Effect of three animal models of inflammation on nerve fibres in the synovium.

OBJECTIVES--Both sensory and sympathetic nerve fibres are depleted in the synovium in rheumatoid arthritis (RA). The hypothesis that the induction of an inflammatory response in the synovium is capable of causing depletion of nerve fibres was tested. METHODS--To investigate this phenomenon experimental arthritis in the rat was induced by three different methods and the synovium was examined for evidence of nerve depletion by immunocytochemistry. RESULTS--In a synovitis induced by latex spheres, a mainly macrophage foreign body type reaction, no nerve depletion was seen. In contrast both in an antigen-induced and a hydrogen peroxide-induced model of arthritis nerve fibre depletion was observed. This appeared to affect sensory and sympathetic nerve fibres equally. Nerve fibre depletion was only seen in areas of inflammatory cell infiltration indicating that a mixed lymphocyte and macrophage population of cells may be necessary for this effect. CONCLUSIONS--An inflammatory response, containing lymphocytes and macrophages, in the synovium is capable of the depletion of the finely myelinated and unmyelinated neuropeptide-containing nerves.     

The rationale for the current boom in anti-TNFalpha treatment. Is there an effective means to define therapeutic targets for drugs that provide all the benefits of anti-TNFalpha and minimise hazards?

Progress in understanding mechanisms of disease are necessary to usher in major changes in treatment. A new era in rheumatoid arthritis (RA) and related chronic autoimmune/inflammatory diseases is now beginning, with a variety of anti-TNFalpha treatments licensed for use in both RA and Crohn's disease. The rationale for this new treatment lies in an understanding that cytokines are critical, rate limiting molecules lying at the heart of the chronic autoimmune/inflammatory disease process. This understanding was developed from the critical evaluation of a hypothesis that was proposed linking cytokines, antigen presentation and autoimmunity in 1983. Detailed analysis focusing on the major site of the disease, the rheumatoid synovium was essential to developing indications that blockade of TNFalpha might be efficacious. This clue was validated using anti-TNFalpha treatment of an animal model of RA, murine collagen induced arthritis, and by immunohistochemical demonstration of upregulated TNF and TNF-R expression in the synovium. With this three pronged rationale, the authors were able to convince Centocor, Inc, which had developed a chimaeric anti-TNFalpha antibody for use in sepsis, to work with them to test the concept that TNFalpha blockade would be beneficial in RA. With the success of that first trial, other companies have subsequently tested their anti-TNF strategies successfully. Current interests extend to understanding the processes that regulate TNF production in the rheumatoid joint. Progress in this area is discussed, using adenoviruses to infect normal macrophages and rheumatoid synovium.     

Stroma: Fertile soil for inflammation

Biological therapies for the management of immune mediated inflammatory diseases such as rheumatoid arthritis have proven to be extremely successful in recent years. Despite these successes, even the most effective of therapies do not lead to cure. Why chronic inflammation persists indefinitely within the rheumatoid synovium despite an absence of continuous stimulation, and why some patients with early synovitis progress to persistent disease whilst others do not, has remained unexplained. In contrast to the paradigm that stromal cells are biochemically active but immunologically passive, there is now growing evidence that stromal components from the rheumatoid synovium play a crucial part in the immunopathology of rheumatoid arthritis. Stromal cells play a central role in the transformation of an acute, resolving to a chronic inflammatory process, and to the persistence of synovial inflammation and joint destruction through a variety of immune mechanisms. Therapeutic manipulation of the stroma is a largely unexplored, yet potentially vital area of research. Targeting pathogenic stromal cells has the potential to provide a cure for chronic inflammatory disorders such as rheumatoid arthritis.     

Synovial collagenase: Its presence in culture from joint disease of diverse etiology

Closed needle biopsy of synovium from inflamed joints yields enough tissue to detect production and/or release of collagenase from these tissues. Collagenase activity was found in synovium from 8 of 8 patients with probable rheumatoid arthritis, in 6 of 9 patients with nonrheumatoid inflammatory synovitis, and in 1 of 6 patients with degenerative joint disease. One of 2 patients with classic rheumatoid arthritis had activity in synovium regrown after synovectomy. Therefore synovial collagenase is not unique to rheumatoid arthritis.     

Secretion of Plasminogen Activator by Rheumatoid and Nonrheumatoid Synovial Cells In Culture

The secretion of plasminogen activator by human synovial cultures established from explants was studied. Thirteen cultures established from patients with rheumatoid disease were hyposecretors of plasminogen activator. Seven cultures derived from patients with nonrheumatoid joint disorders all secreted high levels of this enzyme. Rheumatoid and nonrheumatoid cells contained comparable levels of intracellular activator. It is suggested that the secretion of plasminogen activator is a function of normal synovium and that a defect in this function in the rheumatoid synovium perpetuates the inflammatory process.     

The role of mesenchymal cells in the pathophysiology of inflammatory arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disorder of the joints that can cause severe disability. While the role of inflammatory cells in the pathogenesis of RA has been well established, the specific contribution of resident cells within the synovial membrane, especially those of mesenchymal origin, has become the object of closer scrutiny only recently. The central position of these cells in the disease process of RA is underlined by their involvement in its main pathophysiological features: inflammation, hyperplasia and joint destruction. In this chapter, we provide a characterisation of resident mesenchymal cells, specifically fibroblast-like cells in the rheumatoid synovium, and give an overview of the molecular pathways by which these cells are involved in the initiation and perpetuation of RA.     

Signaling and effector pathways.

There is increasing evidence that distinct signaling and effector pathways in the rheumatoid synovium result in a cascade of pathophysiologic events. These interactions, which finally lead to progressive joint destruction, are different from all other joint diseases in numerous aspects. As outlined in this review, molecular biology techniques allow detection of key pathways ranging from external stimuli to subcellular gene regulation mechanisms operative in various cells within the rheumatoid synovium. To alter these pathways, inhibitory factors need to be applied to these "hot zones" for an extended period, which can be achieved either by repeated drug administration or by local synthesis using genetically altered synovial cells. Both adenovirus and retroviral constructs, as well as ex vivo and in vivo strategies, can be used for gene transfer into these cells, and routine delivery of "protective" genes into the affected joints might be achieved within the next decade.     

The role of peroxynitrite in cyclooxygenase-2 expression of rheumatoid synovium

OBJECTIVE: Reactive oxygen intermediates play an important role in the inflammatory processes of rheumatoid arthritis. Cyclooxygenase-2 is an inducible form of an enzyme involved in prostanoid biosynthesis. This study linked peroxynitrite (ONOO-) to the signaling pathways that induce COX-2. RESULTS: Exposure of rheumatoid synovial cells to peroxynitrite resulted in COX-2 protein expression in a dose-dependent manner. RT-PCR analysis also demonstrated that COX-2 mRNA was induced in peroxynitrite-treated rheumatoid synovial cells. Dexamethasone markedly inhibited this peroxynitrite-mediated COX-2 expression at therapeutic concentrations. CONCLUSION: This study demonstrates that oxidant stress is an important inducer of COX-2 in rheumatoid synovium. This induction may contribute to the amplification of prostanoids in the rheumatoid inflammatory process.     

MRI of rheumatoid arthritis image quantitation for the assessment of disease activity, progression and response to therapy

Magnetic resonance imaging (MRI) allows the direct visualization of many bone and soft tissue changes in rheumatoid arthritis. Synovitis volume, bone marrow oedema and bone erosions are suitable for serial measurement. The outcome measures in rheumatoid arthritis clinical trials (OMERACT) rheumatoid arthritis magnetic resonance imaging (RAMRIS) system is designed to allow straightforward, reproducible scoring of all these features. Alternatively, synovial volumes may be directly and quickly measured using semi-automated techniques. There is the potential for similar systems for measuring erosions. Dynamic contrast enhanced MRI depends on the rate of enhancement of the synovium after intravenous contrast agent. Measurements depend on the underlying physiology of the inflamed synovium, in particular the vascularity and capillary permeability which are expected to closely mirror inflammatory activity in the joint. Measurements from MRI have been shown to correlate with clinical, laboratory, imaging and histological measures of inflammation, predict erosive progression and respond rapidly to various types of treatment. They are, therefore, expected to be good measures of disease activity, progression and response to therapy.     

Subtyping of osteoarthritic synoviopathy

OBJECTIVE: Osteoarthritis research is traditionally concentrating on events within the degenerated articular cartilage. Changes in the synovial membrane are largely neglected. In fact, they are generally interpreted as secondary to the cartilage changes and not pathogenetically involved in the disease process. In this study, we present a systematic analysis of the synovial reaction pattern in early and late stages of the osteoarthritic disease process. METHODS: A large series of synovial specimens derived from early and late stage osteoarthritic cartilage disease were investigated by histological and immunohistochemical means for tissue architecture and inflammatory cell infiltrates. For comparison, also samples with rheumatoid arthritis, seronegative arthritis, and septic arthritis were included as well as normal synovial membrane specimens. RESULTS: In all specimens derived from patients with diagnosed osteoarthritis alterations of the synovial tissue were observed. A large spectrum of alterations was found in different stages of osteoarthritic joint disease and four different basic pattern of synovial reactions could be identified: (i) hyperplastic, (ii) inflammatory, (iii) fibrotic, and (iv) detritus-rich synoviopathy. CONCLUSION: We show that in all cases of clinically overt osteoarthritic joint disease significant synovial pathology is associated. Furthermore, our study clearly documents that in osteoarthritic synovium significant inflammation can occur. This is suggestive of a distinct pathogenetic role of the synovium also in osteoarthritic cartilage degeneration at least in a subset of cases.     

Studies of serum immunoglobulin binding to synovial fibroblast cell cultures from patients with rheumatoid arthritis

Using a sensitive 125I-protein A (PrA) binding assay to detect cell surface IgG, we have studied seven different synovial fibroblast cell cultures from patients with rheumatoid arthritis (RA). When these cultures were incubated in the presence of serum from 18 autologous and allogeneic RA patients (all seropositive), we were unable to detect significant IgG binding. Since IgM rheumatoid factor (RF) can block PrA binding, sera were absorbed with aggregated IgG to remove RF without affecting the results. Similar studies on three cell lines with seven rheumatoid sera were performed by antibody-dependent cell-mediated cytotoxicity. No significant cytotoxicity was observed. Since antibodies to collagen are present in rheumatoid sera, several cultures were incubated with ascorbic acid (12.5 microgram/ml) to optimize synthesis of cell surface collagen. These culture conditions did not affect serum immunoglobulin binding by the 125I-PrA assay. Thus, we can find no evidence for a direct humoral immune mediation of synovial proliferation in rheumatoid arthritis. These data do not support the hypothesis that the inflammatory process within the synovium of RA patients is an immunologic response to a fibroblast-associated antigen in the synovial membrane.     

Mechanisms of tissue destruction and cellular activation in rheumatoid arthritis.

Rheumatoid arthritis is a chronic inflammatory disease of unknown etiology that is marked by synovial inflammation and destruction of articular extracellular matrix. Several studies of the pathogenesis of tissue destruction have focused on the production of metalloproteinases and their inhibitors in synovium as determinants of joint preservation. Also, the role of cytokines in the perpetuation of synovitis and of superantigens in synovial T-cell activation have led to novel hypotheses that attempt to explain abnormalities of synovial structure and function in rheumatoid arthritis. Recent studies that dealt with these topics are briefly reviewed in the context of current paradigms of inflammatory synovitis.     

Protéines S100A8, S100A9 et S100A12 : marqueurs inflammatoires ou acteurs physiopathologiques de la polyarthrite rhumatoïde

Although S100 proteins represent 40% of the neutrophil cytoplasmic proteins, their physiological and pathological functions are still unclear. S100A8, S100A9 and S100A12 protein concentrations are dramatically enhanced in synovial fluid and synovium of patients suffering from rheumatoid arthritis. Their expression seems to correlate with disease activity and joint damage. These proteins are likely involved in rheumatoid arthritis pathogenesis by enhancing extracellular matrix proteolysis, autoimmunity and inducing the pseudotumoral phenotype of the synoviocytes in rheumatoid arthritis. S100A8, S100A9 and S100A12 assessment will probably constitute a relevant tool for rheumatoid arthritis diagnosis and will improve inflammatory arthritides management.     

Detailed analysis of the cell infiltrate and the expression of mediators of synovial inflammation and joint destruction in the synovium of patients with psoriatic arthritis: implications for treatment

BACKGROUND: The synovial tissue is a primary target of many inflammatory arthropathies, including psoriatic arthritis (PsA). Identification of proinflammatory molecules in the synovium may help to identify potentially therapeutic targets. OBJECTIVE: To investigate extensively the features of cell infiltration and expression of mediators of inflammation and joint destruction in the synovium of patients with PsA compared with patients with rheumatoid arthritis matched for disease duration and use of drugs. METHODS: Multiple synovial tissue biopsy specimens were obtained by arthroscopy from an inflamed joint in 19 patients with PsA (eight oligoarthritis, 11 polyarthritis) and 24 patients with rheumatoid arthritis. Biopsy specimens were analysed by immunohistochemistry to detect T cells, plasma cells, fibroblast-like synoviocytes, macrophages, proinflammatory cytokines, matrix metalloproteinases and tissue inhibitor metalloproteinase-1, adhesion molecules and vascular markers. Stained sections were evaluated by digital image analysis. RESULTS: The synovial infiltrate of patients with PsA and rheumatoid arthritis was comparable with regard to numbers of fibroblast-like synoviocytes and macrophages. T cell numbers were considerably lower in the synovium of patients with PsA. The number of plasma cells also tended to be lower in PsA. The expression of tumour necrosis factor alpha (TNFalpha), interleukin (IL) 1beta, IL6 and IL18 was as high in PsA as in rheumatoid arthritis. The expression of matrix metalloproteinases, adhesion molecules and vascular markers was comparable for PsA and rheumatoid arthritis. CONCLUSION: These data show increased proinflammatory cytokine expression in PsA synovium, comparable to results obtained for rheumatoid arthritis, and support the notion that, in addition to TNFalpha blockade, there may be a rationale for treatments directed at IL1beta, IL6 and IL18.     

Immunohistology of rheumatoid nodules and rheumatoid synovium.

The immunohistological features of rheumatoid nodules and rheumatoid synovium were examined using monoclonal and polyclonal antibodies raised against macrophages, HLA-DR, leucocyte common antigen, and immunoglobulin components. The palisading cells surrounding the necrotic centre of the rheumatoid nodule were shown to be HLA-DR positive leucocytes, mostly histiocytes. The inflammatory infiltrate associated with rheumatoid nodules showed many immunohistochemical similarities to that of rheumatoid synovium, including a preponderance of IgG positive plasma cells, and a similar number and microanatomical pattern of distribution of HLA-DR positive cells. The significance of these findings for the cellular immunopathology and aetiology of the rheumatoid lesion is discussed.     

Angiopoietin 1 directly induces destruction of the rheumatoid joint by cooperative, but independent, signaling via ERK/MAPK and phosphatidylinositol 3-kinase/Akt

OBJECTIVE: To determine whether angiopoietin 1 (Ang-1) potentiates overgrowth of the synovium and joint degradation in rheumatoid arthritis (RA), and to clarify the cell-signaling mechanisms of Ang-1 in the rheumatoid joint. METHODS: Expression of Ang-1, TIE-2 (a receptor for Ang-1), and matrix metalloproteinase 3 (MMP-3) was studied by immunohistochemistry. Activation of the ERK/MAPK and phosphatidylinositol (PI) 3-kinase/Akt pathways and of NF-kappaB was determined by Western blotting and an NF-kappaB p65 DNA binding activity assay, respectively. Induction of apoptosis was evaluated by nuclear staining, cell viability assay, and Western blotting of caspases. Synovial cell migration was evaluated by actin polymerization, Western blotting of Rho family proteins, and affinity purification with Rhotekin-Rho and p21-activated kinase 1. Matrix degradation was examined by induction of proMMP-3 secretion from synovial cells followed by in vitro cartilaginous matrix degradation assay. RESULTS: Ang-1 stimulated the ERK/MAPK and PI 3-kinase/Akt pathways in a cooperative but independent manner, which enhanced rheumatoid synovium overgrowth and joint destruction. In addition, Ang-1 activated NF-kappaB via Akt to promote cell growth, but also inhibited cell apoptosis via ERK and Akt. Ang-1 directly potentiated the extension of synovial cells in an ERK- and Akt-dependent manner by up-regulating Rho family proteins, which attenuated Rac signaling and led to membrane ruffling. Ang-1 induced proMMP-3 secretion from synovial cells, which resulted in direct degradation of the cartilaginous matrix. CONCLUSION: Ang-1 stimulates the ERK/MAPK and PI 3-kinase/Akt pathways cooperatively, but in a manner independent of each other, to directly potentiate synovium overgrowth and joint destruction in RA. In addition to inflammatory cytokines, Ang-1/TIE-2 signaling appears to be an independent factor that contributes to the destruction of the rheumatoid joint.     

Anatomic separation of the suprapatellar pouch spares its involvement by rheumatoid synovitis in the knee

Summary Synovectomy of the knee was performed in a 27-year-old female with seropositive rheumatoid arthritis of 6 years duration. At surgery the suprapatellar pouch was found to be separate from the rest of the knee joint, where direct access to articular collagenous tissues remained. The suprapatellar pouch, presumably separate from the knee cavity since birth, was free of disease. The rest of the joint lining, and synovium of the forefoot joints, that had been operated on at the same time, had gross and histological evidence of severe rheumatoid synovitis. The sparing of this suprapatellar pouch by rheumatoid disease is not easily explained, especially since its origin and nature are similar to other synovial parts of the knee that were actively involved. These latter areas had direct access to articular collagenous tissues. The findings of this case question the predilection of rheumatoid arthritis for synovium, and suggest that synovium and articular collagenous tissues are requisites of chronic rheumatoid arthritis.     

A型滑膜细胞与类风湿关节炎血管新生

类风湿关节炎(RA)是一种常见的多系统性炎症性自身免疫性疾病.RA最主要病理特征是关节滑膜血管新生和对关节破坏力极强的血管翳形成.血管的新生是个复杂的过程,多种细胞及其所分泌的细胞因子参与了此过程.近来大量的研究表明,A型滑膜细胞即滑膜巨噬细胞在RA病理过程中起着非常重要的作用,其参与了炎症和血管新生的整个过程.A型滑膜细胞表达黏附分子、趋化因子受体和多种表面抗原物质,还能分泌产生大量的细胞因子、生长因子和其它化学活性物质.它们在RA滑膜病理过程中起着关键性作用.因此,A型滑膜细胞可能将成为RA治疗很好的靶点.     

Nuclear magnetic resonance (NMR) tomographic imaging for popliteal cysts in rheumatoid arthritis.

The ability of nuclear magnetic resonance (NMR) tomographic imaging to show a change in proton spin-lattice relaxation time (T1 value) in the joints of patients with rheumatoid arthritis before and after treatment with intra-articular steroid has been assessed. Six patients with seropositive rheumatoid arthritis and clinical evidence of a popliteal cyst were examined by both NMR tomography and arthrography. In all cases the presence of active rheumatoid arthritis was shown by an increase in the T1 values of the synovium of the joints. After arthrography a consistent but small rise in T1 value was noted which fell to below the initial reading after treatment by intra-articular injection of an anti-inflammatory agent. In all cases the presence of the popliteal cyst was clearly shown by both NMR tomography and arthrography. The findings indicate that NMR tomography provides a sensitive method for the demonstration of inflammatory joint disease, popliteal cysts, and possibly for monitoring response to therapy.