Persistent Synovial Inflammation Research Articles

Macrophage polarization in rheumatoid arthritis: signaling pathways, metabolic reprogramming, and crosstalk with synovial fibroblasts.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by persistent synovial inflammation and progressive joint destruction. Macrophages are key effector cells that play a central role in RA pathogenesis through their ability to polarize into distinct functional phenotypes. An imbalance favoring pro-inflammatory M1 macrophages over anti-inflammatory M2 macrophages disrupts immune homeostasis and exacerbates joint inflammation. Multiple signaling pathways, including Notch, JAK/STAT, NF-κb, and MAPK, regulate macrophage polarization towards the M1 phenotype in RA. Metabolic reprogramming also contributes to this process, with M1 macrophages prioritizing glycolysis while M2 macrophages utilize oxidative phosphorylation. Redressing this imbalance by modulating macrophage polarization and metabolic state represents a promising therapeutic strategy. Furthermore, complex bidirectional interactions exist between synovial macrophages and fibroblast-like synoviocytes (FLS), forming a self-perpetuating inflammatory loop. Macrophage-derived factors promote aggressive phenotypes in FLS, while FLS-secreted mediators contribute to aberrant macrophage activation. Elucidating the signaling networks governing macrophage polarization, metabolic adaptations, and crosstalk with FLS is crucial to developing targeted therapies that can restore immune homeostasis and mitigate joint pathology in RA.

Nuciferine alleviates collagen-induced arthritic in rats by inhibiting the proliferation and invasion of human arthritis-derived fibroblast-like synoviocytes and rectifying Th17/Treg imbalance

Rheumatoid arthritis (RA) is a chronic autoimmune disorder marked by persistent synovial inflammation and joint degradation, posing challenges in the development of effective treatments. Nuciferine, an alkaloid found in lotus leaf, has shown promising anti-inflammatory and anti-tumor effects, yet its efficacy in RA treatment remains unexplored. This study investigated the antiproliferative effects of nuciferine on the MH7A cell line, a human RA-derived fibroblast-like synoviocyte, revealing its ability to inhibit cell proliferation, promote apoptosis, induce apoptosis, and cause G1/S phase arrest. Additionally, nuciferine significantly reduced the migration and invasion capabilities of MH7A cells. The therapeutic potential of nuciferine was further evaluated in a collagen-induced arthritis (CIA) rat model, where it markedly alleviated joint swelling, synovial hyperplasia, cartilage injury, and inflammatory infiltration. Nuciferine also improved collagen-induced bone erosion, decreased pro-inflammatory cytokines and serum immunoglobulins (IgG, IgG1, IgG2a), and restored the balance between T helper (Th) 17 and regulatory T cells in the spleen of CIA rats. These results indicate that nuciferine may offer therapeutic advantages for RA by decreasing the proliferation and invasiveness of FLS cells and correcting the Th17/Treg cell imbalance in CIA rats.

Immunomodulatory roles of metalloproteinases in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic, autoimmune pathology characterized by persistent synovial inflammation and gradually advancing bone destruction. Matrix metalloproteinases (MMPs), as a family of zinc-containing enzymes, have been found to play an important role in degradation and remodeling of extracellular matrix (ECM). MMPs participate in processes of cell proliferation, migration, inflammation, and cell metabolism. A growing number of persons have paid attention to their function in inflammatory and immune diseases. In this review, the details of regulation of MMPs expression and its expression in RA are summarized. The role of MMPs in ECM remodeling, angiogenesis, oxidative and nitrosative stress, cell migration and invasion, cytokine and chemokine production, PANoptosis and bone destruction in RA disease are discussed. Additionally, the review summarizes clinical trials targeting MMPs in inflammatory disease and discusses the potential of MMP inhibition in the therapeutic context of RA. MMPs may serve as biomarkers for drug response, pathology stratification, and precision medicine to improve clinical management of rheumatoid arthritis.

Can pyroptosis be a new target in rheumatoid arthritis treatment?

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease of undefined etiology, with persistent synovial inflammation and destruction of articular cartilage and bone. Current clinical drugs for RA mainly include non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, disease modifying anti-rheumatic drugs (DMARDs) and so on, which can relieve patients' joint symptoms. If we want to have a complete cure for RA, there are still some limitations of these drugs. Therefore, we need to explore new mechanisms of RA to prevent and treat RA radically. Pyroptosis is a newly discovered programmed cell death (PCD) in recent years, which is characterized by the appearance of holes in cell membranes, cell swelling and rupture, and the release of intracellular pro-inflammatory factors into the extracellular space, resulting in a strong inflammatory response. The nature of pyroptosis is pro-inflammatory, and whether it is participating in the development of RA has attracted a wide interest among scholars. This review describes the discovery and mechanism of pyroptosis, the main therapeutic strategies for RA, and the role of pyroptosis in the mechanism of RA development. From the perspective of pyroptosis, the study of new mechanisms of RA may provide a potential target for the treatment of RA and the development of new drugs in the clinics.

Diagnostic gene signatures and aberrant pathway activation based on m6A methylation regulators in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease (AD) characterized by persistent synovial inflammation, bone erosion and progressive joint destruction. This research aimed to elucidate the potential roles and molecular mechanisms of N6-methyladenosine (m6A) methylation regulators in RA. An array of tissues from 233 RA and 126 control samples was profiled and integrated for mRNA expression analysis. Following quality control and normalization, the cohort was split into training and validation sets. Five distinct machine learning feature selection methods were applied to the training set and validated in validation sets. Among the six models, the LASSO_λ-1se model not only performed better in the validation sets but also exhibited more stringent performance. Two m6A methylation regulators were identified as significant biomarkers by consensus feature selection from all four methods. IGF2BP3 and YTHDC2, which are differentially expressed in patients with RA and controls, were used to predict RA diagnosis with high accuracy. In addition, IGF2BP3 showed higher importance, which can regulate the G2/M transition to promote RA-FLS proliferation and affect M1 macrophage polarization. This consensus of multiple machine learning approaches identified two m6A methylation regulators that could distinguish patients with RA from controls. These m6A methylation regulators and their target genes may provide insight into RA pathogenesis and reveal novel disease regulators and putative drug targets.

Mechanistic and therapeutic links between rheumatoid arthritis and diabetes mellitus.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by persistent synovial inflammation and irreversible cartilage and bone damage. Despite its predominant osteoarticular and periarticular manifestations, RA is also a systematic disease associated with organ-specific extra-articular manifestation. Increasing evidence indicates that RA patients are susceptible to diabetes mellitus (DM), and RA aggravates metabolic disordered in DM, indicating the close association between RA and DM. Many factors involved in RA stimulate insulin resistance and DM development. These factors include proinflammatory cytokines (such as TNF-α, IL-6, IL-1β), RA autoantibodies (such as rheumatoid factor, cyclic citrullinated peptide antibodies), excess RA related adipokines (such as leptin, resistin, ANGPTL4), C-creative protein, and other protein (such as TXNDC5, NLRP3, RBP4). Furthermore, commonly used RA drugs, such as conventional synthetic disease-modifying antirheumatic drugs (csDMARDs), biological disease-modifying antirheumatic drugs (bDMARDs), and glucocorticoids, provide potential benefits in improving insulin resistance and inhibiting DM development. This review discusses the mechanistic and therapeutic links between RA and DM, aiming to provide valuable information for the prevention and treatment of DM in RA patients.

Inflammation-Triggered Supramolecular Nanoplatform for Local Dynamic Dependent Imaging-Guided Therapy of Rheumatoid Arthritis.

The aging of population has resulted in a significant increase in the prevalence of rheumatoid arthritis (RA), which is a persistent and recurrent synovial inflammation caused by abnormal immune activation. Herein, the authors designed an inflammation‐triggered disassembly (ITD) nanoplatform by a supramolecular assembly method, which controls the decomposition and drug release through changes in cytokine concentrations and redox potentials during the onset of arthritis, and its dual‐targeted synergistic effect on collagen‐induced arthritis (CIA) rats resulted in higher cell death rate and immunosuppressive rate. Meanwhile, they propose the local dynamic dependent imaging (LDDI) technology to diagnose the disease status, which may produce corresponding changes with the fluctuation of inflammatory activity and improve the accuracy of dual‐target therapy by monitoring the synovial changes through in situ photoactivation of the second near infrared light (NIR‐II). Very importantly, histological analysis shows that ITD strategy relieved joint destruction and cartilage degeneration and its clinical score is similar to that of the healthy group. Their work provides an effective strategy for the early diagnosis and treatment of acute and chronic inflammation diseases, which can interfere to abnormal immune activation, rather than affecting the normal function of immune system.

Critical Role of Synovial Tissue-Resident Macrophage and Fibroblast Subsets in the Persistence of Joint Inflammation.

Rheumatoid arthritis (RA) is a chronic prototypic immune-mediated inflammatory disease which is characterized by persistent synovial inflammation, leading to progressive joint destruction. Whilst the introduction of targeted biological drugs has led to a step change in the management of RA, 30-40% of patients do not respond adequately to these treatments, regardless of the mechanism of action of the drug used (ceiling of therapeutic response). In addition, many patients who acheive clinical remission, quickly relapse following the withdrawal of treatment. These observations suggest the existence of additional pathways of disease persistence that remain to be identified and targeted therapeutically. A major barrier for the identification of therapeutic targets and successful clinical translation is the limited understanding of the cellular mechanisms that operate within the synovial microenvironment to sustain joint inflammation. Recent insights into the heterogeneity of tissue resident synovial cells, including macropahges and fibroblasts has revealed distinct subsets of these cells that differentially regulate specific aspects of inflammatory joint pathology, paving the way for targeted interventions to specifically modulate the behaviour of these cells. In this review, we will discuss the phenotypic and functional heterogeneity of tissue resident synovial cells and how this cellular diversity contributes to joint inflammation. We discuss how critical interactions between tissue resident cell types regulate the disease state by establishing critical cellular checkpoints within the synovium designed to suppress inflammation and restore joint homeostasis. We propose that failure of these cellular checkpoints leads to the emergence of imprinted pathogenic fibroblast cell states that drive the persistence of joint inflammation. Finally, we discuss therapeutic strategies that could be employed to specifically target pathogenic subsets of fibroblasts in RA.

Switching and Discontinuation Pattern of Biologic Disease-Modifying Antirheumatic Drugs and Tofacitinib for Patients With Rheumatoid Arthritis in Taiwan

Rheumatoid arthritis (RA) is a chronic inflammatory systemic disease characterized by persistent joint synovial inflammation and swelling, leading to cartilage damage and bone erosion. This retrospective, longitudinal study is to evaluate the treatment patterns of biologic-naïve RA patients receiving index biologic disease-modifying antirheumatic drug (bDMARD) and tofacitinib by the data of Taiwan National Healthcare Insurance Claims and the Death Registry between 2012 and 2017. Drug survival and treatment patterns were determined by investigating the occurrence of switching and discontinuation from index treatment. At baseline, 70.0% of patients used tumor necrosis factor inhibitors (TNFi) bDMARD with the majority taking etanercept (27.0%) or adalimumab (26.2%). During the follow-up period, 40.0% (n = 3,464) of index users switched (n = 1,479) or discontinued (n = 1,985) the treatment with an average incidence rate of 0.18 per patient-year. Among the six index treatment groups, drug survival was the lowest for adalimumab and highest for tocilizumab. When compared with etanercept, only adalimumab had a higher cumulative probability of switching/discontinuation (adjusted HR = 1.17, 95% CI: 1.08–1.28), whereas golimumab, non-TNFi bDMARDs and tofacitinib were significantly less probable to switch or discontinue. For patients switching the index treatment, tocilizumab (31.2%) and tofacitinib (23.4%) were the main regimens being switched to. In addition, 48.2% of patients who discontinued the index treatment received further retreatment, and 63.8–77.0% of them were retreated with same agent. In conclusion, this population-based study found that TNFi were the preferred agents as the index treatments during 2012–2017. Non-TNFi and tofacitinib were more common second-line agents being switched to. Nearly half of discontinued patients received retreatment, with a majority receiving the same agent.

The heterogeneous human memory CCR6+ T helper-17 populations differ in T-bet and cytokine expression but all activate synovial fibroblasts in an IFN\u03b3-independent manner

BackgroundChronic synovial inflammation is an important hallmark of inflammatory arthritis, but the cells and mechanisms involved are incompletely understood. Previously, we have shown that CCR6+ memory T-helper (memTh) cells and synovial fibroblasts (SF) activate each other in a pro-inflammatory feedforward loop, which potentially drives persistent synovial inflammation in inflammatory arthritis. However, the CCR6+ memTh cells are a heterogeneous population, containing Th17/Th22 and Th17.1 cells. Currently, it is unclear which of these subpopulations drive SF activation and how they should be targeted. In this study, we examined the individual contribution of these CCR6+ memTh subpopulations to SF activation and examined ways to regulate their function.MethodsTh17/Th22 (CXCR3−CCR4+), Th17.1 (CXCR3+CCR4−), DP (CXCR3+CCR4+), and DN (CXCR3−CCR4−) CCR6+ memTh, cells sorted from PBMC of healthy donors or treatment-naïve early rheumatoid arthritis (RA) patients, were cocultured with SF from RA patients with or without anti-IL17A, anti-IFNγ, or 1,25(OH)2D3. Cultures were analyzed by RT-PCR, ELISA, or flow cytometry.ResultsTh17/Th22, Th17.1, DP, and DN cells equally express RORC but differ in production of TBX21 and cytokines like IL-17A and IFNγ. Despite these differences, all the individual CCR6+ memTh subpopulations, both from healthy individuals and RA patients, were more potent in activating SF than the classical Th1 cells. SF activation was partially inhibited by blocking IL-17A, but not by inhibiting IFNγ or TBX21. However, active vitamin D inhibited the pathogenicity of all subpopulations leading to suppression of SF activation.ConclusionsHuman CCR6+ memTh cells contain several subpopulations that equally express RORC but differ in TBX21, IFNγ, and IL-17A expression. All individual Th17 subpopulations are more potent in activating SF than classical Th1 cells in an IFNγ-independent manner. Furthermore, our data suggest that IL-17A is not dominant in this T cell-SF activation loop but that a multiple T cell cytokine inhibitor, such as 1,25(OH)2D3, is able to suppress CCR6+ memTh subpopulation-driven SF activation.

Effect of Moxibustion on β-EP and Dyn Levels of Pain-Related Indicators in Patients with Rheumatoid Arthritis

Background Rheumatoid arthritis (RA) is a systemic immunodeficiency disease characterized by persistent synovial inflammation, pannus formation, and bone and cartilage destruction, resulting in joint malformations and function decline. Objective The purpose of this study is to evaluate the effect of moxibustion on clinical symptoms and levels of pain-related indicators beta-endorphin (β-EP) and dynorphin (Dyn) in patients with RA and to explore the potential anti-inflammatory and analgesic mechanisms of moxibustion in RA treatment. Methods A total of 64 patients with RA who met the inclusion criteria were randomly and equally classified into the control and treatment groups. The control group received conventional treatment (oral methotrexate, folate, or leflunomide prescribed for a long time). The treatment group was treated with moxibustion at ST36 (Zusanli), BL23 (Shenshu), and Ashi points with respect to the control group. Patients' clinical symptoms and routine inspection indexes (rheumatoid factor [RF], erythrocyte sedimentation rate [ESR], and C-reactive protein [CRP]) were recorded before and after treatment. Serum levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), β-EP, and Dyn were determined by enzyme-linked immunosorbent assay (ELISA). The software SPSS24.0 was used for statistical analysis. Results (1) Compared with the pretreatment result, both of the two groups' clinical symptoms and routine inspection indexes (RF, ESR, and CRP) improved (P < 0.05), and the improvement of clinical symptoms in the treatment group outperformed that in the control group (P < 0.05). (2) TNF-α and IL-1β levels decreased significantly in the treatment group after treatment (P < 0.01), while no significant difference was observed in the control group (P > 0.05). (3) β-EP and Dyn levels in the treatment group were significantly increased after treatment (P < 0.01, P < 0.01), but the control group showed no significant difference (P > 0.05, P > 0.05). It is worth mentioning that the serum TNF-α, IL-1β, β-EP, and Dyn levels between the two groups were significantly different after 8 weeks of treatment (P < 0.05). (4) Differences in the serum β-EP and Dyn levels in the patients of the treatment group were correlated with TNF-α and IL-1β levels after treatment, and the correlation was mainly negative (r < 0). Conclusion Moxibustion can improve joint pain in patients with RA using conventional western medicine. One of the mechanisms may affect the serum β-EP and Dyn levels by downregulating the inflammatory factors to play an anti-inflammatory and analgesic role.

Biologic therapies for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that primarily affects the synovial joints. If left untreated, persistent synovial inflammation can lead to cartilage and bone destruction, ultimately causing significant longterm disability and mortality. However, since the late 1990s, the combined use of methotrexate, a synthetic diseasemodifying antirheumatic drug (DMARD), and a biological DMARD has revolutionized the treatment of RA. As of 2021, the Korea Food and Drug Administration has approved seven biological DMARDs for RA treatment: four tumor necrosis factor-alpha inhibitors (infliximab, etanercept, adalimumab, and golimumab) and three non-tumor necrosis factor biological products (abatacept, rituximab, and tocilizumab). Although the use of biological products has allowed significant advances in the treatment of RA, there are certain drawbacks, such as high cost, increased infection risk, and the necessity for parenteral route product administration. Therefore, discontinuation of biological DMARD use without a resulting disease flare is the next treatment goal and a desirable result from the standpoint of risk reduction and cost-effectiveness, especially for patients with clinical remission. It is still unclear which biological product is the best. Clinicians must, therefore, personalize the sequence and strategy of treatment by considering patient characteristics, disease activity, comorbidity, and economic condition

Activation of TGR5 alleviates inflammation in rheumatoid arthritis peripheral blood mononuclear cells and in mice with collagen II‑induced arthritis.

Rheumatoid arthritis (RA) is characterized by chronic inflammatory synovitis resulting in progressive joint destruction. Persistent synovial inflammation is induced by activation of various inflammatory cells. G-protein-coupled bile acid receptor 1 (TGR5) is a G-protein-coupled receptor activated by various bile acids, which has been reported to act as a key adaptor in regulating various signaling pathways involved in inflammatory responses and a diverse array of physiological processes, including bile acid synthesis, lipid and carbohydrate metabolism, carcinogenesis, immunity and inflammation. In the present study, TGR5 expression was detected in RA peripheral blood mononuclear cells (PBMCs), and its association with clinical disease activity, histological synovitis severity and radiological joint destruction was analyzed. Subsequently, the role and potential underlying mechanisms of TGR5 in the PBMCs of patients with RA and mice with collagen II-induced arthritis (CIA) were investigated. PBMCs were obtained from 50 patients with RA and 40 healthy controls (HCs). The mRNA and protein expression levels of TGR5 were detected in PBMCs via reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunofluorescence staining, respectively. Additionally, the levels of proinflammatory cytokines were analyzed by RT-qPCR and enzyme-linked immunosorbent assay (ELISA). The activation of nuclear factor-κB (NF-κB) and IκB kinase a was determined via western blot analysis. The anti-arthritic and anti-inflammatory effects of LCA on mice with CIA were then investigated. The arthritis score was assessed, and the protein levels of proinflammatory cytokines in the plasma of mice were detected via ELISA. TGR5 mRNA expression was significantly downregulated in the PBMCs of patients with RA compared with in those of the HCs (0.53±0.58 for patients vs. 1.49±0.83 for HCs; P<0.001); similar findings were observed at the protein level. The mRNA expression levels of TGR5 in the PBMCs of patients with RA with a high 28-Joint Disease Activity Score (DAS28) were significantly decreased compared with in patients with a low DAS28 (0.81±0.65 for low score vs. 0.35±0.46 for high score; P=0.002). Furthermore, TGR5 expression was significantly correlated with the levels of C-reactive protein (r=−0.429; P=0.002) and the DAS28 (r=−0.383; P=0.006). RT-qPCR and ELISA analyses indicated that lithocholic acid (LCA, 10 mg/kg/day) attenuated lipopolysaccharide-induced proinflammatory cytokine production via inhibition of NF-κB activity in the PBMCs of patients with RA. In addition, the arthritis score was significantly decreased in LCA-treated CIA mice compared with in non-treated CIA mice. The increased production of tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and IL-8 was significantly reduced in the plasma of LCA-treated CIA mice compared with the control. In conclusion, TGR5 may contribute to the inflammation of PBMCs in patients with RA and mice with CIA.

IRF1 is critical for the TNF-driven interferon response in rheumatoid fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is an autoimmune disease characterized by persistent synovial inflammation. The major drivers of synovial inflammation are cytokines and chemokines. Among these molecules, TNF activates fibroblast-like synoviocytes (FLSs), which leads to the production of inflammatory mediators. Here, we show that TNF regulates the expression of the transcription factor interferon regulatory factor 1 (IRF1) in human FLSs as well as in a TNF transgenic arthritis mouse model. Transcriptomic analyses of IRF1-deficient, TNF-stimulated FLSs define the interferon (IFN) pathway as a major target of IRF1. IRF1 expression is associated with the expression of IFNβ, which leads to the activation of the JAK-STAT pathway. Blocking the JAK-STAT pathway with the Janus kinase inhibitor (JAKinib) baricitinib or tofacitinib reduces the expression of IFN-regulated genes (IRGs) in TNF-activated FLSs. Therefore, we conclude that TNF induces a distinct inflammatory cascade, in which IRGs are key elements, in FLSs. The IFN-signature might be a promising biomarker for the efficient and personalized use of new treatment strategies for RA, such as JAKinibs.

Pro-resolving lipid mediator ameliorates obesity induced osteoarthritis by regulating synovial macrophage polarisation

Non-resolved persistent macrophage-mediated synovial inflammation is considered as one of the main drivers of both the establishment and progression of obesity-associated osteoarthritis (OA). Herein, we used clodronate-loaded liposomes (CL) to locally deplete macrophages in the synovial joints to examine the role of macrophages in the progression of obesity-induced OA. Furthermore, resolvin D1 (RvD1), a unique family of pro-resolving lipid mediator derived from the omega-3 polyunsaturated fatty acid, have shown marked potency in changing the pro-inflammatory behaviour of the macrophages. We sought to determine whether RvD1 administration ameliorates obesity-induced OA by resolving macrophage-mediated synovitis. Therapeutic properties of RvD1 and macrophage depletion (CL) were tested for its ability to slow post-traumatic OA (PTOA) in obese mice models. PTOA was induced in C57Bl/6 mice fed with high-fat diet (HFD) by surgically destabilising the meniscus. Firstly, CL treatment showed beneficial effects in reducing synovitis and cartilage destruction in obese mice with PTOA. In vitro treatment with RvD1 decreased the levels of pro-inflammatory markers in CD14+ human macrophages. Furthermore, intra-articular treatment with RvD1 diminishes the progression of OA in the knee joint from mice as follows: (a) decreases macrophages infiltration in synovium, (b) reduces the number of pro-inflammatory macrophages in synovium and (c) improves the severity of synovitis and cartilage degradation. Thus, our results provide new evidence for the potential targeting of macrophages in the treatment of obesity-induced OA.

Move to Nano-Arthrology: Targeted Stimuli-Responsive Nanomedicines Combat Adaptive Treatment Tolerance (ATT) of Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is one of the most popular chronic autoimmune diseases characterized with persistent synovial inflammation and bone destruction. Although considerable developments have been gained in clinical treatment of RA, the major drawback to RA therapy stems from the adaptive treatment tolerance (ATT) following the long-term drug use, which causes compromised efficacy, sustained drug dose increase, and severe adverse events. To address these challenges, it is of great significance to put forward innovative therapeutic approaches for RA treatment. Nowadays, developments of nanotechnology-based nanomedicines (NMs) for RA are in progress. Multifunctional NMs with targeted stimuli-responsive features have been one of the central concepts in designing more accessible formulations for efficient RA treatment. These NMs are able to postpone RA progression effectively, because of their delivery and on-demand release of medicaments at targeted sites in response to external or internal stimuli related to the RA pathophysiology without obvious adverse side-effects on the normal tissues. Therefore, NMs have gained interest from pre-clinical research scientists as well as clinical doctors worldwide. Herein, the authors highlight the recent attempts of targeted stimuli-responsive NMs for RA therapy in the last 5 years. The described progresses may pave the way to novel and highly effective RA NMs.

Persistent synovial inflammation plays important roles in persistent pain development in the rat knee before cartilage degradation reaches the subchondral bone

BackgroundThe major complaint of knee osteoarthritis (OA) is persistent pain. Unlike acute inflammatory pain, persistent pain is usually difficult to manage since its pathology is not fully understood. To elucidate the underlying mechanisms of persistent pain, we established 2 different inflammation-induced arthritis models by injecting monoiodo-acetic acid (MIA) into the joint cavity and performed integrated analyses of the structural changes in the synovial tissue and articular cartilage, sensory neuron rearrangement, and pain avoidance behavior in a rat arthritis model.MethodsMale Wistar rats received intra-articular injections of MIA (0.2 mg/30 μL, low-dose group; 1 mg/30 μL, high-dose group) in the right knee and phosphate buffered saline (PBS; 30 μL, control group) in the left knee. Fluorogold (FG), a retrograde neural tracer, was used to label the nerve fibers for the identification of sensory neurons that dominate the joints in the dorsal root ganglion (DRG). Both knees were subjected to the intra-articular injection of 2% FG in PBS (5 μL) under anesthesia 5–7 days prior to sacrifice. We performed pain avoidance behavior tests (incapacitance and von Frey tests) at 0, 1, 3, 5, 7, 14, 21, and 28 days. At 5, 14, and 28 days, the rats were sacrificed and the knee joint and DRG were excised for histological assessment. The knee joints were stained with hematoxylin and eosin, safranin O, and calcitonin gene-related peptide (CGRP). The DRG were immunostained with CGRP.ResultsA transient inflammatory response followed by mild articular cartilage degeneration was observed in the low-dose MIA model versus persistent inflammation with structural changes in the synovial tissue (fibrosis) in the high-dose model. In the high-dose model, full-thickness cartilage degeneration was observed within 2 weeks post-MIA injection. The pain avoidance behavior tests indicated that persistent synovial inflammation and structural changes of the infrapatellar fat pad may play important roles in persistent knee joint pain before the articular cartilage degeneration reaches the subchondral bone.ConclusionsTransient inflammation without structural changes of the synovial tissues did not induce persistent pain in the rat knee joint before degradation of the articular cartilage reached the subchondral bone plate.

Tetraspanin CD82 affects migration, attachment and invasion of rheumatoid arthritis synovial fibroblasts

Tetraspanins function as membrane adaptors altering cell-cell fusion, antigen presentation, receptor-mediated signal transduction and cell motility via interaction with membrane proteins including other tetraspanins and adhesion molecules such as integrins....

Serum Neopterin Level in Children with Juvenile Idiopathic Arthritis

Background: Juvenile idiopathic arthritis (JIA) is generally considered a clinical syndrome involving several disease subsets, with a number of inflammatory flows, leading to an eventual common pathway in which persistent synovial inflammation and associated damage to articular cartilage and underlying bone are present. Neoptrin is a reliable marker in the assessment of the rate of IFN-γ production. Levels of neoptrin increase in direct proportion with the level of interferon. Measurement of neopterin level is useful because of its relative stability also it is a prognostic indicator for cell-mediated immunity. Aims: This study aims to assess serum level of neopterin in patients with Juvenile Idiopathic Arthritis (JIA) in relation to the disease activity, severity and response to conventional and biological therapy. Methodology: The study was conducted on 30 patients (Group A) previously diagnosed as SoJIA, they were divided into two subgroups according to their therapy into Group AI on biological therapy (15 patients) and Group AII on conventional therapy (15 patients). These in addition to 20 healthy controls (Group B). Results: Basic clinical evaluation and laboratory investigations were done. We found that JIA patients had significantly higher levels of serum neopterin than healthy controls. We also found a highly significant difference between neopterin levels in the activity and remission states among all patients (Group AI and Group AII). Conclusion: We concluded that serum neopterin is a useful marker for cellular immune activation and also indicative of the activity of JIA. Our findings are supported by positive correlations between serum neopterin levels and other markers of activity as TLC, PLT counts, ESR, and CRP. We also concluded that serum neopterin is a sensitive and accurate predictor of disease activity where sensitivity of that test was 93.3% and accuracy was 72.5%. Recommendations: Investigating the serum neopterin measurement in other autoimmune collagen diseases. Assessment the influence of biological therapy on neopterin levels in relation to disease progression.

Chronic synovial inflammation play important roles to establish residual pain in monoiodoacetic acid induced arthritis rat model

Purpose: Osteoarthritis (OA) is a group of diseases and mechanical abnormalities involving degradation of articular cartilage and subchondral bone. Major complaint of OA patients is persistent knee pain, which significantly decreases patients' activity of daily living (ADL). However, causal treatment has not provided for OA patients since OA is multifactorial diseases and etiology has not fully understood. Therefore, most of the current treatment strategies for OA is based on the symptom management and patients with uncontrolled knee pain usually choose knee replacement surgery. In this regard, we consider it is quite important to understand the mechanisms of persistent knee pain development during the progression of OA. We have established two distinct inflammation-induced articular cartilage degeneration models in rats. The first was to induce joint inflammation by intra-articular injection of low-dose (0.2mg) of monoiodoacetate (MIA). In this model, we observed transient synovial inflammation followed by mild articular cartilage degeneration in rat knee. The other was high-dose (1.0mg) of MIA injection method. In this model, chronic synovial inflammation and extensive articular cartilage degeneration were observed by 14 days after injection. In this study, we performed detailed histological assessments and monitored pain avoidance behavior in these rat models to understand the mechanisms how knee pain persistence established after joint inflammation. Here we showed that chronic synovial inflammation may play important roles to establish residual pain in rats. Methods: Male Wistar rats received intra-articular injection of MIA (0.2mg, or 1mg/30μl) in the right knee, and PBS (30μl) in the left knee. We performed pain behavior test (Incapacitnce Test and von Frey Test) at 0,1,3,5,7,14,21, and 28 days. At 5, 14, and 28 days, rats were sacrificed, and knee joint and dorsal root ganglion (DRG) were excised for histological assessments. Results: In the low-dose group (0.2mg), extensive inflammatory cell infiltration in the infra-patella fat pad (IFP) and synovial hyperplasia were observed by 5 days after MIA injection, then quenched by 14 days. Proteoglycan contents in both articular cartilage and meniscus gradually decreased by 28 days. Incapacitance tests indicated that weight-bearing of the MIA injected knee (right knee) was significantly decreased by 7 days after injection and returned to the even levels by 14 days when the acute synovial inflammation was quenched. Percentage of Calcitonin-Gene Related Peptide (CGRP)-positive sensory neuron in L4 DRG was significantly decreased at 28 days if compared to that in day 5. In the high-dose group (1.0mg), onset of inflammatory response was almost the same with that of low-dose group, however, it continued throughout the experimental period (28 days). Signs of articular cartilage degeneration was obviously observed as early as 5 days after injection and superficial layers were almost missing at 28 days. In contrast to the low-dose group, weight-bearing continued decreasing significantly throughout the experimental period. Immunohistochemical analyses indicated that percentage of CGRP-positive sensory neuron was much abundant and did not decrease by 28 days. Conclusions: Data suggest that persistent synovial inflammation plays important roles in establishing residual pain in the knee joint.