Matrix metalloproteinase (MMP)-1, MMP-8 and MMP-13 are interstitial collagenases that degrade type II collagen in cartilage; this is a committed step in the progression of rheumatoid arthritis and osteoarthritis. Of these enzymes, the expression of MMP-1 and MMP-13 is substantially increased in response to IL-1 and tumor necrosis factor-α, and elevated levels of these collagenases are observed in arthritic tissues. Therefore, cytokine-mediated MMP-1 and MMP-13 gene regulation is an important issue in arthritis research. In this review, we discuss current models of MMP-1 and MMP-13 transcriptional regulation, with a focus on signaling intermediates and transcription factors that may be future targets for the development of new arthritis drugs.
arthritis; matrix metalloproteinases; mitogen-activated protein kinases; nuclear factor κB; transcription
A study was done to determine if the differentiation and activation phenotype of T cells in synovial fluid (SF) from patients with juvenile idiopathic arthritis (JIA) is associated with T-cell proliferation in situ. Mononuclear cells were isolated from 44 paired samples of peripheral blood and SF. Differentiation and activation markers were determined on CD4 and CD8 T cells by flow cytometry. Cell-cycle analysis was performed by propidium iodide staining, and surface-marker expression was also assessed after culture of the T cells under conditions similar to those found in the synovial compartment. The majority of the T cells in the SF were CD45RO+CD45RBdull. There was greater expression of the activation markers CD69, HLA-DR, CD25 and CD71 on T cells from SF than on those from peripheral blood. Actively dividing cells accounted for less than 1% of the total T-cell population in SF. The presence or absence of IL-16 in T-cell cultures with SF or in a hypoxic environment did not affect the expression of markers of T-cell activation. T cells from the SF of patients with JIA were highly differentiated and expressed early and late markers of activation with little evidence of in situ proliferation. This observation refines and extends previous reports of the SF T-cell phenotype in JIA and may have important implications for our understanding of chronic inflammation.
activation; chronic inflammation; differentiation; T cells
Genome-wide linkage analysis studies in families with systemic lupus erythematosus (SLE) have revealed consistent evidence of linkage to several regions of the genome. In a previous issue of this journal, Graham and colleagues described their approach to following up the linkage data for one of these regions, 1q41–42. Using methods based on the transmission disequilibrium test, the region likely to harbour a SLE disease gene was refined to 2.3 Mb. This commentary discusses their approach and identifies lessons that may be applicable to the investigation of other complex diseases.
association; linkage; systemic lupus erythematosus; transmission disequilibrium test; whole-genome scan
An excess of the proinflammatory substance IL-18 is present in joints of patients with rheumatoid arthritis (RA), and expression of IL-18 receptor (IL-18R) regulates IL-18 bioactivity in various cell types. We examined the expression of IL-18R α-chain and β-chain and the biologic effects of IL-18 in fibroblast-like synoviocytes (FLS) after long-term culture. The presence of both IL-18R chains was a prerequisite for IL-18 signal transduction in FLS. However, all FLS cultures studied were either resistant or barely responsive to IL-18 stimulation as regards cell proliferation, expression of adhesion molecules ICAM-1 and vascular cell adhesion molecule (VCAM)-1, and the release of interstitial collagenase and stromelysin, IL-6 and IL-8, prostaglandin E2, or nitric oxide. We conclude that the presence of macrophages or IL-18R+ T cells that can respond directly to IL-18 is essential for the proinflammatory effects of IL-18 in synovitis in RA.
fibroblast; interleukin-18; receptor; rheumatoid arthritis; synoviocyte
The role of autoantibodies in the etiology of autoimmune diseases remains unclear. However, an examination of the sequences of these autoantibodies can be informative. Antibody sequences that violate constraints normally imposed during ontogeny and during development point to a failure of regulation. The existence of clonally related sequences indicates that production of these antibodies may frequently be driven by self-antigen. A better understanding of the mechanisms that normally constrain the composition of the antibody repertoire and of the nature of the inciting and/or driving antigens may yield new insights into both the pathogenesis and potential treatment of these crippling diseases.
autoantibody; B cell; development; immunoglobulin genes; sequence analysis
The autoantigenic polymyositis/scleroderma (PM/Scl) complex was recently shown to be the human homologue of the yeast exosome, which is an RNA-processing complex. Our aim was to assess whether, in addition to targeting the known autoantigens PM/Scl-100 and PM/Scl-75, autoantibodies also target recently identified components of the PM/Scl complex. The prevalence of autoantibodies directed to six novel human exosome components (hRrp4p, hRrp40p, hRrp41p, hRrp42p, hRrp46p, hCsl4p) was determined in sera from patients with idiopathic inflammatory myopathy (n = 48), scleroderma (n = 11), or the PM/Scl overlap syndrome (n = 10). The sera were analyzed by enzyme-linked immunosorbent assays and western blotting using the affinity-purified recombinant proteins. Our results show that each human exosome component is recognized by autoantibodies. The hRrp4p and hRrp42p components were most frequently targeted. The presence of autoantibodies directed to the novel components of the human exosome was correlated with the presence of the anti-PM/Scl-100 autoantibody in the sera of patients with idiopathic inflammatory myopathy (IIM), as was previously found for the anti-PM/Scl-75 autoantibody. Other clear associations between autoantibody activities were not found. These results further support the conception that the autoimmune response may initially be directed to PM/Scl-100, whereas intermolecular epitope spreading may have caused the autoantibody response directed to the associated components.
anti-PM/Scl; autoantibody; autoantigen; exosome complex
Human tumour necrosis factor (TNF)-like weak inducer of apoptosis (hTWEAK) and two anti-hTWEAK mAbs were tested for their ability to elicit or block inflammatory responses in cultured human dermal fibroblasts and synoviocytes. Incubation with hTWEAK increased the production of prostaglandin E2, matrix metalloproteinase-1 (MMP-1), IL-6, and the chemokines IL-8, RANTES (regulated on activation, normal T expressed and secreted) and interferon-γ-inducible protein-10 (IP-10) in culture supernatant of fibroblasts and synoviocytes. In combination with TNF or IL-1β, hTWEAK further stimulated the secretion of prostaglandin E2, MMP-1, IL-6 and IL-8 up to fourfold, and IP-10 and RANTES up to 70-fold compared to TNF or IL-1β alone. An anti-hTWEAK mAb, BCB10, blocked the effects of hTWEAK, whereas hTWEAK crosslinked by the anti-hTWEAK mAb, BEB3, further stimulated the inflammatory response of fibroblasts and synoviocytes. The anti-hTWEAK mAbs were ineffective in blocking or increasing the responses of TNF or IL-1β and blocking anti-TNF mAb was ineffective in preventing the responses to TWEAK. These results were also confirmed at the RNA level for MMP-1, macrophage chemoattractant protein-1, RANTES, macrophage inflammatory protein-1α, IP-10 and IL-8. TWEAK in synergism with IL-1 and TNF may be an additional cytokine that plays a role in destructive chronic arthritic diseases.
chemokines; cytokines; metalloproteinases; rheumatoid arthritis; TNF
Cartilage serves multiple functions in the developing embryo and in postnatal life. Genetic mutations affecting cartilage development are relatively common and lead to skeletal malformations, dysfunction or increased susceptibility to disease or injury. Characterization of these mutations and investigation of the molecular pathways in which these genes function have contributed to an understanding of the mechanisms regulating skeletal patterning, chondrogenesis, endochondral ossification and joint formation. Extracellular growth and differentiation factors including bone morphogenetic proteins, fibroblast growth factors, parathyroid hormone-related peptide, extracellular matrix components, and members of the hedgehog and Wnt families provide important signals for the regulation of cell proliferation, differentiation and apoptosis. Transduction of these signals within the developing mesenchymal cells and chondrocytes results in changes in gene expression mediated by transcription factors including Smads, Msx2, Sox9, signal transducer and activator of transcription (STAT), and core-binding factor alpha 1. Further investigation of the interactions of these signaling pathways will contribute to an understanding of cartilage growth and development, and will allow for the development of strategies for the early detection, prevention and treatment of diseases and disorders affecting the skeleton.
cartilage; chondrogenesis; endochondral ossification; limb bud; neural crest cells
Constitutive mRNA expression and secretion of proinflammatory and anti-inflammatory cytokines was comparatively analyzed in rheumatoid arthritis (RA) synovial fibroblasts (SFB), isolated from primary culture or derived by repeated passage; normal-skin fibroblasts were used as controls. First-passage RA-SFB (n = 3) secreted large amounts of IL-6 (15,800 ± 2,110 pg/ml; mean ± SEM), but only limited amounts of tumor necrosis factor (TNF)-α (22.1 ± 1.1 pg/ml) or IL-10 (35.7 ± 34.2 pg/ml; only one of three samples was positive). IL-1β, IL-15, and IL-18 were not detectable at the protein level and showed very low mRNA levels by semiquantitative RT-PCR. In repeated-passage RA-SFB (tenth passage), protein secretion was significantly lower for IL-6 (one-twentieth of the initial level) and TNF-α (two-thirds), and markedly reduced for IL-10 (one-quarter, with only one of three samples positive). While the decrease of IL-10 protein from first to tenth passage was paralleled by a corresponding decrease of mRNA, the relative mRNA levels for IL-6 and TNF-α were actually increased (20-fold and 300-fold, respectively), indicating post-transcriptional and/or post-translational regulation of these cytokines. Due to highly variable levels among individual patients, however, no significant differences were observed for any cytokine mRNA between primary-culture and repeated-passage RA-SFB (ninth passage). Likewise, no significant differences were detectable between RA-SFB and normal-skin fibroblasts (primary-culture and repeated-passage). By producing high amounts of IL-6 and limited amounts of TNF-α, RA-SFB may contribute to the (im)balance of proinflammatory and anti-inflammatory cytokines in the inflamed joint.
cytokines; inflammation; mRNA; rheumatoid arthritis; synovial fibroblasts
The diagnosis of rheumatoid arthritis (RA) is primarily based on clinical symptoms, so it is often difficult to diagnose RA in very early stages of the disease. A disease-specific autoantibody that could be used as a serological marker would therefore be very useful. Most autoimmune diseases are characterized by a polyclonal B-cell response targeting multiple autoantigens. These immune responses are often not specific for a single disease. In this review, the most important autoantibody/autoantigen systems associated with RA are described and their utility as a diagnostic and prognostic tool, including their specificity, sensitivity and practical application, is discussed. We conclude that, at present, the antibody response directed to citrullinated antigens has the most valuable diagnostic and prognostic potential for RA.
autoantibodies; autoimmunity; citrulline; rheumatoid arthritis
During our careers, we have developed new and innovative concepts pertaining to the pathophysiology of osteoarthritis which have assisted in the development of new therapeutic approaches. Moreover, our laboratory has long sought to develop protective agents for osteoarthritic structural joint tissues. The most significant concepts that have originated from our lab are briefly outlined in this commentary.
joint articular tissue; magnetic resonance imaging; osteoarthritis; therapeutic
Hip osteoarthritis (OA) is a degenerative joint disease that results in substantial morbidity. The disease may be preventable in some instances by reducing risk factors associated with the disease. We undertook a study to determine whether being overweight or obese, a health risk that applies to younger and older age groups, is commonly associated with hip joint OA. The body mass indices (BMIs) of 1021 males and females ranging in age from 23 to 94 years and requiring surgery for end-stage hip joint OA were analyzed to find the prevalence of high body weights at the time of surgery. Being overweight was defined as having a BMI of 25–29.9 kg/m2 and being obese as having a BMI >30 kg/m2. BMIs indicative of overweight were recorded for 68% of the patients surveyed. Of 35 patients aged 30–39 years, 53.3% had BMIs >25, with a mean of 28.8, which nearly reaches the lower limit defined for obesity. On average, patients who had had previous surgery and complications warranting reimplantation of new surgical devices had BMIs in the obese range. Our findings suggest that a high percentage of patients with end-stage hip OA are overweight, including younger adults and those with symptoms of 3–6 months' duration. Moreover, patients whose BMIs are in the obese range may be at increased risk for removal and reimplantation of their prosthesis.
arthroplasty surgery; body mass index; hip joint; osteoarthritis
Wegener's granulomatosis (WG) is a form of systemic vasculitis. It is characterized by granulomatous inflammation in the upper and lower airways, vasculitis and necrotizing glomerulonephritis, and is strongly associated with antineutrophil cytoplasmic antibodies against proteinase 3. Since the etiology of the disease is not clear, treatment, consisting of corticosteroids and immunosuppressives, is nonspecific and associated with severe side effects. Pinpointing the trigger(s) of the disease would highly improve treatment. Clinical evidence shows that an infectious agent, the bacterium Staphylococcus aureus, is a risk factor for disease relapse, suggesting its involvement in the pathogenesis of WG. Here we review both clinical and experimental data that either indicate or support a role for S. aureus in WG.
autoimmunity; co-trimoxazole; Staphylococcus aureus; superantigens; Wegener's granulomatosis
Circulating CD8+ CD28- T cells were found to be expanded more in patients with ankylosing spondylitis than in an age-matched healthy population (41.2 ± 17.7% versus 18.6 ± 7.6%). The level of CD8+CD28- T cells was dependent on the disease status, but was independent of age. Most of the CD8+ CD28- T cells produced perforin after stimulation in vitro, in contrast to their CD8+CD28+ counterparts. From the clinical perspective, the percentage of the cytotoxic CD8+ CD28- T cells reflected a more severe course of disease, as it correlated with distinct movement restrictions, as well as the metrology score summarizing cervical rotation (in sitting position), chin-to-jugulum distance, thoracic Schober, chest expansion, and fingers-to-floor distance (P = 0.032).
ankylosing spondylitis; CD8+ T suppressor cells; CD28 molecule; cytotoxicity; interferon-γ
Clinical practice guidelines are important tools to assist clinical decision-making. Recently, several guidelines addressing the management of osteoarthritis (OA) have been published. Clinicians treating patients with OA must ensure that these guidelines are developed with consistency and methodological rigour. We undertook a qualitative summary and critical appraisal of six medical treatment guidelines for the management of lower-limb OA published in the medical literature within the past 5 years. A review of these six guidelines revealed that each possesses strengths and weakness. While most described the scope and intended patient populations, the guidelines varied considerably in the rigour of their development, coverage of implementation issues, and disclosure of conflicts of interest.
clinical practice guidelines; osteoarthritis
IL-10 is an anti-inflammatory cytokine produced in the joint in rheumatoid arthritis by macrophages and infiltrating blood lymphocytes. Regulation of its expression is poorly understood, but previous findings have suggested that physical interactions with T cells may play a role. This report investigates signalling mechanisms involved in the production of macrophage IL-10 upon interaction with fixed, cytokine-stimulated T cells (Tck). Elutriated monocytes were differentiated to macrophages by macrophage-colony-stimulating factor (M-CSF) and co-cultured with fixed T cells chronically stimulated in a cytokine cocktail of IL-2/IL-6/tumour necrosis factor (TNF)-α in the presence or absence of wortmannin and LY294002, inhibitors of phosphatidylinositol 3-kinase (PI3K), or of rapamycin, an inhibitor of p70 S6-kinase (p70S6K). Spontaneous IL-10 production by rheumatoid arthritis synovial-membrane mononuclear cells (RA-SMCs) and co-cultures of rheumatoid arthritis T cells (RA-Ts) and macrophages was also assessed. RA-T and Tck induction of macrophage IL-10 production was suppressed by cell separation and inhibition of PI3K and p70S6K. PI3K involvement was also shown by phosphorylation of the downstream effector protein kinase B. Spontaneous IL-10 production by RA-SMCs was also inhibited by LY294002 and depletion of the nonadherent (T-cell-enriched) fraction of the cell population. IL-10 production in RA-SMCs and M-CSF-primed macrophages, activated by interaction with Tck, is PI3K- and p70S6K-dependent.
IL-10; macrophage; PI3K; rheumatoid arthritis; T cells
Synovial fibroblasts (SFs) have become a major target for ex vivo gene transfer in rheumatoid arthritis (RA), but efficient transduction of RA-SFs still is a major problem. The low proliferation rate and heterogeneity of RA-SFs, together with their lack of highly specific surface receptors, have hampered a more extensive application of this technique. Improving transduction protocols with conventional viral vectors, therefore, as well as developing novel strategies, such as alternative target cells, and novel delivery systems constitute a major challenge. Recent progress in this field will lead to the achievement of high transgene expression, and will facilitate the use of gene transfer in human trials.
ex vivo approach; gene therapy; rheumatoid arthritis; viral vector
Urogenital infection with Chlamydia trachomatis can lead to development of an acute inflammatory arthritis, and this acute disease becomes chronic in some individuals. Research indicates that the organism is present in synovial tissue of patients with chronic disease in a persistent, rather than an actively growing, form. Importantly, metabolic and other characteristics of persistent Chlamydia differ from those of actively growing bacteria. Other studies suggest that Chlamydia pneumoniae can be found in a persistent state in the synovium and that it too may be involved in joint pathogenesis. These and other observations suggest a more complex role for the Chlamydiae in joint disease than previously recognized. This realization should engender a realignment of thinking among clinicians and researchers concerning both mechanisms of chlamydial pathogenesis in the synovium and design of new treatments for the disease.
Chlamydia pneumoniae; Chlamydia trachomatis; inflammation; molecular genetics; pathogenesis; reactive arthritis
The extracellular framework and two-thirds of the dry mass of adult articular cartilage are polymeric collagen. Type II collagen is the principal molecular component in mammals, but collagens III, VI, IX, X, XI, XII and XIV all contribute to the mature matrix. In developing cartilage, the core fibrillar network is a cross-linked copolymer of collagens II, IX and XI. The functions of collagens IX and XI in this heteropolymer are not yet fully defined but, evidently, they are critically important since mutations in COLIX and COLXI genes result in chondrodysplasia phenotypes that feature precocious osteoarthritis. Collagens XII and XIV are thought also to be bound to fibril surfaces but not covalently attached. Collagen VI polymerizes into its own type of filamentous network that has multiple adhesion domains for cells and other matrix components. Collagen X is normally restricted to the thin layer of calcified cartilage that interfaces articular cartilage with bone.
articular cartilage; collagens; extracellular matrix
Osteolysis, which is considered to be a major source of morbidity following total hip joint replacement, has been notoriously difficult to measure accurately, particularly in the acetabular area. In order to study periacetabular osteolysis, specialized software for computerized tomography (CT) scan image analysis has been developed. This software (3D-CT) eliminates metal artifacts, allows three-dimensional segmentation of the CT image, and reconstructs the segmented image to provide an accurate representation and measurement of volume for osteolytic lesions. In the present study, 20 patients underwent periacetabular osteolytic volume determination using 3D-CT, functional assessment (using the Harris Hip Scale, the Western Ontario and McMaster University Osteoarthritis Index, and the short form 36 questionnaire), and two-dimensional analysis of volumetic polyethylene wear using digitalized plain films. Periacetabular osteolysis correlated directly with the polyethylene wear rate (relative risk [RR] = 0.494, P = 0.027). If one patient with an acetabular revision, one patient with recurrent dislocation, and one patient with a Biomet prosthesis are excluded, then the correlation between wear and osteolysis is improved (RR = 0.685, P = 0.002). In summary, the current study demonstrates both the feasibility of CT imaging of periacetabular osteolysis and the correlation between polyethylene wear and osteolytic volume, providing a potential outcome measure for clinical trials that are designed to examine interventions in this complex disease process.
3D-segmented computerized tomography; aseptic loosening; osteolysis; prosthesis
BALB/c mice immunized with human cartilage proteoglycan (PG) develop arthritis accompanied by the production of autoantibodies to mouse cartilage PG. To determine whether the autoantibody isotype contributes to the onset and severity of arthritis, PG-specific serum IgG1 (Th2, IL-4-cytokine-supporting) and IgG2a (Th1, IFN-γ-controlling) concentrations were monitored during immunization with PG in IL-4-deficient and IFN-γ-deficient mice. Paradoxically, despite elevated IFN-γ, the PG-specific IgG1 isotype was significantly higher than the PG-specific IgG2a response, and the PG-specific IgG1 isotype was independent of IL-4. In contrast, the serum concentration of PG-specific IgG2a isotype was six times higher in IL-4-deficient mice than in wild-type controls. Moreover, the high concentration of PG-specific IgG2a isotype in IL-4-deficient mice corresponded to an increased severity of arthritis. The concentration of PG-specific IgG2a isotype was lower in IFN-γ-deficient mice than in wild-type mice, and the incidence and severity of arthritis also were significantly lower. Concentrations of PG-specific IgG2a isotype autoantibody correlated with the onset and severity of arthritis, suggesting a pathological role of this isotype, probably locally in the joint.
antibody; arthritis; autoimmunity; cytokines; T cells
Lyme disease is a tick-borne multisystem disease that affects primarily the skin, nervous system, heart and joints. At least three species of Borrelia burgdorferi sensu lato, namely Borrelia burgdorferi sensu stricto, Borrelia garinii, and Borrelia afzelii, can cause the disease. This review will focus mainly on the pathophysiology of Lyme arthritis, the long-term outcome of Lyme disease, and the recently licensed vaccine against Lyme disease.
arthritis; autoimmunity; infection; Lyme disease; T lymphocytes
In rheumatic diseases, autoantibody-producing cells of interest are often hidden in a polyclonal B-lymphocyte population. Immunoglobulin gene fingerprinting is a useful approach to screen for expanding clones and to detect recirculation between different locations. The gene fingerprinting approach and the Southern blot technique have been amalgamated, using electrophoretic transfer of a PCR product from an acrylamide gel onto a nylon membrane followed by hybridization with specific oligonucleotide probes. In contrast to conventional fingerprinting, the authenticity of immunoglobulin genes can be confirmed, individual genes can be detected and handling radionucleotides can be avoided. Also, the membrane may be reused for further investigations.
B-lymphocytes; immunoglobulin gene fingerprinting; rheumatoid arthritis; Southern blot; VH genes
The 2nd Annual European League Against Rheumatism (EULAR) Congress, held in Prague, 13–16 June 2001, was an impressive event with a record turnout of 8300 delegates. It offered a large variety of first-class state of the art lectures by some 180 invited worldwide speakers. Several new and ongoing therapeutic developments were discussed. The aim to attract the young scientific community was only partly achieved, and the dependence on industry posed some problems. The organization, however, was a big improvement compared with the previous congress in this series. The number of submitted abstracts was relatively low (1200) compared with the number of delegates. Accommodation of satellite symposia and organization of poster sessions remain problem areas of this meeting. The Annual EULAR Congress emerges as one of the two most important annual congresses of rheumatology, the other being the American College of Rheumatology meeting.
ACR; EULAR; poster sessions; rheumatology congress; satellite symposia
Weight loss is typically found during severe infections, e.g. septic arthritis. The aim of our study was to evaluate the role of leptin, regulator of food intake and energy expenditure, for the development of Staphylococcus aureus-triggered arthritis. Leptin production was found to be decreased during murine S. aureus-induced arthritis. Treatment with recombinant leptin neither restored the basal leptin levels nor affected the weight loss during the disease, but it significantly decreased the severity of septic arthritis. Exogenous leptin did not affect the staphylococcal load as measured in blood, joints and kidneys. Preceding the effects on joint manifestations, serum levels of interleukin-6 decreased in leptin-treated mice. In conclusion, the treatment with recombinant leptin reduced both the severity of joint manifestations in S.aureus-induced arthritis and the inflammatory response, as measured by serum IL-6 levels, without affecting the survival of bacteria in vivo.
arthritis; interleukin-6; leptin; Staphylococcus aureus