Fibrin and fibronectin in rheumatoid synovial membrane and rheumatoid synovial fluid

Normal synovial membranes and synovial membranes from patients with classic rheumatoid arthritis were investigated for the presence of fibrin and fibronectin by an indirect immunoperoxidase technique. In normal synovial membranes, fibronectin was found around the monolayer of the synovial lining cells. Staining was most intense on the surface and beneath the lining cells, but not detectable in the cytoplasm. Fibronectin was also found in the cytoplasm of the endothelial cells. No staining for fibrin was found in the normal synovial membrane. In synovial membranes from patients with rheumatoid arthritis, large amounts of fibronectin were found around the multilayer of synovial lining cells, in the cytoplasm of the endothelial cells, and in argyrophilic fiber-rich connective tissue. In superficial areas denuded of synovial lining cells, high amounts of fibronectin were found incorporated in fibrin. In some areas with noninjured synovial lining cells, fibrin was also found, but in this case no fibronectin was incorporated. No fibronectin was found in connective tissue in areas with infiltration of inflammatory cells. After treatment of normal and rheumatoid synovial membranes with hyaluronidase, fibronectin was still present around the lining cells but the staining was found to be more distinct. This study relates the presence of fibrin and fibronectin in the rheumatoid synovial membrane to the high amount of these proteins, recently described, in rheumatoid synovial fluid. It also suggests that fibronectin present in the synovial membrane is produced and secreted by the endothelial cells.     

Different molecular forms of fibronectin in rheumatoid synovial fluid

The concentration of fibronectin in rheumatoid synovial fluid was found to be 2–3 times higher than in the corresponding plasma. Normal plasma revealed a homogeneous precipitate by cross-immunoelectrophoresis using antifibronectin, while rheumatoid plasma and rheumatoid synovial fluid exhibited a heterogeneous precipitate. The heterogeneous precipitate in rheumatoid plasma was found to be a complex between fibronectin and fibrinogen as evidenced by cross-immunoelectrophoresis. Synovial fluid fibronectin demonstrated a lower molecular weight by gelfiltration on Sepharose CL6B than did normal plasma fibronectin. We suggest that the presence of degraded fibronectin in rheumatoid synovial fluid may be the result of either the degradation of fibrin–fibronectin complexes or the destruction of matrix fibronectin from the synovial tissue.     

Identification of citrullinated cellular fibronectin in synovial fluid from patients with rheumatoid arthritis

Abstract

Objectives. Cellular fibronectin (cFn) has been implicated in the pathogenesis of rheumatoid arthritis (RA), and we previously demonstrated the presence of citrullinated cFn in rheumatoid synovial tissues. The present study aimed to investigate whether citrullinated cFn can be detected in the plasma or synovial fluid of RA patients.

Methods. Twenty-five rheumatoid arthritis synovial fluid (RASF), seven osteoarthritis synovial fluid (OASF) and 12 plasma samples from RA patients were examined. Citrullination of cFn was determined by immunoprecipitation (IP), western blotting and enzyme-linked immunosorbent assay (ELISA), in which peptidyl-citrulline within cFn was detected using a specific anti-cFn monoclonal antibody in combination with anti-modified citrulline antibody after chemical modification.

Results. Levels of citrullination associated with cFn, as determined by ELISA, were significantly higher in RASF than in OASF samples. IP and western blotting detected citrullinated cFn in RASF but not in plasma samples from RA patients. Levels of total cFn were elevated in RASF compared with OASF, and 24 out of 25 RASF samples were positive for anti-CCP antibody. However, no correlation was observed between levels of citrullinated cFn and those of total cFn or anti-CCP antibody in RASF. On the other hand, a significant positive correlation was observed between the levels of matrix metalloproteinase-3 (MMP-3) and cFn citrullination in RASF.

Conclusions. Citrullinated cFn appears to be produced within the affected joint and might be involved in the pathogenesis of rheumatoid synovitis.     

Differences between plasma and synovial fluid fibronectin

Summary Fibronectin is a high molecular weight glycoprotein of plasma and tissue fluids, and one of its functions is to opsonise particulate material. Chromatographic and electrophoretic analyses showed that the main components of fibronectin are biochemically similar in rheumatoid patients' plasma and synovial fluid. But synovial fluid fibronectin also contains a slow-moving component seen on two-dimensional immunoelectrophoresis, suggesting the presence of fibronectin complexes. Affinity chromatography provided evidence that these involved IgG, and in vitro studies showed that fibronectin influenced the reaction between IgG and anti-IgG. Synovial fluid fibronectin is functionally active in binding to gelatin in an haemagglutination assay, and it gave a relatively higher degree of haemagglutination than did plasma fibronectin, supporting the concept of multivalent fibronectin complexes in synovial fluid. These results suggest synovial fluid fibronectin may be involved in the opsonic removal of IgG-containing complexes from synovial fluid.     

Resistin in rheumatoid arthritis synovial tissue, synovial fluid and serum

BACKGROUND: Resistin is a newly identified adipocytokine which has demonstrated links between obesity and insulin resistance in rodents. In humans, proinflammatory properties of resistin are superior to its insulin resistance-inducing effects. OBJECTIVES: To assess resistin expression in synovial tissues, serum and synovial fluid from patients with rheumatoid arthritis, osteoarthritis and spondylarthropathies (SpA), and to study its relationship with inflammatory status and rheumatoid arthritis disease activity. METHODS: Resistin expression and localisation in synovial tissue was determined by immunohistochemistry and confocal microscopy. Serum and synovial fluid resistin, leptin, interleukin (IL)1beta, IL6, IL8, tumour necrosis factor alpha, and monocyte chemoattractant protein-1 levels were measured. The clinical activity of patients with rheumatoid arthritis was assessed according to the 28 joint count Disease Activity Score (DAS28). RESULTS: Resistin was detected in the synovium in both rheumatoid arthritis and osteoarthritis. Staining in the sublining layer was more intensive in patients with rheumatoid arthritis compared with those with osteoarthritis. In rheumatoid arthritis, macrophages (CD68), B lymphocytes (CD20) and plasma cells (CD138) but not T lymphocytes (CD3) showed colocalisation with resistin. Synovial fluid resistin was higher in patients with rheumatoid arthritis than in those with SpA or osteoarthritis (both p<0.001). In patients with rheumatoid arthritis and SpA, serum resistin levels were higher than those with osteoarthritis (p<0.01). Increased serum resistin in patients with rheumatoid arthritis correlated with both CRP (r=0.53, p<0.02), and DAS28 (r=0.44, p<0.05), but not with selected (adipo) cytokines. CONCLUSION: The upregulated resistin at local sites of inflammation and the link between serum resistin, inflammation and disease activity suggest a role for resistin in the pathogenesis of rheumatoid arthritis.     

Demonstration of fibronectin associated with platelets in synovial fluid from patients with rheumatoid arthritis

Paired samples of peripheral blood and synovial fluid (SF) aspirated from inflamed knee joints from 15 adult patients with classical rheumatoid arthritis, as well as peripheral blood obtained from 15 healthy subjects, were anticoagulated with ACD. Peripheral blood platelets were separated from other plasma constituents by gel filtration of platelet-rich plasma on Sepharose 2B. When using this technique on SF, it was found that platelets could be isolated from other SF constituents, and that each of the SF's gave a high yield of eluted platelets. Direct immunofluorescent staining for human fibronectin was performed with isolated and suspended platelets obtained from the three different sources. Aliquots of both intact and permeabilized platelets were stained. Intact peripheral platelets from all patients and normal subjects revealed a weakly positive staining, whereas the staining of intact SF platelets from all patients was clear and bright. The fluorescence of intact cells was surface-located and speckled. For permeabilized platelets, the staining had a punctate intracellular pattern, with a varying number of discrete and bright fluorescent foci per cell. Counting of the foci in each platelet specimen revealed that this number, which was also found in peripheral platelets from all patients and normal subjects, was distinctly greater than the number of foci in all the SF platelet specimens. No relationship was found between the various staining results and medical treatment or Waaler-Rose serology of the patients. The findings indicate that the SF platelets had large amounts of surface-bound and small amounts of intracellular fibronectin, whereas the converse was found in the case of peripheral platelets from the patients and normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Alternatively spliced EDA-containing fibronectin in synovial fluid as a predictor of rheumatoid joint destruction

OBJECTIVES: Fibronectin containing the EDA region (EDA(+)Fn), a molecule important for rheumatoid joint destruction, was measured in relation to the progression of joint destruction in rheumatoid arthritis (RA). METHODS: Total Fn and EDA(+)Fn were measured by ELISA, and the concentrations of Fn in plasma and synovial fluid were compared prospectively for 2 yr with the progression of joint destruction in 41 knee joints of 37 patients with RA. The extent of joint destruction was assessed by the Larsen score and joint space narrowing in X-ray films taken before and 2 yr after measurement of EDA(+)Fn. RESULTS: The concentration of synovial fluid EDA(+)Fn showed a positive correlation with the progression of joint destruction in RA (r=0.78). While total Fn in synovial fluid also showed a correlation with joint destruction (r=0.54), total Fn and EDA(+)Fn in plasma showed no correlation with joint destruction. The concentration of synovial fluid EDA(+)Fn was significantly higher in patients who underwent joint replacement after the measurement of EDA(+)Fn than in those who did not receive surgery (P<0.029). CONCLUSION: Synovial fluid EDA(+)Fn can be a predictor of subsequent joint destruction in RA.     

Citrullination of fibronectin in rheumatoid arthritis synovial tissue

OBJECTIVES: Citrullination, catalysed by peptidylarginine deiminase (PAD), is the post-translational modification of peptidylarginine to citrulline, which is intimately involved in the pathogenesis of rheumatoid arthritis (RA). Fibronectin (Fn), a large glycoprotein, is expressed at high levels in arthritic joints and it mediates various physiological processes through interactions with cell-surface integrin receptors and growth factors. We investigated the citrullination of Fn and its potential contribution to the pathogenesis of RA. METHODS: We localized Fn expression and citrullination in RA synovial tissue by immunohistochemistry, immunoprecipitation and western blotting. We also determined levels of citrullinated Fn in plasma from RA patients using sandwich enzyme-linked immunosorbent assay (ELISA). After incubating Fn with rabbit skeletal muscle PAD, we examined the binding ability of citrullinated Fn to vascular endothelial growth factor (VEGF) and integrin beta1 using a solid-phase receptor binding assay as well as the effect of the citrullinated Fn on apoptosis using cultured HL-60 cells. RESULTS: Immunohistochemistry and western blotting analysis indicated that Fn formed extracellular aggregates that were specifically citrullinated in RA synovial tissue. No Fn deposits were observed in synovial tissues of osteoarthritis (OA). Sandwich ELISA detected higher levels of citrullinated Fn in plasma from patients with RA than from healthy controls or those with systemic lupus erythematosus. Following citrullination in vitro, the affinity of Fn for VEGF increased, but binding activity to integrin beta1 decreased and Fn no longer stimulated the apoptosis of monocytes induced from cultured HL-60 cells. CONCLUSIONS: Our results suggest that the citrullination of Fn is a specific event for RA synovium, although others have detected citrullinated total proteins in inflamed synovial tissue of RA and non-RA patients. Citrullination of Fn could alter interactions between Fn and its receptors and growth factors, consequently contributing to mechanisms of RA pathogenesis such as perturbed angiogenesis and apoptosis.     

The effect of rheumatoid synovial fluid macrophages on DNA,glycosaminoglycan and collagen synthesis by synovial fibroblasts

Summary The effects of soluble factors secreted by peripheral blood monocytes and rheumatoid synovial fluid macrophages were tested on human synovial fibroblast cultures. Both monocytes and macrophages liberated factors which reduced DNA synthesis (³H-thymidine incorporation) by synovial fibroblasts. Monocyte and macrophage factors stimulated hyaluronic acid synthesis. The activation obtained with rheumatoid synovial macrophages was considerably greater than that with monocytes. Foetal bovine serum was found to have a clear stimulatory effect on the synthesis of collagen and other proteins by fibroblasts. The effects of monocyte and macrophage factors on protein synthesis in synovial fibroblasts were small: collagen synthesis was slightly increased relative to other extracellular proteins.     

Protease inhibitors in rheumatoid synovial fluid

Summary Paired plasma and synovial fluids from 17 patients with seropositive rheumatoid arthritis were examined for electrophoretic homogeneity/heterogeneity and enzymic inhibitory capacity of the protease inhibitors. The high degree of saturation (90%) of the polyvalent protease inhibitor ₂-macroglobulin in the rheumatoid synovial fluid contrasts sharply with the low saturation of ₁-antitrypsin. The inhibitory reactivity of the non-complexed fraction of both of these dominating antiproteases was retained (85–90%). Thus, a selective inactivation of synovial ₁-antitrypsin could not be demonstrated. ₁-Anti-chymotrypsin revealed electrophoretic homogeneity in all synovial fluids. Electrophoretic heterogeneity of the plasmin inhibitor antiplasmin was detected in the majority of synovial fluids indicating plasmin activation. The existence of a protease-antiprotease imbalance in the rheumatoid joint was indicated by the high degree of saturation of ₂-macroglobulin and a cleavage of C3 in rheumatoid synovial fluids.     

Eda-containing fibronectin is synthesized from rheumatoid synovial fibroblast-like cells

Objective. To identify the cells that synthesize EDA-containing fibronectin (FN) and examine the role of EDA+ FN in the pathogenesis of rheumatoid joint lesions. Methods. Localization of EDA+ FN and c-Fos protein in rheumatoid joints was studied immunohistochemically by utilizing antibodies for EDA+ FN and c-Fos. Expression of EDA+ FN was studied by immunoelectron microscopy and in situ hybridization. The amount of EDA+ FN was measured by enzymelinked immunosorbent assay. Results. EDA+ FN was specifically localized in the synovial lining layer of synovium with active rheumatoid arthritis (RA) (n = 17), but not in that with osteoarthritis (n = 4) or with inactive fibrous RA (n = 2). EDA+ FN messenger RNA was localized in the synovial lining layer. EDA+ FN was immunoelectron microscopically localized in the synovial lining fibroblast-like (type B) cells. EDA+ FN was also detected at the cartilage–pannus junction and on the surface of RA cartilage. Double staining showed that EDA+ FN colocalized with c-Fos protein in the rheumatoid synovial lining layer. Quantification of EDA+ FN showed that it was highly concentrated in rheumatoid synovial fluids. Conclusion. EDA+ FN is synthesized by the synovial lining fibroblast-like (type B) cells in situ in rheumatoid synovium, and appears to be expressed in association with activated or transformed states of synovium.     

硫氧还蛋白5在类风湿关节炎患者滑膜组织滑液及血液中表达的研究

目的 在蛋白和mRNA水平上进一步研究硫氧还蛋白5(TXNDC5)在类风湿关节炎(RA)患者滑膜和血液中的表达水平与临床指标的关系,探讨该基因对RA的病理作用.方法 用免疫组织化学法、免疫荧光定量分析、实时荧光定量聚合酶链反应(PCR)、蛋白免疫印迹定量分析TXNDC5在RA滑膜中的表达水平;以骨关节炎(OA)、系统性红斑狼疮(SEE)、强直性脊柱炎(AS)及健康人为对照,用夹心酶联免疫吸附法(Sandwich-ELISA)分析TXNDC5在RA患者血液和滑液中的表达水平.采用单因素方差分析,LSD检验、Spearman相关分析进行统计学处理.结果 免疫组织化学法和免疫荧光定量分析显示TXNDC5在RA滑膜组织中高表达(100%,40±9),在OA滑膜中无表达,在AS滑膜中表达量(200%.4±4)也较低.实时定量PCR和Western blotting均证实TXNDC5在RA滑膜中高表达(P均<0.01).SandwichELISA显示,TXNDC5在RA患者血液及滑液中高表达(A值=1.31±0.37),但在OA、SEE、AS以及健康人低表达或无表达(P均<0.05).RA血液中TXNDC5的水平(A值=0.8185±0.299)与抗环瓜氨酸肽(CCP)抗体水平存在正相关(r=0.350,P=0.027).结论 TXNDC5在RA滑膜和血液中表达量明显升高,可能通过刺激RA滑膜血管翳形成参与RA病理进程.     

Antigenic specificity of rheumatoid synovial fluid lymphocytes

The majority of rheumatoid arthritis (RA) synovial fluid lymphocytes (SFL) demonstrate markers that are suggestive of prior activation. While the mechanism(s) responsible is unknown, prior studies have suggested that certain Mycobacterium tuberculosis (MT) antigens may preferentially activate SFL in vitro. We therefore examined the ability of RA SFL to respond to purified protein derivative and an acetone-precipitable MT antigenic complex (AP-MT) and compared this with the responses by peripheral blood lymphocytes (PBL). The responses were contrasted with those elicited with tetanus toxoid (TT) and mitogenic anti-CD3. In patients with RA, the SF proliferative responses to both TT and anti-CD3 were reduced compared with responses by PB. In contrast, the SF response to purified protein derivative was maintained, and that to AP-MT was significantly increased, compared with PB. SF responses to AP-MT antigens were significantly greater than those to TT. The AP-MT activation of T lymphocytes from RA SF was characterized by an earlier peak proliferative response than that noted with matched PB. AP-MT responsiveness was not restricted to HLA-DR4 positive patients. These observations suggest that an epitope(s) contained within the MT complex of antigens, and enriched in the AP-MT complex, may be important in maintaining the chronic inflammation in at least some patients with RA.     

Demonstration of mast cell chemotactic activity in synovial fluid from rheumatoid patients

OBJECTIVES: The significance of the mast cell in the pathogenesis of rheumatic diseases has become more evident. Although mast cell hyperplasia is a feature of rheumatoid arthritis, the nature of mast cell chemoattractants involved in the recruitment of mast cells in joint diseases has not been studied in any detail. In this study the presence of mast cell chemotactic activity in synovial fluids was examined. METHODS: Synovial fluids from seven rheumatoid patients were tested in a modified Boyden chamber, where a human mast cell line was used as responder. The presence of stem cell factor (SCF) and transforming growth factor beta (TGFbeta) was measured by enzyme linked immunosorbent assay (ELISA). RESULTS: Six of the seven synovial fluids tested exhibited mast cell chemotactic activity. Two characterised human mast cell chemotaxins, SCF and TGFbeta, were highly expressed in the synovium. Soluble SCF could be detected in all fluids analysed. Blocking antibodies against SCF or TGFbeta almost completely blocked the activity in one fluid, partially blocked the activity in three, and did not affect the activity in two. Treatment of the responder cells with pertussis toxin reduced the migratory response against seven fluids, indicating the presence of chemoattractants mediating their effect through G(i) coupled receptors. CONCLUSION: These data demonstrate the presence of multiple factors in synovial fluid acting as mast cell chemoattractants, two of which are SCF and TGFbeta that contribute to the effect. These findings may be of importance for developing new strategies to inhibit mast cell accumulation in rheumatic diseases.     

Production of mononuclear cell factor by mononuclear phagocytes from rheumatoid synovial fluid

Collagenase-and PGE1-stimulating activities (mononuclear cell factor or MCF) have been found in culture supernatants from synovial fluid macrophages (SF-M phi) of patients wih rheumatoid arthritis. The apparent molecular weight of the MCF activity present in SF-M phi supernatants was between 15-20,000 daltons, which is similar to interleukin I. All the SF-M phi supernatants from patients tested showed the MCF activity. Our study presents evidence for MCF production by monocyte-macrophages at the local site of the lesion.     

Natural killer (NK) cell activity of peripheral blood, synovial fluid, and synovial tissue lymphocytes from patients with rheumatoid arthritis and juvenile rheumatoid arthritis.

Natural killer (NK) cell activity was investigated in peripheral blood, synovial fluid, and synovial tissue lymphocytes from patients with rheumatoid arthritis (RA) and juvenile rheumatoid arthritis (JRA). Unfractionated lymphocytes, T lymphocytes, and non-T lymphocytes from the 3 compartments of JRA patients had reduced activity compared with that of normal peripheral blood lymphocytes (with p values usually between 0.05 and 0.1). Unfractionated synovial tissue lymphocytes of RA patients also showed reduced cytotoxicity (0.05 less than p less than 0.1), whereas peripheral blood lymphocytes exerted normal NK cell activity. The NK activity was exerted by cells both with and without Fc gamma receptors. The highest cytotoxicity was observed in Fc gamma receptor-positive cells, both in peripheral blood and synovial fluid, since more than 70% reduction in NK activity was found after depletion of Fc gamma receptor-positive cells. No evidence of lymphocytotoxic antibodies or other factors with influence on NK cells was observed in the patients' sera.     

Metalloproteinases and collagenase inhibitors in rheumatoid synovial fluid

The levels of metalloproteinases and metalloproteinase inhibitors were measured in rheumatoid synovial fluid. Reliable estimates of total enzyme and inhibitor levels in the synovial fluids were obtained only after hyaluronidase treatment and gel filtration. Three latent metalloproteinases were found which, after activation, degraded collagen, proteoglycan, and gelatin. These enzymes closely resembled the metalloproteinases secreted into connective tissue culture medium. In addition to alpha 2 macroglobulin, an Mr 30,000 collagenase inhibitor was detected which closely resembled the tissue inhibitor of metalloproteinase found in tissue culture medium.