Increased frequency of peripheral blood follicular helper T cells and elevated serum IL‑21 levels in patients with knee osteoarthritis

The Role of MicroRNAs in the Pathophysiology of Osteoarthritis

Worldwide, osteoarthritis (OA) is the most common cause of joint pain in older people. Many factors contribute to osteoarthritis' development and progression, including secondary osteoarthritis' underlying causes. It is important to note that osteoarthritis affects all four tissues: cartilage, bone, joint capsule, and articular apparatus. An increasingly prominent area of research in osteoarthritis regulation is microRNAs (miRNAs), a small, single-stranded RNA molecule that controls gene expression in eukaryotes. We aimed to assess and summarize current knowledge about the mechanisms of the action of miRNAs and their clinical significance. Osteoarthritis (OA) is affected by the interaction between miRNAs and inflammatory processes, as well as cartilage metabolism. MiRNAs also influence cartilage cell apoptosis, contributing to the degradation of the cartilage in OA. Studies have shown that miRNAs may have both an inhibitory and promoting effect on osteoporosis progression through their influence on molecular mechanisms. By identifying these regulators, targeted treatments for osteoarthritis may be developed. In addition, microRNA may also serve as a biomarker for osteoarthritis. By using these biomarkers, the disease could be detected faster, and early intervention can be instituted to prevent mobility loss and slow deterioration.

Transcriptomic analyses and machine-learning methods reveal dysregulated key genes and potential pathogenesis in human osteoarthritic cartilage

Aims

This study aimed to explore the biological and clinical importance of dysregulated key genes in osteoarthritis (OA) patients at the cartilage level to find potential biomarkers and targets for diagnosing and treating OA.

Methods

Six sets of gene expression profiles were obtained from the Gene Expression Omnibus database. Differential expression analysis, weighted gene coexpression network analysis (WGCNA), and multiple machine-learning algorithms were used to screen crucial genes in osteoarthritic cartilage, and genome enrichment and functional annotation analyses were used to decipher the related categories of gene function. Single-sample gene set enrichment analysis was performed to analyze immune cell infiltration. Correlation analysis was used to explore the relationship among the hub genes and immune cells, as well as markers related to articular cartilage degradation and bone mineralization.

Results

A total of 46 genes were obtained from the intersection of significantly upregulated genes in osteoarthritic cartilage and the key module genes screened by WGCNA. Functional annotation analysis revealed that these genes were closely related to pathological responses associated with OA, such as inflammation and immunity. Four key dysregulated genes (cartilage acidic protein 1 (CRTAC1), iodothyronine deiodinase 2 (DIO2), angiopoietin-related protein 2 (ANGPTL2), and MAGE family member D1 (MAGED1)) were identified after using machine-learning algorithms. These genes had high diagnostic value in both the training cohort and external validation cohort (receiver operating characteristic > 0.8). The upregulated expression of these hub genes in osteoarthritic cartilage signified higher levels of immune infiltration as well as the expression of metalloproteinases and mineralization markers, suggesting harmful biological alterations and indicating that these hub genes play an important role in the pathogenesis of OA. A competing endogenous RNA network was constructed to reveal the underlying post-transcriptional regulatory mechanisms.

Conclusion

The current study explores and validates a dysregulated key gene set in osteoarthritic cartilage that is capable of accurately diagnosing OA and characterizing the biological alterations in osteoarthritic cartilage; this may become a promising indicator in clinical decision-making. This study indicates that dysregulated key genes play an important role in the development and progression of OA, and may be potential therapeutic targets.

The modulation effects of the mind-body and physical exercises on the basolateral amygdala-temporal pole pathway on individuals with knee osteoarthritis

Background/Objective

To investigate the modulatory effects of different physical exercise modalities on connectivity of amygdala subregions and its association with pain symptoms in patients with knee osteoarthritis (KOA).

Methods

140 patients with KOA were randomly allocated either to the Tai Chi, Baduanjin, Stationary cycling, or health education group and conducted a 12 week-long intervention in one of the four groups. The behavioral, magnetic resonance imaging (MRI), and blood data were collected at baseline and the end of the study.

Results

Compared to the control group, all physical exercise modalities lead to significant increases in Knee Injury and Osteoarthritis Outcome Score (KOOS) pain score (pain relief) and serum Programmed Death-1 (PD-1) levels. Additionally, all physical exercise modalities resulted in decreased resting state functional connectivity (rsFC) of the basolateral amygdala (BA)-temporal pole and BA-medial prefrontal cortex (mPFC). The overlapping BA-temporal pole rsFC observed in both Tai Chi and Baduanjin groups was significantly associated with pain relief, while the BA-mPFC rsFC was significantly associated with PD-1 levels. In addition, we found increased fractional anisotropy (FA) values, a measurement of water diffusion anisotropy of tissue that responded to changes in brain microstructure, within the mind-body exercise groups' BA-temporal pole pathway. The average FA value of this pathway was positively correlated with KOOS pain score at baseline across all subjects.

Conclusions

Our findings suggest that physical exercise has the potential to modulate both functional and anatomical connectivity of the amygdala subregions, indicating a possible shared pathway for various physical exercise modalities.

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.

Identification of cuproptosis-related subtypes, characterization of immune microenvironment infiltration, and development of a prognosis model for osteoarthritis

Background

Osteoarthritis (OA) is a prevalent chronic joint disease with an obscure underlying molecular signature. Cuproptosis plays a crucial role in various biological processes. However, the association between cuproptosis-mediated immune infifiltration and OA progression remains unexplored. Therefore, this study elucidates the pathological process and potential mechanisms underlying cuproptosis in OA by constructing a columnar line graph model and performing consensus clustering analysis.

Methods

Gene expression profifile datasets GSE12021, GSE32317, GSE55235, and GSE55457 of OA were obtained from the comprehensive gene expression database. Cuproptosis signature genes were screened by random forest (RF) and support vector machine (SVM). A nomogram was developed based on cuproptosis signature genes. A consensus clustering was used to distinguish OA patients into different cuproptosis patterns. To quantify the cuproptosis pattern, a principal component analysis was developed to generate the cuproptosis score for each sample. Single-sample gene set enrichment analysis (ssGSEA) was used to provide the abundance of immune cells in each sample and the relationship between these significant cuproptosis signature genes and immune cells.To quantify the cuproptosis pattern, a principal component analysis technique was developed to generate the cuproptosis score for each sample. Cuproptosis-related genes were extracted and subjected to differential expression analysis to construct a disease prediction model and confifirmed by RT-qPCR.

Results

Seven cuproptosis signature genes were screened (DBT, LIPT1, GLS, PDHB, FDX1, DLAT, and PDHA1) to predict the risk of OA disease. A column line graph model was developed based on these seven cuproptosis signature genes, which may assist patients based on decision curve analysis. A consensus clustering method was used to distinguish patients with disorder into two cuproptosis patterns (clusters A and B). To quantify the cuproptosis pattern, a principal component analysis technique was developed to generate the cuproptosis score for each sample. Furthermore, the OA characteristics of patients in cluster A were associated with the inflflammatory factors IL-1b, IL-17, IL-21, and IL-22, suggesting that the cuproptosis signature genes play a vital role in the development of OA.

Discussion

In this study, a risk prediction model based on cuproptosis signature genes was established for the fifirst time, and accurately predicted OA risk. In addition, patients with OA were classifified into two cuproptosis molecule subtypes (clusters A and B); cluster A was highly associated with Th17 immune responses, with higher IL-1b, IL-17, and IL-21 IL-22 expression levels, while cluster B had a higher correlation with cuproptosis. Our analysis will help facilitate future research related cuproptosis-associated OA immunotherapy. However, the specifific mechanisms remain to be elucidated.

Two Amnion-Derived Mesenchymal Stem-Cells Injections to Osteoarthritic Elbows in Dogs-Pilot Study

The aim of the study was to investigate the potential of cell-based regenerative therapy for elbow joints affected by osteoarthritis. Interest was focused on two intra-articular applications of amnion-derived mesenchymal stem cells (A-MSCs) to a group of different breeds of dogs with elbow osteoarthritis (13 joints). Two injections were performed 14 days apart. We evaluated synovial fluid biomarkers, such as IFN-γ, IL-6, IL-15, IL-10, MCP-1, TNF-α, and GM-CSF, by multiplex fluorescent micro-bead immunoassay in the treated group of elbows (n = 13) (day 0, day 14, and day 28) and in the control group of elbows (n = 9). Kinematic gait analysis determined the joint range of motion (ROM) before and after each A-MSCs application. Kinematic gait analysis was performed on day 0, day 14, and day 28. Kinematic gait analysis pointed out improvement in the average range of motion of elbow joints from day 0 (38.45 ± 5.74°), day 14 (41.7 ± 6.04°), and day 28 (44.78 ± 4.69°) with statistical significance (p < 0.05) in nine elbows. Correlation analyses proved statistical significance (p < 0.05) in associations between ROM (day 0, day 14, and day 28) and IFN-γ, IL-6, IL-15, MCP-1, TNF-α, and GM-CSF concentrations (day 0, day 14, and day 28). IFN-γ, IL-6, IL-15, MCP-1, GM-CSF, and TNF- α showed negative correlation with ROM at day 0, day 14, and day 28, while IL-10 demonstrated positive correlation with ROM. As a consequence of A-MSC application to the elbow joint, we detected a statistically significant (p < 0.05) decrease in concentration levels between day 0 and day 28 for IFN-γ, IL-6, and TNF-α and statistically significant increase for IL-10. Statistical significance (p < 0.05) was detected in TNF-α, IFN-γ, and GM-CSF concentrations between day 14 and the control group as well as at day 28 and the control group. IL-6 concentrations showed statistical significance (p < 0.05) between day 14 and the control group.

Mesenchymal Stromal Cells-Derived Extracellular Vesicles as Potential Treatments for Osteoarthritis

Osteoarthritis (OA) is a degenerative disease of the joints characterized by cartilage damage and severe pain. Despite various pharmacological and surgical interventions, current therapies fail to halt OA progression, leading to high morbidity and an economic burden. Thus, there is an urgent need for alternative therapeutic approaches that can effectively address the underlying pathophysiology of OA. Extracellular Vesicles (EVs) derived from mesenchymal stromal cells (MSCs) represent a new paradigm in OA treatment. MSC-EVs are small membranous particles released by MSCs during culture, both in vitro and in vivo. They possess regenerative properties and can attenuate inflammation, thereby promoting cartilage healing. Importantly, MSC-EVs have several advantages over MSCs as cell-based therapies, including lower risks of immune reactions and ethical issues. Researchers have recently explored different strategies, such as modifying EVs to enhance their delivery, targeting efficiency, and security, with promising results. This article reviews how MSC-EVs can help treat OA and how they might work. It also briefly discusses the benefits and challenges of using MSC-EVs and talks about the possibility of allogeneic and autologous MSC-EVs for medical use.

The immune role of the intestinal microbiome in knee osteoarthritis: a review of the possible mechanisms and therapies

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by cartilage damage and synovial inflammation and carries an enormous public health and economic burden. It is crucial to uncover the potential mechanisms of OA pathogenesis to develop new targets for OA treatment. In recent years, the pathogenic role of the gut microbiota in OA has been well recognized. Gut microbiota dysbiosis can break host-gut microbe equilibrium, trigger host immune responses and activate the "gut-joint axis", which aggravates OA. However, although the role of the gut microbiota in OA is well known, the mechanisms modulating the interactions between the gut microbiota and host immunity remain unclear. This review summarizes research on the gut microbiota and the involved immune cells in OA and interprets the potential mechanisms for the interactions between the gut microbiota and host immune responses from four aspects: gut barrier, innate immunity, adaptive immunity and gut microbiota modulation. Future research should focus on the specific pathogen or the specific changes in the gut microbiota composition to identify the related signaling pathways involved in the pathogenesis of OA. In addition, future studies should include more novel interventions on immune cell modifications and gene regulation of specific gut microbiota related to OA to validate the application of gut microbiota modulation in the onset of OA.

Impact of T helper cells on bone metabolism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE), an autoimmune disease affecting multiple organs and tissues, is often complicated by musculoskeletal diseases. T helper cells (Th) play an important role in mediating lupus. With the rise of osteoimmunology, more studies have shown shared molecules and interactions between the immune system and bones. Th cells are vital in the regulation of bone metabolism by directly or indirectly regulating bone health by secreting various cytokines. Therefore, by describing the regulation of Th cells (including Th1, Th2, Th9, Th17, Th22, regulatory T cells (Treg), and follicular T helper cells (Tfh) in bone metabolism in SLE, this paper offers certain theoretical support for abnormal bone metabolism in SLE and provides new prospects for future drug development.

Inflammaging and Osteoarthritis

Osteoarthritis is a highly prevalent disease particularly in subjects over 65 years of age worldwide. While in the past it was considered a mere consequence of cartilage degradation leading to anatomical and functional joint impairment, in recent decades, there has been a more dynamic view with the synovium, the cartilage, and the subchondral bone producing inflammatory mediators which ultimately lead to cartilage damage. Inflammaging is defined as a chronic, sterile, low-grade inflammation state driven by endogenous signals in the absence of infections, occurring with aging. This chronic status is linked to the production of reactive oxygen species and molecules involved in the development of age-related disease such as cancer, diabetes, and cardiovascular and neurodegenerative diseases. Inflammaging contributes to osteoarthritis development where both the innate and the adaptive immune response are involved. Elevated systemic and local inflammatory cytokines and senescent molecules promote cartilage degradation, and antigens derived from damaged joints further trigger inflammation through inflammasome activation. B and T lymphocyte populations also change with inflammaging and OA, with reduced regulatory functions, thus implicating self-reactivity as an additional mechanism of joint damage. The discovery of the underlying pathogenic pathways may help to identify potential therapeutic targets for the management or the prevention of osteoarthritis. We will provide a comprehensive evaluation of the current literature on the role of inflammaging in osteoarthritis and discuss the emerging therapeutic strategies.

Osteopontin: A Bone-Derived Protein Involved in Rheumatoid Arthritis and Osteoarthritis Immunopathology

Osteopontin (OPN) is a bone-derived phosphoglycoprotein related to physiological and pathological mechanisms that nowadays has gained relevance due to its role in the immune system response to chronic degenerative diseases, including rheumatoid arthritis (RA) and osteoarthritis (OA). OPN is an extracellular matrix (ECM) glycoprotein that plays a critical role in bone remodeling. Therefore, it is an effector molecule that promotes joint and cartilage destruction observed in clinical studies, in vitro assays, and animal models of RA and OA. Since OPN undergoes multiple modifications, including posttranslational changes, proteolytic cleavage, and binding to a wide range of receptors, the mechanisms by which it produces its effects, in some cases, remain unclear. Although there is strong evidence that OPN contributes significantly to the immunopathology of RA and OA when considering it as a common denominator molecule, some experimental trial results argue for its protective role in rheumatic diseases. Elucidating in detail OPN involvement in bone and cartilage degeneration is of interest to the field of rheumatology. This review aims to provide evidence of the OPN’s multifaceted role in promoting joint and cartilage destruction and propose it as a common denominator of AR and OA immunopathology.

Identification and validation of BCL6 and VEGFA as biomarkers and ageing patterns correlating with immune infiltrates in OA progression

Osteoarthritis (OA), the most common type of arthritis, is a complex biological response caused by cartilage wear and synovial inflammation that links biomechanics and inflammation. The progression of OA correlates with a rise in the number of senescent cells in multiple joint tissues. However, the mechanisms by which senescent cells and their involvement with immune infiltration promote OA progression are not fully understood. The gene expression profiles and clinical information of OA and healthy control synovial tissue samples were retrieved from the Gene Expression Omnibus database, and then differential analysis of senescence regulators between OA and normal samples was performed. The random forest (RF) was used to screen candidate senescence regulators to predict the occurrence of OA. The reverse transcription quantitative real-time PCR experiments at tissue's level was performed to confirm these biomarkers. Moreover, two distinct senescence patterns were identified and systematic correlation between these senescence patterns and immune cell infiltration was analyzed. The senescence score and senescence gene clusters were constructed to quantify senescence patterns together with immune infiltration of individual OA patient. 73 senescence differentially expressed genes were identified between OA patients and normal controls. The RF method was utilized to build an OA risk model based on two senescence related genes: BCL6 and VEGFA. Next, two distinct aging patterns were determined in OA synovial samples. Most patients from senescence cluster A were further classified into gene cluster B and high senescence score group correlated with a non-inflamed phenotype, whereas senescence cluster B were classified into gene cluster A and low senescence score group correlated with an inflamed phenotype. Our study revealed that senescence played an important role in in OA synovial inflammation. Evaluating the senescence patterns of individuals with OA will contribute to enhancing our cognition of immune infiltration characterization, providing novel diagnostic and prognostic biomarkers, and guiding more effective immunotherapy strategies.

Role of Hemin in the Immune Response of T Follicular Helper Lymphocytes Expressing T-Cell Immunoreceptor with Immunoglobulin and Immunoreceptor Tyrosine-Based Inhibitory Domains, Programmed Cell Death-1, and Interleukin-21 in Allo-Auto Positive and Negative Thalassemia

Introduction

Repeated transfusions in thalassemia patients can cause several complications, including alloimmunization and autoimmunization.

Purpose

This study compares the immune response of T follicular helper (Tfh) lymphocytes expressing T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory domains (TIGIT), programmed cell death-1 (PD-1), and interleukin-21 (IL-21) between patients with allo-auto positive and negative thalassemia before and after hemin administration.

Materials and Methods

This study used a quasi-experimental pre- and post-test design and was performed between April and November 2021 at the Dr. Soetomo General Academic Hospital in Surabaya, Indonesia. It enrolled 29 patients with allo-auto positive thalassemia and 28 with allo-auto negative, and 9 mL of whole blood (WB) was drawn from each patient. Hemin solution (20 µM) was added to 5 mL of WB, incubated for two hours, processed into peripheral blood mononuclear cells (PBMCs) in RPMI media, and cultured with 5% CO₂ for three days. The 4 mL WB sample was also processed into PBMCs. PBMC cells cultured and without cultured were examined by flow cytometry using a BD FACSCalibur after surface and intracellular staining. Differences in Tfh cells expressing TIGIT, PD-1, and IL-21 between thalassemia groups before and after hemin administration were compared using independent t-tests or Mann-Whitney U-tests (p < 0.05).

Results

Tfh cell expression did not differ between groups before hemin administration and increased after hemin administration. The increase in Tfh cell expression was higher in the allo-auto positive group. TIGIT and PD-1 expression in Tfh cells did not differ between groups, but TIGIT decreased after hemin administration in contrast to PD-1 result. IL-21 expression in Tfh cells did not differ between groups and did not change after hemin administration.

Conclusion

Hemin affected the expression of Tfh cells in both group thalassemia, but there was no difference of Tfh cell expression between the groups.

Impact of Hemin on Interleukin-21 Levels and Plasma Cells in Transfusion-Dependent Thalassemia with Positive and Negative Allo-Autoantibody

Introduction

Antibody formation in transfusion-dependent thalassemia is associated with chronic hemolysis and repeated transfusions. Hemolysis produces heme, which mediates B-cell differentiation into plasma cells and produces antibodies influenced by interleukin-21 (IL-21).

Objective

This study aimed to compare IL-21 levels, plasma cell percentage, and red blood cell antibodies between positive and negative allo-autoantibody thalassemia before and after hemin administration.

Materials and Methods

This research employed a quasi-experimental nonequivalent control group pre-test and post-test design performed from April to November 2021 at Soetomo Academic Hospital in Surabaya, Indonesia. Heparinized blood samples of 5 mL and 4 mL and EDTA blood samples of 3 mL were taken from positive (29 patients) and negative (28 patients) allo-autoantibody thalassemia participants. Hemin 20 µM was added to 5 mL of heparinized blood, incubated for 2 hours, prepared into peripheral blood mononuclear cells (PBMCs), and cultured for 3 days. The percentage of plasma cells (CD38+CD184+) of cultured and uncultured PBMCs was measured by BD FACSCalibur Flow Cytometer. IL-21 levels of plasma and supernatants were measured with Sandwich Enzyme-Linked Immunosorbent Assay by Elabscience. Red blood cell antibodies were detected by QWALYS 3 E.M. Technology. Autoantibodies were determined by the Grifols gel tube method.

Results

IL-21 levels were significantly different in the positive and negative allo-autoantibody thalassemia groups after hemin administration. The percentage of plasma cells in the positive allo-autoantibody group increased significantly after the administration of hemin. The percentage of plasma cells between thalassemia groups was not significantly different before the hemin administration but increased significantly after it. Red blood cell antibodies after the administration of hemin were significantly different in the negative allo-autoantibody group but not significantly different in the positive allo-autoantibody group.

Conclusion

Hemin administration affected IL-21 levels, plasma cell percentage, and antibody formation in positive and negative allo-auto antibody thalassemia.

Interferon-gamma modulates articular chondrocyte and osteoblast metabolism through protein kinase R-independent and dependent mechanisms

Osteoarthritis (OA) affects multiple tissues of the synovial joint and is characterised by articular cartilage degeneration and bone remodelling. Interferon-γ (IFN-γ) is implicated in osteoarthritis pathology exerting its biological effects via various mechanisms including activation of protein kinase R (PKR), which has been implicated in inflammation and arthritis. This study investigated whether treatment of articular cartilage chondrocytes and osteoblasts with IFN-γ could induce a degradative phenotype that was mediated through the PKR signalling pathway. IFN-γ treatment of chondrocytes increased transcription of key inflammatory mediators (TNF-α, IL-6), matrix degrading enzymes (MMP-13), the transcription factor STAT1, and PKR. Activation of PKR was involved in the regulation of TNF-α, IL-6, and STAT1. In osteoblasts, IFN-γ increased human and mouse STAT1, and human IL-6 through a mechanism involving PKR. ALP, COL1A1 (human and mouse), RUNX2 (mouse), and PHOSPHO1 (mouse) were decreased by IFN-γ. The number of PKR positive cells were increased in post-traumatic OA (PTOA). This study has revealed that IFN-γ propagates inflammatory and degenerative events in articular chondrocytes and osteoblasts via PKR activation. Since IFN-γ and PKR signalling are both activated in early PTOA, these mechanisms are likely to contribute to joint degeneration after injury and might offer attractive targets for therapeutic intervention.

•IFN-γ treatment of chondrocytes increased transcription of TNF-α, IL-6, and STAT1 via PKR activation.

•In osteoblasts, IFN-γ increased STAT1 and IL-6 via PKR activation.

•The number of PKR positive cells were increased in post-traumatic OA (PTOA).

•IFN-γ propagates inflammatory and degenerative events in articular chondrocytes and osteoblasts via PKR activation.

•IFN-γ and PKR signalling are both activated in early PTOA and are likely to contribute to joint degeneration after injury.

Identification of susceptibility modules and hub genes of osteoarthritis by WGCNA analysis

Osteoarthritis (OA) is a major cause of pain, disability, and social burden in the elderly throughout the world. Although many studies focused on the molecular mechanism of OA, its etiology remains unclear. Therefore, more biomarkers need to be explored to help early diagnosis, clinical outcome measurement, and new therapeutic target development. Our study aimed to retrieve the potential hub genes of osteoarthritis (OA) by weighted gene co-expression network analysis (WGCNA) and assess their clinical utility for predicting OA. Here, we integrated WGCNA to identify novel OA susceptibility modules and hub genes. In this study, we first selected 477 and 834 DEGs in the GSE1919 and the GSE55235 databases, respectively, from the Gene Expression Omnibus (GEO) website. Genes with p-value&lt;0.05 and | log2FC | &gt; 1 were included in our analysis. Then, WGCNA was conducted to build a gene co-expression network, which filtered out the most relevant modules and screened out 23 overlapping WGCNA-derived hub genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses elucidated that these hub genes were associated with cell adhesion molecules pathway, leukocyte activation, and inflammatory response. In addition, we conducted the protein–protein interaction (PPI) network in 23 hub genes, and the top four upregulated hub genes were sorted out (CD4, SELL, ITGB2, and CD52). Moreover, our nomogram model showed good performance in predicting the risk of OA (C-index = 0.76), and this model proved to be efficient in diagnosis by ROC curves (AUC = 0.789). After that, a single-sample gene set enrichment (ssGSEA) analysis was performed to discover immune cell infiltration in OA. Finally, human primary synoviocytes and immunohistochemistry study of synovial tissues confirmed that those candidate genes were significantly upregulated in the OA groups compared with normal groups. We successfully constructed a co-expression network based on WGCNA and found out that OA-associated susceptibility modules and hub genes, which may provide further insight into the development of pre-symptomatic diagnosis, may contribute to understanding the molecular mechanism study of OA risk genes.

The Waxing, Waning, and Predictors of Humoral Responses to Vector-Based SARS-CoV-2 Vaccine in Hemodialysis Patients

Hemodialysis (HD) patients are vulnerable to coronavirus disease 2019 (COVID-19) and have a high mortality rate. We evaluated the anti-SARS-CoV-2 spike protein antibody (ACOV2S) levels in 385 HD patients before and 4 and 8 weeks after the second dose of vector-based ChAdOx1 nCoV-19 vaccine. For study control, week 4 ACOV2S levels after the second vaccination dose were measured in 66 healthcare workers (HCWs). The seroconversion rate of HD patients was 98.96% 4 weeks after the second vaccination. Despite low antibody levels before the second dose (week 0), week 4 ACOV2S levels after the second vaccine dose in HD patients increased prominently and were compatible with those in HCWs (p = 0.814 for HCWs vs. HD patients). The ACOV2S levels in HD patients waned significantly 8 weeks after the second vaccination dose (p < 0.001 at week 8 vs. 4). Older age and immunosuppressant use were negative predictors, while higher C-reactive protein (CRP) levels were positive predictors of ACOV2S waxing after the second vaccine dose in HD patients. Higher CRP levels and platelet counts were independently associated with decreased ACOV2S waning. The ChAdOx1 nCoV-19 vaccine is effective and safe for primary vaccination in HD patients and a booster dose is necessary.

Long non-coding RNA Gm37494 alleviates osteoarthritis chondrocyte injury via the microRNA-181a-5p/GABRA1 axis

Objective

This study was conducted to investigate the effect of long non-coding RNA (lncRNA) Gm37494 on osteoarthritis (OA) and its related molecular mechanism.

Methods

The cartilage tissues were obtained from OA patients, and an OA mouse model was induced by the destabilization of the medial meniscus, followed by measurement of Gm37494, microRNA (miR)-181a-5p, GABRA1 mRNA, and the encoded GABA_AR_α1 protein expression. Thereafter, a cellular model was induced by interleukin-1β (IL-1β) treatment in chondrocytes, followed by ectopic and silencing experiments. Chondrocyte proliferation was detected by CCK-8 and EdU assays, chondrocyte apoptosis by flow cytometry and western blot, and the levels of inflammatory factors by ELISA. The binding of Gm37494 to miR-181a-5p was evaluated by dual-luciferase reporter gene and RIP assays, and that of GABRA1 to miR-181a-5p by dual-luciferase reporter gene and RNA pull-down assays.

Results

OA patients and mice had decreased GABRA1 mRNA and GABA_AR_α1 protein levels and elevated miR-181a-5p expression in cartilage tissues. Additionally, Gm37494 was poorly expressed in OA mice. Mechanistically, Gm37494 directly bound to and inversely modulated miR-181a-5p that negatively targeted GABRA1. In IL-1β-induced chondrocytes, Gm37494 overexpression enhanced cell proliferation and suppressed cell apoptosis and inflammation, whereas further miR-181a-5p up-regulation or GABRA1 silencing abolished these trends.

Conclusions

Conclusively, Gm37494 elevated GABRA1 expression by binding to miR-181a-5p, thus ameliorating OA-induced chondrocyte damage.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03202-5.

Relationship of mRNA Expression of Selected Genes in Peripheral Blood and Synovial Fluid in Cranial Cruciate Ligament Deficient Stifles of Dogs

Simple Summary

The cranial cruciate ligament rupture is characterized by chronic inflammation, osteoarthritis of the stifle joint, and extracellular matrix degeneration of the ligament itself in dogs. Early pre-clinical cranial cruciate ligament alteration cannot be detected by clinical examination or standard radiography. Therefore, we assessed the possible relationship of inflammatory markers in peripheral blood and synovial fluid of affected stifle joints in comparison to a control. We also evaluated components of the extracellular matrix of ruptured ligaments and finally compared the tibial plateau angle and the anatomical-mechanical angle between groups. Some of the assessed inflammatory markers were significantly increased in both the peripheral blood and synovial fluid compared with the control, as were collagens. The tibial plateau angle was not significantly different; however, the anatomical-mechanical angle significantly increased in the ruptured ligaments. Our results suggest a possible positive relationship between inflammatory markers of blood and synovial fluid in cranial cruciate ligament deficient stifles compared to the control. These findings may support both local and systemic inflammation process at the same time during osteoarthritis progression. Based on this, it would be interesting to investigate the predictive osteoarthritis pathway of inflammatory cytokines, matrix metalloproteinases, and their effect on the extracellular matrix components of the cranial cruciate ligament in future studies.

Abstract

The cranial cruciate ligament rupture (CrCLR) is characterized by chronic inflammation and osteoarthritis (OA) of the stifle joint and extracellular matrix (ECM) degeneration of the ligament itself in dogs. Generally, OA may arise from chronic low-grade systemic inflammation. We assessed the possible relationship of inflammatory markers in the peripheral blood (PB) and synovial fluid (SF) of affected stifle joints in comparison to a control. Moreover, no study has shown the possible association between PB and SF levels of inflammatory markers in CrCLR stifles of dogs in veterinary medicine yet. We also evaluated components of ECM of CrCLR and finally compared the tibial plateau angle (TPA) and the anatomical-mechanical angle (AMA) between groups. Samples from PB and SF were examined for mRNA expression of interleukins, TNF-α and INF-γ. ECM components—collagen 1A1 and 3A1 and elastin—were examined for mRNA expression from SF. The level of relative expression for IL-1β, IL-8 and IFN-γ was significantly increased in both PB and SF in CrCLR stifles as compared with the control. Collagens were also significantly increased in CrCLR stifles. TPA was not significantly different; however, the AMA angle significantly increased in the CrCLR group. Our results suggest a possible relationship between PB and SF levels of inflammatory markers in CrCLR stifles of dogs.

Association Between Gut Microbiota and Osteoarthritis: A Review of Evidence for Potential Mechanisms and Therapeutics

Osteoarthritis (OA) is a multifactorial joint disease characterized by degeneration of articular cartilage, which leads to joints pain, disability and reduced quality of life in patients with OA. Interpreting the potential mechanisms underlying OA pathogenesis is crucial to the development of new disease modifying treatments. Although multiple factors contribute to the initiation and progression of OA, gut microbiota has gradually been regarded as an important pathogenic factor in the development of OA. Gut microbiota can be regarded as a multifunctional “organ”, closely related to a series of immune, metabolic and neurological functions. This review summarized research evidences supporting the correlation between gut microbiota and OA, and interpreted the potential mechanisms underlying the correlation from four aspects: immune system, metabolism, gut-brain axis and gut microbiota modulation. Future research should focus on whether there are specific gut microbiota composition or even specific pathogens and the corresponding signaling pathways that contribute to the initiation and progression of OA, and validate the potential of targeting gut microbiota for the treatment of patients with OA.

Mesenchymal Stem Cell-Derived Exosomes: A Potential Therapeutic Avenue in Knee Osteoarthritis

Knee osteoarthritis is the leading cause of functional disability in adults. The goals of knee osteoarthritis management are directed toward symptomatic pain relief along with the attainment of the functional quality of life. The treatment strategy ranges from conservative to surgical management with reparative and restorative techniques. The emergence of cell-based therapies has paved the way for the usage of mesenchymal stem cells (MSCs) in cartilage disorders. Currently, global researchers are keen on their research on nanomedicine and targeted drug delivery. MSC-derived exosomes act as a directed therapy to halt the disease progression and to provide a pain-free range of movements with increased quality of cartilage on regeneration. International Society for Extracellular Vesicles and the European Network on Microvesicles and Exosomes in Health and Disease have formed guidelines to foster the use of the growing therapeutic potential of exosomal therapy in osteoarthritis. Although regenerative therapies with MSC are being seen to hold a future in the management of osteoarthritis, extracellular vesicle-based technology holds the key to unlock the potential toward knee preservation and regeneration. The intricate composition and uncertain functioning of exosomes are inquisitive facets warranting further exploration.

Cytokines and Chemokines Involved in Osteoarthritis Pathogenesis

Osteoarthritis is a common cause of disability worldwide. Although commonly referred to as a disease of the joint cartilage, osteoarthritis affects all joint tissues equally. The pathogenesis of this degenerative process is not completely understood; however, a low-grade inflammation leading to an imbalance between anabolic and katabolic processes is a well-established factor. The complex network of cytokines regulating these processes and cell communication has a central role in the development and progression of osteoarthritis. Concentrations of both proinflammatory and anti-inflammatory cytokines were found to be altered depending on the osteoarthritis stage and activity. In this review, we analyzed individual cytokines involved in the immune processes with an emphasis on their function in osteoarthritis.

[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.

Soluble Biomarkers of Osteoporosis and Osteoarthritis, from Pathway Mapping to Clinical Trials: An Update

Serum biomarkers of osteoarticular diseases have been in the limelight of current clinical research trends. Laboratory validation of defined and candidate biomarkers for both osteoarthritis and osteoporosis is of key importance for future decisional algorithms in the diagnosis, monitoring, and prognosis of these diseases. The current guidelines recommend the use of collagen degradation remnants, eg, CTX-I and CTX-II, in the complementary diagnosis of both osteoporosis and osteoarthritis. Besides the collagen degradation markers, enzymes that regulate bone and articular metabolism are useful in the clinical evaluation of osteoarticular pathologies. Along these, several other recommended and new nominee molecules have been recently studied. Wnts and Wnt-related molecules have a cardinal role in the bone-joint homeostasis, making them a promising target not only for pharmaceutical modulation, but also to be considered as soluble biomarkers. Sclerostin and dickkopf, two inhibitor molecules of the Wnt/β-catenin signaling, might have a dual role in the assessment of the clinical manifestations of the osteoarticular unit. In osteoarthritis, besides fragments of collagen type II many pathway-related molecules have been studied and proposed for biomarker validation. The most serious limitation is that a significant proportion of studies lack statistical power due to the reduced number of cases enrolled. Serum biomarkers of bone and joint turnover markers represent an encouraging possibility for the diagnosis and prognosis of osteoarticular diseases, although further studies and laboratory validations should be carried out as to solely rely on them.

GRB10 and E2F3 as Diagnostic Markers of Osteoarthritis and Their Correlation with Immune Infiltration

This study aimed to find potential diagnostic markers for osteoarthritis (OA) and analyze the role of immune cells infiltration in this pathology. We used OA datasets from the Gene Expression Omnibus database. First, R software was used to identify differentially expressed genes (DEGs) and perform functional correlation analysis. Then least absolute shrinkage and selection operator (LASSO) logistic regression and support vector machine-recursive feature elimination algorithms were used to screen and verify the diagnostic markers of OA. Finally, CIBERSORT was used to evaluate the infiltration of immune cells in OA tissues, and the correlation between diagnostic markers and infiltrating immune cells was analyzed. A total of 458 DEGs were screened in this study. GRB10 and E2F3 (AUC = 0.962) were identified as diagnostic markers of OA. Immune cell infiltration analysis found that resting mast cells, T regulatory cells, CD4 memory resting T cells, activated NK cells, and eosinophils may be involved in the OA process. In addition, GRB10 was correlated with NK resting cells, naive CD4 + T cells, and M1 macrophages, while E2F3 was correlated with resting mast cells. In conclusion, GRB10 and E2F3 can be used as diagnostic markers of osteoarthritis, and immune cell infiltration plays an important role in the occurrence and progression of OA.

The Role of Inflammation in the Pathogenesis of Osteoarthritis

A joint is the point of connection between two bones in our body. Inflammation of the joint leads to several diseases, including osteoarthritis, which is the concern of this review. Osteoarthritis is a common chronic debilitating joint disease mainly affecting the elderly. Several studies showed that inflammation triggered by factors like biomechanical stress is involved in the development of osteoarthritis. This stimulates the release of early-stage inflammatory cytokines like interleukin-1 beta (IL-1β), which in turn induces the activation of signaling pathways, such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), phosphoinositide 3-kinase/protein kinase B (PI3K/AKT), and mitogen-activated protein kinase (MAPK). These events, in turn, generate more inflammatory molecules. Subsequently, collagenase like matrix metalloproteinases-13 (MMP-13) will degrade the extracellular matrix. As a result, anatomical and physiological functions of the joint are altered. This review is aimed at summarizing the previous studies highlighting the involvement of inflammation in the pathogenesis of osteoarthritis.

Antithymocyte Globulin Antibody Titer Congruent With Kidney Transplantation: Analysis of Incidence, Outcomes, Cost, and Alternative Targets

Rabbit antithymocyte globulin (rATG) use for immunosuppression induction is widespread but is contraindicated by the presence of anti-rATG antibodies. This study reports the incidence of positive anti-rATG antibody titers in patients before and after renal transplant and evaluates associated outcomes and costs. In addition, it will correlate CD40L and interleukin (IL)-21 with anti-rATG antibody titers.

METHODS

Clinical and billing records from the Indiana University Transplant Laboratory were reviewed for positive versus negative anti-rATG antibody titers, graft survival, and 7-day readmission costs between 2004 and 2018. Serum from patients with positive and negative rATG antibody titers were quantitated for CD40L and IL-21 by enzyme-linked immunosorbent assay.

RESULTS

On average, between 2004 and May 2018, 163 kidney transplants per year were performed. Anti-rATG antibody titers were ordered for 17 patients/year, of which 18.2% were positive at 1:100 titer either pre- or post-transplant. Time to graft loss correlated with a positive rATG titer at time of readmission. Moreover, second kidney transplant increased the anti-rATG positive rate. A weak correlation was observed between anti-rATG titer and recipient age. Seven-day readmission treatment costs were significantly lower in patients with positive anti-rATG titer. IL-21 and CD40L were significantly greater in patients with positive anti-rATG titers after transplant when compared with negative anti rATG patients.

CONCLUSIONS

Positive anti-rATG antibody titer is associated with a significant negative impact on outcomes. Monitoring of anti-rATG antibody titer is recommended to optimize treatment options in patients, especially in the setting of second transplants. Elucidation of the mechanisms associated with positive anti-rATG antibody is required. IL-21 and CD40L are potential targets for future study.

Computational deconvolution of synovial tissue cellular composition: presence of adipocytes in synovial tissue decreased during arthritis pathogenesis and progression

Osteoarthritis (OA) and rheumatoid arthritis (RA) are the most common forms of arthritis. The synovial tissue is the major site of inflammation of OA and RA and consists of diverse cells. Synovial tissue cell composition changes during arthritis pathogenesis and progression have not been systematically characterized and may provide critical insights into disease processes. In this study we aimed at systematically examining cellular changes in synovial tissue. Publicly available synovial tissue transcriptomic data sets were used. We computationally estimated cell compositions in synovial tissue based on transcriptomic data and compared cell compositions in different diseases or at different disease stages. Synovial fibroblasts, macrophages, adipocytes, and immune cells were the major cell types in all synovial tissue. Both OA and RA patients had a significantly lower adipocyte fraction compared with healthy controls. The decrease trend was also observed during OA and RA progression. The fraction of monocytes was also increased in both OA and RA arthritis patients, consistent with the observations that inflammation involved in both OA and RA. But the monocyte fraction in RAs was much higher than the ones in healthy controls and OAs. The M2 macrophage fraction was reduced in RA compared with OA, the reduction trend continued during RA progression from the early- to the late-stage. There were consistent cell composition differences between different types or stages of arthritis. Both in RA and OA, the new discovery of changes in the adipocyte and M2 macrophage fractions has potential leading to novel therapeutic development.

Osteoarthritis year in review 2018: biomarkers (biochemical markers)

OBJECTIVE

The aim of this narrative review is to summarize important findings from biochemical marker studies relevant to osteoarthritis (OA) in the context of new discoveries and clinical and scientific need.

DESIGN

We conducted a systematic search of electronic medical databases (Embase, Medline, Web of Science, Cochrane central) between 01-03-2017 and 31-03-2018. The search was restricted to human studies, English language and full text available publications while reviews were excluded. Only papers describing protein based biomarkers measured in human body fluids (blood, urine and synovial fluid (SF)) were included. Of the 992 papers, 86 were reviewed here, with inclusion primarily based on relevance to OA biochemical markers.

RESULTS

This review highlights a selection of studies based on their quality and perceived importance to the field mainly including those that¹ evaluate prognostic value of biomarkers for OA progression (i.e., biomarkers reflecting change in composition of joint tissues and biomarkers of inflammation)², help in assessment of intervention efficacy, and³ are innovative and uncover new candidate biomarkers, or use new approaches in biomarker discovery.

CONCLUSIONS

Key findings and implications for possible clinical utility of biochemical markers are summarized and discussed. Given the paucity of robust biomarkers within the field, and the heterogeneity of the condition, enormous works are needed for development and validation of novel and clinically applicable biomarkers to reduce the impact of this highly prevalent and debilitating condition.

Immune cell subset differentiation and tissue inflammation

Immune cells were traditionally considered as major pro-inflammatory contributors. Recent advances in molecular immunology prove that immune cell lineages are composed of different subsets capable of a vast array of specialized functions. These immune cell subsets share distinct duties in regulating innate and adaptive immune functions and contribute to both immune activation and immune suppression responses in peripheral tissue. Here, we summarized current understanding of the different subsets of major immune cells, including T cells, B cells, dendritic cells, monocytes, and macrophages. We highlighted molecular characterization, frequency, and tissue distribution of these immune cell subsets in human and mice. In addition, we described specific cytokine production, molecular signaling, biological functions, and tissue population changes of these immune cell subsets in both cardiovascular diseases and cancers. Finally, we presented a working model of the differentiation of inflammatory mononuclear cells, their interaction with endothelial cells, and their contribution to tissue inflammation. In summary, this review offers an updated and comprehensive guideline for immune cell development and subset differentiation, including subset characterization, signaling, modulation, and disease associations. We propose that immune cell subset differentiation and its complex interaction within the internal biological milieu compose a “pathophysiological network,” an interactive cross-talking complex, which plays a critical role in the development of inflammatory diseases and cancers.

Identification of antibodies against extracellular matrix proteins in human osteoarthritis

We investigated the presence of autoantibodies against the extracellular matrix proteins thrombospondin-4 (TSP-4), cartilage oligomeric matrix protein (COMP), C-type lectin domain family 3 member A (CLEC3A), collagen II, collagen VI, matrilin-3, and fibrillin-2 in the serum of osteoarthritis (OA) patients. We compared those results with the presence of such antibodies in rheumatoid arthritis (RA) patients and in healthy donors (HD). Our study examines whether antibodies against extracellular proteins can be used as potential biomarkers to support the clinical diagnosis of OA. 10 OA, 10 RA patients and 10 HD were enrolled in this explorative cross-sectional study. SDS-PAGE and immunoblot were used to investigate the presence of antibodies against extracellular matrix proteins. The serum of 5/10 OA patients but 0/10 HD exhibited TSP-4 IgG isotype antibodies (P = 0.033). The serum of 8/10 OA patients but only 1/10 HD exhibited IgG isotype antibodies against TSP-4 or COMP (P = 0.005). The serum of 9/10 OA patients but only 1/10 HD exhibited IgG isotype antibodies against TSP-4, COMP or CLEC3A (P = 0.005). We found strong evidence for the presence of IgG isotype autoantibodies against the cartilage extracellular matrix proteins TSP-4, COMP and CLEC3A in OA. The detection of IgG isotype autoantibodies against TSP-4, COMP and CLEC3A may support the clinical diagnosis of OA. OA with autoantibodies against cartilage extracellular matrix proteins defines a new OA subgroup suggesting that patients with high concentrations of autoantibodies may benefit from an immune suppressive therapy.

Osteoarthritis biomarkers: year in review

OBJECTIVE

To summarise important findings from biomarker studies relevant to osteoarthritis (OA), published between April 2016 and March 2017; to consider these findings in the context of new discoveries and technologies, and clinical and scientific need in OA.

DESIGN

Studies were selected by PubMed search, conducted between 01/04/2016 and 01/03/2017. MeSH terms [biomarker] AND [OA] were used; the search was restricted to Human, English language and Full Text Available publications, which yielded 50 eligible publications. Any biomarker was considered, including non-proteins and other clinical measurements.

RESULTS

Three main areas are overviewed: 1) Studies examining highly validated biomarkers, in the FNIH OA Biomarkers Consortium and elsewhere, particularly their ongoing application and validation. Control reference intervals, work on predictive validity and other longitudinal studies examining prognostic value of biomarkers in large cohorts are reviewed. 2) Novel studies relating to biomarkers of inflammation are discussed, including complement, the performance of markers of so-called 'cold inflammation' and results from clinical trials including biomarkers. 3) Discovery studies, including whole blood RNA, proteomics and metabolomics are reviewed, with an emphasis on new technologies.

CONCLUSIONS

Discovery, characterisation and qualification of various biomarkers is ongoing; several novel protein and non-protein candidate biomarkers have been reported this year. Biomarkers provide us with an opportunity to better diagnose and stratify the disease, via established panels or new discovery approaches. Improving quality of sampling and testing, and measuring large numbers of markers simultaneously in large cohorts would seem likely to identify new clinically applicable biomarkers, which are still much needed in this disease.

Immune Contributions to Osteoarthritis

PURPOSE OF THE REVIEW

Mounting evidence supports a role of low-grade inflammation in the pathophysiology of osteoarthritis (OA). We review and discuss the role of synovitis, complement activation, cytokines, and immune cell population in OA.

RECENT FINDINGS

Using newer imaging modalities, synovitis is found in the majority of knees with OA. Complement activation and pro-inflammatory cytokines play a significant role in the development of cartilage destruction and synovitis. Immune cell infiltration of OA synovial tissue by sub-populations of T cells and activated macrophages correlates with OA disease progression and pain. The innate and acquired immune system plays a key role in the low-grade inflammation found associated with OA. Targets of these pathways my hold promise for future disease-modifying osteoarthritis drugs (DMOADs).

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.