Synovial Tissue Explants Research Articles

Promotion of macrophage activation by Tie2 in the context of the inflamed synovia of rheumatoid arthritis and psoriatic arthritis patients.

ObjectiveTo examine the role of Tie2 signalling in macrophage activation within the context of the inflammatory synovial microenvironment present in patients with RA and PsA.MethodsClinical responses and macrophage function were examined in wild-type and Tie2-overexpressing (Tie2-TG) mice in the K/BxN serum transfer model of arthritis. Macrophages derived from peripheral blood monocytes from healthy donors, RA and PsA patients, and RA and PsA synovial tissue explants were stimulated with TNF (10 ng/ml), angiopoietin (Ang)-1 or Ang-2 (200 ng/ml), or incubated with an anti-Ang2 neutralizing antibody. mRNA and protein expression of inflammatory mediators was analysed by quantitative PCR, ELISA and Luminex.ResultsTie2-TG mice displayed more clinically severe arthritis than wild-type mice, accompanied by enhanced joint expression of IL6, IL12B, NOS2, CCL2 and CXCL10, and activation of bone marrow-derived macrophages in response to Ang-2 stimulation. Ang-1 and Ang-2 significantly enhanced TNF-induced expression of pro-inflammatory cytokines and chemokines in macrophages from healthy donors differentiated with RA and PsA SF and peripheral blood-derived macrophages from RA and PsA patients. Both Ang-1 and Ang-2 induced the production of IL-6, IL-12p40, IL-8 and CCL-3 in synovial tissue explants of RA and PsA patients, and Ang-2 neutralization suppressed the production of IL-6 and IL-8 in the synovial tissue of RA patients.ConclusionTie2 signalling enhances TNF-dependent activation of macrophages within the context of ongoing synovial inflammation in RA and PsA, and neutralization of Tie2 ligands might be a promising therapeutic target in the treatment of these diseases.

The anti-ADAMTS-5 nanobody®, M6495, protects against cartilage breakdown in cartilage and synovial joint tissue explant models

The anti-ADAMTS-5 nanobody®, M6495, protects against cartilage breakdown in cartilage and synovial joint tissue explant models

Monosodium urate crystals induce oxidative stress in human synoviocytes.

BackgroundGout is the most common inflammatory arthropathy of metabolic origin and it is characterized by intense inflammation, the underlying mechanisms of which are unknown. The aim of this study was to evaluate the oxidative stress in human fibroblast-like synoviocytes (FLS) exposed to monosodium urate (MSU) crystals, which trigger an inflammatory process.MethodsHuman FLS isolated from synovial tissue explants were stimulated with MSU crystals (75 μg/mL) for 24 h. Cellular viability was evaluated by crystal violet staining, apoptosis was assessed using Annexin V, and the cellular content of reactive oxygen species (ROS) and nitrogen species (RNS) (O2-, H2O2, NO) was assessed with image-based cytometry and fluorometric methods. In order to determine protein oxidation levels, protein carbonyls were detected through oxyblot analysis, and cell ultrastructural changes were assessed by transmission electron microscopy.ResultsThe viability of FLS exposed to MSU crystals decreased by 30 % (P < 0.05), while apoptosis increased by 42 % (P = 0.01). FLS stimulated with MSU crystals exhibited a 2.1-fold increase in H2O2 content and a 1.5-fold increase in O2- and NO levels. Oxyblots revealed that the spots obtained from FLS protein lysates exposed to MSU crystals exhibited protein carbonyl immunoreactivity, which reflects the presence of oxidatively modified proteins. Concomitantly, MSU crystals triggered the induction of changes in the morphostructure of FLS, such as the thickening and discontinuity of the endoplasmic reticulum, and the formation of vacuoles and misfolded glycoproteins.ConclusionsOur results prove that MSU crystals induce the release of ROS and RNS in FLS, subsequently oxidizing proteins and altering the cellular oxidative state of the endoplasmic reticulum, which results in FLS apoptosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-1012-3) contains supplementary material, which is available to authorized users.

Investigating the Role of Toll-Like Receptors in Models of Arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by persistent synovial inflammation leading to tissue destruction and progressive loss of joint function. Here we describe two methods that can be used to assess the contribution of toll-like receptors (TLRs), and their potential ligands, to RA pathogenesis. We focus on the antigen-induced model of murine arthritis and human synovial tissue explant models. Both enable detection of TLR, and TLR ligand, expression, as well as investigation of the effect of inhibition of these molecules. Each offers a unique insight into disease; with murine models allowing kinetic analysis in live animals and explant models allowing examination of inflamed human tissue, which together can help us to dissect the role of TLRs in the onset and progression of RA.

Toll-like receptor 2 (TLR2) induces migration and invasive mechanisms in rheumatoid arthritis.

IntroductionThis study investigates the role of Toll-like receptor 2 (TLR2) in the regulation of migratory and invasive mechanisms in rheumatoid arthritis (RA).MethodsInvasion, migration, matrix metalloproteinase (MMP)-1, -3 and tissue inhibitor of matrix metalloproteinase-3 (TIMP-3) expression, β-integrin binding, cytoskeletal rearrangement and Ras-related C3 botulinum toxin substrate 1 (Rac1) activation in response to a TLR2-ligand, Pam3CSK4 (1 μg/ml), in ex vivo RA synovial tissue explants, primary RA synovial fibroblasts (RASFC) and microvascular endothelial cells (HMVEC) were assessed by Transwell Matrigel™ invasion chambers, enzyme-linked immunosorbent assay (ELISA), multiplex adhesion binding assay, reverse transcription polymerase chain reaction (RT-PCR), F-actin immunofluorescent staining, matrigel synovial outgrowths, Rac1 pull-down assays/Western blot and zymography. β1-integrin expression in RA/control synovial tissue was assessed by immunohistology. The effect of Pam3CSK4 on cell migration, invasion, MMP-3 and Rac1 activation was examined in the presence or absence of anti-β1-integrin (10 μg/ml) or anti-IgG control (10 μg/ml). The effect of an anti-TLR-2 mAb (OPN301)(1 μg/ml) or immunoglobulin G (IgG) control (1 μg/ml) on RASFC migration and RA synovial tissue MMP activity was assessed by wound assays, ELISA and zymography.ResultsPam3CSK4 significantly induced cell migration, invasion, MMP-1, MMP-3, MMP-2 and MMP-9 expression and induced the MMP-1/TIMP-3 and MMP-3/TIMP-3 ratio in RASFC and explants (p <0.05). β1-integrin expression was significantly higher in RA synovial tissue compared to controls (p <0.05). Pam3CSK4 specifically induced β1-integrin binding in RASFC (p <0.05), with no effect observed for β2-4, β6, αvβ5 or α5β1. Pam3CSK4 increased β1-integrin mRNA expression, Rac1 activation, RASFC outgrowths and altered cytoskeletal dynamic through induction of filopodia formation. Pam3CSK4-regulated cell migration and invasion processes, but not MMP-3, were inhibited in the presence of anti-β1-integrin (p <0.05), with no effect observed for anti-IgG control. Furthermore, anti-β1-integrin inhibited Pam3CSK4-induced Rac1 activation. Finally, blockade of TLR2 with OPN301 significantly decreased spontaneous release of MMP-3, MMP-2 and MMP-9 and increased TIMP-3 secretion from RA synovial explant cultures (p <0.05). Incubation of RASFC with OPN301 RA ex vivo conditioned media inhibited migration and invasion compared to IgG control.ConclusionsTLR2 activation induces migrational and invasive mechanisms, which are critically involved in the pathogenesis of RA, suggesting TLR2 as a potential therapeutic target for the treatment of RA.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-015-0664-8) contains supplementary material, which is available to authorized users.

Role of the NLRP3 inflammasome in the transient release of IL-1β induced by monosodium urate crystals in human fibroblast-like synoviocytes.

BackgroundTo investigate whether monosodium urate (MSU) crystals induce interleukin (IL)-1β in human fibroblast-like synoviocytes (FLS), and whether the NLRP3 inflammasome is involved in the inflammatory mechanism.MethodsHuman FLS isolated from explants of synovial tissue were stimulated with MSU crystals (0.001 to 0.5 mg/ml) for different time course (6 hours to 48 hours). The expressions of IL-1β, IL-6, TNF-α and NLRP3 were evaluated with ELISA, Western blot and quantitative real-time PCR.ResultsExposure of FLS to MSU crystals transiently induced a significant increase in IL-1β expression in culture medium with a peak at 6 h. The mRNA level of IL-1β in the FLS cells had a similar pattern at this time point. Changes in IL-6 and TNF-α expression were not observed. Simultaneously, intercellular pro-IL-1β was detected at 6 h. Furthermore, MSU crystals also induced NLRP3 mRNA and protein expression at 6 h to 48 h after MSU treatment.ConclusionsMSU crystals directly increased IL-1β and intercellular NLRP3 expression in FLS cells. It is suggested that the NLRP3 inflammasome may be associated with IL-1β in FLS treated with MSU. Altogether, MSU could induce production and release of IL-1β through the NLRP3 inflammasome in human synoviocytes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12950-015-0070-7) contains supplementary material, which is available to authorized users.

Brief report: successful in vitro culture of rheumatoid arthritis synovial tissue explants at the air-liquid interface.

To establish a method to culture synovial tissue explants from patients with rheumatoid arthritis (RA). Synovial tissue explants obtained from 10 patients with RA were cultured at the air-liquid interface or were submerged in culture medium. As a control, synovial explants were engrafted subcutaneously into SCID mice. The synovial explants were harvested at different time points, and histologic or flow cytometric analysis was performed. Cytokine levels in the culture supernatants were measured by enzyme-linked immunosorbent assay. Infliximab was added to the air-liquid interface culture to evaluate the effect of tumor necrosis factor α blockade on inflammatory cytokine production. The histologic features of RA synovitis, including a hyperplastic lining layer and the presence of cellular infiltrate in the sublining layer, were maintained in synovial tissue explants in air-liquid interface culture. In synovial grafts harvested from SCID-HuRAg mice, the cellular infiltrate was well maintained in the sublining, but the lining layer was lost. Viable CD4+ T cells and macrophages were abundant after air-liquid interface culture but were virtually absent after submerged culture. Furthermore, synovial tissue explants in air-liquid interface culture produced interleukin-6 (IL-6) and IL-8 for a prolonged period of time. The addition of infliximab effectively reduced cytokine production. RA synovial explants can be maintained for weeks using an air-liquid interface culture. This simple culture system might be useful for analyzing the pathogenesis of RA synovitis and for developing antirheumatic drugs.

AB0089 Tofacitinib Mediates Synovial Angiogenesis in Psoriatic Arthritis

BackgroundPsoriatic Arthritis (PsA) is a common, chronic immune-mediated inflammatory disease, characterised by synovitis, progressive destruction of articular cartilage/bone, and is associated with psoriasis. Janus Kinase and Signal Transducer and Activator...

Btk inhibition suppresses agonist-induced human macrophage activation and inflammatory gene expression in RA synovial tissue explants

ObjectivesBruton's tyrosine kinase (Btk) is required for B lymphocyte and myeloid cell contributions to pathology in murine models of arthritis. Here, we examined the potential contributions of synovial Btk expression...

AB0117 NK cells isolated from synovial fluid amplify the inflammatory response of fibroblast-like synoviocytes

BackgroundNatural killer (NK) cells represent one of the major components of innate immune system and are very important in both early and chronic phases of inflammatory responses. NK cells might...

OP0304 BTK Inhibition Suppresses Inflammatory Cytokine Production and Affects Gene Expression in Human Macrophages and RA Synovial Tissue Explants

BackgroundRheumatoid arthritis (RA) is a chronic and progressive autoinflammatory disorder characterized by the infiltration of inflammatory cells, including B-cells, T-cells and macrophages, in the synovial membrane ultimately leading to cartilage...

Profiling the Secretion of Soluble Mediators by End Stage Osteoarthritis Synovial Tissue Explants Reveals a Reduced Responsiveness to an Inflammatory Trigger

ObjectiveEvidence is accumulating that synovial tissue plays an active role in osteoarthritis (OA), however, exact understanding of its contribution is lacking. In order to further elucidate its role in the OA process, we aimed to identify the secretion pattern of soluble mediators by synovial tissue and to assess its ability to initiate cartilage degeneration.MethodsSynovial tissue explants (STEs) obtained from donors without history of OA (n = 8) or from end stage OA patients (n = 16) were cultured alone or together with bovine cartilage explants in the absence or presence of IL-1α. The secretion of 48 soluble mediators was measured and the effect on glycosaminoglycan (GAG) release and matrix metalloproteinase (MMP) activity was determined.ResultsNormal and OA STEs secreted comparable levels of almost all measured soluble mediators. However, in the presence of IL-1α these mediators were less secreted by OA than by normal STEs of which 15 differed significantly (p<0.01). No effect of normal or OA STEs on GAG release from the cartilage explants was observed, and no differences in MMP activity between OA and normal STEs were detected.ConclusionsUnexpectedly, a comparable secretion profile of soluble mediators was found for OA and normal STEs while the reduced responsiveness of OA STEs to an inflammatory trigger indicates a different state of this tissue in OA patients. The effects could be the result of prolonged exposure to an inflammatory environment in OA development. Further understanding of the pro-inflammatory and inflammation resolving mechanisms during disease progression in synovial tissue may provide valuable targets for therapy in the future.

A mechanistic view of the effects of manzamine A (MZA) on rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) (167.8)

Abstract Previous studies suggested that MZA, an alkaloid extracted from a marine sponge, has anti-inflammatory properties which may act via mitogen-activated protein (MAP) kinases. We hypothesized that MZA would decrease phosphorylation of MAP kinases in RA FLS and reduce secretion of proinflammatory cytokines from RA synovial tissue (ST) explants. RA FLS were treated with 10 μM MZA or DMSO (vehicle) for 1 hour prior to stimulation with various dilutions of RA synovial fluid (SF) for 5 minutes and Western blotting was performed on cell lysates. Western blotting with phospho-specific antibodies demonstrated that RA SF increases the phosphorylation of the MAP kinases ERK 1/2 and JNK in RA FLS at dilutions of 1:10 and 1:25. However, pretreatment with MZA did not consistently alter RA SF-stimulated RA FLS phosphorylation of ERK 1/2 or JNK. RA ST explants were incubated with either DMSO or MZA (10, 1.0 or 0.1 µM) and conditioned media (CM) was collected after 24 hours for analysis by ELISA. CM collected 24 hrs after treatment of RA ST explants with MZA or vehicle revealed no significant differences in secretion of RANTES (CCL5) or interleukin (IL)-10. We conclude that RA SF dilutions can be used as a biologically relevant stimulant of RA FLS MAP kinase phosphorylation. We have also shown that MZA has no consistent effect on the phosphorylation of the MAP kinases ERK 1/2 or JNK. We also note that MZA may not alter secretion of IL-10 or RANTES using a RA ST explant model.

Involvement of mitogen-activated protein kinases and peroxisome proliferator-activated receptor γ in monosodium urate crystal-induced vascular cell adhesion molecule 1 expression in human rheumatoid arthritis synovial fibroblasts

To investigate whether monosodium urate (MSU) crystals could induce the production of VCAM-1 (vascular cell adhesion molecule1) in human synovial cells and its possible signaling pathways, human synovial cells isolated from synovial tissue explants were stimulated with various doses of MSU crystals for different time intervals. Expression of VCAM-1 was evaluated with Western blotting. To explore the underlying mechanisms, VCAM-1 protein expression was also evaluated after activation of several signaling molecules including mitogen-activated protein kinases (MAPKs) and peroxisome proliferator-activated receptorγ (PPARγ) were blocked. Exposure of synovial cells to MSU crystals induced VCAM-1 expression in culture medium in a dose- and time-dependent manner, reaching a plateau at 1000µM and 24h. Inhibition of the activation of MAPKs and PPARγ could block this increase. The present results demonstrated that MSU crystals could induce VCAM-1 expression. MAPKs and PPARγ signaling pathways regulated the induced VCAM-1 expression.

Blockade of Toll-like receptor 2 prevents spontaneous cytokine release from rheumatoid arthritis ex vivo synovial explant cultures

IntroductionThe aim of this study was to examine the effect of blocking Toll-like receptor 2 (TLR2) in rheumatoid arthritis (RA) synovial cells.MethodsRA synovial tissue biopsies, obtained under direct visualization at arthroscopy, were established as synovial explant cultures ex vivo or snap frozen for immunohistology. Mononuclear cell cultures were isolated from peripheral blood and synovial fluid of RA patients. Cultures were incubated with the TLR1/2 ligand, Pam3CSK4 (200 ng, 1 and 10 μg/ml), an anti-TLR2 antibody (OPN301, 1 μg/ml) or an immunoglobulin G (IgG) (1 μg/ml) matched control. The comparative effect of OPN301 and adalimumab (anti-tumour necrosis factor alpha) on spontaneous release of proinflammatory cytokines from RA synovial explants was determined using quantitative cytokine MSD multiplex assays or ELISA. OPN301 penetration into RA synovial tissue explants cultures was assessed by immunohistology.ResultsPam3CSK4 significantly upregulated interleukin (IL)-6 and IL-8 in RA peripheral blood mononuclear cells (PBMCs), RA synovial fluid mononuclear cells (SFMCs) and RA synovial explant cultures (P < 0.05). OPN301 significantly decreased Pam3CSK4-induced cytokine production of tumour necrosis factor alpha (TNF-α), IL-1β, IL-6, interferon (IFN)-γ and IL-8 compared to IgG control in RA PBMCs and SFMCs cultures (all P < 0.05). OPN301 penetration of RA synovial tissue cultures was detected in the lining layer and perivascular regions. OPN301 significantly decreased spontaneous cytokine production of TNF-α, IL-1β, IFN-γ and IL-8 from RA synovial tissue explant cultures (all P < 0.05). Importantly, the inhibitory effect of OPN on spontaneous cytokine secretion was comparable to inhibition by anti-TNFα monoclonal antibody adalimumab.ConclusionsThese findings further support targeting TLR2 as a potential therapeutic agent for the treatment of RA.

Acute Serum Amyloid A Induces Migration, Angiogenesis, and Inflammation in Synovial Cells In Vitro and in a Human Rheumatoid Arthritis/SCID Mouse Chimera Model

Serum amyloid A (A-SAA), an acute-phase protein with cytokine-like properties, is expressed at sites of inflammation. This study investigated the effects of A-SAA on chemokine-regulated migration and angiogenesis using rheumatoid arthritis (RA) cells and whole-tissue explants in vitro, ex vivo, and in vivo. A-SAA levels were measured by real-time PCR and ELISA. IL-8 and MCP-1 expression was examined in RA synovial fibroblasts, human microvascular endothelial cells, and RA synovial explants by ELISA. Neutrophil transendothelial cell migration, cell adhesion, invasion, and migration were examined using transwell leukocyte/monocyte migration assays, invasion assays, and adhesion assays with or without anti-MCP-1/anti-IL-8. NF-kappaB was examined using a specific inhibitor and Western blotting. An RA synovial/SCID mouse chimera model was used to examine the effects of A-SAA on cell migration, proliferation, and angiogenesis in vivo. High expression of A-SAA was demonstrated in RA patients (p < 0.05). A-SAA induced chemokine expression in a time- and dose-dependent manner (p < 0.05). Blockade with anti-scavenger receptor class B member 1 and lipoxin A4 (A-SAA receptors) significantly reduced chemokine expression in RA synovial tissue explants (p < 0.05). A-SAA induced cell invasion, neutrophil-transendothelial cell migration, monocyte migration, and adhesion (all p < 0.05), effects that were blocked by anti-IL-8 or anti-MCP-1. A-SAA-induced chemokine expression was mediated through NF-kappaB in RA explants (p < 0.05). Finally, in the RA synovial/SCID mouse chimera model, we demonstrated for the first time in vivo that A-SAA directly induces monocyte migration from the murine circulation into RA synovial grafts, synovial cell proliferation, and angiogenesis (p < 0.05). A-SAA promotes cell migrational mechanisms and angiogenesis critical to RA pathogenesis.

High-density lipoproteins downregulate CCL2 production in human fibroblast-like synoviocytes stimulated by urate crystals

IntroductionTo investigate whether monosodium urate (MSU) crystals induce the production of CCL2 (monocyte chemoattractant protein-1; MCP-1) in human fibroblast-like synoviocytes (FLS) and whether this mechanism would be affected by high-density lipoproteins (HDL).MethodsHuman FLS isolated from synovial tissue explants were stimulated with MSU crystals (0.01 to 0.5 mg/ml) or interleukin (IL)-1β (10 pg/ml) in the presence or absence of HDL (50 and 100 μg/ml). The production and expression of CCL2 was evaluated with ELISA, confocal microscopy, immunofluorescence microscopy, chemotaxis assay, and real-time quantitative PCR.ResultsExposure of FLS to MSU crystals induced CCL2 accumulation in culture medium in a dose- and time-dependent manner, reaching a plateau at 50 to 75 μg/ml MSU crystals and 20 to 24 hours. Although low, the induced CCL2 levels were sufficient to trigger mononuclear cell migration. In resting FLS, CCL2 was localized in small cytoplasmic vesicles whose number diminished with MSU crystal stimulation. Concomitantly, MSU crystals triggered the induction of CCL2 mRNA expression. All these processes were inhibited by HDL, which cause a 50% decrease in CCL2 mRNA levels and a dose-dependent inhibition of the release of CCL2. Similar results were obtained when FLS were pretreated with HDL and washed before activation by MSU crystals or IL-1β, suggesting a direct effect of HDL on the FLS activation state.ConclusionsThe present results demonstrate that MSU crystals induce FLS to release CCL2 that is stored in vesicles in resting conditions. This mechanism is inhibited by HDL, which may limit the inflammatory process by diminishing CCL2 production and, in turn, monocytes/macrophages recruitment in joints. This study confirms the antiinflammatory functions of HDL, which might play a part in the limitation of acute gout attack.

When Selecting an Adeno‐associated Viral Vector Serotype, Cell Monolayer Transduction Efficiency Does Not Accurately Predict Tissue Transduction Efficiency in Equine Synovial Tissues

Low transduction efficiency of synovial tissues is a key concern in osteoarthritis gene therapy approaches. To determine the most efficient gene transfer strategy for effective in‐situ treatment of articular tissues, eight adeno‐associated viral vector (AAV) serotypes were assessed in monolayer‐cultured equine synovial cells and synovial tissue explants. Of the eight serotypes tested at 1x102 genome copies (GC) per cell, AAV2/2 produced the highest transduction efficiency in monolayer‐cultured cells followed by vector AAV2/5. When GC per cell was increased 10‐fold, again vector AAV2/2 produced the highest transduction efficiency followed by vector AAV2/5. However, when the same candidate vectors were used to transduce freshly‐collected synovial tissue explants, the hierarchy in transduction efficiency had changed. At approximately 3x102 GC per cell, vector AAV2/6.2 now produced the highest transduction efficiency followed by vector AAV2/5. When the GC per cell was increased 10‐fold, again vector AAV2/6.2 produced the highest transduction efficiency followed by vector AAV2/5. We conclude that vector AAV2/6.2 appears to be a superior vector for transduction of fibrous synovial joint tissues and that cell monolayer transduction efficiency does not accurately predict tissue transduction efficiency. Research support was provided by Brushwood Stables.

Human rheumatoid arthritis tissue production of IL-17A drives matrix and cartilage degradation: synergy with tumour necrosis factor-alpha, Oncostatin M and response to biologic therapies.

IntroductionThe aim of this study was to examine IL-17A in patients, following anti-TNF-α therapy and the effect of IL-17A on matrix turnover and cartilage degradation.MethodsIL-17A expression was examined by ELISA and immunohistology in the rheumatoid arthritis (RA) joints. RA whole synovial tissue explant (RA ST), primary synovial fibroblasts (RASFC), human cartilage and chondrocyte cultures were stimulated with IL-17A +/- TNF-α and Oncostatin M (OSM). Matrix metalloproteinase (MMP) and tissue inhibitor (TIMP-1) were assessed by ELISA and zymography. Cartilage proteoglycan release was assessed histologically by Safranin-O staining. Clinical parameters, IL-17A, MMP/TIMP were assessed in patients pre/post biologic therapy.ResultsIL-17A levels were higher in RA vs osteoarthritis (OA)/normal joints (P < 0.05). IL-17A up-regulated MMP-1, -2, -9, and -13 in RA ST, RASFC, cartilage and chondrocyte cultures (P < 0.05). In combination with TNF-α and OSM, IL-17A shifted the MMP:TIMP-1 ratio in favor of matrix degradation (all P < 0.05). Cartilage proteoglycan depletion in response to IL-17A was mild; however, in combination with TNF-α or OSM showed almost complete proteoglycan depletion. Serum IL-17A was detected in 28% of patients commencing biologic therapy. IL-17A negative patients demonstrated reductions post therapy in serum MMP1/TIMP4, MMP3/TIMP1 and MMP3/TIMP4 ratios and an increase in CS846 (all P < 0.05). No significant changes were observed in IL-17A positive patients.ConclusionsIL-17A is produced locally in the inflamed RA joint. IL-17A promotes matrix turnover and cartilage destruction, especially in the presence of other cytokines, mimicking the joint environment. IL-17A levels are modulated in vivo, following anti-TNF therapy, and may reflect changes in matrix turnover.

Hyaluronan Suppresses IL-1β-induced Metalloproteinase Activity from Synovial Tissue

Intraarticular injection of hyaluronan (viscosupplementation) is commonly used to treat knee pain from osteoarthritis. The therapeutic benefit might derive from hyaluronan inhibition of the activity of the cytokine-regulated catabolic enzymes that attack joint cartilage (matrix metalloproteinases). We tested the hypothesis that hyaluronan inhibited interleukin-1beta-induced matrix metalloproteinase activity secreted by explants of synovial tissue from patients with osteoarthritis and investigated the mechanism of the effect. Hyaluronan with a molecular mass of 12.8 MDa (number average) antagonized induced metalloproteinase activity in proportion to hyaluronan concentration in the clinically relevant range of 2 to 8 mg/mL. The effect was not attributable solely to molecular mass because 1.2-MDa hyaluronan produced comparable inhibition. Based on measurements involving hyaluronans of different average molecular masses, polydispersity and viscosity were similarly ruled out as primary responsible factors. The effect of hyaluronan on induced metalloproteinase activity was mediated partially by CD44, the principal cell surface receptor for hyaluronan. Hyaluronan inhibited interleukin-1beta-induced metalloproteinase production from osteoarthritic synovial tissue by a process that was not solely dependent on hyaluronan molecular mass but that was partly mediated by hyaluronan binding to CD44. The efficacy of viscosupplementation could be explained if hyaluronan also blocked catabolic enzyme activity in the joint.