The role of T cells in the pathogenesis of osteoarthritis

Shedding light on the effects of blood on meniscus tissue: the role of mononuclear leukocytes in mediating meniscus catabolism

OBJECTIVE

Traumatic meniscal injuries can cause acute pain, hemarthrosis (bleeding into the joint), joint immobility, and post-traumatic osteoarthritis (PTOA). However, the exact mechanism(s) by which PTOA develops following meniscal injuries is unknown. Since meniscus tears commonly coincide with hemarthrosis, investigating the direct effects of blood and its constituents on meniscus tissue is warranted. The goal of this study was to determine the direct effects of blood and blood components on meniscus tissue catabolism.

METHODS

Porcine meniscus explants or primary meniscus cells were exposed to whole blood or various fractions of blood for 3 days to simulate blood exposure following injury. Explants were then washed and cultured for an additional 3 days prior to collection for biochemical analyses.

RESULTS

Whole blood increased matrix metalloproteinase (MMP) activity. Fractionation experiments revealed blood-derived red blood cells did not affect meniscus catabolism. Conversely, viable mononuclear leukocytes induced MMP activity, nitric oxide (NO) production, and loss of tissue sulfated glycosaminoglycan (sGAG) content, suggesting that these cells are mediating meniscus catabolism.

CONCLUSIONS

These findings highlight the potential challenges of meniscus healing in the presence of hemarthrosis and the need for further research to elucidate the in vivo effects of blood and blood-derived mononuclear leukocytes due to both hemarthrosis and blood-derived therapeutics.

Identification and verification of a novel signature that combines cuproptosis-related genes with ferroptosis-related genes in osteoarthritis using bioinformatics analysis and experimental validation

BACKGROUND

Exploring the pathogenesis of osteoarthritis (OA) is important for its prevention, diagnosis, and treatment. Therefore, we aimed to construct novel signature genes (c-FRGs) combining cuproptosis-related genes (CRGs) with ferroptosis-related genes (FRGs) to explore the pathogenesis of OA and aid in its treatment.

MATERIALS AND METHODS

Differentially expressed c-FRGs (c-FDEGs) were obtained using R software. Enrichment analysis was performed and a protein-protein interaction (PPI) network was constructed based on these c-FDEGs. Then, seven hub genes were screened. Three machine learning methods and verification experiments were used to identify four signature biomarkers from c-FDEGs, after which gene set enrichment analysis, gene set variation analysis, single-sample gene set enrichment analysis, immune function analysis, drug prediction, and ceRNA network analysis were performed based on these signature biomarkers. Subsequently, a disease model of OA was constructed using these biomarkers and validated on the GSE82107 dataset. Finally, we analyzed the distribution of the expression of these c-FDEGs in various cell populations.

RESULTS

A total of 63 FRGs were found to be closely associated with 11 CRGs, and 40 c-FDEGs were identified. Bioenrichment analysis showed that they were mainly associated with inflammation, external cellular stimulation, and autophagy. CDKN1A, FZD7, GABARAPL2, and SLC39A14 were identified as OA signature biomarkers, and their corresponding miRNAs and lncRNAs were predicted. Finally, scRNA-seq data analysis showed that the differentially expressed c-FRGs had significantly different expression distributions across the cell populations.

CONCLUSION

Four genes, namely CDKN1A, FZD7, GABARAPL2, and SLC39A14, are excellent biomarkers and prospective therapeutic targets for OA.

Mechanical loading of joint modulates T cells in lymph nodes to regulate osteoarthritis

OBJECTIVE

The crosstalk of joint pathology with local lymph nodes in osteoarthritis (OA) is poorly understood. We characterized the change in T cells in lymph nodes following load-induced OA and established the association of the presence and migration of T cells to the onset and progression of OA.

METHODS

We used an in vivo model of OA to induce mechanical load-induced joint damage. After cyclic tibial compression of mice, we analyzed lymph nodes for T cells using flow cytometry and joint pathology using histology and microcomputed tomography. The role of T-cell migration and the presence of T-cell type was examined using T-cell receptor (TCR)α-/- mice and an immunomodulatory drug, Sphingosine-1-phosphate (S1P) receptor inhibitor-treated mice, respectively.

RESULTS

We demonstrated a significant increase in T-cell populations in local lymph nodes in response to joint injury in 10, 16, and 26-week-old mice, and as a function of load duration, 1, 2, and 6 weeks. T-cell expression of inflammatory cytokine markers increased in the local lymph nodes and was associated with load-induced OA progression in the mouse knee. Joint loading in TCRα-/- mice reduced both cartilage degeneration (Osteoarthritis Research Society International (OARSI) scores: TCRα 0.568, 0.981-0.329 confidence interval (CI); wild type (WT) 1.328, 2.353-0.749 CI) and osteophyte formation. Inhibition of T-cell egress from lymph nodes attenuated load-induced cartilage degradation (OARSI scores: Fingolimod: 0.509, 1.821-0.142 CI; Saline 1.210, 1.932-0.758 CI) and decreased localization of T cells in the synovium.

CONCLUSIONS

These results establish the association of lymph node-resident T cells in joint damage and suggest that the S1P receptor modulators and T-cell immunotherapies could be used to treat OA.

Synovial inducible costimulator is correlated with severity in knee osteoarthritis

Osteoarthritis (OA) is a joint disease characterized by articular cartilage loss, which afflicts many people worldwide. Knowing the disease severity can improve the recovery rate of OA. Antibody array technology was utilized for protein expression profiling of synovial fluid from eight mild knee OA patients, eight severe knee OA patients and 16 healthy persons. Subsequently, 48 mild OA patients, 56 severe OA patients and 24 healthy controls were utilized for validation by ELISA. In the protein expression profiling, inducible costimulator (ICOS) levels were markedly higher in OA patients compared with those in the healthy population, and were significantly higher in severe OA than those in mild OA. Furthermore, ICOS levels were shown to be significantly correlated with WOMAC, MRI-MOAKS and MRI-UTE-T2* scores. The multivariate logistic regression analysis indicated that higher levels of ICOS could significantly increase the risk of severe OA. Synovial ICOS levels were positively correlated with the radiographic severity of OA. ICOS may represent a biomarker for predicting the OA severity and may be involved in the development and progression of knee OA.

Harnessing knee joint resident mesenchymal stem cells in cartilage tissue engineering

Osteoarthritis (OA) is a widespread clinical disease characterized by cartilage degeneration in middle-aged and elderly people. Currently, there is no effective treatment for OA apart from total joint replacement in advanced stages. Mesenchymal stem cells (MSCs) are a type of adult stem cell with diverse differentiation capabilities and immunomodulatory potentials. MSCs are known to effectively regulate the cartilage microenvironment, promote cartilage regeneration, and alleviate OA symptoms. As a result, they are promising sources of cells for OA therapy. Recent studies have revealed the presence of resident MSCs in synovial fluid, synovial membrane, and articular cartilage, which can be collected as knee joint-derived MSCs (KJD-MSC). Several preclinical and clinical studies have demonstrated that KJD-MSCs have great potential for OA treatment, whether applied alone, in combination with biomaterials, or as exocrine MSCs. In this article, we will review the characteristics of MSCs in the joints, including their cytological characteristics, such as proliferation, cartilage differentiation, and immunomodulatory abilities, as well as the biological function of MSC exosomes. We will also discuss the use of tissue engineering in OA treatment and introduce the concept of a new generation of stem cell-based tissue engineering therapy, including the use of engineering, gene therapy, and gene editing techniques to create KJD-MSCs or KJD-MSC derivative exosomes with improved functionality and targeted delivery. These advances aim to maximize the efficiency of cartilage tissue engineering and provide new strategies to overcome the bottleneck of OA therapy. STATEMENT OF SIGNIFICANCE: This research will provide new insights into the medicinal benefit of Joint resident Mesenchymal Stem Cells (MSCs), specifically on its cartilage tissue engineering ability. Through this review, the community will further realize promoting joint resident mesenchymal stem cells, especially cartilage progenitor/MSC-like progenitor cells (CPSC), as a preventive measure against osteoarthritis and cartilage injury. People and medical institutions may also consider cartilage derived MSC as an alternative approach against cartilage degeneration. Moreover, the discussion presented in this study will convey valuable information for future research that will explore the medicinal benefits of cartilage derived MSC.

Tolerogenic nanoparticles induce type II collagen-specific regulatory T cells and ameliorate osteoarthritis

Local inflammation in the joint is considered to contribute to osteoarthritis (OA) progression. Here, we describe an immunomodulating nanoparticle for OA treatment. Intradermal injection of lipid nanoparticles (LNPs) loaded with type II collagen (Col II) and rapamycin (LNP-Col II-R) into OA mice effectively induced Col II-specific anti-inflammatory regulatory T cells, substantially increased anti-inflammatory cytokine expression, and reduced inflammatory immune cells and proinflammatory cytokine expression in the joints. Consequently, LNP-Col II-R injection inhibited chondrocyte apoptosis and cartilage matrix degradation and relieved pain, while injection of LNPs loaded with a control peptide and rapamycin did not induce these events. Adoptive transfer of CD4⁺CD25⁺ T cells isolated from LNP-Col II-R-injected mice suggested that T_regs induced by LNP-Col II-R injection were likely responsible for the therapeutic effects. Collectively, this study suggests nanoparticle-mediated immunomodulation in the joint as a simple and effective treatment for OA.

Expanded CD1c+CD163+ DC3 Population in Synovial Tissues Is Associated with Disease Progression of Osteoarthritis

The mechanisms underlying osteoarthritis (OA) have recently been hypothesized to involve a dysfunctional immune system. In this study, we collected synovium, synovial fluid (SF), and peripheral blood from 21 patients. Mononuclear cells were characterized using FCM. H&E staining and mIHC histological assessment of synovium were performed. Cytokine levels in the SF were measured using ELISA. We observed similar frequencies of immune cells in the synovium and SF, which were enriched in DCs. Notably, CD1c⁺CD163⁺ DC3s were expanded in the synovium and SF. Furthermore, we found that DC3s were primarily located within the ectopic lymphoid-like structure (ELLS) in close proximity to CD8⁺ T cells. Finally, the level of TNF-α and IL12p70 in the SF correlated with the severity of OA. These data suggest that OA is an immune system-related disease and that DC3s may play an active role in OA progression by promoting ELLS formation and inflammatory responses.

Human abdominal aortic aneurysm (AAA): Evidence for an autoimmune antigen-driven disease

Abdominal aortic aneurism (AAA) is a complex immunological disease with a strong genetic component, and one of the ten leading causes of death of individuals 55-74 years old worldwide. Strong evidence has been accumulated suggesting that AAA is an autoimmune specific antigen-driven disease. Mononuclear cells infiltrating AAA lesions comprised of T and B lymphocytes and other cells expressing early-, intermediate- and late-activation antigens, and the presence of antigen-presenting cells have been documented, demonstrating an ongoing immune response. The three components of the trimolecular complex, T-cell receptor (TCR)/peptide (antigen)/HLA have been identified in AAA, and specifically: (i) clonal expansions of T-cell clones in AAA lesions; (ii) the association of AAA with particular HLA Class I and Class II; and (iii) self or nonself putative AAA-associated antigens. IgG autoantibodies recognizing proteins present in normal aortic tissue have been reported in patients with AAA. Molecular mimicry, defined as the sharing of antigenic epitopes between microorganisms (bacteria, viruses) and self antigens, maybe is responsible for T-cell responses and antibody production in AAA. Also, the frequency and the suppressor activity of CD4 + CD25 + FOXP3+ Tregs and the expression of FOXP3 transcripts and protein have been reported to be significantly impaired in AAA patients vs normal donors.

Obesity, Inflammation, and Immune System in Osteoarthritis

Obesity remains the most important risk factor for the incidence and progression of osteoarthritis (OA). The leading cause of OA was believed to be overloading the joints due to excess weight which in turn leads to the destruction of articular cartilage. However, recent studies have proved otherwise, various other factors like adipose deposition, insulin resistance, and especially the improper coordination of innate and adaptive immune responses may lead to the initiation and progression of obesity-associated OA. It is becoming increasingly evident that multiple inflammatory cells are recruited into the synovial joint that serves an important role in pathological changes in the synovial joint. Polarization of macrophages and macrophage-produced mediators are extensively studied and linked to the inflammatory and destructive responses in the OA synovium and cartilage. However, the role of other major innate immune cells such as neutrophils, eosinophils, and dendritic cells in the pathogenesis of OA has not been fully evaluated. Although cells of the adaptive immune system contribute to the pathogenesis of obesity-induced OA is still under exploration, a quantity of literature indicates OA synovium has an enriched population of T cells and B cells compared with healthy control. The interplay between a variety of immune cells and other cells that reside in the articular joints may constitute a vicious cycle, leading to pathological changes of the articular joint in obese individuals. This review addresses obesity and the role of all the immune cells that are involved in OA and summarised animal studies and human trials and knowledge gaps between the studies have been highlighted. The review also touches base on the interventions currently in clinical trials, different stages of the testing, and their shortcomings are also discussed to understand the future direction which could help in understanding the multifactorial aspects of OA where inflammation has a significant function.

The Effects of Crocin on Bone and Cartilage Diseases

Crocin, the main biologically active carotenoid of saffron, generally is derived from the dried trifid stigma of Crocus sativus L. Many studies have demonstrated that crocin has several therapeutic effects on biological systems through its anti-oxidant and anti-inflammatory properties. The wide range of crocin activities is believed to be because of its ability to anchor to many proteins, triggering some cellular pathways responsible for cell proliferation and differentiation. It also has therapeutic potentials in arthritis, osteoarthritis, rheumatoid arthritis, and articular pain probably due to its anti-inflammatory properties. Anti-apoptotic effects, as well as osteoclast inhibition effects of crocin, have suggested it as a natural substance to treat osteoporosis and degenerative disease of bone and cartilage. Different mechanisms underlying crocin effects on bone and cartilage repair have been investigated, but remain to be fully elucidated. The present review aims to undertake current knowledge on the effects of crocin on bone and cartilage degenerative diseases with an emphasis on its proliferative and differentiative properties in mesenchymal stem cells.

T cell transgressions: Tales of T cell form and function in diverse disease states

Insights into T cell form, function, and dysfunction are rapidly evolving. T cells have remarkably varied effector functions including protecting the host from infection, activating cells of the innate immune system, releasing cytokines and chemokines, and heavily contributing to immunological memory. Under healthy conditions, T cells orchestrate a finely tuned attack on invading pathogens while minimizing damage to the host. The dark side of T cells is that they also exhibit autoreactivity and inflict harm to host cells, creating autoimmunity. The mechanisms of T cell autoreactivity are complex and dynamic. Emerging research is elucidating the mechanisms leading T cells to become autoreactive and how such responses cause or contribute to diverse disease states, both peripherally and within the central nervous system. This review provides foundational information on T cell development, differentiation, and functions. Key T cell subtypes, cytokines that create their effector roles, and sex differences are highlighted. Pathological T cell contributions to diverse peripheral and central disease states, arising from errors in reactivity, are highlighted, with a focus on multiple sclerosis, rheumatoid arthritis, osteoarthritis, neuropathic pain, and type 1 diabetes.

Immunofluorescence Analysis of NF-kB and iNOS Expression in Different Cell Populations during Early and Advanced Knee Osteoarthritis

Synovitis of the knee synovium is proven to be a precursor of knee osteoarthritis (OA), leading to a radiologically advanced stage of the disease. This study was conducted to elucidate the expression pattern of different inflammatory factors—NF-kB, iNOS, and MMP-9 in a subpopulation of synovial cells. Thirty synovial membrane intra-operative biopsies of patients (ten controls, ten with early OA, and ten with advanced OA, according to the Kellgren–Lawrence radiological score) were immunohistochemically stained for NF-kB, iNOS, and MMP9, and for different cell markers for macrophages, fibroblasts, leukocytes, lymphocytes, blood vessel endothelial cells, and blood vessel smooth muscle cells. The total number of CD68+/NF-kB+ cells/mm² in the intima of early OA patients (median = 2359) was significantly higher compared to the total number of vimentin+/Nf-kB+ cells/mm² (median = 1321) and LCA+/NF-kB+ cells/mm² (median = 64) (p < 0.001 and p < 0.0001, respectively). The total number of LCA+/NF-kB+ cells/mm² in the subintima of advanced OA patients (median = 2123) was significantly higher compared to the total number of vimentin+/NF-kB+ cells/mm² (median = 14) and CD68+/NF-kB+ cells/mm² (median = 29) (p < 0.0001). The total number of CD68+/iNOS+ cells/mm² in the intima of both early and advanced OA patients was significantly higher compared to the total number of vimentin+/iNOS+ cells/mm² and LCA+/iNOS+ cells/mm² (p < 0.0001 and p < 0.001, respectively). The total number of CD68+/MMP-9+ cells/mm² in the intima of both early and advanced OA patients was significantly higher compared to the total number of vimentin+/MMP-9+ cells/mm² and CD5+/MMP-9+ cells/mm² (p < 0.0001). Macrophages may have a leading role in OA progression through the NF-kB production of inflammatory factors (iNOS and MMP-9) in the intima, except in advanced OA, where leukocytes could have a dominant role through NF-kB production in subintima. The blocking of macrophageal and leukocyte NF-kB expression is a possible therapeutic target as a disease modifying drug.

Effect of Epstein-Barr Virus DNA on the Incidence and Severity of Arthritis in a Rheumatoid Arthritis Mouse Model

Objective

We recently demonstrated that EBV DNA is correlated with proinflammatory responses in mice and in rheumatoid arthritis (RA) patients; hence, we utilized an RA mouse model to examine whether EBV DNA enhances the risk and severity of arthritis and to assess its immunomodulatory effects.

Methods

C57BL/6J mice were treated with collagen (arthritis-inducing agent), EBV DNA 6 days before collagen, EBV DNA 15 days after collagen, Staphylococcus epidermidis DNA 6 days before collagen, EBV DNA alone, or water. Mice were then monitored for clinical signs and affected joints/footpads were histologically analysed. The relative concentration of IgG anti- chicken collagen antibodies and serum cytokine levels of IL-17A and IFNϒ were determined by ELISA. The number of cells co-expressing IL-17A and IFNϒ in joint histological sections was determined by immunofluorescence.

Results

The incidence of arthritis was significantly higher in mice that received EBV DNA prior to collagen compared to mice that only received collagen. Similarly, increased clinical scores, histological scores and paw thicknesses with a decreased gripping strength were observed in groups treated with EBV DNA and collagen. The relative concentration of IgG anti-chicken collagen antibodies was significantly increased in the group that received EBV DNA 6 days prior to collagen in comparison to the collagen receiving group. On the other hand, the highest number of cells co-expressing IFNϒ and IL-17A was observed in joints from mice that received both collagen and EBV DNA.

Conclusion

EBV DNA increases the incidence and severity of arthritis in a RA mouse model. Targeting mediators triggered by viral DNA may hence be a potential therapeutic avenue.

Expression Pattern of iNOS, BCL-2 and MMP-9 in the Hip Synovium Tissue of Patients with Osteoarthritis

Hip osteoarthritis (HOA) is characterized by degradation of the cartilage and synovitis. However, the pathohistological effects of synovial tissue inflammation on HOA are not clear. The aim of this study was to evaluate the expression of iNOS, BCL-2 and MMP-9 markers in different synovial cell populations. A total of 32 patients were evaluated retrospectively. Age, sex, height, weight, body mass index were recorded and lymphocyte, fibrocytes and macrophages were analysed in tissue sections. Osteoarthritis cartilage histopathology assessment system (OARSI), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Krenn score, Harris Hip Score (HHS) and Kellgren–Lawrence (K-L) grading of the hip joints were performed. Total hip arthroplasty was performed on 32 patients and controls. Patients were divided into two groups according to their disease severity. The tissues were immunohistochemically analysed. K-L grade and Krenn score differ between all three groups, but also between moderate and severe OA. Synovial lining cell layer, resident cells in stroma and especially inflammatory infiltration were increasing with severity of OA. iNOS expression in both intima and subintima was positively correlated with Krenn score in moderate and severe osteoarthritis (OA) groups. Expression of BCL-2 in intima of severe OA patients was positively correlated with Krenn score. In conclusion, iNOS, BCL-2 and MMP-9 are involved in the regulation of HOA. Our study indicates a relationship between the pathohistological features, the synovial inflammation and the cartilage condition at the time of hip replacement due to OA or femoral neck fracture.

[The role of helper T cell in the pathogenesis of osteoarthritis]

Objective

To review and summarize the role of helper T cell (Th) in the pathogenesis of osteoarthritis (OA) and research progress of Th cell-related treatment for OA.

Methods

The domestic and foreign literature in recent years was reviewed. The role of Th cells [Th1, Th2, Th9, Th17, Th22, and follicular helper T cell (Tfh)] and related cytokines in the pathogenesis of OA and the latest research progress of treatment were summarized.

Results

Th cells play an important role in the pathogenesis of OA. Th1, Th9, and Th17 cells are more important than Th2, Th22, and Tfh cells in the pathogenesis of OA. Cytokines such as tumor necrosis factor α and interleukin 17 can cause damage to articular cartilage significantly.

Conclusion

At present, the role of Th cells in the pathogenesis of OA has been played in the spotlight. The specific mechanism has not been clear. Regulating the Th cell-associated cytokines, intracellular and extracellular signals, and cellular metabolism is a potential method for prevention and treatment of OA.

Double-blind trial of solid lipid Boswellia serrata particles (SLBSP) vs. standardized Boswellia serrata gum extract (BSE) for osteoarthritis of knee

Objectives The present study was planned to investigate the efficacy of SLBSP vs. standardized BSE for symptomatic knee osteoarthritis (OA) treatment. Methods It was a prospective, randomized, double-blind, double-dummy, placebo-controlled, and single-centre clinical trial for symptomatic osteoarthritis of knee. Subjects were randomized to receive SLBSP capsule+BSE Placebo or BSE tablet+SLBSP placebo for two months. Patients were allowed to take rescue analgesics (Acelofenac 100 mg). Improvement in pain and function was assessed utilizing WOMAC, VAS. Level of CTX-II in urine and serum levels of inflammatory cytokines including IL-2, IL-4, IL-6, TNF-α, and IFN-γ was measured initially and at end of treatment. Results and conclusions Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and Visual Analog Scale score improved markedly in SLBSP as well as in BSE arm (p < 0.05). Difference in VAS and WOMAC scores between the two arms was not statistically significant. Most significant effect was observed in the need for rescue analgesics. SLBSP caused marked lowering of pro-inflammatory cytokines levels whereas a several fold increase was noted in the BSE arm (p < 0.05). Both groups showed marked improvement in pain, SLBSP being superior to BSE with respect to reducing the need for rescue analgesics in addition to modulating inflammatory cytokines.

Pathophysiological landscape of osteoarthritis

A sharp rise in osteoarthritis (OA) incidence is expected as over 25% of world population ages in the coming decade. Although OA is considered a degenerative disease, mounting evidence suggests a strong connection with chronic metabolic conditions and low-grade inflammation. OA pathology is increasingly understood as a complex interplay of multiple pathological events including oxidative stress, synovitis and immune responses revealing its intricate nature. Cellular, biochemical and molecular aspects of these pathological events along with major outcomes of the relevant research studies in this area are discussed in the present review. With reference to their published and unpublished work, the authors strongly propose synovitis as a central OA pathology and the key OA pathological events are described in connection with it. Recent research outcomes also have succeeded to establish a linkage between metabolic syndrome and OA, which has been precisely included in the present review. Impact of aging process cannot be neglected in OA. Cell senescence is an important mechanism of aging through which it facilitates development of OA like other degenerative disorders, also discussed within a frame of OA. Conclusively, the reviewers urge low-grade inflammation linked to aging and derailed immune function as a pathological platform for OA development and progression. Thus, interventions targeted to prevent inflammaging hold a promising potential in effective OA management and efforts should be invested in this direction.

Impact of Mononuclear Cell Infiltration on Chondrodestructive MMP/ADAMTS Production in Osteoarthritic Knee Joints-An Ex Vivo Study

Progressive loss of joint function in osteoarthritis (OA) is driven by degenerative and inflammatory processes and their complex interaction. Decoding the link between degeneration and inflammation is one of the most exciting approaches in understanding OA pathophysiology and holds the promise to open new therapeutic avenues. The overarching goal of this project was to analyze the impact of mononuclear cells (MNC) on enzymatic chondrodestructive processes (MMP/ADAMTS) in OA. Synovial membrane (SM), articular cartilage (AC) and peripheral blood (PB) were obtained from a total of 21 patients with advanced knee OA who underwent arthroplastic surgery. In supernatants of native synovial cell cultures, T cell-depleted synovial cell cultures and macrophage-depleted synovial cell cultures, the concentrations of various metalloproteinases were examined by Enzyme Linked Immunosorbent Assay (ELISA). Furthermore, ELISA was used to analyze concentrations of metalloproteinases in supernatants of chondrocyte monocultures and chondrocyte co-cultures with CD4⁺CD127^dim/- enriched peripheral blood mononuclear cells (PBMC), Treg depleted CD4⁺CD25^-CD127^dim/- enriched PBMC and CD4⁺CD25⁺CD127^dim/- Treg. Compared to native synovial cell culture, T cell depletion led to significantly lower levels of MMP-1, MMP-3 and MMP-9 and macrophage depletion led to a significant decline of MMP-1, MMP-3, MMP-9 and ADAMTS-5 concentration. Compared to T cell depletion, macrophage depletion resulted in a significantly stronger reduction of MMP-1, MMP-3, MMP-9 and ADAMTS-5. In chondrocyte co-culture with CD4⁺CD127^dim/- enriched PBMC the concentration of MMP-1 and ADAMTS-5 was significantly increased compared to chondrocyte monoculture. No significant differences were found between chondrocyte monoculture and chondrocyte co-culture with Treg as well as between co-culture with CD4⁺CD127^dim/- enriched PBMC containing Treg and co-culture with Treg-depleted CD4⁺CD25^-CD127^dim/- enriched PBMC. In conclusion, our data suggests that both synovial macrophages and T cells have a catabolic potential by inducing the release of chondrodestructive metalloproteinases in OA synovium. This study also supports the hypothesis that MNC affect the release of metalloproteinases by chondrocytes and are hereby involved in the cartilage-induced chondrodestructive process. In this study no suppressive effect of Treg was shown.

Recent advances in understanding the phenotypes of osteoarthritis

Recent research in the field of osteoarthritis (OA) has focused on understanding the underlying molecular and clinical phenotypes of the disease. This narrative review article focuses on recent advances in our understanding of the phenotypes of OA and proposes that the disease represents a diversity of clinical phenotypes that are underpinned by a number of molecular mechanisms, which may be shared by several phenotypes and targeted more specifically for therapeutic purposes. The clinical phenotypes of OA supposedly have different underlying etiologies and pathogenic pathways and they progress at different rates. Large OA population cohorts consist of a majority of patients whose disease progresses slowly and a minority of individuals whose disease may progress faster. The ability to identify the people with relatively rapidly progressing OA can transform clinical trials and enhance their efficiency. The identification, characterization, and classification of molecular phenotypes of rapidly progressing OA, which represent patients who may benefit most from intervention, could potentially serve as the basis for precision medicine for this disabling condition. Imaging and biochemical markers (biomarkers) are important diagnostic and research tools that can assist with this challenge.

Nanosome-Mediated Delivery Of Protein Kinase D Inhibitor Protects Chondrocytes From Interleukin-1β-Induced Stress And Apoptotic Death

Background

Inflammatory stress caused by protein kinase D (PKD) plays a critical role in damaging chondrocytes and extracellular matrix (ECM) during osteoarthritis (OA). The PKD inhibitor (PKDi) (CRT0066101) has been used to overcome inflammation in different cell types. However, the efficacy of a therapeutic drug can be limited due to off-target distribution, slow cellular internalization, and limited lysosomal escape. In order to overcome this issue, we developed nanosomes carrying CRT0066101 (PKDi-Nano) and tested their efficacy in vitro in chondrocytes.

Methods

Chondrocytes were subjected to IL-1β-induced inflammatory stress treated with either PKDi or PKDi-Nano. Effects of treatment were measured in terms of cytotoxicity, cellular morphology, viability, apoptosis, phosphorylation of protein kinase B (Akt), and anabolic/catabolic gene expression analyses related to cartilage tissue.

Results and Discussion

The effects of PKDi-Nano treatment were more pronounced as compared to PKDi treatment. Cytotoxicity and apoptosis were significantly reduced following PKDi-Nano treatment (P < 0.001). Cellular morphology was also restored to normal size and shape. The viability of chondrocytes was significantly enhanced in PKDi-Nano-treated cells (P < 0.001). The data indicated that PKDi-Nano acted independently of the Akt pathway. Gene expression analyses revealed significant increases in the expression levels of anabolic genes with concomitant decreases in the level of catabolic genes. Our results indicate that PKDi-Nano attenuated the effects of IL-1β via the nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB) pathway.

Conclusion

Taken together, these results suggest that PKDi-Nano can be used as a successful strategy to reduce IL1β-induced inflammatory stress in chondrocytes.

Elevated frequencies of total and MAIT cell subsets in patients with knee osteoarthritis

Background

Osteoarthritis (OA) is characterized by the degeneration of joint cartilage, with concomitant changes in the synovium and subchondral bone. Recently, the inflammatory response and involvement of several types of T-cells has been implicated in the development of OA. This study investigated the frequency of MR1-restricted mucosal-associated invariant T (MAIT) cells in patients with knee OA.

Methods

Forty-five patients recently diagnosed with knee OA and 21 age- and gender-matched healthy controls were recruited for this study. Percentages of circulating MAIT cells were assessed by flow cytometry. Plasma cytokine levels were measured using cytometric bead arrays. Associations between the percentages of MAIT cells, plasma cytokine levels, and clinical parameters of OA (erythrocyte sedimentation rate [ESR] and the Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]) were analyzed using the Spearman correlation test.

Results

The percentages of total, CD8αα, and CD8αβ MAIT cells were higher in patients with OA compared to healthy controls. The percentages of total and CD8αα MAIT cells were higher in patients with multi-joint OA (MOA) compared to patients with knee-only OA (KOA). Plasma IFN-γ and TNF-α levels were elevated in patients with OA compared to healthy controls, and there was a positive correlation between plasma IFN-γ levels and the percentages of total, CD8αα, and CD8αβ MAIT cells. Plasma IFN-γ and IL-17 levels were higher in patients with MOA compared to healthy controls or patients with KOA. There were positive correlations between the percentages of total and CD8αα MAIT cells and clinical parameters (ESR and WOMAC scores) in patients with OA or MOA. Binary logistic regression analysis shown the frequency of MAIT cells was associated with the risk of OA.

Conclusions

MAIT cells and their subpopulations were significantly increased in patients with OA and have potential as biological markers of OA disease severity, especially in patients with MOA.

Osteoimmunology of Oral and Maxillofacial Diseases: Translational Applications Based on Biological Mechanisms

The maxillofacial skeleton is highly dynamic and requires a constant equilibrium between the bone resorption and bone formation. The field of osteoimmunology explores the interactions between bone metabolism and the immune response, providing a context to study the complex cellular and molecular networks involved in oro-maxillofacial osteolytic diseases. In this review, we present a framework for understanding the potential mechanisms underlying the immuno-pathobiology in etiologically-diverse diseases that affect the oral and maxillofacial region and share bone destruction as their common clinical outcome. These otherwise different pathologies share similar inflammatory pathways mediated by central cellular players, such as macrophages, T and B cells, that promote the differentiation and activation of osteoclasts, ineffective or insufficient bone apposition by osteoblasts, and the continuous production of osteoclastogenic signals by immune and local stromal cells. We also present the potential translational applications of this knowledge based on the biological mechanisms involved in the inflammation-induced bone destruction. Such applications can be the development of immune-based therapies that promote bone healing/regeneration, the identification of host-derived inflammatory/collagenolytic biomarkers as diagnostics tools, the assessment of links between oral and systemic diseases; and the characterization of genetic polymorphisms in immune or bone-related genes that will help diagnosis of susceptible individuals.

A predominant Th1 polarization is present in synovial fluid of end-stage osteoarthritic knee joints: analysis of peripheral blood, synovial fluid and synovial membrane

Thorough understanding of the complex pathophysiology of osteoarthritis (OA) is necessary in order to open new avenues for treatment. The aim of this study was to characterize the CD4⁺ T cell population and evaluate their activation and polarization status in OA joints. Fifty-five patients with end-stage knee OA (Kellgren-Lawrence grades III-IV) who underwent surgery for total knee arthroplasty (TKA) were enrolled into this study. Matched samples of synovial membrane (SM), synovial fluid (SF) and peripheral blood (PB) were analysed for CD3⁺ CD4⁺ CD8^- T cell subsets [T helper type 1 (Th1), Th2, Th17, regulatory T cells] and activation status (CD25, CD69, CD45RO, CD45RA, CD62L) by flow cytometry. Subset-specific cytokines were analysed by cytometric bead array (CBA). SM and SF samples showed a distinct infiltration pattern of CD4⁺ T cells. In comparison to PB, a higher amount of joint-derived T cells was polarized into CD3⁺ CD4⁺ CD8^- T cell subsets, with the most significant increase for proinflammatory Th1 cells in SF. CBA analysis revealed significantly increased immunomodulating cytokines [interferon (IFN)-γ, interleukin (IL)-2 and IL-10] in SF compared to PB. Whereas in PB only a small proportion of CD4⁺ T cells were activated, the majority of joint-derived CD4⁺ T cells can be characterized as activated effector memory cells (CD69⁺ CD45RO⁺ CD62L^- ). End-stage OA knees are characterized by an increased CD4⁺ T cell polarization towards activated Th1 cells and cytokine secretion compared to PB. This local inflammation may contribute to disease aggravation and eventually perpetuate the disease process.

CCR2 upregulated on peripheral T cells in osteoarthritis but not in bone marrow

Osteoarthritis (OA) is a condition affecting millions of patients around the world, causing pain and disability and often resulting in joint replacement surgery. The aetiology of OA has long been attributed to mechanical wear mainly due to the increased prevalence of OA in load bearing joints among older patients. However, recent studies reveal a complex molecular disease causality in which inflammation, nutritional deficit and angiogenesis lead to the destruction of the joint structure. The aim of this study was to examine chemokine receptor expression in peripheral blood and bone marrow in OA patients. We devised a protocol for extracting healthy bone marrow from patients undergoing hip arthroplasty due to coxarthrosis. Flow cytometry was used to determine the expression of 18 chemokine receptors on CD4 and CD8 T cells from bone marrow and blood from 7 osteoarthritis patients and peripheral blood from 9 healthy controls. We found a significantly increased fraction of CCR2 expressing CD4 and CD8 T cell in peripheral blood compared to healthy controls. Also, there was a significant decrease in CXCR3 (Th1) (P < 0.01) expressing T cells in peripheral blood from OA patients. Finally, multivariate analysis was used to separate T cell profiles from healthy controls and OA patients and demonstrate that the divergence of chemokine receptor expression occurs in the mature T cell subsets. In conclusion, we find increased CCR2 expression in peripheral blood from OA patients that possibly may be targeted in future clinical studies.

Functional and T Cell Receptor Repertoire Analyses of Peripheral Blood and Infrapatellar Fat Pad T Cells in Knee Osteoarthritis

Objective.

Osteoarthritis (OA) is a condition that features inflammation and immune responses of innate and adaptive immunity. The role of T cells in knee OA pathogenesis is still unclear. Our aim was to characterize T cell functions and their clonality in patients with knee OA in peripheral blood (PB) and infrapatellar fat pads (IPFP).

Methods.

We isolated T cells from PB and IPFP of patients with knee OA and PB of healthy individuals and determined soluble mediators produced from these cells. In addition, we performed a clonal analysis of activated CD8+ T cells and compared the T cell receptor β-variable gene chain (TRBV) usages between T cells in PB and IPFP of patients with knee OA.

Results.

Our results suggest that in patients with knee OA, circulating T cells possess a more “cytotoxic” profile or rather impaired cytokine production, but the knee microenvironment allows for these T cells to produce proinflammatory cytokines [interleukin (IL)-1β, IL-6, tumor necrosis factor], IL-17, and interferon-γ within IPFP. Activated CD8+ IPFP T cells carry different repertoire distribution from those present in PB of patients with knee OA. Shared TRBV usage of activated CD8+ IPFP T cells among the 3 patients with knee OA was also observed.

Conclusion.

Our study describes the nature of T cells in knee OA that may be due to “unhealthy” aging or other factors that drive healthy aging T cells into a state of imbalance, thus contributing to the pathogenesis of knee OA.

Cartilage diseases

Hyaline cartilages, fibrocartilages and elastic cartilages play multiple roles in the human body including bearing loads in articular joints and intervertebral discs, providing joint lubrication, forming the external ears and nose, supporting the trachea, and forming the long bones during development and growth. The structure and organization of cartilage's extracellular matrix (ECM) are the primary determinants of normal function. Most diseases involving cartilage lead to dramatic changes in the ECM which can govern disease progression (e.g., in osteoarthritis), cause the main symptoms of the disease (e.g., dwarfism caused by genetically inherited mutations) or occur as collateral damage in pathological processes occurring in other nearby tissues (e.g., osteochondritis dissecans and inflammatory arthropathies). Challenges associated with cartilage diseases include poor understanding of the etiology and pathogenesis, delayed diagnoses due to the aneural nature of the tissue and drug delivery challenges due to the avascular nature of adult cartilages. This narrative review provides an overview of the clinical and pathological features as well as current treatment options available for various cartilage diseases. Late breaking advances are also described in the quest for development and delivery of effective disease modifying drugs for cartilage diseases including osteoarthritis, the most common form of arthritis that affects hundreds of millions of people worldwide.

Gender-related differences observed among immune cells in synovial fluid in knee osteoarthritis

OBJECTIVE

There is no existing comprehensive report on the cellular composition of synovial fluids (SFs) from knee osteoarthritis (OA). We therefore aimed to characterise the immune cell composition in SFs from knee OA (KOA) and in subgroups according to gender.

DESIGN

The immunophenotyping of monocyte/macrophage lineage cells, T and B cells, NK cells, neutrophils, dendritic and mast cells (MC) present in SFs from 53 patients (24 males/29 females) with KOA was performed using 6-colour flow cytometry.

RESULTS

SFs from patients with OA contained 90% hematopoietic cells. Lymphocytes were the predominant cell population (44.8%) in the SFs of OA patients, with CD4⁺ T lymphocytes being more prevalent than CD8⁺ T cells (CD4⁺/CD8⁺ ratio = 1.3). Within the monocyte/macrophage lineage gating, monocytes accounted for 33.9%, macrophages 14.8%, myeloid dendritic cells 16.4%. The rest of the hematopoietic cells were comprised of neutrophils (8%), NK cells (3.8%), T regulatory cells (1.2%), plasmacytoid dendritic cells (1.1%), mast cells (0.3%). In OA females, a higher percentage of CD4⁺ T cells (P = 0.023), macrophages (P = 0.012), and a lower percentage of monocytes (P = 0.008) and CD8⁺ T cells (P = 0.002) were detected in comparison to OA males.

CONCLUSIONS

Based on the immune cell composition of SFs, data mining analysis revealed distinct phenotypes (monocyte- and lymphocyte-predominant) within each gender group. This first study on the cellular complexity of SFs in KOA showed marked differences between male and female patients. The findings give a rational starting point for patient stratification according to their phenotypes, as is required for phenotype-specific treatment strategies.

Epstein-Barr virus DNA modulates regulatory T-cell programming in addition to enhancing interleukin-17A production via Toll-like receptor 9

Infection with the Epstein-Barr virus (EBV) has been associated with several autoimmune diseases including rheumatoid arthritis (RA). We have previously reported that DNA from this virus enhances production of the pro-autoimmune interleukin 17A (IL-17A) in mice. In this study we assessed the effect of EBV DNA on regulatory T cell programming and examined whether it mediated its effects via Toll-like receptor 9 (TLR9) in mice; moreover, we evaluated whether EBV DNA in humans had similar effects to those seen in mice. For this purpose, we assessed the linearity of the correlation between EBV DNA and IL-17A levels in RA subjects and matched controls. A modulatory effect for the viral DNA was observed for regulatory T cell markers with an inhibitory effect observed for CTLA4 expression in the EBV DNA-treated mice. To examine whether TLR9 mediated the detection of EBV DNA and enhancement of IL-17A production, mouse peripheral blood mononuclear cells were treated with the DNA in the presence or absence of the TLR9 inhibitor ODN 2088. Subsequently, IL-17A production from these cells was assessed. Treatment with the TLR9 inhibitor resulted in a significant decrease in IL-17A production indicating that TLR9 is involved in this pathway. In human subjects, examining the linearity of the correlation between EBV DNA and IL-17A levels in RA subjects showed a propensity for linearity that was not observed in controls. Our data thus indicates that EBV DNA itself acts as a modulator of the Th17 compartment as well as that of regulatory T cell mechanisms. The involvement of TLR9 in the EBV DNA-triggered induction of IL-17A suggests therapeutic targeting of this endosomal receptor in EBV positive subjects with an autoimmune flare-up or possibly for prophylactic purposes.

Protein kinase D3 modulates MMP1 and MMP13 expression in human chondrocytes

Many catabolic stimuli, including interleukin-1 (IL-1) in combination with oncostatin M (OSM), promote cartilage breakdown via the induction of collagen-degrading collagenases such as matrix metalloproteinase 1 (MMP1) and MMP13 in human articular chondrocytes. Indeed, joint diseases with an inflammatory component are characterised by excessive extracellular matrix (ECM) catabolism. Importantly, protein kinase C (PKC) signalling has a primary role in cytokine-induced MMP1/13 expression, and is known to regulate cellular functions associated with pathologies involving ECM remodelling. At present, substrates downstream of PKC remain undefined. Herein, we show that both IL-1- and OSM-induced phosphorylation of protein kinase D (PKD) in human chondrocytes is strongly associated with signalling via the atypical PKCι isoform. Consequently, inhibiting PKD activation with a pan-PKD inhibitor significantly reduced the expression of MMP1/13. Specific gene silencing of the PKD isoforms revealed that only PKD3 (PRKD3) depletion mirrored the observed MMP repression, indicative of the pharmacological inhibitor specifically affecting only this isoform. PRKD3 silencing was also shown to reduce serine phosphorylation of signal transducer and activator of transcription 3 (STAT3) as well as phosphorylation of all three mitogen-activated protein kinase groups. This altered signalling following PRKD3 silencing led to a significant reduction in the expression of the activator protein-1 (AP-1) genes FOS and JUN, critical for the induction of many MMPs including MMP1/13. Furthermore, the AP-1 factor activating transcription factor 3 (ATF3) was also reduced concomitant with the observed reduction in MMP13 expression. Taken together, we highlight an important role for PKD3 in the pro-inflammatory signalling that promotes cartilage destruction.

Senescent cells and osteoarthritis: a painful connection

Senescent cells (SnCs) are associated with age-related pathologies. Osteoarthritis is a chronic disease characterized by pain, loss of cartilage, and joint inflammation, and its incidence increases with age. For years, the presence of SnCs in cartilage isolated from patients undergoing total knee artificial implants has been noted, but these cells' relevance to disease was unclear. In this Review, we summarize current knowledge of SnCs in the multiple tissues that constitute the articular joint. New evidence for the causative role of SnCs in the development of posttraumatic and age-related arthritis is reviewed along with the therapeutic benefit of SnC clearance. As part of their senescence-associated secretory phenotype, SnCs secrete cytokines that impact the immune system and its response to joint tissue trauma. We present concepts of the immune response to tissue trauma as well as the interactions with SnCs and the local tissue environment. Finally, we discuss therapeutic implications of targeting SnCs in treating osteoarthritis.

Elevated Galectin-9 Suppresses Th1 Effector Function and Induces Apoptosis of Activated CD4+ T Cells in Osteoarthritis

T cell immunoglobulin and mucin domain 3 (Tim-3) is a critical regulatory molecule found on activated Th1 cells, exhausted CD8⁺ T cells, and resting monocytes/macrophages. Galectin-9 (Gal-9) is an identified ligand for Tim-3. Interaction between Tim-3 and Gal-9 is thought to inhibit Th1 responses. The regulation and function of Tim-3 and Gal-9 in osteoarthritis (OA) have not been intensively investigated. We found that in peripheral blood, CD4⁺ T cells, but not CD8⁺ T cells or CD14⁺ monocytes, from OA patients presented significantly elevated Tim-3 and Gal-9 expression compared to those from healthy controls (HC). The CD4⁺ T cells from OA did not present altered Th1, Th2, and Th17 composition in the peripheral blood, but secreted less Th1 cytokine interleukin 2 (IL-2) and interferon gamma (IFN-γ) after activation. Further investigation demonstrated that Gal-9 induced high levels of apoptosis in activated CD4⁺ T cells from OA patients. Inhibition of Gal-9 resulted in significantly higher IL-2 and IFN-γ expression that was directly correlated with the number of non-apoptotic cells. In the synovial fluid, both secreted Gal-9 and surface Gal-9 levels were significantly higher in less-severe grade 2 OA patients than in more-severe grade 4 OA patients. Surface Tim-3 was also higher in synovial fluid CD8⁺ T cells and CD14⁺ monocytes from grade 2 OA patients and lower in grade 4 OA patients. Together, these results suggested that Tim-3 and Gal-9 could downregulate T cell inflammation in OA, and could be utilized as a novel therapeutic strategy.

Beneficial effects of natural eggshell membrane versus placebo in exercise-induced joint pain, stiffness, and cartilage turnover in healthy, postmenopausal women

PURPOSE

Despite its many health benefits, moderate exercise can induce joint discomfort when done infrequently or too intensely even in individuals with healthy joints. This study was designed to evaluate whether NEM® (natural eggshell membrane) would reduce exercise-induced cartilage turnover or alleviate joint pain or stiffness, either directly following exercise or 12 hours post exercise, versus placebo.

PATIENTS AND METHODS

Sixty healthy, postmenopausal women were randomly assigned to receive either oral NEM 500 mg (n=30) or placebo (n=30) once daily for two consecutive weeks while performing an exercise regimen (50-100 steps per leg) on alternating days. The primary endpoint was any statistically significant reduction in exercise-induced cartilage turnover via the biomarker C-terminal cross-linked telopeptide of type-II collagen (CTX-II) versus placebo, evaluated at 1 and 2 weeks of treatment. Secondary endpoints were any reductions in either exercise-induced joint pain or stiffness versus placebo, evaluated daily via participant questionnaire. The clinical assessment was performed on the per protocol population.

RESULTS

NEM produced a significant absolute treatment effect (TEabs) versus placebo for CTX-II after both 1 week (TEabs -17.2%, P=0.002) and 2 weeks of exercise (TEabs -9.9%, P=0.042). Immediate pain was not significantly different; however, rapid treatment responses were observed for immediate stiffness (Day 7) and recovery pain (Day 8) and recovery stiffness (Day 4). No serious adverse events occurred and the treatment was reported to be well tolerated by study participants.

CONCLUSION

NEM rapidly improved recovery from exercise-induced joint pain (Day 8) and stiffness (Day 4) and reduced discomfort immediately following exercise (stiffness, Day 7). Moreover, a substantial chondroprotective effect was demonstrated via a decrease in the cartilage degradation biomarker CTX-II. Clinical Trial Registration number: NCT02751944.

Do immune cells lead the way in subchondral bone disturbance in osteoarthritis?

Osteoarthritis (OA) is a whole-joint disorder, and non-cartilage articular pathologies, e.g. subchondral bone disturbance, contribute substantially to the onset and progression of the disease. In the early stage of OA, abnormal mechanical loading leads to micro-cracks or micro-fractures that trigger a reparative process with angiogenesis and inflammatory response. With the progression of disease, cystic lesion, sclerosis and osteophytosis occur at tissue level, and osteoblast dysfunction at cellular level. Osteoblasts derived from OA sclerotic bone produce increased amount of type I collagen with aberrant Col1A1/A2 ratio and poor mineralization capability. The coupling mechanism of bone resorption with formation is also impaired with elevated osteoclastic activities. All these suggest a view that OA subchondral bone presents a defective fracture repair process in a chronic course. It has been found that T and B cells, the major effectors in the adaptive immunity, take part in the hard callus formation at fracture site in addition to the initial phase of haematoma and inflammation. Infiltration of lymphocytes could interplay with osteoclasts and osteoblasts via a direct physical cell-to-cell contact. Several lines of evidence have consistently shown the involvement of T and B cells in osteoclastogenesis and bone erosion in arthritic joints. Yet the biological link between immune cells and osteoblastic function remains ambiguous. This review will discuss the current knowledge regarding the role of immune cells in bone remodelling, and address its implications in emerging basic and clinical investigations into the pathogenesis and management of subchondral bone pathologies in OA.

Differentiation potential of synoviocytes derived from joints with cranial cruciate ligament rupture and medial patella luxation in dogs

The objective of this study was to assess the differentiation capability of synoviocytes derived from dogs with inflammatory joint conditions. Cranial cruciate ligament ruptured (CCLr) (n=12) and medial patella luxated (MPL) (n=10) knee joints of the dogs were used to collect the synovial membrane (SM). Synoviocytes were enzymatically released from the SM and analyzed by flow cytometry for specific cellular markers (CD44 and CD90) of mesenchymal stem cells (MSCs), while doing histopathology from another part of SM sections. Under specific culture conditions, synoviocytes were forced to differentiate into chondrogenesis, adipogenesis, osteogenesis and osteoclastogenesis to investigate the multipotency. Upon treatments phenotypes of cell cultures were analyzed by histopathology and by semi-quantitative reverse transcriptase polymerase chain reaction for the expression of each differentiation marker genes. Although flow cytometry showing similar MSCs populations in CCLr and MPL synovium, synovial cells derived from CCLr showed higher multipotency compared to MPL-derived samples. Further, synovial changes such as vascularity, mononuclear cell infiltration and cellular hypertrophy were more pronounced in CCLr-derived synovial tissue than in MPL. Taken together, these findings suggested that the differentiation capability of SM-derived multipotent stem cells varies with inflammatory severity occurring in different joint conditions.

Immunogenicity and immunomodulatory effects of the human chondrocytes, hChonJ

Background

Invossa™ (TissueGene-C) is a cell and gene therapy for osteoarthritis. It is composed of primary human chondrocytes (hChonJ cells) and irradiated human chondrocytes modified to express TGF-β1 (hChonJb#7 cells). The hChonJ cells were isolated from a polydactyly donor, and TGF-β1 cDNA was delivered to the cells, generating hChonJb#7 cells. Since the cells are allogeneic, the concern of immune response against cells has been raised. In this study, we investigated the immunogenicity of allogenic human chondrocyte, hChonJ cells.

Methods

The immunological properties of hChonJ cells were investigated through the analysis of surface marker expression and the effect on allogeneic T cell proliferation. Flow cytometry and RT-PCR analysis were performed to analyze the surface marker expression related to immune response, such as major histocompatibility complex (MHC) class I, class II, T cell co-stimulatory molecules and T cell co-inhibitory molecules. A mixed lymphocyte reaction (MLR) was conducted to evaluate how allogeneic T cells would respond to hChonJ cells.

Results

We observed that hChonJ cells did not express MHC class II and T cell co-stimulatory molecules, but expressed T cell co-inhibitory molecule PD-L2. IFN-γ treatment induced the expression of PD-L1, and up-regulated the expression of PD-L2. Also, we observed that hChonJ cells did not stimulate T cell proliferation from a MHC-mismatched donor. Further, they could suppress the proliferation of activated T cells. We also observed that the blockade of PD-L1 and/or PD-L2 with specific neutralizing antibody could lead to the restoration of allo-reactive T cell proliferation.

Conclusions

We showed that hChonJ cells were not immunogenic but immunosuppressive, and that this phenomenon was mediated by co-inhibitory molecules PD-L1 and PD-L2 on hChonJ cells in a contact-dependent manner.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1547-8) contains supplementary material, which is available to authorized users.

T Cells in Osteoarthritis: Alterations and Beyond

Although osteoarthritis (OA) has been traditionally regarded as a non-inflammatory disease, reports increasingly suggest that it is inflammatory, at least in certain patients. OA patients often exhibit inflammatory infiltration of synovial membranes by macrophages, T cells, mast cells, B cells, plasma cells, natural killer cells, dendritic cells, granulocytes, etc. Although previous reviews have summarized the knowledge of inflammation in the pathogenesis of OA, as far as we know, no report review our current understanding about T cells, especially, each T cell subtype, in the biology of OA. This review highlights the current understanding of the role of T cells in the pathogenesis of OA, with attention to Th1 cells, Th2 cells, Th9 cells, Th17 cells, Th22 cells, regulatory T cells, follicular helper T cells, cytotoxic T cells, T memory cells, and even unconventional T cells (e.g., γδ T cells and cluster of differentiation 1 restricted T cells). The findings highlight the importance of T cells to the development and progression of OA and suggest new therapeutic approaches for OA patients based on the manipulation of T-cell responses.

A Role for Soluble IL-6 Receptor in Osteoarthritis

Interleukin-6 (IL-6) is one of several pro-inflammatory cytokines present at elevated levels in the synovial fluid of individuals with confirmed clinical diagnosis of rheumatoid arthritis (RA) and osteoarthritis (OA). The mechanism of action of IL-6 was shown to involve its capacity to interact with a membrane-bound IL-6 receptor (mIL-6Rα), also known as the "classical" IL-6 pathway, or through its interaction with a soluble IL-6 receptor (sIL-6R) termed the "trans-signaling" pathway. Activation of downstream signaling is transduced via these IL-6 receptors and principally involves the Janus Kinase/Signal Transduction and Activators of Transcription (JAK/STAT) signaling pathway that is further regulated by glycoprotein-130 (gp130) interacting with the IL-6/mIL-6R complex. Phosphorylation of STAT proteins via JAK activation facilitates STAT proteins to act as transcription factors in inflammation. However, the biological function(s) of the sIL-6R in human chondrocytes requires further elucidation, although we previously showed that exogenous sIL-6R significantly suppressed the synthesis of neutrophil gelatinase-associated lipocalin (NGAL) in the immortalized line of human chondrocytes, C28/I2. NGAL was shown to regulate the activity of matrix metalloproteinase-9 (MMP-9), whose activity is crucial in OA for the destruction of articular cartilage. The "shedding" of sIL-6R from the plasma membrane is carried out by a family of enzymes known as A Distintegrin and Metalloproteinase (ADAM), which are also elevated in OA. In this paper, we have systematically reviewed the role played by IL-6 in OA. We have proposed that sIL-6R may be an important target for future drug development in OA by ameliorating cartilage extracellular protein degradation.

Immune Mediators in Osteoarthritis: Infrapatellar Fat Pad-Infiltrating CD8+ T Cells Are Increased in Osteoarthritic Patients with Higher Clinical Radiographic Grading

Osteoarthritis is a condition of joint failure characterized by many pathologic changes of joint-surrounding tissues. Many evidences suggest the role of both innate and adaptive immunity that interplay, resulting either in initiation or in progression of osteoarthritis. Adaptive immune cells, in particular T cells, have been demonstrated to play a role in the development of OA in animal models. However, the underlying mechanism is yet unclear. Our aim was to correlate the frequency and phenotype of tissue-infiltrating T cells in the synovial tissue and infrapatellar fat pad with radiographic grading. Our results show that CD8+ T cells are increased in osteoarthritic patients with higher radiographic grading. When peripheral blood CD8+ T cells were examined, we show that CD8+ T cells possess a significantly higher level of activation than its CD4+ T cell counterpart (P < 0.0001). Our results suggest a role for CD8+ T cells and recruitment of these activated circulating peripheral blood CD8+ T cells to the knee triggering local inflammation within the knee joint.

Altered microRNA expression profile in synovial fluid from patients with knee osteoarthritis with treatment of hyaluronic acid

OBJECTIVE

The aim of this study was to investigate the microRNA (miRNA) expression pattern in synovial fluid from patients with knee osteoarthritis (OA) after treatment with intra-articular injection of hyaluronan (HA).

METHODS

Twelve OA patients were enrolled in accordance with the Kellgren-Lawrence classification of knee OA. All patients received intra-articular injection of HA once a week for 5 weeks and were evaluated with the Western Ontario and McMaster Universities (WOMAC) index at baseline. TaqMan miRNA assay profiling was performed on synovial fluid RNAs extracted from OA patients pre-injection and after 5 weeks of treatment with HA. Validation was performed using independent samples, including ten healthy controls and ten matched OA patients.

RESULTS

Forty-three miRNAs (21 overexpressed miRNAs and 22 underexpressed miRNAs) were differentially expressed in OA patients before and after treatment with HA (P < 0.05, false discovery rate corrected). Further bioinformatics prediction by mirPath indicated that the differential miRNA signatures in synovial fluid extracted from the OA patients demonstrated primarily upregulation of the PI3K-Akt signaling pathway, mitogen-activated protein kinase signaling pathway, regulation of autophagy, mRNA surveillance pathway, and B cell receptor signaling pathway. In addition, TaqMan real-time reverse transcription polymerase chain reaction was performed for validation on miR-146a, miR-155, let-7a, miR-181a, miR-454, and let-7b, which were significantly changed in abundance, using an independent cohort of ten healthy controls and ten OA patients as compared with those with intra-articular injection of HA.

CONCLUSION

Our results demonstrated that dysregulation in miRNAs in synovial fluid from OA patients and their affected biologic cellular processes might play important role in OA pathogenesis and HA-mediated therapeutics.

vIL-10-overexpressing human MSCs modulate naïve and activated T lymphocytes following induction of collagenase-induced osteoarthritis

BACKGROUND

Recent efforts in osteoarthritis (OA) research have highlighted synovial inflammation and involvement of immune cells in disease onset and progression. We sought to establish the in-vivo immune response in collagenase-induced OA and investigate the ability of human mesenchymal stem cells (hMSCs) overexpressing viral interleukin 10 (vIL-10) to modulate immune populations and delay/prevent disease progression.

METHODS

Eight-week-old male C57BL/6 mice were injected with 1 U type VII collagenase over two consecutive days. At day 7, 20,000 hMSCs overexpressing vIL-10 were injected into the affected knee. Control groups comprised of vehicle, 20,000 untransduced or adNull-transduced MSCs or virus alone. Six weeks later knees were harvested for histological analysis and popliteal and inguinal lymph nodes for flow cytometric analysis.

RESULTS

At this time there was no significant difference in knee OA scores between any of the groups. A trend toward more damage in animals treated with hMSCs was observed. Interestingly there was a significant reduction in the amount of activated CD4 and CD8 T cells in the vIL-10-expressing hMSC group.

CONCLUSIONS

vIL-10-overexpressing hMSCs can induce long-term reduction in activated T cells in draining lymph nodes of mice with collagenase-induced OA. This could lead to reduced OA severity or disease progression over the long term.

Targeting VEGF and Its Receptors for the Treatment of Osteoarthritis and Associated Pain

Increased vascular endothelial growth factor (VEGF) levels are associated with osteoarthritis (OA) progression. Indeed, VEGF appears to be involved in OA-specific pathologies including cartilage degeneration, osteophyte formation, subchondral bone cysts and sclerosis, synovitis, and pain. Moreover, a wide range of studies suggest that inhibition of VEGF signaling reduces OA progression. This review highlights both the potential significance of VEGF in OA pathology and pain, as well as potential benefits of inhibition of VEGF and its receptors as an OA treatment. With the emergence of the clinical use of anti-VEGF therapy outside of OA, both as high-dose systemic treatments and low-dose local treatments, these particular therapies are now more widely understood. Currently, there is no established disease-modifying drug available for patients with OA, which warrants continued study of the inhibition of VEGF signaling in OA, as stand-alone or adjuvant therapy. © 2016 American Society for Bone and Mineral Research.

A Systematic Study of the Effect of Different Molecular Weights of Hyaluronic Acid on Mesenchymal Stromal Cell-Mediated Immunomodulation

Introduction

Osteoarthritis (OA) is associated with chronic inflammation, and mesenchymal stromal cells (MSCs) have been shown to provide pain relief and reparative effects in clinical investigations. MSCs are often delivered with hyaluronic acid (HA), although the combined mechanism of action is not fully understood; we thus investigated the immunomodulatory effects of combining MSCs with different molecular weights (MW) of HA.

Methods

HAs with MWs of 1.6 MDa (hHA), 150 kDa or 7.5 kDa, were added to MSCs alone or MSC-immune cell co-cultures. Gene expression analyses, flow cytometry and cytokine measurements were assessed to determine the effect of HAs on the MSC interactions with immune cells.

Results

MSCs in the presence of HAs, in both normal and lymphocyte-conditioned medium, showed negligible changes in gene expression. While addition of hHA resulted in increased proliferation of activated lymphocytes, both in the presence and absence of MSCs, the overall combined effect was a more regulated, homeostatic one; this was supported by higher ratios of secreted IL10/IFNγ and IL10/IL2, in lymphocyte cultures, than with lower MW HAs or no HA, both in the presence and absence of MSCs. In addition, examination of monocyte-derived macrophages showed an increased M2 macrophage frequency (CD14+CD163+CD206+) in the presence of hHA, both with and without MSCs.

Conclusions

hHA produces a less pro-inflammatory environment than lower MW HAs. Moreover, combining hHA with MSCs has an additive effect on the MSC-mediated immunomodulation, suggestive of a more potent combination treatment modality for OA.

Biologic basis of osteoarthritis: state of the evidence

PURPOSE OF REVIEW

Evidence accumulated since 2010 indicates that human osteoarthritis should now be reclassified as a systemic musculoskeletal disease rather than a focal disorder of synovial joints.

RECENT FINDINGS

Inflammation was seen as the key component promoting synovitis as well as progression of cartilage and bone destruction in osteoarthritis. Thus, metabolic-triggered inflammation involving cytokines, adipokines, abnormal metabolites, acute phase reactants and even complement, all appear to play major roles in osteoarthritis pathophysiology. Immune-mediated inflammation involving T cells and B cells as well as macrophages is now considered a common finding in osteoarthritis synovial tissue. Many experimental and clinical analyses showed that the proinflammatory cytokines, which stimulate matrix metalloproteinase and a disintegrin and metalloproteinase with thrombospondin motif gene transcription in normal and osteoarthritis human chondrocyte cultures, are also present at significantly elevated levels in the synovial fluid of osteoarthritis patients compared with nonarthritic synovial fluids.

SUMMARY

Human osteoarthritis is a systemic musculoskeletal disorder involving activation of innate and adaptive immune systems accompanied by inflammation exemplified by the elevated production of proinflammatory cytokines, which play a significant role in the progression of the disease. The future of novel therapies for osteoarthritis should consider developing drug development strategies designed to inhibit proinflammatory cytokine-induced signal transduction. These strategies have been successful in the development of drugs for the treatment of rheumatoid arthritis.

Wnts talking with the TGF-β superfamily: WISPers about modulation of osteoarthritis

The Wnt signalling pathway is gaining increasing attention in the field of joint pathologies, attributable to its role in the development and homeostasis of the tissues found in the joint, including bone and cartilage. Imbalance in this pathway has been implicated in the development and progression of OA, and interference with the pathway might therefore depict an effective treatment strategy. Though offering multiple opportunities, it is yet to be decided which starting point will bring forth the most promising results. The complexity of the pathway and its interaction with other pathways (such as the TGF-β signalling pathway, which also has a central role in the maintenance of joint homeostasis) means that acting directly on proteins in this signalling cascade entails a high risk of undesired side effects. Therefore, interference with Wnt-induced proteins, such as WISP1, might be an overall more effective and safer therapeutic approach to inhibit the pathological events that take place during OA.

Unicompartmental and bicompartmental knee osteoarthritis show different patterns of mononuclear cell infiltration and cytokine release in the affected joints

It is still controversial which cell types are responsible for synovial inflammation in osteoarthritic (OA) joints. The aim of this study was to quantify the mononuclear cell populations and their cytokines in patients with different knee OA subtypes. Synovial membrane (SM), synovial fluid (SF) and peripheral blood (PB) were harvested from patients with unicompartmental (UC) and bicompartmental (BC) knee OA. Frequencies of mononuclear cells were assessed by flow cytometry in PB and SM. Naive SF samples were analysed for a broad variety of cytokines by multiplex analysis. SM of both groups displayed a distinct mononuclear cell infiltration, with CD14(+) macrophages being the major cell population, followed by CD4(+) T cells and only small numbers of CD8(+) T, CD19(+) B and CD16(+) CD56(+) natural killer (NK) cells. Between the two groups, SM of BC OA showed significantly higher amounts of mononuclear cells (135·7 ± 180 versus 805 ± 675 cells/mg, P = 0·0009) and higher CD4(+) T cell presence (3·4 ± 4·6 versus 9·1 ± 7·5%, P = 0·0267). SF of BC OA displayed significantly higher concentrations for a number of proinflammatory cytokines [CXCL1, eotaxin, interferon (IFN)-γ, interleukin (IL)-7, IL-8, IL-9, IL-12]. UC and BC OA show significant differences in their synovial inflammatory pattern. Whereas in UC OA CD14(+) macrophages are the predominant cell population, BC OA has a higher inflammatory profile and seems to be driven by CD14(+) macrophages and CD4(+) T cells. Inclusion of clinical information into the analysis of cellular and molecular results is pivotal in understanding the pathophysiology of OA.

UP3005, a Botanical Composition Containing Two Standardized Extracts of Uncaria gambir and Morus alba, Improves Pain Sensitivity and Cartilage Degradations in Monosodium Iodoacetate-Induced Rat OA Disease Model

Osteoarthritis (OA) is a multifactorial disease primarily noted by cartilage degradation in association with inflammation that causes significant morbidity, joint pain, stiffness, and limited mobility. Present-day management of OA is inadequate due to the lack of principal therapies proven to be effective in hindering disease progression where symptomatic therapy focused approach masks the actual etiology leading to irreversible damage. Here, we describe the effect of UP3005, a composition containing a proprietary blend of two standardized extracts from the leaf of Uncaria gambir and the root bark of Morus alba, in maintaining joint structural integrity and alleviating OA associated symptoms in monosodium-iodoacetate- (MIA-) induced rat OA disease model. Pain sensitivity, micro-CT, histopathology, and glycosaminoglycans (GAGs) level analysis were conducted. Diclofenac at 10 mg/kg was used as a reference compound. UP3005 resulted in almost a complete inhibition in proteoglycans degradation, reductions of 16.6% (week 4), 40.5% (week 5), and 22.0% (week 6) in pain sensitivity, statistically significant improvements in articular cartilage matrix integrity, minimal visual subchondral bone damage, and statistically significant increase in bone mineral density when compared to the vehicle control with MIA. Therefore, UP3005 could potentially be considered as an alternative therapy from natural sources for the treatment of OA and/or its associated symptoms.

Anti-inflammatory and chondroprotective effects of atorvastatin in a cartilage explant model of osteoarthritis

OBJECTIVE

This study aimed to assess the chondroprotective potential of atorvastatin in rat's cartilage explant culture model of osteoarthritis, stimulated by interleukin-1β (IL-1β).

MATERIALS AND METHODS

The cartilage explants were treated with 20 ng/ml IL-1β alone or with 20 ng/ml IL-1β + various concentration of atorvastatin (1, 3, or 10 µM dissolved in DMSO) and incubated at 37 °C for 24 h. Also, control (0.25% DMSO), stimulated (20 ng IL-1β) and treatment (atorvastatin 10 µM) cartilage explants were incubated without and with 1400W (10 µM). After 24 h of incubation, TNF-α, PGE2, MMP-13, TIMP-1, NO, and superoxide anion formation (O2(-)) concomitant with glycosaminoglycans (GAGs) were estimated in the medium.

RESULTS

Atorvastatin inhibited IL-1β-induced GAGs release, TNF-α, MMP-13, and O2(-) with no effect on TIMP-1 and NO. In addition, the source of NO in normal and atorvastatin-treated cartilage was eNOS, while for IL-1β-stimulated cartilage it was iNOS. The cartilage degradation was associated with the combined effects of increased NO and O2 (-) rather than only NO.

CONCLUSION

The present study suggests that atorvastatin has the ability to protect cartilage degradation following IL-1β-stimulated cartilage in in vitro OA model and supports additional therapeutic application of atorvastatin in OA.

Effects of hyaluronic acid (HA) viscosupplementation on peripheral Th cells in knee and hip osteoarthritis

OBJECTIVE

Determine Th lymphocytes concentration in patients with knee or hip osteoarthritis (OA). Evaluate their change after HA viscosupplementation.

METHODS

Patients with early primary knee or hip OA (ACR Criteria) were recruited in two groups: group A was only observed longitudinally, group B was treated with a course of three weekly intra-articular injections of HA. A healthy control group gender and age matched was enrolled too. All subjects were followed for 3 months. Flow cytometry was performed from blood samples to assess T cells subpopulations (CD3, CD4, CD8, CCR6, CD38, CxCR3, HLA DR) at baseline and at 3-months visit.

RESULTS

86 patients were recruited with OA: 49 in Group A (35 knee OA, 14 hip OA), 37 in Group B (24 knee OA, 13 hip OA). 23 in Control Group. Activated CD4 T cells (CD4(+)CD38(+)DR(+), CD4(+)CD38(-)DR(+)), Th2 (CD4(+)CXCR3(-)CCR6(-)),Th1 (CD4(+)CXCR3(+)CCR6(-)) were higher at baseline in group A and B than in control group. After the HA course activated T cells were lower in group B than in group A (P = 0.01). Th17 (CD4(+)CXCR3(-)CCR6(+)) at baseline were higher in groups A and B than in control group and decreased levels in Group B after the HA course were observed (P = 0.03).

CONCLUSION

The presence of activated T cells in patients with OA confirm that OA is a disease with an immunological/inflammatory involvement. Our preliminary results seems to show that HA injections could lower the levels of activated T cells, and so regulate the articular milieu.