Synovial tissue protease gene expression and joint erosions in early rheumatoid arthritis

Synovial biopsy for establishing a definite diagnosis in undifferentiated chronic knee monoarthritis

BACKGROUND

Undifferentiated arthritis is a condition in which the problem cannot be classified into any definite diagnosis category. Various methods have been suggested to clarify the definite diagnosis in this class. The synovial biopsy is suggested as the last diagnostic approach to determine the precise histopathological diagnosis. In this study, we aimed to evaluate the efficacy of synovial biopsy for establishing a definite diagnosis in patients with undifferentiated chronic knee monoarthritis.

METHODS

The present retrospective case series was conducted in 2005 in the rheumatology research center of Shariati hospital and the 501 hospital in Tehran, Iran. The study included the synovial biopsy of patients with chronic knee monoarthritis who did not have a definite diagnosis after all the diagnostic steps before the synovial biopsy. Pathology slides of the patients' synovial biopsy were reevaluated with a senior expert pathologist.

RESULTS

Eighty patients with a mean age of 37.6 ± 17.32 years (range: 6-68) were included, of whom 50% were female. The gap time between the onset of knee monoarthritis and the decision-making for synovial biopsy was 14.34 ± 19.61 months. Histopathologic evaluations revealed non-specific synovitis in 65% of the patients and a definite diagnosis in 35%. The most common definite diagnosis was rheumatoid arthritis (9%), followed by septic arthritis (5%). The most common pathologic findings were endothelial proliferation (89%) and synovial proliferation (88%), and the most common infiltrating cell was lymphocyte (54%). Patients with non-specific synovitis were more likely to have neovascularization, cellular infiltration (p-value < 0.001), synovial proliferation, endothelial proliferation (p-value = 0.001), pannus formation (p-value = 0.009), and fibrosis (p-value = 0.022) compared to the patients with a definite pathologic diagnosis. However, age, gender, and the gap time between disease symptoms to synovial biopsy were not significantly different between the different groups of diagnosis (p-value > 0.05).

CONCLUSION

Non-specific synovitis remains the most common histopathologic finding, highlighting the importance of physician expert opinion for most of the patients with undifferentiated chronic knee monoarthritis. Studies with larger samples and immunohistochemistry analyses are needed to clarify this uncategorized entity further.

Disease status in human and experimental arthritis, and response to TNF blockade, is associated with MHC class II invariant chain (CD74) isoform expression

Splice variants of CD74 differentially modulate the activity of cathepsin L (CTSL). As CD74 and CTSL participate in the pathogenesis of inflammatory diseases such as rheumatoid arthritis (RA), we determined whether splice variants of CD74 could be biomarkers of disease activity. Gene expression was measured in mice with collagen-induced arthritis using quantitative PCR (qPCR). In vitro studies using murine macrophage/DC-lineage cells determined the relative influence of macrophage phenotype on isoform expression and the potential to produce CTSL in response to TNF. CD74 splice variants were measured in human RA synovium and RA patients' monocytes. In arthritic mice, the expression of the p41 CD74 isoform was significantly higher in severely affected paws compared with unaffected paws or the paws of naïve mice; the p41 isoform significantly correlated with the expression of TNF in arthritic paws. Compared with M2-like macrophages, M1-like macrophages expressed increased levels of CD74 and had higher expression, secretion and activity of CTSL. RA patients that responded to TNF blockade had significantly higher expression levels of CD74 in circulating monocytes after treatment, compared with non-responders. The expression of the human CD74 isoform a was significantly higher in RA synovia, compared with osteoarthritis synovia, and was associated with CSTL enzymatic activity. This study is the first to demonstrate differential expression of the CD74 p41 isoform in an auto-immune disorder and in response to therapy. The differential expression of CD74 splice variants indicates an association, and potentially a mechanistic role, in the pathogenesis of RA.

The Expression of Inflammasomes NLRP1 and NLRP3, Toll-Like Receptors, and Vitamin D Receptor in Synovial Fibroblasts From Patients With Different Types of Knee Arthritis

Activated rheumatoid arthritis (RA) synovial fibroblasts (SFs) are among the most important cells promoting RA pathogenesis. They are considered active contributors to the initiation, progression, and perpetuation of the disease; therefore, early detection of RASF activation could advance contemporary diagnosis and adequate treatment of undifferentiated early inflammatory arthritis (EA). In this study, we investigated the expression of nucleotide-binding, oligomerization domain (NOD)-like receptor family, pyrin domain containing (NLRP)1, NLRP3 inflammasomes, Toll-like receptor (TLR)1, TLR2, TLR4, vitamin D receptor (VDR), and secretion of matrix metalloproteinases (MMPs) in SFs isolated from patients with RA, osteoarthritis (OA), EA, and control individuals (CN) after knee surgical intervention. C-reactive protein, general blood test, anticyclic citrullinated peptide (anti-CCP), rheumatoid factor (RF), and vitamin D (vitD) in patients’ sera were performed. Cells were stimulated or not with 100 ng/ml tumor necrosis factor alpha (TNF-α) or/and 1 nM or/and 0.01 nM vitamin D3 for 72 h. The expression levels of NLRP1, NLRP3, TLR1, TLR2, TLR4, and VDR in all examined SFs were analyzed by quantitative real-time PCR (RT-qPCR). Additionally, the secretion of IL-1β by SFs and MMPs were determined by ELISA and Luminex technology. The expression of NLRP3 was correlated with the levels of CRP, RF, and anti-CCP, suggesting its implication in SF inflammatory activation. In the TNF-α-stimulated SFs, a significantly lower expression of NLRP3 and TLR4 was observed in the RA group, compared with the other tested forms of arthritis. Moreover, upregulation of NLRP3 expression by TNF-α alone or in combination with vitD3 was observed, further indicating involvement of NLRP3 in the inflammatory responses of SFs. Secretion of IL-1β was not detected in any sample, while TNF-α upregulated the levels of secreted MMP-1, MMP-7, MMP-8, MMP-12, and MMP-13 in all patient groups. Attenuating effects of vitD on the expression of NLRP3, TLR1, and TLR4 suggest potential protective effects of vitD on the inflammatory responses in SFs. However, longer studies may be needed to confirm or fully rule out the potential implication of vitD in SF activation in inflammatory arthritis. Both VDR and NLRP3 in the TNF-α-stimulated SFs negatively correlated with the age of patients, suggesting potential age-related changes in the local inflammatory responses.

Circulating Biomarkers and Cardiac Structure and Function in Rheumatoid Arthritis

Background: Rheumatoid arthritis (RA) increases the risk for abnormalities of the cardiac structure and function, which may lead to heart failure (HF). Studying the association between circulating biomarkers and echocardiographic parameters is important to screen patients with RA with a higher risk of cardiac dysfunction.

Aim: To study the association between circulating biomarkers and echocardiographic parameters in patients with RA.

Methods: Echocardiography was performed in 355 patients with RA from RA Porto cohort and the associations between echocardiographic characteristics and 94 circulating biomarkers were assessed. These associations were also assessed in the Metabolic Road to Diastolic Heart Failure (MEDIA-DHF) [392 patients with HF with preserved ejection fraction (HFpEF)] and the Suivi Temporaire Annuel Non-Invasif de la Santé des Lorrains Assurés Sociaux (STANISLAS) (1,672 healthy population) cohorts.

Results: In the RA Porto cohort, mean age was 58 ± 13 years, 23% were males and mean RA duration was 12 ± 10 years. After adjustment and multiple testing correction, left ventricular mass index (LVMi), left atrial volume index (LAVi), and E/e′ were independently associated with biomarkers reflecting inflammation [i.e., bone morphogenetic protein 9 (BMP9), pentraxin-related protein 3 (PTX3), tumor necrosis factor receptor superfamily member 11a (TNFRSF11A)], extracellular matrix remodeling [i.e., placental growth factor (PGF)], congestion [i.e., N-terminal pro-brain natriuretic peptide (NT-proBNP), adrenomedullin (ADM)], and myocardial injury (e.g., troponin). Greater LVMi [hazard ratio (HR) (95% CI) per 1 g/m² = 1.03 (1.02–1.04), p < 0.001], LAVi [HR (95% CI) per 1 ml/m² = 1.03 (1.01–1.06), p < 0.001], and E/e′ [HR (95% CI) per 1 = 1.08 (1.04–1.13), p < 0.001] were associated with higher rates of cardiovascular events. These associations were externally replicated in patients with HFpEF and asymptomatic individuals.

Conclusion: Circulating biomarkers reflecting inflammation, extracellular matrix remodeling, congestion, and myocardial injury were associated with underlying alterations of cardiac structure and function. Biomarkers might be used for the screening of cardiac alterations in patients with RA.

Will rheumatologists ever pick up the arthroscope again?

Conditions prompting physicians and surgeons first adapting endoscopes to peer into joints were mainly the sort of synovial conditions that would concern today's rheumatologists. Rheumatologists were among the pre-World War II pioneers developing and documenting arthroscopy. The post-War father of modern arthroscopy, Watanabe, found rheumatologists among his early students, who took back the technique to their home countries, teaching orthopedists and rheumatologists alike. Rheumatologists described and analyzed the intra-articular features of their common diseases in the '60s and '70s. A groundswell of interest from academic rheumatologists in adapting arthroscopy grew considerably in the '90s with development of "needle scopes" that could be used in an office setting. Rheumatologists helped conduct the very trials the findings of which reduced demand for their arthroscopic services by questioning the efficacy of arthroscopic debridement in osteoarthritis (OA) and also developing biological compounds that greatly reduced the call for any resective intervention in inflammatory arthropathies. The arthroscope has proven an excellent tool for viewing and sampling synovium and continues to serve this purpose at several international research centers. While cartilage is now imaged mainly by magnetic resonance imaging, some OA features - such as a high prevalence of visible calcinosis - beg further arthroscopy-directed investigation. A new generation of "needle scopes" with far superior optics awaits future investigators, should they develop interest.

Proteinase-Mediated Macrophage Signaling in Psoriatic Arthritis

Objective

Multiple proteinases are present in the synovial fluid (SF) of an arthritic joint. We aimed to identify inflammatory cell populations present in psoriatic arthritis (PsA) SF compared to osteoarthritis (OA) and rheumatoid arthritis (RA), identify their proteinase-activated receptor 2 (PAR2) signaling function and characterize potentially active SF serine proteinases that may be PAR2 activators.

Methods

Flow cytometry was used to characterize SF cells from PsA, RA, OA patients; PsA SF cells were further characterized by single cell 3’-RNA-sequencing. Active serine proteinases were identified through cleavage of fluorogenic trypsin- and chymotrypsin-like substrates, activity-based probe analysis and proteomics. Fluo-4 AM was used to monitor intracellular calcium cell signaling. Cytokine expression was evaluated using a multiplex Luminex panel.

Results

PsA SF cells were dominated by monocytes/macrophages, which consisted of three populations representing classical, non-classical and intermediate cells. The classical monocytes/macrophages were reduced in PsA compared to OA/RA, whilst the intermediate population was increased. PAR2 was elevated in OA vs. PsA/RA SF monocytes/macrophages, particularly in the intermediate population. PAR2 expression and signaling in primary PsA monocytes/macrophages significantly impacted the production of monocyte chemoattractant protein-1 (MCP-1). Trypsin-like serine proteinase activity was elevated in PsA and RA SF compared to OA, while chymotrypsin-like activity was elevated in RA compared to PsA. Tryptase-6 was identified as an active serine proteinase in SF that could trigger calcium signaling partially via PAR2.

Conclusion

PAR2 and its activating proteinases, including tryptase-6, can be important mediators of inflammation in PsA. Components within this proteinase-receptor axis may represent novel therapeutic targets.

Anti-Inflammatory Effects of Melatonin and 5-Methoxytryptophol on Lipopolysaccharide-Induced Acute Pulpitis in Rats

Aim

The aim of this study was to investigate the possible therapeutic impacts of two pineal hormones, melatonin and 5-methoxytryptophol (5-MTX), in a rat model of acute pulpitis by analyzing biochemical and histopathological parameters.

Methods

This research was done using 32 male and female Wistar albino rats with weight between 200 and 250 g. The rats were randomly divided into four groups: a control group (rats without any treatment), acute pulpitis (AP) group, AP+melatonin group, and AP+5-MTX group. In the AP-induced groups, the crowns of the upper left incisors were removed horizontally. Lipopolysaccharide solution was applied to the exposed pulp tissue before the canal orifices were sealed with a temporary filling material. Melatonin (10 mg/kg) and 5-MTX (5 mg/kg) were administered intraperitoneally. The rats were sacrificed 24 hours after pulp injury, and trunk blood and pulp samples were collected. The concentrations of TNF-α, IL-1β, MMP-1, and MMP-2 in sera and pulp samples were determined using ELISA assay kits.

Results

TNF-α, IL-1β, MMP-1, and MMP-2 levels in the serum and pulp tissues were considerably higher in the AP group than the control group (p < 0.01‐0.001). In the AP+melatonin and AP+5-MTX groups, TNF-α, IL-1β, MMP-1, and MMP-2 levels in the serum and pulp tissues were significantly lower than in the AP group (p < 0.05‐0.001).

Conclusions

Both melatonin and 5-MTX provided protective effects on acute pulpitis, which indicates they may be promising as a therapeutic strategy for oral disease.

Cadmium Toxicity on Chondrocytes and the Palliative Effects of 1α, 25-Dihydroxy Vitamin D3 in White Leghorns Chicken's Embryo

Cadmium (Cd) can causes osteoporosis and joint swelling. However, the mechanism of Cd toxicity in chondrocytes and how to alleviate Cd poisoning to chondrocytes are still unclear. Herein, we evaluated the toxicity of Cd to chicken chondrocytes, and whether vitamin D can relieve the toxicity of Cd to chondrocytes. Primary chondrocytes were collected from knee-joint cartilage of 15-day-old chicken embryos. They were treated with (0, 1, 2, and 4) μM Cd alone, 10^-8 M 1α,25-(OH)₂D₃ alone, or 2 μM Cd combined with 10^-8 M 1α,25-(OH)₂D₃. We found that Cd significantly inhibited Sox9 and ACAN mRNA expression, which are markers for chondrocyte differentiation, downregulated the mitochondrial membrane potential, upregulated the Bax/B-cell lymphoma 2 ratio. Furthermore, Cd significantly promoted matrix metalloproteinase (MMP)-9 expression, thus accelerating the degradation of extracellular matrix. And Cd also inhibited the expression of main macromolecular protein of extracellular matrix, Collagen type IIα1 (COL2A1) and acid mucopolysaccharide. However, 1α,25-(OH)₂D₃ pretreatment significantly alleviated the toxicity effects of Cd on the differentiation, apoptosis and extracellular matrix gene expression in primary chondrocytes. Conclusively, Cd exposure could inhibited chicken embryo chondrocytes differentiation, extracellular matrix gene expression, and induced chondrocyte apoptosis. However, these toxic effects of Cd are alleviated by the pretreatment of chondrocytes with 1α,25-(OH)₂D₃.

A novel indomethacin/methotrexate/MMP-9 siRNA in situ hydrogel with dual effects of anti-inflammatory activity and reversal of cartilage disruption for the synergistic treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammatory cell infiltration, and cartilage and bone disruption, which ultimately leads to loss of joint function. Current treatments for RA only focus on anti-inflammatory activity but neglect to prevent further damage to articular cartilage and bone. Here we attempted to co-deliver indomethacin (IND), methotrexate (MTX) and a small-interfering RNA targeting MMP-9 using an in situ hydrogel loaded with PEI-SS-IND-MTX-MMP-9 siRNA nanoparticles (D/siRNA-NGel) to treat RA synergistically and comprehensively. IND, MTX and MMP-9 siRNA were able to escape from the endosome and down-regulate the expression of MMP-9 and inflammatory cytokines of Raw-264.7 cells. After intra-articular injection in arthritic mice, the D/siRNA-NGel effectively relieved joint swelling and significantly reduced the expression of TNF-α, IL-6 and MMP-9 in the ankle fluid, knee joint fluid and plasma of RA mice without causing any side effects. Most importantly, the co-delivery system restored the morphological parameters of the ankle joints close to normal. The D/siRNA-NGel could achieve good anti-inflammatory activity and reverse cartilage disruption through a synergistic effect between chemical drugs and MMP-9 siRNA. This co-delivery system should have promising applications in the treatment of rheumatoid arthritis and other metabolic bone diseases which cause serious bone erosion.

The association between synovial fluid serine proteinase activity and response to intra-articular corticosteroid injection in psoriatic arthritis

INTRODUCTION/OBJECTIVES

Intra-articular corticosteroid (IAS) injections are often used for the immediate relief of pain and inflammation in the joint of psoriatic arthritis (PsA) patients. However, studies identifying factors that predict response to the IAS injections are lacking. We aimed to assess the usefulness of serine proteinase activity measurements in PsA synovial fluid (SF) samples obtained at the time of injection in predicting clinical response.

METHODS

The PsA patients with available SF samples from the knee joint were identified from the University of Toronto PsA cohort. Clinical response was defined as an absence of tenderness or swelling in the injected joint at the first post-injection visit, at either 3 or 6 months. SF proteinase activity was determined by measuring cleavage of fluorogenic tri-peptide substrates for trypsin-like (VPR-AMC and VLK-AMC) and chymotrypsin-like (AAPF-AMC) serine proteinases. Generalized estimating equation (GEE) models were used to investigate factors associated with response.

RESULTS

A total of 32 patients with 60 injected joints and data available for follow-up at 3 or 6 months were included in the analysis, with 25 (41.7%) injected joints resulting in clinical response. Age, sex, active joint count, systemic medications and SF serine proteinase activity at the time of injection were included as covariates. Only treatment with biologics was significantly associated with response at 3 or 6 months in the multivariate reduced model (OR 3.02, p = 0.027).

CONCLUSIONS

We could not demonstrate an association between SF serine proteinase activity and response to IAS injection. Biologic agents significantly improve the likelihood of achieving clinical response.

Proteinases and their receptors in inflammatory arthritis: an overview

Proteinases are enzymes with established roles in physiological and pathological processes such as digestion and the homeostasis, destruction and repair of tissues. Over the past few years, the hormone-like properties of circulating proteinases have become increasingly appreciated. Some proteolytic enzymes trigger cell signalling via proteinase-activated receptors, a family of G protein-coupled receptors that have been implicated in inflammation and pain in inflammatory arthritis. Proteinases can also regulate ion flux owing to the cross-sensitization of transient receptor potential cation channel subfamily V members 1 and 4, which are associated with mechanosensing and pain. In this Review, the idea that proteinases have the potential to orchestrate inflammatory signals by interacting with receptors on cells within the synovial microenvironment of an inflamed joint is revisited in three arthritic diseases: osteoarthritis, spondyloarthritis and rheumatoid arthritis. Unanswered questions are highlighted and the therapeutic potential of modulating this proteinase-receptor axis for the management of disease in patients with these types of arthritis is also discussed.

Cathepsin G and Its Role in Inflammation and Autoimmune Diseases

Cathepsin G belongs to the neutrophil serine proteases family, known for its function in killing pathogens. Studies over the past several years indicate that cathepsin G has important effects on inflammation and immune reaction, and may be a key factor in the pathogenesis of some autoimmune diseases. In this article, we discuss the roles of cathepsin G in inflammation, immune reaction, and autoimmune diseases. To our knowledge, this is the first study providing important information about cathepsin G in the pathogenesis of autoimmune diseases and suggesting that cathepsin G may be a new biomarker or treatment target.

The clinical utility of gene expression examination in rheumatology

Rheumatoid arthritis (RA) is a chronic inflammatory disease with unknown etiology that affects various pathways within the immune system, involves many other tissues and is associated with pain and joint destruction. Current treatments fail to address pathophysiological and biochemical mechanisms involved in joint degeneration and the induction of pain. Moreover, RA patients are extremely heterogeneous and require specific treatments, the choice of which is complicated by the fact that not all patients equally respond to therapy. Gene expression analysis offer tools for patient management and personalization of patient’s care to meet individual needs in controlling inflammation and pain and delaying joint destruction.

Proprotein convertase subtilisin/kexin type 6 promotes in vitro proliferation, migration and inflammatory cytokine secretion of synovial fibroblast‑like cells from rheumatoid arthritis via nuclear‑κB, signal transducer and activator of transcription 3 and extracellular signal regulated 1/2 pathways

Our previous studies demonstrated that expression of proprotein convertase subtilisin/kexin type 6 (PCSK6) is greatly enhanced in rheumatoid arthritis fibroblast‑like synoviocytes (RASFs), and that PCSK6 inhibition decreases cell proliferation, migration and invasion. The present study aimed to investigate the functional role of PCSK6 in the hyperplasia of RASFs. Cultured RASFs from RA patients were stimulated with recombinant human (rh)PCSK6. Subsequent changes in proliferation, invasion, migration and the secretion of inflammatory cytokines were measured in vitro using MTT, wound healing and Transwell assays, and ELISA. Cell cycle and apoptosis were analyzed by flow cytometry. Influence on downstream gene expression levels were analyzed using reverse transcription‑quantitative polymerase chain reaction. Specific signaling pathways responsible for these effects were analyzed using western blotting and confirmed with pathway‑specific inhibitors. It was demonstrated that rhPCSK6 significantly increased RASF cell invasion, migration and proliferation, which was influenced through both reduced cell cycle arrest and reduced apoptosis. Furthermore, rhPCSK6 stimulated RASFs to secrete the inflammatory cytokines interleukin (IL)‑1α, IL‑1β and IL‑6, and exhibit altered expression of genes involved in angiogenesis, hypoxia, proliferation and inflammation. These cellular effects were mediated via the nuclear factor (NF)‑κB, signal transducer and activator of transcription 3 (STAT3) and extracellular signal regulated (ERK)1/2 signaling pathways. The results demonstrated that signaling via NF‑κB and STAT3 mediated cell cycle arrest, and signaling through NF‑κB mediated apoptosis in RASF cells stimulated with PCSK6. PCSK6 can activate NF‑κB, STAT3 and ERK1/2 signaling pathways in vitro to enhance cell proliferation, migration, invasion and inflammation in RASF cells. These findings suggest that PCSK6 may be an important therapeutic target in RA.

Structural cartilage damage attracts circulating rheumatoid arthritis synovial fibroblasts into affected joints

BACKGROUND

Rheumatoid arthritis synovial fibroblasts (RASFs) are known to travel via the bloodstream from sites of cartilage destruction to new locations where they reinitiate the destructive processes at distant articular cartilage surfaces. In this study, we examined the role of interleukin (IL)-1-induced cartilage changes and their chemotactic effect on RASF transmigratory capacity.

METHODS

To investigate synovial fibroblast (SF) transmigration through endothelial layers, we used a modified Boyden chamber with an endothelioma cell layer (bEnd.5) as a barrier and IL-1-treated murine cartilage explants as a chemotactic stimulus for SFs from human tumor necrosis factor-transgenic (hTNFtg) mice. We injected recombinant IL-1 or collagenase into knee joints of wild-type mice, followed by tail vein injection of fluorescence-labeled hTNFtg SFs. The distribution and intensity of transmigrating hTNFtg SFs were measured by fluorescence reflectance imaging with X-ray coregistration. Toluidine blue staining was performed to evaluate the amount of cartilage destruction.

RESULTS

Histomorphometric analyses and in vivo imaging revealed a high degree of cartilage proteoglycan loss after intra-articular IL-1 and collagenase injection, accompanied by an enhanced in vivo extravasation of hTNFtg SFs into the respective knee joints, suggesting that structural cartilage damage contributes significantly to the attraction of hTNFtg SFs into these joints. In vitro results showed that degraded cartilage was directly responsible for the enhanced transmigratory capacity because stimulation with IL-1-treated cartilage, but not with IL-1 or cartilage alone, was required to increase hTNFtg SF migration.

CONCLUSIONS

The present data indicate that structural cartilage damage facilitates the migration of arthritic SF into affected joints. The prevention of early inflammatory cartilage damage may therefore help prevent the progression of rheumatoid arthritis and its spread to previously unaffected joints.

Lack of association of matrix metalloproteinase-3 gene polymorphism with susceptibility to rheumatoid arthritis: a meta-analysis

Background

Epidemiological studies have investigated the association between matrix metalloproteinase-3(MMP-3) gene-1171 5A/6A polymorphism and rheumatoid arthritis (RA), but the results were inconsistent. To evaluate the specific relationship, we performed a meta-analysis to clarify the controversies.

Methods

The relevant literatures dated to December 07th 2013 were retrieved from PubMed, EMBASE and the China National knowledge Infrastructure (CNKI) databases. The number of the alleles and genotypes for MMP-3 were obtained. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to estimate the association between MMP-3 5A/6A promoter polymorphism and RA. All of the statistical analyses were conducted by STATA11.0 software.

Results

A total of 6 case-control studies covering 1451 cases and 1239 controls were included in the final meta-analysis. There was no significant association between MMP-3 5A/6A promoter polymorphism and RA in all genetic models (for 6A versus 5A: OR = 1.19, 95% CI = 0.91-1.56, P = 0.203; 5A/6A versus 5A/5A: OR = 1.31, 95% CI = 0.89-1.92, P = 0.174; 6A/6A versus 5A/5A: OR = 1.78, 95% CI = 0.68-4.61, P = 0.238; the recessive model: OR = 1.48, 95% CI = 0.88-2.47, P = 0.141; and the dominant model: OR = 1.46, 95% CI = 0.71-3.00, P = 0.299). In the subgroup analysis by ethnicity, we obtained the similar results.

Conclusions

We systematically investigate the association between MMP-3-1171 5A/6A polymorphism and RA susceptibility; however, the results show a lack of correlation. Considering the small sample size and the selection bias existed in some studies, further studies are needed to confirm the findings.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-376) contains supplementary material, which is available to authorized users.

Patients with rheumatoid arthritis in clinical remission manifest persistent joint inflammation on histology and imaging studies

OBJECTIVE

The purpose of our study was to test the hypothesis that synovitis on magnetic resonance imaging (MRI) and ultrasound (US) observed in patients with rheumatoid arthritis (RA) who meet remission criteria reflects active inflammation on histopathology.

METHODS

We analyzed 15 synovial specimens obtained during surgical procedures from 14 patients with RA in clinical remission as defined by the American College of Rheumatology criteria. Histological specimens were scored for hyperplasia of synovial lining and synovial stroma, inflammation, lymphoid follicles, and vascularity. The histology scores were classified as minimal, mild, moderate, or severe disease activity. US and MRI performed within a 4-month period of surgery were scored for disease activity. The correlation between histology and imaging scores was examined.

RESULTS

Four of 14 patients were receiving anti-tumor necrosis factor (TNF) therapy, 4 were receiving methotrexate (MTX) alone, 4 were taking MTX and hydroxychloroquine (HCQ), and 1 was taking HCQ and sulfasalazine. Four specimens had severe, 6 moderate, 3 mild, and 2 minimal disease activity on histology. Three of 4 specimens with minimal and mild histology were observed in subjects receiving anti-TNF therapy. Synovitis was noted on greyscale in 80% of joints and Doppler signal in 60%. MRI demonstrated synovitis and bone marrow edema in 86% of images. Positive but not significant correlations were noted between histology and synovitis scores on US.

CONCLUSION

Despite clinical remission, histology and imaging studies documented a persistently active disease state that may explain the mechanism for radiographic progression.

Endogenous MMP-9 and not MMP-2 promotes rheumatoid synovial fibroblast survival, inflammation and cartilage degradation

OBJECTIVE

The aim of this study was to investigate the effect of endogenous matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) on the invasive characteristics of RA synovial fibroblasts.

METHODS

Synovial fibroblasts isolated from patients with RA or OA were treated with MMP small interfering RNA (siRNA), inhibitors and recombinant proteins or TNF-α, with or without cartilage explants. Cell viability and proliferation were measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide and 5-bromo-2-deoxyuridine (BrdU) proliferation assays, respectively; apoptosis by an in situ cell death detection kit; migration and invasion by CytoSelect invasion assay, scratch migration and collagen gel assays; cartilage degradation by 1,9-dimethylmethylene blue assay; and inflammatory mediators and MMPs by ELISA, western blot and zymography.

RESULTS

MMP-2 was expressed by both OA and RA synovial fibroblasts, whereas only RA synovial fibroblasts expressed MMP-9. Suppressing MMP-2 or MMP-9 reduced RA synovial fibroblast proliferation equally. However, MMP-9 siRNA had greater effects compared with MMP-2 siRNA on promoting apoptosis and suppressing RA synovial fibroblast viability, migration and invasion. Suppression/inhibition of MMP-9 also decreased the production of IL-1β, IL-6, IL-8 and TNF-α, inactivated nuclear factor κB (NF-κB), extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) and suppressed RA synovial fibroblast-mediated cartilage degradation. In contrast, suppression/inhibition of MMP-2 stimulated TNF-α and IL-17 secretion and activated NF-κB, while recombinant MMP-2 (rMMP-2) inactivated NF-κB and suppressed RA synovial fibroblast-mediated cartilage degradation. Results using specific inhibitors and rMMPs provided supportive evidence for the siRNA results.

CONCLUSION

Endogenous MMP-2 or MMP-9 contribute to RA synovial fibroblast survival, proliferation, migration and invasion, with MMP-9 having more potent effects. Additionally, MMP-9 stimulates RA synovial fibroblast-mediated inflammation and degradation of cartilage, whereas MMP-2 inhibits these parameters. Overall, our data indicate that MMP-9 derived from RA synovial fibroblasts may directly contribute to joint destruction in RA.

Mast cell-restricted, tetramer-forming tryptases induce aggrecanolysis in articular cartilage by activating matrix metalloproteinase-3 and -13 zymogens

Mouse mast cell protease (mMCP)-6-null C57BL/6 mice lost less aggrecan proteoglycan from the extracellular matrix of their articular cartilage during inflammatory arthritis than wild-type (WT) C57BL/6 mice, suggesting that this mast cell (MC)-specific mouse tryptase plays prominent roles in articular cartilage catabolism. We used ex vivo mouse femoral head explants to determine how mMCP-6 and its human ortholog hTryptase-β mediate aggrecanolysis. Exposure of the explants to recombinant hTryptase-β, recombinant mMCP-6, or lysates harvested from WT mouse peritoneal MCs (PMCs) significantly increased the levels of enzymatically active matrix metalloproteinases (MMP) in cartilage and significantly induced aggrecan loss into the conditioned media, relative to replicate explants exposed to medium alone or lysates collected from mMCP-6-null PMCs. Treatment of cartilage explants with tetramer-forming tryptases generated aggrecan fragments that contained C-terminal DIPEN and N-terminal FFGVG neoepitopes, consistent with MMP-dependent aggrecanolysis. In support of these data, hTryptase-β was unable to induce aggrecan release from the femoral head explants obtained from Chloe mice that resist MMP cleavage at the DIPEN↓FFGVG site in the interglobular domain of aggrecan. In addition, the abilities of mMCP-6-containing lysates from WT PMCs to induce aggrecanolysis were prevented by inhibitors of MMP-3 and MMP-13. Finally, recombinant hTryptase-β was able to activate latent pro-MMP-3 and pro-MMP-13 in vitro. The accumulated data suggest that human and mouse tetramer-forming tryptases are MMP convertases that mediate cartilage damage and the proteolytic loss of aggrecan proteoglycans in arthritis, in part, by activating the zymogen forms of MMP-3 and MMP-13, which are constitutively present in articular cartilage.

Nuclear receptors in bone physiology and diseases

During the last decade, our view on the skeleton as a mere solid physical support structure has been transformed, as bone emerged as a dynamic, constantly remodeling tissue with systemic regulatory functions including those of an endocrine organ. Reflecting this remarkable functional complexity, distinct classes of humoral and intracellular regulatory factors have been shown to control vital processes in the bone. Among these regulators, nuclear receptors (NRs) play fundamental roles in bone development, growth, and maintenance. NRs are DNA-binding transcription factors that act as intracellular transducers of the respective ligand signaling pathways through modulation of expression of specific sets of cognate target genes. Aberrant NR signaling caused by receptor or ligand deficiency may profoundly affect bone health and compromise skeletal functions. Ligand dependency of NR action underlies a major strategy of therapeutic intervention to correct aberrant NR signaling, and significant efforts have been made to design novel synthetic NR ligands with enhanced beneficial properties and reduced potential negative side effects. As an example, estrogen deficiency causes bone loss and leads to development of osteoporosis, the most prevalent skeletal disorder in postmenopausal women. Since administration of natural estrogens for the treatment of osteoporosis often associates with undesirable side effects, several synthetic estrogen receptor ligands have been developed with higher therapeutic efficacy and specificity. This review presents current progress in our understanding of the roles of various nuclear receptor-mediated signaling pathways in bone physiology and disease, and in development of advanced NR ligands for treatment of common skeletal disorders.

Association of circulating levels of MMP-8 with mortality from respiratory disease in patients with rheumatoid arthritis

Introduction

Matrix metalloproteinases (MMPs) are implicated in the destruction of the joint and have been shown to be strongly associated with inflammation in rheumatoid arthritis (RA). Circulating MMPs have also been associated with cardiovascular disease in the general population, and are predictive of cardiovascular mortality. The purpose of the present study was to determine whether circulating levels of MMPs are predictive of mortality in RA.

Methods

A multiplex suspension array system (Luminex^®) was used to measure levels of MMPs (1, 2, 3, 8 and 9) in sera taken at recruitment of RA patients (n = 487) in a study of factors associated with mortality in RA. Patients were tracked on the National Health Service Central Register for notification of death, and the relationship between baseline MMP levels and mortality was analysed using Cox proportional hazards regression analysis.

Results

At the time of follow-up, 204/486 patients had died, of which 94 (46.1%) had died of circulatory diseases, 49 of malignancy (24.0%), and 42 (20.6%) of respiratory diseases. In a stepwise analysis which included all MMPs, only MMP-8 was significantly associated with all cause mortality (P = 0.0007, 0.6% hazard ratio increase per ng/ml). No association was found between MMP levels and mortality due to circulatory disease or malignancy. However MMP-8 levels were strongly associated with mortality due to respiratory disease (P < 0.0001, 1.3% hazard ratio increase per ng/ml). The association with respiratory disease related mortality remained highly significant in multivariate models which included smoking as well as markers of severity and disease activity such as rheumatoid factor, nodular disease, and C-reactive protein (CRP).

Conclusions

The serum level of MMP-8 is a strong predictor of mortality in RA, especially that due to respiratory disease. This finding is consistent with increased activation of neutrophils in RA and identifies serum MMP-8 as a useful marker for increased risk of premature death.

The inhibition of hyaluronan degradation reduced pro-inflammatory cytokines in mouse synovial fibroblasts subjected to collagen-induced arthritis

Hyaluronan (HA) degradation produces small oligosaccharides that are able to increase pro-inflammatory cytokines in rheumatoid arthritis synovial fibroblasts (RASF) by activating both CD44 and the toll-like receptor 4 (TLR-4). CD44 and TLR-4 stimulation in turn activate the NF-kB that induces the production of pro-inflammatory cytokines. Degradation of HA occurs via two mechanisms: one exerted by reactive oxygen species (ROS) and one controlled by different enzymes in particular hyaluronidases (HYALs). We aimed to investigate the effects of inhibiting HA degradation (which prevents the formation of small HA fragments) on synovial fibroblasts obtained from normal DBA/J1 mice (NSF) and on synovial fibroblasts (RASF) obtained from mice subjected to collagen induced arthritis (CIA), both fibroblast types stimulated with tumor necrosis factor alpha (TNF-α). TNF-α stimulation produced high mRNA expression and the related protein production of CD44 and TLR-4 in both NSF and RASF, and activation of NF-kB was also found in all fibroblasts. TNF-α also up-regulated the inflammatory cytokines, interleukin-1beta (IL-1beta) and interleukin-6 (IL-6), and other pro-inflammatory mediators, such as matrix metalloprotease-13 (MMP-13), inducible nitric oxide synthase (iNOS), as well as HA levels and small HA fragment production. Treatment of RASF with antioxidants and specific HYAL1, HYAL2, and HYAL3 small interference RNA (siRNAs) significantly reduced TLR-4 and CD44 increase in the mRNA expression and the related protein synthesis, as well as the release of inflammatory mediators up-regulated by TNF-α. These data suggest that the inhibition of HA degradation during arthritis may contribute to reducing TLR-4 and CD44 activation and the inflammatory mediators response.

The vitamin D receptor regulates rheumatoid arthritis synovial fibroblast invasion and morphology

Serum levels of vitamin D levels are commonly reduced in patients with rheumatoid arthritis (RA) and have been implicated in disease pathogenesis. We recently identified a new vitamin D receptor transcriptional signature in synovial tissues from rats with mild and nonerosive arthritis, suggesting a vitamin D-mediated protective effect. In the present study, we address the hypothesis that part of the vitamin D protective effect is mediated via interference with fibroblast-like synoviocyte (FLS) invasive properties, an in vitro cellular phenotype that correlates with radiographic and histological damage in pristane-induced arthritis and RA. FLSs derived from DA rats with pristane-induced arthritis and RA patients were studied in an in vitro model of invasion through a collagen-rich barrier (Matrigel) over a 24-h period, in the presence or absence of calcitriol, an active form of vitamin D. Matrix metalloprotease (MMP) expression levels were analyzed with zymography and quantitative real-time polymerase chain reaction, and the cytoskeleton was studied with immunofluorescense microscopy. Calcitriol significantly inhibited DA and RA FLS invasion by 54% and 53%, respectively. Calcitriol also reduced interleukin (IL)-1β-induced expression of MMP-1 by 95% in DA FLSs and by 73.5% in RA FLS. Calcitriol treatment reduced actin cytoskeleton reorganization, reduced polarized formation of lamellipodia and reduced colocalization of phosphorylated focal adhesion kinase (p-FAK) with lamellipodia, all consistent with reduced cell ability to move and invade. In conclusion, we identified a new effect of calcitriol in FLS invasion. This discovery suggests that the reduced serum levels of vitamin D and its metabolites commonly seen in RA might increase risk for FLS-mediated cartilage and bone invasion and erosions. Treatment with vitamin D or its analogs has the potential to become a helpful adjuvant aimed at preventing or reducing joint destruction.

Synovium CD20 expression is a potential new predictor of bone erosion progression in very-early arthritis treated by sequential DMARDs monotherapy -- a pilot study from the VErA cohort

OBJECTIVE

Because available biomarkers (rheumatoid factors [RF], anti-cyclic citrullinated autoantibodies [anti-CCP2], erythrocyte sedimentation rate at 1st hour [ESR]/C-reactive peptide [CRP] and bone erosions) are insufficient to predict rheumatoid arthritis (RA) structural damage, to determine whether synovium expression of greater or equal to 1 markers could constitute new prognostic factor(s).

METHOD

The study was conducted on 18 prospectively enrolled disease-modifying anti-rheumatic drug (DMARD)- and glucocorticoid-naïve, VErA cohort patients with very-early arthritis (median duration: 4months). Recorded at baseline were: clinical and biological (serum ESR, CRP, RF-isotypes, anti-CCP2, osteoprotegerin, receptor activator of nuclear κB-ligand [RANK-L] and cartilage oligomeric matrix protein [COMP] levels) data; synovium expression (HLA-DR, CD163, CD3, CD20, VEGF, osteoprotegerin, RANK-L, Bcl2 and global inflammation index) for a metacarpophalangeal joint-synovium biopsy. Baseline and 3-year hand-and-foot X-rays were graded with the van der Heijde-modified-Sharp score; the judgment criterion was its progression during follow-up. Pearson's product moment correlation statistics were used to test for association between paired samples.

RESULTS

A baseline, a significant relationship was found between erosive damage and markers of B-cell activation, notably the synovium CD20 expression (r=0.68; P=0.0001). Quantified by the modified-Sharp erosion score variation, the 3-year structural damage progression was significantly correlated with: serum levels of RF-IgG (r=0.75; P=0.0003), -IgM (r=0.69; P=0.001), anti-CCP2 (r=0.53; P=0.02) and RANK-L (r=0.61; P=0.007); synovium CD20 expression (r=0.70; P=0.001).

CONCLUSION

This analysis of the prognostic value of a large panel of synovium markers in a limited sample of prospectively followed, well-documented patients suggested that both synovial CD20 and serum RANK-L levels might be new predictors of structural damage progression in very-early RA.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Synovial tissue response to treatment in rheumatoid arthritis

The recognition of the synovial tissue, as the primary target of inflammation in RA, has driven research in this field, not only to clarify the disease pathogenesis but also to evaluate local changes in response to treatment. Special interest has been given to the identification of sensitive synovial biomarkers that could be of help in demonstrating proof of principle in early stages of drug development. Synovial sublining macrophages have been shown to correlate with scores for disease activity in cross-sectional studies. Moreover, decreased disease activity as measured by the disease activity score evaluated in 28 joints (DAS28) after effective treatment, has consistently been associated with a reduction of the number of CD68+ synovial sublining macrophages across different therapies. This observation highlights a possible final common pathway in the mechanism of action of various therapies and supports the notion that macrophages have a central role in RA pathogenesis.

When considering experimental therapies, the study of serial synovial biopsies in relatively small numbers of patients, in the context of proof of principle trials, successfully distinguished between effective and ineffective treatments. This attractive approach can be used during early drug development for screening proposes, supporting which new treatments have higher probability to be beneficial in a large scale clinical trial.

In this paper we review the effects of RA treatments on the synovial tissue, including targeted therapies, with particular attention to their effect on synovial biomarkers.

Lectin-like oxidized low-density lipoprotein receptor 1 signal is a potent biomarker and therapeutic target for human rheumatoid arthritis

OBJECTIVE

To determine whether lectin-like oxidized low-density lipoprotein (ox-LDL) receptor 1 (LOX-1) and the soluble form of LOX-1 (sLOX-1) are novel target molecules for the diagnosis and treatment of rheumatoid arthritis (RA).

METHODS

Expression of ox-LDL and LOX-1 proteins in human RA synovium was evaluated by immunohistochemistry. Human RA fibroblast-like synoviocytes (FLS) were assessed for ox-LDL-induced expression of LOX-1 and ox-LDL-induced production of matrix metalloproteinase 1 (MMP-1) and MMP-3. Levels of sLOX-1 in the plasma and synovial fluid of patients with RA, compared with patients with osteoarthritis (OA), were determined by a specific chemiluminescence enzyme-linked immunoassay. In animal experiments, ox-LDL was injected into the knee joints of mice, with or without an anti-LOX-1 neutralizing antibody or sLOX-1, and the severity of arthritis was analyzed by histology and immunohistochemistry.

RESULTS

Oxidized LDL and LOX-1 proteins were detected in the RA synovial tissue. Levels of MMP-1 and MMP-3 were enhanced by stimulation of RA FLS with ox-LDL, and the production of both MMPs was inhibited by blockade of the ox-LDL-LOX-1 interaction with the anti-LOX-1 neutralizing antibody or sLOX-1. Levels of sLOX-1 in the plasma and synovial fluid of RA patients were significantly higher than those in OA patients and healthy controls and were positively correlated with inflammation markers and the extent of RA disease activity. In the knees of mice, blockade of the ox-LDL-LOX-1 interaction suppressed arthritic changes and reduced the expression of MMP-3 induced by ox-LDL.

CONCLUSION

These findings strongly indicate that sLOX-1 is a novel biomarker that may be useful for the diagnosis of RA and for the evaluation of disease activity in RA. Furthermore, the results suggest that LOX-1 may be a potent therapeutic target for RA.

Serum cysteine proteases and their inhibitors in rheumatoid arthritis: relation to disease activity and radiographic progression

This study aims to investigate the serum levels of cysteine proteases cathepsins B and H and their inhibitors stefin A, stefin B, and cystatin C, as well as traditional inflammatory markers such as C-reactive protein in patients with rheumatoid arthritis and to correlate these markers with scores of disease activity and radiographic progression. Seventy-two patients with rheumatoid arthritis were included from two previously described cohorts of patients with chronic polyarthritis. At inclusion, disease activity was assessed by a 28-joint count, patient global assessment, and serum C-reactive protein. Erosive status of hands and wrists was expressed by the Larsen score and recorded at inclusion and after 1 year. Serum levels of cathepsin B, cathepsin H, stefin A, stefin B, and cystatin C were determined by enzyme-linked immunosorbent assay. Neither cathepsin B nor cathepsin H serum levels were associated with disease activity, presence or progression of erosive disease. Number of swollen joints correlated with serum levels of stefin A and B and correlated negatively with cystatin C serum levels. Erosive disease was associated with high serum levels of C-reactive protein and stefin A and low serum levels of cystatin C. Progression of radiographic destruction was associated with high serum levels of C-reactive protein, stefin A and B, whereas serum levels of cystatin C were not associated with radiographic progression. The findings in this study support further investigation in the regulation of the activity of cathepsins and their inhibitors in erosive rheumatoid arthritis.

Honokiol inhibits the progression of collagen-induced arthritis by reducing levels of pro-inflammatory cytokines and matrix metalloproteinases and blocking oxidative tissue damage

Plant-derived compounds with potent anti-inflammatory activity have attracted a great deal of attention as a source for novel anti-arthritic agents with minimal side effects. We attempted to determine the anti-arthritic effects of orally administered honokiol isolated from Magnolia species. The oral administration of honokiol inhibited the progression and severity of type II collagen (CII)-induced arthritis (CIA) by reducing clinical arthritis scores and paw swelling. The histological analysis demonstrated preserved joint space; and the immunohistochemical data showed that the levels of interleukin (IL)-17, matrix metalloproteinase (MMP)-3, MMP-9, MMP-13, and receptor activator for nuclear factor-κB ligand, as well as nitrotyrosine formation, were substantially suppressed in the honokiol-treated CIA mice. The elevated serum levels of tumor necrosis factor-α and IL-1β in the CIA mice were also restored to control levels via honokiol treatment. In the CIA mice, honokiol inhibited CII- or lipopolysaccharide-stimulated cytokine secretion in spleen cells, as well as CII-stimulated spleen cell proliferation. Furthermore, honokiol treatment reduced CIA-induced oxidative damage in the liver and kidney tissues of CIA mice. Collectively, the oral administration of honokiol inhibited CIA development by reducing the production of pro-inflammatory cytokines, MMP expressions, and oxidative stress. Thus, honokiol is an attractive candidate for an anti-arthritic agent.

Cathepsin B and cystatin C play an inflammatory role in gouty arthritis of the knee

BACKGROUND

To relate the expression of the matrix degrading proteinase cathepsin B and its endogenous inhibitor cystatin C in the synovial fluid (SF) to the clinical and laboratory variables of joint inflammation in gouty arthritis of the knee.

METHODS

Thirty-nine SF samples were obtained from inflamed knees of patients with acute gout. The levels of cathepsin B, cystatin C, urokinase-type plasminogen activator (uPA), soluble uPA receptor (suPAR) and PA inhibitor type-1 (PAI-1), activities of matrix metalloproteinase-2 (MMP-2) and MMP-9, and cell counts as well as local arthritis activity scores (LAS) were examined.

RESULTS

The increases of cathepsin B levels correlated with increased leukocyte and neutrophil counts, latent MMP-9 (pro-MMP-9) activities, uPA, suPAR and PAI-1 levels, and uPA/PAI-1 ratios. Increased cystatin C levels corresponded closely with increased LAS, leukocyte and neutrophil counts, pro-MMP-9 activities, uPA, suPAR and PAI-1 levels, and uPA/PAI-1 ratios. Moreover, there was a correlation between cathepsin B and cystatin C levels.

CONCLUSIONS

These results show a high correlation between the cathepsin B/cystatin C system and markers of joint inflammation in acute gout of the knee, demonstrating the pathologic role of cathepsin B and cystatin C in inflammation.

Interferon-gamma inhibits interleukin-1beta-induced matrix metalloproteinase production by synovial fibroblasts and protects articular cartilage in early arthritis

Introduction

The first few months after symptom onset represents a pathologically distinct phase in rheumatoid arthritis (RA). We used relevant experimental models to define the pathological role of interferon-γ (IFN-γ) during early inflammatory arthritis.

Methods

We studied IFN-γ's capacity to modulate interleukin-1β (IL-1β) induced degenerative responses using RA fibroblast-like synoviocytes (FLS), a bovine articular cartilage explant (BACE)/RA-FLS co-culture model and an experimental inflammatory arthritis model (murine antigen-induced arthritis (AIA)).

Results

IFN-γ modulated IL-1β driven matrix metalloproteinases (MMP) synthesis resulting in the down-regulation of MMP-1 and MMP-3 production in vitro. IFN-γ did not affect IL-1β induced tissue inhibitor of metalloproteinase-1 (TIMP-1) production by RA FLS but skewed the MMP/TIMP-1 balance sufficiently to attenuate glycosaminoglycan-depletion in our BACE model. IFN-γ reduced IL-1β expression in the arthritic joint and prevented cartilage degeneration on Day 3 of AIA.

Conclusions

Early therapeutic intervention with IFN-γ may be critical to orchestrate tissue-protective responses during inflammatory arthritis.

Utility of synovial biopsy

Synovial biopsies, gained either by blind needle biopsy or minimally invasive arthroscopy, offer additional information in certain clinical situations where routine assessment has not permitted a certain diagnosis. In research settings, synovial histology and modern applications of molecular biology increase our insight into pathogenesis and enable responses to treatment with new therapeutic agents to be assessed directly at the pathophysiological level. This review focuses on the diagnostic usefulness of synovial biopsies in the light of actual developments.

The expression of collagenase 3 (MMP-13) mRNA in the synovial tissue is associated with histopathologic type II synovitis in rheumatoid arthritis

The histopathologic analysis of the synovial tissue is important to distinguish rheumatoid arthritis (RA) from other forms of synovitis and to provide information about prognosis and therapeutic strategies at early stages of the disease. In this context, the present study was performed to investigate the correlation between immunohistopathological and morphological features of synovitis and the expression of collagenase 3 (MMP-13) known to contribute significantly to cartilage degradation in RA. In the histopathologic scoring system used in this study, type I synovitis is characterized by B lymphocyte infiltration and an intact lining, and is only mild destructive to cartilage and bone. Type II shows marked diffuse infiltrations of macrophages and T lymphocytes, an ulcerated lining, fibrin exudation, and invasive growth into cartilage and bone tissue. Investigating 36 patients with RA, 21 patients (58%) were positive for the expression of collagenase 3 mRNA in the synovial tissue. Among these patients, 19 showed a histopathologic type II synovitis and only 2 patients had undifferentiated synovitis. In contrast, synovial tissue samples from patients without collagenase 3 mRNA expression were characterized in 6 cases by type I, in 5 cases by type II and in 4 cases by undifferentiated synovitis. The analysis of the clinical data revealed that RA patients with a histopathologic type II synovitis and synovial tissue collagenase 3 mRNA expression had elevated levels of systemic markers of inflammation and received stronger therapies. The data suggest, that collagenase 3 expression and the histopathologic type II synovitis are associated with a severe and destructive course of RA.

In vitro model for the analysis of synovial fibroblast-mediated degradation of intact cartilage

Introduction

Activated synovial fibroblasts are thought to play a major role in the destruction of cartilage in chronic, inflammatory rheumatoid arthritis (RA). However, profound insight into the pathogenic mechanisms and the impact of synovial fibroblasts in the initial early stages of cartilage destruction is limited. Hence, the present study sought to establish a standardised in vitro model for early cartilage destruction with native, intact cartilage in order to analyse the matrix-degrading capacity of synovial fibroblasts and their influence on cartilage metabolism.

Methods

A standardised model was established by co-culturing bovine cartilage discs with early-passage human synovial fibroblasts for 14 days under continuous stimulation with TNF-α, IL-1β or a combination of TNF-α/IL-1β. To assess cartilage destruction, the co-cultures were analysed by histology, immunohistochemistry, electron microscopy and laser scanning microscopy. In addition, content and/or neosynthesis of the matrix molecules cartilage oligomeric matrix protein (COMP) and collagen II was quantified. Finally, gene and protein expression of matrix-degrading enzymes and pro-inflammatory cytokines were profiled in both synovial fibroblasts and cartilage.

Results

Histological and immunohistological analyses revealed that non-stimulated synovial fibroblasts are capable of demasking/degrading cartilage matrix components (proteoglycans, COMP, collagen) and stimulated synovial fibroblasts clearly augment chondrocyte-mediated, cytokine-induced cartilage destruction. Cytokine stimulation led to an upregulation of tissue-degrading enzymes (aggrecanases I/II, matrix-metalloproteinase (MMP) 1, MMP-3) and pro-inflammatory cytokines (IL-6 and IL-8) in both cartilage and synovial fibroblasts. In general, the activity of tissue-degrading enzymes was consistently higher in co-cultures with synovial fibroblasts than in cartilage monocultures. In addition, stimulated synovial fibroblasts suppressed the synthesis of collagen type II mRNA in cartilage.

Conclusions

The results demonstrate for the first time the capacity of synovial fibroblasts to degrade intact cartilage matrix by disturbing the homeostasis of cartilage via the production of catabolic enzymes/pro-inflammatory cytokines and suppression of anabolic matrix synthesis (i.e., collagen type II). This new in vitro model may closely reflect the complex process of early stage in vivo destruction in RA and help to elucidate the role of synovial fibroblasts and other synovial cells in this process, and the molecular mechanisms involved in cartilage degradation.

Mechanical stretch regulates the expression of matrix metalloproteinase in rheumatoid arthritis fibroblast-like synoviocytes

Mechanical stretch plays a crucial role in articular joints. In rheumatoid arthritis (RA), it is well known that fibroblast-like synoviocytes (FLS) produce matrix metalloproteinases (MMPs), resulting in local invasion into and degradation of bone and cartilage. We sought to examine whether mechanical stretch regulates the expression and underlying signal pathways of MMP secretion (MMP-1, -3, -13) in RA-FLS. FLS were grown on elastic silicone membrane in an equibiaxial strain apparatus and were exposed to 6% mechanical stretch (equivalent to gentle stretch exercise) for 15 min and 75 min, respectively. Semiquantitative PCR and real-time PCR were used to measure and analyze gene expression. Protein levels were determined by Western blotting. The results showed that 15 min of mechanical stretch inhibited MMP-1 and MMP-13 mRNA and protein level. However, the degree of inhibition by 75 min of stretch in expression of MMP-1 and MMP-13 was lower compared with 15 min stretch groups. The mRNA expression of ERK-1, ets-1 and citied-2 were increased by 6% mechanical stretch under both time points, however c-jun and c-fos mRNA level were affected differently after 15 min and 75 min mechanical stretch compared to control group. There were no significant changes on MMP-3 and ets-2 mRNA level under both 6% mechanical stretch time points. In the presence of pro-inflammatory cytokines (IL-1beta and TNF-alpha), the stretch also reduced the mRNA expression of MMP-1 and MMP-13. In short, our results showed that gentle mechanical strain affects MMP-1 and MMP-13 expression, potentially through the ERK-1-ets-1-cited-2-c-jun signaling pathway.

Serum levels of tissue inhibitor of metalloproteinase-1 and periarticular bone loss in early rheumatoid arthritis

We investigated the relationship between disease activity, serum biological mediators of joint damage, and periarticular bone loss in inflammatory arthritis. Patients with early inflammatory arthritis were recruited from a dedicated early arthritis clinic. At the time of recruitment, all had clinical evidence of synovitis. Patients were assessed at baseline and at 1-year follow-up. Periarticular and axial bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. Serum levels of matrix metalloproteinase 1 and tissue inhibitor of metalloproteinases 1 (TIMP-1) were measured by enzyme-linked immunosorbent assay. A total 38 patients were included in the study. Twenty had rheumatoid arthritis (RA) and 18 had a seronegative spondylarthropathy (SpA). At baseline, periarticular hand BMD measurements were similar in RA and SpA. At 1 year, the mean periarticular hand BMD was significantly lower in RA (p < 0.05). Significant inverse correlations between both the Ritchie articular index and C-reactive protein levels and the change in periarticular hand BMD at 1 year were observed in RA (r = -0.792, p < 0.001 and r = -0.478, p = 0.045, respectively). Baseline TIMP-1 levels correlated with the change in periarticular hand BMD at 1 year in RA (r = 0.519, p = 0.02). At 1 year, radiographic measures of joint damage were highest in RA. Inverse correlations between the change in periarticular hand BMD and the changes in erosion score (r = -0.90, p = 0.04) were observed in patients demonstrating significant periarticular bone loss. Persistent disease activity was associated with increased periarticular bone loss in the hands in patients with RA, consistent with synovitis-mediated periarticular bone loss. The correlation between baseline TIMP-1 levels and periarticular bone loss over 1 year suggests that TIMP-1 may have utility as a biomarker of periarticular bone loss in early RA.

Annexin-1 mediates TNF-alpha-stimulated matrix metalloproteinase secretion from rheumatoid arthritis synovial fibroblasts

Annexins are intracellular molecules implicated in the down-regulation of inflammation. Recently, annexin-1 has also been identified as a secreted molecule, suggesting it may have more complex effects on inflammation than previously appreciated. We studied the role of annexin-1 in mediating MMP-1 secretion from rheumatoid arthritis (RA) synovial fibroblasts (SF) stimulated with TNF-alpha. TNF-alpha induced a biphasic secretion of annexin-1 from RA SF. Early (< or = 60 min), cycloheximide-independent secretion from preformed intracellular pools was followed by late (24 h) cycloheximide-inhibitable secretion requiring new protein synthesis. Exogenous annexin-1 N-terminal peptide Ac2-26 stimulated MMP-1 secretion in a dose- (EC(50) approximately 25 microM) and time- (8-24 h) dependent manner; full-length annexin-1 had a similar effect. Down-regulation of annexin-1 using small interfering RNA resulted in decreased secretion of both annexin-1 and MMP-1, confirming that annexin-1 mediates TNF-alpha-stimulated MMP-1 secretion. Erk, Jnk, and NF-kappaB have been implicated in MMP-1 secretion. Erk, Jnk, and NF-kappaB inhibitors had no effect on annexin-1 secretion stimulated by TNF-alpha but inhibited MMP-1 secretion in response to Ac2-26, indicating that these molecules signal downstream of annexin-1. Annexin-1 stimulation of MMP-1 secretion was inhibited by both a formyl peptide receptor antagonist and pertussis toxin, suggesting that secreted annexin-1 acts via formyl peptide family receptors, most likely FPLR-1. In contrast to its commonly appreciated anti-inflammatory roles, our data indicate that annexin-1 is secreted by RA SF in response to TNF-alpha and acts in an autacoid manner to engage FPRL-1, activate Erk, Jnk, and NF-kappaB, and stimulate MMP-1 secretion.

Cells of the synovium in rheumatoid arthritis. Chondrocytes

Rheumatoid arthritis (RA) is one of the inflammatory joint diseases in a heterogeneous group of disorders that share features of destruction of the extracellular matrices of articular cartilage and bone. The underlying disturbance in immune regulation that is responsible for the localized joint pathology results in the release of inflammatory mediators in the synovial fluid and synovium that directly and indirectly influence cartilage homeostasis. Analysis of the breakdown products of the matrix components of joint cartilage in body fluids and quantitative imaging techniques have been used to assess the effects of the inflammatory joint disease on the local remodeling of joint structures. The role of the chondrocyte itself in cartilage destruction in the human rheumatoid joint has been difficult to address but has been inferred from studies in vitro and in animal models. This review covers current knowledge about the specific cellular and biochemical mechanisms that account for the disruption of the integrity of the cartilage matrix in RA.

Proteinases in the joint: clinical relevance of proteinases in joint destruction

Proteinases are involved in essential steps in cartilage and bone homeostasis. Consequently, efforts have been made to establish their potential role in the pathology of rheumatic conditions such as rheumatoid arthritis, osteoarthritis and spondyloarthritis. Matrix metalloproteinases (MMPs) are sensitive markers of disease severity and response to treatment, and therefore they have potential in the assessment of rheumatic diseases. Despite disappointing early results with synthetic inhibitors of MMPs, there is still much scope for developing effective and safe MMPs inhibitors, and consequently to deliver new options to inhibit joint destruction.

Immunohistochemistry of the inflamed synovium

The development in the techniques for obtaining synovial tissue biopsy, especially through arthroscopy, have resulted in greater access to high-quality synovial tissue. The use of immunohistochemistry in arthritis research has greatly furthered our understanding of the varied immunological and biochemical pathways involved in inflammatory arthropathopies such as rheumatoid and psoriatic arthritis. Immunohistochemistry provides a strikingly visual narrative of the essential elements involved in inflammatory arthritis, from the infiltrating inflammatory cells (e.g., T-cells, macrophages, B-cells, and neutrophils), their products (e.g., cytokines, metalloproteinases) and their varied receptor molecules. This chapter describes the standard three-stage immunoperoxidase technique used in our laboratory and widely in the literature. Some problems that may be encountered and how they may be overcome are commented on. Also described is a method for dual-labeled immunofluoresence staining.