis and may be a valuable tool for targeting RA FLS hyperplasia.

Objective Neovascularization, with an increased number of synovial vessels with a characteristic morphology, seems to contribute to the progression of psoriatic arthritis (PsA). Accordingly, angiogenesis may be an important therapeutic target in PsA. The aim of this study was to analyze the effects of infliximab on angiogenesis in the synovial membrane of patients with PsA who responded to this therapy. Methods The study group comprised 9 patients with PsA who were selected for the presence of active polyarthritis (including knee synovitis) despite methotrexate therapy. Clinical and biologic evaluations were performed at each visit. Arthroscopy and synovial biopsies were performed at week 0, before infliximab therapy was initiated, and at week 8, after administration of 3 intravenous infusions of infliximab (5 mg/kg). We used immunohistochemistry to identify changes in infiltrating cells and in the angiogenesis modulators αvβ3 integrin, vascular endothelial growth factor (VEGF), angiopoietin 2 (Ang-2), flt-1 (VEGF receptor 1 [VEGFR-1]), kinase insert domain receptor [KDR]/flk-1 (VEGFR-2), and stromal cell–derived factor 1 (SDF-1). Neovascularization was assessed by automated histomorphometry of CD31+ vessels and by measuring αvβ3 expression. Results Rapid and significant clinical and biological improvement were observed after treatment in all patients. In the synovium, infliximab therapy induced a significant reduction in macrophages, the CD31+ vascular area, αvβ3+ neovessels/Ulex europaeus agglutinin+ vessels, VEGF and its receptor KDR/flk-1 (VEGFR-2), and SDF-1+ vessels. Expression of flt-1 (VEGFR-1), and SDF-1 in lining cells showed a nonsignificant reduction, whereas expression of Ang-2 increased. In 3 patients, reverse transcription–polymerase chain reaction confirmed the changes in some of these markers at the messenger RNA level. Conclusion These results show consistent changes in several factors involved in angiogenesis regulation, in parallel with the clinical response to infliximab in patients with PsA. The pattern of reduced VEGF with increased Ang-2 suggests vascular regression as a potential mechanism underlying the antiangiogenic effect of infliximab.

Objective Chemokines are important mediators in the chemoattraction of leukocytes to sites of inflammation. This study investigated the potential contribution of systemic sclerosis (SSc) fibroblasts to chemokine production and its potential relevance to the pathogenesis of SSc. Methods The expression of messenger RNA (mRNA) for different C-C and C-X-C chemokines by SSc and normal fibroblasts was studied by RNase protection assay. Monocyte chemoattractant protein 1 (MCP-1) protein production was analyzed by enzyme-linked immunosorbent assay. The chemotactic effect of fibroblast-derived MCP-1 on monocytic cells was analyzed in a transmigration assay. Nuclear factor κB (NF-κB) and activator protein 1 (AP-1) activation in fibroblasts was studied by electromobility shift analysis. MCP-1 expression in SSc skin sections was studied by immunohistochemistry. Results Among all chemokine genes studied, only MCP-1 and interleukin-8 mRNA were expressed by nonstimulated normal and SSc fibroblasts. SSc fibroblasts displayed increased constitutive expression of MCP-1 mRNA and protein and showed a blunted response to oxidative stress. Increased MCP-1 production was associated with higher chemotactic activity for monocytic cells. Increased NF-κB or AP-1 activation was not responsible for the constitutive overexpression of MCP-1 by SSc fibroblasts. In SSc skin sections, MCP-1 expression was detected in fibroblasts, keratinocytes, and mononuclear cells, whereas it was undetectable in normal skin. Conclusion SSc fibroblasts display a specific pattern of chemokine gene expression that is characterized by constitutively increased and abnormally regulated expression of MCP-1 in vitro. MCP-1 is also expressed in lesional skin and can participate in the pathogenesis of SSc.

Objective To investigate whether the pathogenesis of rheumatoid arthritis (RA) is associated with the functional chemokine receptor CCR5, which is the primary CC chemokine receptor expressed by T cells in rheumatoid synovium, and its nonfunctional receptor, Δ32CCR5, which is generated by the homozygous 32-basepair deletion (Δ32) in the CCR5 gene. Methods The frequency of the CCR5 genotype was compared among 673 patients with RA, 113 patients with systemic lupus erythematosus (SLE), and 815 control subjects. The CCR5 genotype was studied by polymerase chain reaction amplification of the region flanking the Δ32 deletion (Δ32CCR5). Results Frequencies of the wild-type CCR5 alleles (0.929, 0.907, and 0.942, respectively) and Δ32CCR5 alleles (0.071, 0.093, and 0.058, respectively) in controls, SLE patients, and RA patients did not differ significantly. However, none of the RA patients had the homozygous Δ32CCR5 genotype, compared with a frequency of 0.009 in controls (P = 0.014 by Fisher's exact test; χ2 = 4.12 with Yates' correction, P = 0.042) and 0.027 in SLE patients (P = 0.003 by Fisher's exact test; χ2= 11.63 with Yates' correction, P = 0.0006). Conclusion The results suggest that the CCR5 receptor plays an important role in RA and may be a suitable target for therapy.