Integrative Proteomics and N-Glycoproteomics Analyses of Rheumatoid Arthritis Synovium Reveal Immune-Associated Glycopeptides.

Rheumatoid arthritis (RA) is a typical autoimmune disease characterized by synovial inflammation, synovial tissue hyperplasia, and destruction of bone and cartilage. Protein glycosylation plays key roles in the pathogenesis of RA but in-depth glycoproteomics analysis of synovial tissues is still lacking. Here, by using a strategy to quantify intact N-glycopeptides, we identified 1260 intact N-glycopeptides from 481 N-glycosites on 334 glycoproteins in RA synovium. Bioinformatics analysis revealed that the hyper-glycosylated proteins in RA were closely linked to immune responses. By using DNASTAR software, we identified 20 N-glycopeptides whose prototype peptides were highly immunogenic. We next calculated the enrichment scores of nine types of immune cells using specific gene sets from public single-cell transcriptomics data of RA and revealed that the N-glycosylation levels at some sites, such as IGSF10_N2147, MOXD2P_N404, and PTCH2_N812, were significantly correlated with the enrichment scores of certain immune cell types. Furthermore, we showed that aberrant N-glycosylation in the RA synovium was related to increased expression of glycosylation enzymes. Collectively, this work presents, for the first time, the N-glycoproteome of RA synovium and describes immune-associated glycosylation, providing novel insights into RA pathogenesis.

Heat Shock Protein Is Associated with Inhibition of Inflammatory Cytokine Production by 630 nm Light-Emitting Diode Irradiation in Fibroblast-Like Synoviocytes Based on RNA Sequencing Analysis.

Background: Inflammatory cytokine secretion from fibroblast-like synoviocytes (FLS) plays a vital role in the pathological process of rheumatoid arthritis (RA). Photobiomodulation (PBM) has been widely used in the treatment of RA. However, the mechanism of PBM in RA has not been clarified. Objective: In this study, we investigated the underlying mechanism of 630 nm light-emitting diode (LED) irradiation on anti-inflammation using mRNA sequencing analysis. Methods and results: Reverse transcription (RT)-quantitative polymerase chain reaction (RT-qPCR) results showed that 630 nm LED irradiation significantly inhibited interleukin (IL)-1ß, IL-6, and IL-8 mRNA expression in rheumatoid arthritis fibroblast synovial cells (RA-FLS) and MH7A cells. A total of 1730 differentially expressed genes (DEGs) were identified between tumor necrosis factor α (TNF-α)+LED and TNF-α-treated RA-FLS and 1219 DEGs in MH7A cells by mRNA sequencing analysis. A total of 646 intersecting DEGs from the 2 cell models were used for gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses. Protein-protein interaction (PPI) network of DEGs was used, and 502 nodes and 1452 edges were found. A total of 14 clusters were generated in MCODE, and the top 3 clusters were selected as hub modules. PPI network showed that most of the nodes were DEGs of the heat shock protein (HSP) family. RT-qPCR verified that 630 nm LED irradiation significantly increased HSP70 mRNA expression in FLS. Conclusions: Taken together, our results revealed the correlation between HSP70 and the inhibition of inflammation caused by 630 nm LED irradiation. These findings suggested that HSP may be a novel target of 630 nm LED irradiation to alleviate inflammation in the treatment of RA.

Roles of CD3, CD4 and CD8 in synovial lymphocytes of rheumatoid arthritis.

In this study, the immunohistochemical EnVision method was applied to detect CD3, CD4 and CD8 in synovial tissues of 40 patients with rheumatoid arthritis (RA) and 10 patients with osteoarthritis (OA). In 92.5% (37/40) RA cases, lymphocytes were focally aggregated, and even germinal centers appeared, forming lymphoid follicle-like structures. The expression of CD3, CD4, and CD8 were high in synovial tissue of RA group, but low in OA group. The number of CD3, CD4+, and CD8+ lymphocytes in OA group were significantly lower than that in RA group (p < 0.05); CD4+lymphocytes in RA accounted for the majority, and mostly were focally distributed. The number of CD8+lymphocytes in the synovial tissue were small, and were mostly scattered. The number of CD4+lymphocytes were significantly higher than CD8+lymphocytes (p<0.05). Compared with the OA group, the number of CD4+T and CD8+T lymphocytes in RA group were higher, and the ratio of CD4/CD8 was higher in RA group (p < 0.05). In conclusion, the CD3, CD4 and CD8 with high level may promote the occurrence and development of RA. The ratio of CD4+/CD8+ may be used as a reference index for the diagnosis and prognosis of RA.

Measurement of synovium and serum dual specificity phosphatase 22 level: Their inter-correlation and potency as biomarkers in rheumatoid arthritis.

BACKGROUND: Dual specificity phosphatase 22 (DUSP22), also named as Jun N-terminal kinase pathway associated phosphatase recently, is reported to be closely engaged in immune and inflammation regulation. This study aimed to investigate the interaction between synovium DUSP22 and serum DUSP22 levels and to explore their correlation with rheumatoid arthritis (RA) risk, inflammation, and disease activity. METHODS: Synovium and serum samples from 42 RA patients with knee involvement underwent arthroscopy, and 20 knee trauma patients were collected. Besides, serum samples from 40 healthy controls were also obtained. Synovium DUSP22 expression was detected by reverse transcription quantitative polymerase chain reaction, while serum DUSP22 level was detected by enzyme-linked immunosorbent assay. RESULTS: Synovium DUSP22 level was greatly decreased in RA patients compared to trauma controls (p < 0.001), and it was negatively correlated with tender joint count (TJC) (r = -0.318, p = 0.040), C-reactive protein (CRP) (r = -0.330, p = 0.033), and Lysholm score (r = -0.423, p = 0.005) in RA patients. Serum DUSP22 level was lowest in RA patients, followed by trauma controls, then highest in healthy controls (p < 0.001). Serum DUSP22 level was negatively associated with TJC (r = -0.438, p = 0.004), swollen joint count (SJC) (r = -0.372, p = 0.015), CRP (r = -0.391, p = 0.011), and disease activity score in 28 joints (DAS28ESR ) score (r = -0.406, p = 0.008), and it increased after treatment (p = 0.001) in RA patients. In addition, serum DUSP22 level positively related to synovium DUSP22 level in RA patients (r = 0.394, p = 0.010). CONCLUSION: Synovium and serum DUSP22 are intercorrelated and insufficiently expressed in RA patients; meanwhile, their deficiency correlates with increased systemic inflammation, disease activity, and joint dysfunction.

IL-40: A New B Cell-Associated Cytokine Up-Regulated in Rheumatoid Arthritis Decreases Following the Rituximab Therapy and Correlates With Disease Activity, Autoantibodies, and NETosis.

Background: Interleukin 40 (IL-40) is a newly identified B cell-associated cytokine implicated in humoral immune responses and B cell homeostasis. As B cells play a pivotal role in autoimmunity, we investigated the function of IL-40 in rheumatoid arthritis (RA). Methods: IL-40 expression was determined in the synovial tissue from RA and osteoarthritis (OA) patients. IL-40 was analysed in the serum/synovial fluid of patients with RA (n=50), systemic lupus erythematosus (SLE, n=69), OA (n=44), and healthy controls (HC, n=50). We assessed the changes of IL-40 levels in RA patients following the B cell depletion by rituximab (n=29) or after the TNF inhibition by adalimumab (n=25). We examined the relationship between IL-40, disease activity, autoantibodies, cytokines, and NETosis markers. Effect of IL-40 on synovial fibroblasts was determined. Results: IL-40 was overexpressed in RA synovial tissue, particularly by synovial lining and infiltrating immune cells. The levels of IL-40 were up-regulated in the synovial fluid of RA versus OA patients (p<0.0001). Similarly, IL-40 was increased in the serum of RA patients compared to HC, OA, or SLE (p<0.0001 for all) and decreased after 16 and 24 weeks (p<0.01 and p<0.01) following rituximab treatment. No significant effect of adalimumab on IL-40 was observed. IL-40 levels in RA patients correlated with rheumatoid factor-IgM and anti-cyclic citrullinated peptides (anti-CCP) in the serum (p<0.0001 and p<0.01), as well as in the synovial fluid (p<0.0001 and p<0.001). Synovial fluid IL-40 was also associated with disease activity score DAS28 (p<0.05), synovial fluid leukocyte count (p<0.01), neutrophil attractants IL-8 (p<0.01), MIP-1α (p<0.01), and markers of neutrophil extracellular traps externalization (NETosis) such as proteinase 3 (p<0.0001) and neutrophil elastase (p<0.0001). Synovial fibroblasts exposed to IL-40 increased the secretion of IL-8 (p<0.01), MCP-1 (p<0.05), and MMP-13 (p<0.01) compared to the unstimulated cells. Conclusions: We show the up-regulation of IL-40 in RA and its decrease following B cell depleting therapy. The association of IL-40 with autoantibodies, chemokines, and markers of NETosis may imply its potential involvement in RA development. Moreover, IL-40 up-regulates the secretion of chemokines and MMP-13 in synovial fibroblasts, indicating its role in the regulation of inflammation and tissue destruction in RA.

ASIC1a promotes the proliferation of synovial fibroblasts via the ERK/MAPK pathway.

Synovial hyperplasia, a profound alteration in the structure of synovial tissue, is the basis for cumulative joint destruction in rheumatoid arthritis (RA). It is generally accepted that controlling synovial hyperplasia can delay the progression of RA. As one of the most intensively studied isoforms of acid-sensing ion channels (ASICs), ASIC1a contributes to various physiopathologic conditions, including RA, due to its unique property of being permeable to Ca2+. However, the role and the regulatory mechanisms of ASIC1a in synovial hyperplasia are poorly understood. Here, rats induced with adjuvant arthritis (AA) and human primary synovial fibroblasts were used in vivo and in vitro to investigate the role of ASIC1a in the proliferation of RA synovial fibroblasts (RASFs). The results show that the expression of ASIC1a was significantly increased in synovial tissues and RASFs obtained from patients with RA as well as in the synovium of rats with AA. Moreover, extracellular acidification improved the ability of RASFs colony formation and increased the expression of proliferation cell nuclear antigen (PCNA) and Ki67, which was abrogated by the specific ASIC1a inhibitor psalmotoxin-1 (PcTX-1) or ASIC1a-short hairpin RNA (ASIC1a-shRNA), suggesting that extracellular acidification promotes the proliferation of RASFs by activating ASIC1a. In addition, the activation of c-Raf and extracellular signal-regulated protein kinases (ERKs) signaling was blocked with PcTX-1 or ASIC1a-shRNA and the proliferation of RASFs was further inhibited by the ERK inhibitor (U0126), indicating that ERK/MAPK signaling contributes to the proliferation process of RASFs promoted by the activation of ASIC1a. These findings gave us an insight into the role of ASIC1a in the proliferation of RASFs, which may provide solid foundation for ASIC1a as a potential target in the treatment of RA.

Extraction and identification of synovial tissue-derived exosomes by different separation techniques.

OBJECTIVE: The aim of this study is to compare the efficiency of different separation techniques for extracting synovial tissue-derived exosomes. METHODS: The synovial tissue discarded during knee arthroscopy or total knee arthroplasty surgery was collected from the Third Affiliated Hospital of Beijing University of Chinese Medicine. Ultracentrifugation (UC), filtration combined with size exclusion chromatography (SECF), and 8% polyethylene glycol (PEG) were used to extract synovial tissue-derived exosomes. Transmission electron microscopy (TEM), nanoparticle tracer analysis (NTA), and Western Blot (WB) were used to detect the morphology, particle size, and biomarker proteins (CD9, CD63, Flotillin-1, and calnexin) of exosomes. RESULTS: The extracts of enriched round and discoid vesicles were successfully extracted with UC, SECF, and PEG. The results of TEM have shown that all three extraction methods can extract circular or elliptical vesicles with disc- and cup-shaped structures from the synovial tissue, with the diameter is about 30-150 nm. NTA suggested the main peaks of three groups of exosomes are around 100-120 nm, and the concentration of the three groups of exosomes was greater than 1 × 1010/ml. The results of WB showed that three positive protein markers (CD9, CD63, and Flotillin-1) were highly expressed in the suspension extracted by the three methods and low in the synovial tissue. However, the negative protein (calnexin) was highly expressed in synovial tissues and PEG group, while low in UC and SECF group. CONCLUSION: Morphology, particle size, and labeled protein marker detection confirmed that UC, SECF, and PEG can extract exosomes derived from synovial tissue; UC and SECF are more recommended for the extraction of synovial tissue-derived exosomes, which provides a methodological basis for studying the function and mechanism of synovial tissue exosomes in the future.

Identification of differentially expressed miRNAs and mRNAs in synovial of osteoarthritis via RNA-sequencing.

BACKGROUND: Osteoarthritis (OA) is the most common form of arthritis and a leading cause of disability. This study attempted to investigate the key mRNAs and miRNAs related to OA. PATIENTS AND METHODS: From April 17th, 2018 to May 17th, 2018, five patients with OA and three normal controls were enrolled in this present study. To identify the differentially expressed mRNAs (DEmRNAs) and miRNAs (DEmiRNAs) between patients with OA and normal controls, RNA-sequencing was performed. Then, DEmiRNA-target DEmRNAs analysis and functional annotation of DEmiRNA-target DEmRNAs were performed. To validate the RNA-sequencing results, quantitative real time-PCR (RT-PCR) and western blot analysis were performed as well. RESULTS: A total of 1068 DEmRNAs, 21 DEmiRNAs and 395 DEmiRNA-DEmRNA pairs were identified in synovial tissues of patients with OA. The functional annotation of DEmiRNA-target DEmRNAs revealed that Pathways in cancer and PI3K-Akt signaling pathway were significantly enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. QRT-PCR and western blot results revealed that except for TLR7, the expression level of the others was consistent with the RNA-sequencing results, generally. CONCLUSION: The findings of this present study may provide new clues for the roles of DEmRNAs and DEmiRNAs in the pathogenesis of OA.

Rabbit Model of Extending Knee Joint Contracture: Progression of Joint Motion Restriction and Subsequent Joint Capsule Changes after Immobilization.

This study aimed to develop a rabbit model of knee contracture in extension and investigate the natural history of motion loss and time-dependent changes in the joint capsule after immobilization. We immobilized the unilateral knee joints of 32 rabbits by maintaining the knee joint in a plaster cast at full extension. Eight rabbits were euthanized at 2, 4, 6, and 8 weeks after casting, respectively, and the lower extremities were disarticulated at the hip joint. Eight control group rabbits that did not undergo immobilization were also examined. We assessed the progression of joint contracture by measuring the joint range of motion, evaluating the histologic alteration of the capsule, and assessing the mRNA levels of transforming growth factor ß1 (TGF-ß1) in the anterior and posterior joint capsules. After 2 weeks of joint immobilization, the knee joint range of motion was limited, the synovial membrane of the suprapatellar and posterior joint capsules was thickened, the collagen deposition was increased, and the mRNA levels of TGF-ß1 were elevated in the anterior and posterior joint capsules. These changes progressed rapidly until 6 weeks of immobilization and may advance slowly after 6 weeks. Joint contracture developed at the early stage of immobilization and progressed over time. The changes in the anterior and posterior joint capsules after joint immobilization may contribute to the limitation in flexion. The elevated mRNA expression of TGF-ß1 may be related to joint capsule fibrosis and may be one of the causes of joint contracture.

Intra-articular delivery of synovium-resident mesenchymal stem cells via BMP-7-loaded fibrous PLGA scaffolds for cartilage repair.

Delivery of synovium-resident mesenchymal stem cells (synMSCs) to cartilage defect site might provide a novel therapeutic modality for treatment of articular cartilage diseases. However, low isolation efficiency of synMSCs limits their therapeutic application. Niche-preserving non-enzymatic isolation of synMSCs was firstly attempted by employing micro-organ culture system based on recapitulating tissue-specific homeostasis ex vivo. The isolated synMSCs retained superior long-term growth competency, proliferation and chondrogenic potential to bone marrow-derived MSCs (BMSCs). It was noted that synMSCs demonstrated 9-fold increase in cartilaginous micro-tissue formation and 13-fold increase in sulfated proteoglycans deposition compared to BMSCs. For delivery of synMSCs, fibrous PLGA scaffolds were specifically designed for full-thickness osteochondral defects in rabbits. The scaffolds provided effective micro-environment for growth and host-integration of synMSCs. Combined delivery of synMSCs with bone morphogenetic proteins-7 (BMP-7) was designed to achieve synergistic therapeutic efficacy. BMP-7-loaded PLGA nanoparticles electrosprayed onto the scaffolds released BMP-7 over 2 weeks to conform with its aimed role in stimulating early stage endochondral ossification. Scaffold-supported combined administration of synMSCs with BMP-7 resulted in high proteoglycan and collagen type II induction and thick hyaline cartilage formation. Intra-articular co-delivery of synMSCs with BMP-7 via fibrous PLGA scaffolds may be a promising therapeutic modality for articular cartilage repair.

Histopathology of the synovial tissue: perspectives for biomarker development in chronic inflammatory arthritides.

The histopathological and molecular analysis of the synovial tissue has contributed to fundamental advances in our comprehension of arthritis pathogenesis and of the mechanisms of action of currently available treatments. On the other hand, its exploitation in clinical practice for diagnostic or prognostic purposes as well as for the prediction of treatment response to specific disease-modifying anti-rheumatic drugs is still limited. In this review, we present an overview of recent advances in the field of synovial tissue research with specific reference to the methods for synovial tissue collection, approaches to synovial tissue analysis and current perspectives for the exploitation of synovial tissue-derived biomarkers in chronic inflammatory arthritides.

Therapeutic Effect of Penta-acetyl Geniposide on Adjuvant-Induced Arthritis in Rats: Involvement of Inducing Synovial Apoptosis and Inhibiting NF-κB Signal Pathway.

Previous studies demonstrated that penta-acetyl geniposide ((Ac)5GP, an acetylated derivative of geniposide) exhibited better pharmacological functions than geniposide. This study was aimed to observe the potential effect of (Ac)5GP on adjuvant-induced arthritis (AIA) in rat and explore the involved mechanisms. Rat AIA was induced by complete Freund's adjuvant. (Ac)5GP (30, 60, 120 mg/kg) was given to AIA rats by intragastric administration. Paw swelling, polyarthritis index, serum pro-inflammatory cytokines levels, histological assessments of ankle joint, and proteoglycan expression were respectively measured to evaluate the therapeutic effect of (Ac)5GP on rat AIA. Immunohistochemistry for Ki67 and TUNEL assay were performed to reveal the anti-proliferative and pro-apoptotic effects of (Ac)5GP on AIA synoviocytes in vivo. Protein levels of Bcl-2, Bax, caspase 3, IκBα, p-IκBα, and NF-κB p65 in synovial tissues were detected by Western blot. We found that (Ac)5GP treatment could suppress secondary hind paw swelling, reduce polyarthritis index, decrease TNF-α and IL-1ß serum levels, attenuate pathological damage of ankle joint, and promote proteoglycans expression. (Ac)5GP treatment also could reduce Ki67 positive expression rate and raise the synovial apoptosis index in synovial tissues. Additionally, (Ac)5GP (120 mg/kg) could significantly decrease Bcl-2 protein level, increase Bax and cleaved caspase 3 protein levels, and normalize the ratio of Bcl-2 to Bax. Moreover, (Ac)5GP (120 mg/kg) could inhibit the degradation and phosphorylation of IκBα and reduce NF-κB p65 protein level in nuclear extracts. In conclusion, (Ac)5GP showed a potent anti-arthritic effect on AIA rats via inducing synovial apoptosis and inhibiting NF-κB activation in synovial tissues.

Localization of surfactant protein-D in the rheumatoid synovial membrane.

Surfactant protein-D (SP-D) is a collectin, which plays an important role in airway protection and inflammation. The molecule has both pro- and anti-inflammatory capacities depending on its molecular size. Its involvement in joint diseases is largely unknown and the aim of this investigation was to study SP-D occurrence and distribution in the synovial membrane of patients with long-standing rheumatoid arthritis (RA) and osteoarthritis (OA). Six RA patients and six OA patients, who underwent total hip arthroplasty, were included in the study. Synovial tissue biopsies were obtained during surgery and subsequently prepared for immunohistochemistry. In this first, small-scale comparative study on the occurrence of SP-D in the synovial membrane of RA and OA, we report that SP-D was only present in the microvascular endothelium in subsynovial and pannus tissue and that the immunostaining was much stronger than in OA. This distribution pattern suggests that SP-D modulates RA inflammatory activities.

A Protocol to Prepare Decellularized Stem Cell Matrix for Rejuvenation of Cell Expansion and Cartilage Regeneration.

Traditional ex vivo expansion of adult stem cells yields an insufficient quantity of less potent cells. Here we describe the fabrication of decellularized matrix deposited by synovium-derived stem cells (SDSCs). This matrix could serve as a three-dimensional expansion system to rejuvenate cells for proliferation and tissue-specific differentiation potential, which could benefit cartilage regeneration. The decellularized stem cell matrix (DSCM) might be a powerful system for tissue engineering and regeneration.

Osteoclast-Associated Receptor (OSCAR) Distribution in the Synovial Tissues of Patients with Active RA and TNF-α and RANKL Regulation of Expression by Osteoclasts In Vitro.

Osteoclast-associated receptor (OSCAR) is a co-stimulatory receptor in osteoclastogenesis. Synovial tissues from active rheumatoid arthritis (RA) patients express higher levels of OSCAR compared with osteoarthritic and normal patients; however, the comparison of OSCAR levels in different regions of active RA synovium has not been reported. The regulation of OSCAR by TNF-α and receptor activator of NF kappa ß ligand (RANKL) in pre-osteoclasts/osteoclasts in vitro is unclear. OSCAR and tartrate-resistant acid phosphatase (TRAP) expression levels did not differ between the cartilage pannus junction (CPJ) and non-CPJ regions in active RA. We demonstrate a similar pattern of OSCAR expression in the CPJ and non-CPJ synovial tissue from patients with active RA. OSCAR was associated with mononuclear cells in both the lining and sub-lining and endothelial cells (von Willebrand factor positive). Pre-osteoclasts (TRAP-positive cells) were present in the lining and sub-lining of both regions. OSCAR messenger RNA (mRNA) expression and release by pre-oscteoclasts/osteoclasts was modulated by RANKL with/without TNF-α in vitro. Osteoclast resorption on dentine slices was significantly greater with TNF-α pre-treatment and RANKL (10 ng/ml) than RANKL 10 or 50 ng/ml alone or RANKL 10 ng/ml with TNF-α given from day 3 post-RANKL. The lower levels of OSCAR mRNA expression corresponded with high osteoclast activity levels.

Toward understanding the role of cartilage particulates in synovial inflammation.

OBJECTIVE: Arthroscopy with lavage and synovectomy can remove tissue debris from the joint space and the synovial lining to provide pain relief to patients with osteoarthritis (OA). Here, we developed an in vitro model to study the interaction of cartilage wear particles with fibroblast-like synoviocytes (FLS) to better understand the interplay of cartilage particulates with cytokines on cells of the synovium. METHOD: In this study sub-10 µm cartilage particles or 1 µm latex particles were co-cultured with FLS ±10 ng/mL interleukin-1α (IL-1α) or tumor necrosis factor-α (TNF-α). Samples were analyzed for DNA, glycosaminoglycan (GAG), and collagen, and media samples were analyzed for media GAG, nitric oxide (NO) and prostaglandin-E2 (PGE2). The nature of the physical interaction between the particles and FLS was determined by microscopy. RESULTS: Both latex and cartilage particles could be phagocytosed by FLS. Cartilage particles were internalized and attached to the surface of both dense monolayers and individual cells. Co-culture of FLS with cartilage particulates resulted in a significant increase in cell sheet DNA and collagen content as well as NO and PGE2 synthesis compared to control and latex treated groups. CONCLUSION: The proliferative response of FLS to cartilage wear particles resulted in an overall increase in extracellular matrix (ECM) content, analogous to the thickening of the synovial lining observed in OA patients. Understanding how cartilage particles interface with the synovium may provide insight into how this interaction contributes to OA progression and may guide the role of lavage and synovectomy for degenerative disease.

[Intra-articular injections of hyaluronic acid for anterior disc displacement of temporomandibular joint].

Anterior disc displacement (ADD) of temporomandibular joint (TMJ) is regarded as one of the major findings in temporomandibular disorders (TMD). It is related to joint noise, pain, mandibular dysfunction, degenerative change and osteoarthritis. In the mean time, the pathological changes were found in synovial membrane and synovial fluid. Hyaluronic acid is a principal component of the synovial fluid which plays an important role in nutrition, lubrication, anti-inflammation and cartilage repair. The synthesis, molecule weight, and concentration of hyaluronic acid are decreased during TMD and cause TMJ degenerative changes. The clinical conditions, pathological changes, the mechanism of action for hyaluronic acid and the treatment of anterior disc displacement of TMJ are discussed in this article.

Immunogenic HLA-DR-Presented Self-Peptides Identified Directly from Clinical Samples of Synovial Tissue, Synovial Fluid, or Peripheral Blood in Patients with Rheumatoid Arthritis or Lyme Arthritis.

Human leukocyte antigen-antigen D related (HLA-DR) molecules are highly expressed in synovial tissue (ST), the target of the immune response in chronic inflammatory forms of arthritis. Here, we used LC-MS/MS to identify HLA-DR-presented self-peptides in cells taken directly from clinical samples: ST, synovial fluid mononuclear cells (SFMC), or peripheral blood mononuclear cells (PBMC) from five patients with rheumatoid arthritis (RA) and eight with Lyme arthritis (LA). We identified 1593 non-redundant HLA-DR-presented peptides, derived from 870 source proteins. A total of 67% of the peptides identified in SFMC and 55% of those found in PBMC were found in ST, but analysis of SFMC/PBMC also revealed new antigen-presented peptides. Peptides were synthesized and examined for reactivity with the patients' PBMC. To date, three autoantigens in RA and four novel autoantigens in LA, presented in ST and/or PBMC, were shown to be targets of T- and B-cell responses in these diseases; ongoing analyses may add to this list. Thus, immunoprecipitation and LC-MS/MS can now identify hundreds of HLA-DR-presented self-peptides from individual patients' tissues or fluids with mixed cell populations. Importantly, identification of HLA-DR-presented peptides from SFMC or PBMC allows testing of more patients, including those early in the disease. Direct analysis of clinical samples facilitates identification of novel immunogenic T-cell epitopes.

Treating experimental arthritis with the innate immune inhibitor interleukin-37 reduces joint and systemic inflammation.

OBJECTIVES: The IL-1 family member IL-37 was recently characterized as a fundamental inhibitor of innate inflammation. We investigated the effects of recombinant IL-37 in joint inflammation and joint pathology in a mouse model of arthritis. In addition, we explored the potential for therapeutic use in human joint inflammation. METHODS: Wild-type mice were treated systemically with a recombinant form of the naturally occurring human IL-37, and then the knee joints were injected with streptococcal cell wall fragments; joint inflammation, synovial cytokine concentrations and histology were evaluated after 24 h. Mice deficient in the IL-1 family decoy receptor IL-1R8 were treated in a similar manner. The effects of IL-37 treatment were also assessed in a model of streptococcal cell wall-induced systemic inflammation. Changes in IL37 and IL1R8 gene expression were evaluated in the synovia of patients with rheumatoid arthritis. RESULTS: In wild-type mice, low doses (40 µg/kg) of IL-37 suppressed joint inflammation by 51.7% (P < 0.001) and significantly decreased synovial IL-1ß by 84%, IL-6 by 73%, TNF-α by 33%, chemokine (C-X-C motif) ligand 1 by 58%, Chemokine (C-C motif) ligand 3 or macrophage inflammatory protein 1-alpha by 64%, IL-1α by 40% and MPO by 60%. These reductions were associated with a lower recruitment of neutrophils into the joint. The anti-inflammatory properties of IL-37 were dependent on the presence of IL-1R8, also in streptococcal cell wall-induced peritonitis. We found that gene expression of IL1R8, but not IL37, is markedly increased in the synovia of patients with rheumatoid arthritis. CONCLUSION: IL-37 emerges as a key suppressor of joint and systemic inflammation. These findings indicate a rationale for using recombinant IL-37 in the treatment of arthritis.

Hypoxia and its implications in rheumatoid arthritis.

Alterations in tissue oxygen pressure contribute to a number of diseases, including rheumatoid arthritis (RA). Low partial pressure of oxygen, a condition known as hypoxia, is a relevant feature in RA since it is involved in angiogenesis, inflammation, apoptosis, cartilage degradation, energy metabolism, and oxidative damage. Therefore, alterations in hypoxia-related signaling pathways are considered potential mechanisms of disease pathogenesis. The objective of this review is to highlight and update our current knowledge of the role of hypoxia in the pathogenesis of RA. We describe the experimental evidence that RA synovial tissue exists in a hypoxic state, as well as the origin and involvement of synovial hypoxia in different aspects of the pathogenic process.