Loss of balance between protective and pro-inflammatory synovial tissue T-cell polyfunctionality predates clinical onset of rheumatoid arthritis

The role of gut flora-driven Th cell responses in preclinical rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder with an immune pathogenesis that evolves over decades. Preclinical RA (PreRA) represents a dynamic immune phase preceding clinical RA, marked by the loss of autoimmune tolerance, the appearance of tissue-invasive effector T cells, and the production of autoantibodies (such as antibodies against citrullinated proteins and rheumatoid factors). Extensive research has demonstrated that gut microbiota influence mucosal T-cell responses, driving the progression of PreRA through multiple mechanisms, including altered intestinal permeability, gene-environment interactions, bacterial antigenic specificity, molecular mimicry, and metabolite production. Environmental risk factors such as smoking, hormonal changes, and high-sodium (Na) diets, may contribute to RA pathogenesis via the gut microbiome. The next challenge in RA research lies in developing therapeutic strategies to intervene during the asymptomatic autoimmune phase, where dietary adjustments, natural compounds, probiotics, and other approaches could effectively modulate gut flora to prevent or delay RA onset.

Effects of dioscin from Dioscorea nipponica on TL1A/DR3 and Th9 cells in a collagen-induced arthritis mouse model

Rheumatoid arthritis (RA) is a systemic autoimmune disease, and TL1A and its receptor DR3 play important roles in its pathogenesis. Th9 cells are involved in RA development. Dioscin from Dioscorea nipponica (DDN) has a therapeutic effect on RA, but its effect on TL1A/DR3 and Th9 cells remains unclear. A collagen-induced arthritis (CIA) model was established in DBA/1 mice, and the therapeutic effects of DDN were determined using pathological sections and arthritis index scores. Western blotting and PCR were used to detect TL1A, DR3, PU.1, TGF-β and IRF-4. Enzyme-linked immunosorbent assay was used to detect the expression of TL1A and IL-9 in the serum. Immunofluorescence was used to detect the localization and expression of TL1A, DR3, and PU.1 in synovial tissue. Flow cytometry was used to detect TL1A and DR3 expression in different immune cells and Th9 cells. DDN ameliorated bone destruction, inflammatory cell infiltration, synovial inflammation, cartilage tissue destruction, and proteoglycan loss. DDN downregulated TL1A, DR3, and PU.1 in the synovium of the lymph nodes and spleen and TL1A and IL-9 in the serum. DDN decreased the number of TL1A-expressing APCs and macrophages, DR3-expressing CD4 + T cells, and Th9 cells. Th9 cell differentiation-related factors TGF-β and IRF-4 were also inhibited by DDN. We conclude that DNN inhibited the expression of TL1A/DR3 in CIA mice and suppressed the expression of the Th9 cell-specific transcription factor PU.1, Th9 cell number, and IL-9 secretion. DDN inhibited the function of Th9 cells by targeting TGF-β and IRF-4 in the TL1A/DR3 pathway, thereby reducing inflammation.

Non-invasive imaging with ICOS-targeting monoclonal antibody for preclinical diagnosis of rheumatoid arthritis in a humanized mouse model

BACKGROUND

Activated T cells play a pivotal role in rheumatoid arthritis (RA) pathogenesis, and imaging of activated T cells may provide a non-invasive tool for RA detection. Here, we first developed an optical probe targeting human inducible T cell co-stimulator (ICOS) and tested its capacity in RA diagnosis by capturing ICOS+ activated T cells in vivo in a humanized mouse model.

METHODS

The humanized arthritis model, Human peripheral blood mononuclear cells- adjuvant induced arthritis (HuPBMC-AIA) was established, and flow cytometry and immunofluorescence were employed to determine ICOS expression in huPBMC-AIA model. Anti-human ICOS monoclonal antibody (mAb) was conjugated to Cy7 via NHS ester amine reaction. A cell uptake study was used to confirm the specificity of Cy7-ICOS mAb to activated T cells. 4-view near-infrared fluorescence (NIRF) imaging study was performed to test Cy7-ICOS mAb in detecting RA in vivo.

FINDINGS

ICOS was confirmed as an indicator of RA pathogenesis via RNA-seq, flow cytometry and immunofluorescence data. An in-vitro cellular uptake study validated the specificity of Cy7-ICOS mAb to activated T cells. Cy7-ICOS mAb could detect ICOS+ activated T cells in vivo through 4-view NIRF imaging. The receiver operating characteristic (ROC) curve created based on NIRF imaging quantification could distinguish the huPBMC-AIA group from the control group at all time points imaged.

CONCLUSION

In this study, we first developed an optical imaging probe targeting human ICOS, Cy7-ICOS mAb. The 4-view NIRF imaging with Cy7-ICOS mAb could detect pathogenic ICOS+ activated T cells with high sensitivity and specificity in vivo, which indicated the great potential of this imaging probe in RA early diagnosis.

Enhancing the effectiveness of immunotherapy in rheumatoid arthritis by delaying immunosenescence triggered by fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a prevalent autoimmune disorder primarily targeting the diarthrodial joints. During the progression of RA, fibroblast-like synoviocytes (FLSs) exhibit tumor-like behavior, including increased proliferation, inflammation mediation, and aggressive phenotypes, leading to bone erosion. Additionally, T cells in RA acquire pro-inflammatory characteristics, exacerbating the inflammatory environment in affected joints and associated tissues. Notably, senescent T cells contribute to inflammation, further accelerating the disease process. Metabolic changes in rheumatoid FLSs not only maintain their tumor-like properties but also trigger inflammatory cascades, particularly affecting T lymphocytes. This review examines the molecular alterations in RA FLSs in the context of systemic immune aging, with a focus on thymic insufficiency-associated T cell senescence, and explores potential therapeutic avenues.

CD4+CD8αlow T Cell Clonal Expansion Dependent on Costimulation in Patients With Rheumatoid Arthritis

OBJECTIVE

CD4+CD8+ T cells are increased in patients with rheumatoid arthritis (RA). They are not only associated with joint erosions in established disease but are also present in the preclinical stages of RA. This study aims to further investigate their expansion in the context of T cell clonality in patients with RA, as well as their responsiveness to T cell-targeted treatment.

METHODS

Single-cell RNA (scRNA) and single-cell T cell receptor (TCR) sequencing data were used to determine coreceptor expression and TCR sequences to assess the clonality of CD4+CD8+ T cells in patients with RA (n = 3) and healthy controls (n = 2). Peripheral CD4+CD8+ T cells and their subpopulations were measured in patients with RA (n = 53), patients with psoriatic arthritis (PsA; n = 52), and healthy donors (n = 50) using flow cytometry. In addition, changes in CD4+CD8+ T cell frequency were prospectively observed in patients with RA receiving therapy with abatacept for 12 weeks.

RESULTS

We observed an increase of CD4+ T cells expressing CD8α in patients with RA, both in comparison to patients with PsA and healthy controls. Clonality analysis revealed that these CD4+CD8αlow T cells are part of large T cell clones, which cluster separately from CD4+CD8- T cell clones in the scRNA sequencing (scRNA-seq) gene expression analysis. Treatment with abatacept significantly reduced the frequency of peripheral CD4+CD8αlow T cells, and this was linked to reduction in disease activity.

CONCLUSION

In patients with RA, clonal expansion of CD4+ T cell culminates in the emergence of peripheral CD4+CD8αlow T cells, which are associated with disease activity and diminished upon abatacept treatment and could contribute to disease pathogenesis.

Analysis of the causal relationship between immune cells and rheumatoid arthritis from the perspective of genetic variation: a bidirectional two-sample Mendelian randomization study

BACKGROUND

Immune factors are crucial in the pathogenesis of rheumatoid arthritis (RA), and immune cells play a key role in the development of RA. However, there is still disagreement regarding the specific roles of each type of immune cell in the pathological process of RA.

METHODS

This study used bidirectional two-sample Mendelian randomization (MR) analysis to determine the causal relationship between immune cell characteristics and RA. Utilizing publicly available genetic data, we initially treated immune cell characteristics as exposures to investigate their causal effects on the risk of RA. Subsequently, we performed reverse two-sample MR using the positively selected cells from the initial analysis as outcomes, aiming to identify the core immune cells involved. Finally, a comprehensive sensitivity analysis was conducted to validate the robustness, heterogeneity, and horizontal pleiotropy of the results.

RESULTS

Using data from 731 immune cells as exposures and cell SNPs as instruments, we independently conducted two-sample MR analysis for each patient with RA. The main analytical method used was the IVW method, with a significance level set at P < 0.05 for inclusion. In total, we identified 42 immune cell phenotypes that were causally associated with the onset of RA. For the reverse MR analysis, we used RA as the exposure factor and focused on 42 immune cell phenotypes as outcomes. Our analysis revealed causal relationships between the onset of RA and 7 immune cell phenotypes. Among these, 6 showed positive causal relationships, while 1 exhibited a negative causal relationship.

CONCLUSIONS

Our study emphasized the causal relationship between immune cells and RA through bidirectional two-sample MR analysis, identifying the immune cells causally associated with RA.

Butyrate: a bridge between intestinal flora and rheumatoid arthritis

In patients with rheumatoid arthritis (RA), intestinal flora imbalance and butyrate metabolism disorders precede clinical arthritis and are associated with the pathogenesis of RA. This imbalance can alter the immunology and intestinal permeability of the intestinal mucosa, leading to damage to the intestinal barrier. In this context, bacteria and their metabolites can enter the bloodstream and reach the distant target tissues of the host, resulting in local inflammation and aggravating arthritis. Additionally, arthritis is also exacerbated by bone destruction and immune tolerance due to disturbed differentiation of osteoclasts and adaptive immune cells. Of note, butyrate is a metabolite of intestinal flora, which not only locally inhibits intestinal immunity and targets zonulin and tight junction proteins to alleviate intestinal barrier-mediated arthritis but also inhibits osteoclasts and autoantibodies and balances the immune responses of T and B lymphocytes throughout the body to repress bone erosion and inflammation. Therefore, butyrate is a key intermediate linking intestinal flora to the host. As a result, restoring the butyrate-producing capacity of intestinal flora and using exogenous butyrate are potential therapeutic strategies for RA in the future.

Effect of the immune cells and plasma metabolites on rheumatoid arthritis: a mediated mendelian randomization study

Background

Increasing evidence indicates a close relationship between alterations in human immune cells and plasma metabolites with Rheumatoid Arthritis (RA). However, limited studies have left the causal relationships behind these links unclear.

Methods

A bidirectional Mendelian Randomization (MR) study was conducted, combined with mediation analysis, using data from genome-wide association study database covering 731 immune cell phenotypes and 1,400 plasma metabolite traits to explore their causal relationships with RA and potential mediating effects. The primary method used for MR analysis was inverse-variance weighted and False Discovery Rate (FDR) correction was applied to verify the robustness of our results.

Results

HLA DR on CD33- HLA DR+ (myeloid cell group) (OR, 1.422; 95% CI, 1.194-1.694; P < 0.001; PFDR = 0.012) increased the risk of developing RA. CD19 on IgD+ CD38- naive (B cell group) (OR, 0.969; 95% CI, 0.954-0.985; P < 0.001; PFDR = 0.021) reduced the risk of developing RA. RA was a risk factor for HLA DR on CD14- CD16+ monocytes (monocyte group) (OR, 1.242; 95% CI, 1.102-1.401; P < 0.001; PFDR  = 0.047). RA was a protective factor for memory B cell %lymphocyte (B cell group) (OR, 0.861; 95% CI, 0.795-0.933; P < 0.001; PFDR = 0.050), CD4+ CD8dim T cell %lymphocyte (TBNK group) (OR, 0.802; 95% CI, 0.711-0.904; P < 0.001; PFDR  = 0.043), CD4+ CD8dim T cell %leukocyte (TBNK group) (OR, 0.814; 95% CI, 0.726-0.913; P < 0.001; PFDR  = 0.046), CD24 on IgD+ CD24+ B cells (B cell group) (OR, 0.857; 95% CI, 0.793-0.927; P < 0.001; PFDR  = 0.038), and CD24 on unswitched memory B cells (B cell group) (OR, 0.867; 95% CI, 0.797-0.942; P < 0.001; PFDR  = 0.050). Increasing levels of docosatrienoate (22:3n3) (OR, 0.886; 95% CI, 0.838-0.936; P < 0.001; PFDR = 0.023) significantly reduced the risk of developing RA. The mediating effect of plasma metabolites in this context was not established.

Conclusion

This study provides genetic evidence for the intricate relationships between immune cells, plasma metabolites, and RA, highlighting the potential mechanisms involved. This will contribute to future directions in precision medicine and research.

Effect of Lactiplantibacillus plantatum HFY11 on Colitis in Mice

This study aimed to examine the potential impact of the intervention of Lactiplantibacillus plantatum HFY11 (LP-HFY11) on colitis using in vivo animal trials. The impact of LP-HFY11 intervention on colitis was determined by measuring the levels of relevant indicators in the intestine, colon, and blood after oxazolone-induced colitis in BALB/c mice. The results of the trial show that LP-HFY11 improved the colon weight-to-length ratio, reduced the colitis-induced colon length shortening, and reduced colonic abstinence. Furthermore, it decreased the levels of myeloperoxidase, nitric oxide, and malondialdehyde activities while increasing the glutathione content in the colon tissue of colitis-affected animals. LP-HFY11 lowered the interleukin-10 (IL-10) level and increased the IL-2 level in the serum of colitis mice. LP-HFY11 also upregulated the expression of neuronal nitric oxide synthase, endothelial nitric oxide synthase, c-Kit, and stem cell factor (SCF), and downregulated the expression of IL-8, C-X-C chemokine receptor type 2 (CXCR2), and inducible nitric oxide synthase (iNOS) in the colon tissue of mice with colitis. LP-HFY11 decreased the expression of Firmicutes in the gut while increasing the expression of Bacteroidetes, Bifidobacteria, and Lactobacillus. This indicates that LP-HFY11 could control physiological alterations in the serum and colon tissue, as well as the expression of gut microorganism.

Rheumatoid Arthritis: The Continuum of Disease and Strategies for Prediction, Early Intervention, and Prevention

Rheumatoid arthritis (RA) is known to include a pre-RA stage that can be defined as the presence of familial or genetic risk factors, biomarker abnormalities (eg, anticitrullinated protein antibodies [ACPA]), symptoms, and even abnormal imaging findings prior to the development of the onset of clinical RA with inflammatory arthritis that is apparent on physical examination. Indeed, there are multiple completed or ongoing retrospective case-control as well as prospective observational studies to identify the key biologic drivers of disease. Further, building on the predictive ability of combinations of biomarkers, symptoms, and imaging for future RA, there are multiple clinical trials completed, underway, or in development to identify approaches that may prevent, delay, or ameliorate future clinical RA in at-risk individuals. Importantly, however, although an effective preventive intervention has not yet been identified, at-risk individuals are being increasingly identified in clinical care; this presents a challenge of how to manage these individuals in clinical practice. This review will discuss the current understanding of the biology and natural history of RA development, nomenclature, and current models for prediction of future RA, as well as evaluate the current and ongoing clinical prevention trials with the overall goal to provide insights into the challenges and opportunities in the field of RA prevention. Moreover, this review will provide up-to-date options for clinical management of individuals at risk for RA.

The differentiation courses of the Tfh cells: a new perspective on autoimmune disease pathogenesis and treatment

The follicular helper T cells are derived from CD4+T cells, promoting the formation of germinal centers and assisting B cells to produce antibodies. This review describes the differentiation process of Tfh cells from the perspectives of the initiation, maturation, migration, efficacy, and subset classification of Tfh cells, and correlates it with autoimmune disease, to provide information for researchers to fully understand Tfh cells and provide further research ideas to manage immune-related diseases.

Current situation and trend of non-coding RNA in rheumatoid arthritis: a review and bibliometric analysis

Background

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease that affects multiple joints and has adverse effects on various organs throughout the body, often leading to a poor prognosis. Recent studies have shown significant progress in the research of non-coding RNAs (ncRNAs) in RA. Therefore, this study aims to comprehensively assess the current status and research trends of ncRNAs in RA through a bibliometric analysis.

Methods

This study retrieved articles relevant to ncRNAs and RA from the Science Citation Index Expanded Database of the Web of Science Core Collection between January 1st, 2003, and July 31st, 2023. The relevant articles were screened based on the inclusion criteria. VOSviewer and CiteSpace are utilized for bibliometric and visual analysis.

Results

A total of 1697 publications were included in this study, and there was a noticeable increase in annual publications from January 1st, 2003, to July 31st, 2023. China, the United States, and the United Kingdom were the most productive countries in this field, contributing to 43.81%, 13.09%, and 3.87% of the publications. Anhui Medical University and Lu Qianjin were identified as the most influential institution and author. Frontiers In Immunology stood out as the most prolific journal, while Arthritis & Rheumatology was the most co-cited journal. Additionally, the research related to "circular RNA", "oxidative stress", "proliferation", and "migration" have emerged as new hotspots in the field.

Conclusion

In this study, we have summarized the publication characteristics related to ncRNA and RA and identified the most productive countries, institutions, authors, journals, hot topics, and trends.

Impaired immune tolerance mediated by reduced Tfr cells in rheumatoid arthritis linked to gut microbiota dysbiosis and altered metabolites

BACKGROUND

Patients with rheumatoid arthritis (RA) showed impaired immune tolerance characterized by reduced follicular regulatory T (Tfr) cells, and they also exhibited altered gut microbiotas and their metabolites in RA. However, the association of gut microbiotas and their metabolites with the immune tolerance mediated by Tfr cells in RA remains unclear.

METHODS

Peripheral blood and stool samples were collected from 32 new-onset RA patients and 17 healthy controls (HCs) in the Second Hospital of Shanxi Medical University between January 2022 and June 2022. The peripheral blood was used to detect the circulating regulatory T (Treg), helper T(Th)17, Tfr, and follicular helper T (Tfh) cells by modified flow cytometry. The stool samples were used to analyze the gut microbiotas and their metabolites via 16S rDNA sequencing and metabolomic profiling. We aimed to characterize the gut microbiotas and their metabolites in RA and identified their association with Tfr cell-mediated immune tolerance.

RESULTS

The new-onset RA demonstrated reduced Treg and Tfr cells, associated with the disease activity and autoantibodies. There were significant differences in gut microbiotas between the two groups as the results of β diversity analysis (P = 0.039) including 21 differential gut microbiotas from the phylum to genus levels. In which, Ruminococcus 2 was associated with the disease activity and autoantibodies of RA, and it was identified as the potential biomarker of RA [area under curve (AUC) = 0.782, 95% confidence interval (CI) = 0.636-0.929, P = 0.001]. Eleven differential metabolites were identified and participated in four main pathways related to RA. Arachidonic acid might be the potential biomarker of RA (AUC = 0.724, 95% CI = 0.595-0.909, P = 0.038), and it was the core metabolite as the positive association with six gut microbiotas enriched in RA. The reduced Tfr cells were associated with the altered gut microbiotas and their metabolites including the Ruminococcus 2, the arachidonic acid involved in the biosynthesis of unsaturated fatty acid pathway and the 3-methyldioxyindole involved in the tryptophan metabolism pathway.

CONCLUSION

The breakdown of immune tolerance mediated by reduced Tfr cells was associated with the altered gut microbiotas and their metabolites implying the possible mechanism of RA pathogenesis from the perspective of microecology-metabolism-immune.

Comparison and subsets analysis of peripheral CD4+T cells in patients with psoriasis and psoriatic arthritis

Psoriatic arthritis (PsA) is a disease that transformed from psoriasis (PsO), and its underlying mechanisms are still not fully understood. Overactivation of the immune system is a key factor driving inflammatory diseases. Our goal is to define the unbalanced subsets of peripheral blood CD4 +T cells between PsO and PsA patients. Blood samples from 43 patients (23 PsA and 20 PsO) and 36 healthy donors (HD) were studied. Peripheral blood mononuclear cells (PBMC) were separated from blood and underwent fluorescent staining to assess CD4+T cell subsets by flow cytometry. We found that frequencies of various CD4+T cells including Th1, Th2, Th17, and Tfh were higher in the patients with PsO or PsA than those of healthy donors, indicating the general expansion of CD4+T cells in inflammatory conditions. More importantly, we observed the significant imbalance of Th1/Th2 between patients with PsO and PsA. Pearson correlation analysis showed that Th1/Th2 ratio was positively correlated with disease activity in psoriatic arthritis (DAPSA), Tfh/Tfr ratio was positively correlated with DAPSA score and visual analogue scale (VAS) score in PsA patients. Together, our results highlight the CD4+T cell changes in the transition from PsO to PsA, may contribute to early assessment and intervention.

Peripheral CD4+ /CD8+ T cell composition distinct from healthy individuals is shared by ankylosing spondylitis and rheumatoid arthritis

OBJECTIVE

Ankylosing spondylitis (AS) and rheumatoid arthritis (RA) are chronic inflammatory joint diseases, linking to the alterations of immune cells. We attempted to assess whether the alterations in the composition of CD4+ /CD8+ T cells are different between AS and RA and identify the characteristic cells between male and female patients.

METHODS

The proportions of CD3+ or double positive T cells, 6 CD4+ T subsets and 9 CD8+ T cell subsets were detected by flow cytometry and compared in 30 healthy individuals, 42 AS patients and 45 RA patients. The differentially altered cells were individually analyzed for associations with disease activity parameters. In addition, their proportions were compared between different genders in the 3 groups.

RESULTS

The proportions of CD4+ T cells, naive CD4+ T cells and central memory CD4+ T cells were lower in AS patients (P = 0.001, P = 0.002 and P = 0.007, respectively) and RA patients (P = 0.032, P < 0.001 and P = 0.016, respectively), but the proportion of effector memory ones was higher when compared with healthy populations (both P < 0.001), as were the decrease of naive/central memory CD8+ T cells in AS (P = 0.003 and P = 0.016, respectively) and RA (P < 0.001 and P = 0.006, respectively), and the increased tendency of terminally differentiated CD8+ T cells. However, these above-mentioned cells, regulatory T (Treg) cells and CD8+ T cells with different CD127 expressions between AS and RA were similar in proportion. Furthermore, naive CD4+ T cells were positively associated with C-reactive protein (CRP) in AS, whereas CD4+ T cells and terminally differentiated CD8+ T of RA patients were associated with CRP in RA. The gender-related alterations predominantly displayed the overexpressions of Treg cells and naive CD8+ T cells in female patients with AS and RA, respectively.

CONCLUSIONS

AS patients and RA patients have some similar peripheral CD4+ /CD8+ T cell subsets but are distinct from healthy individuals, which may contribute to disease severity. Females are respectively characterized by the up-regulation of Treg cells and naive CD8+ T cells in AS patients and RA patients. The study offers an in-depth understanding of the role of T cell subsets in the similarities of the disorders and helps us to monitor disease changes and may offer a theoretical basis of developing novel therapies against common targets.

Treatment of rheumatoid arthritis with baricitinib or upadacitinib is associated with reduced scaffold protein NEDD9 levels in CD4+ T cells

The JAK/STAT pathway plays a crucial role in the pathogenesis of rheumatoid arthritis (RA) and JAK inhibitors have emerged as a new group of effective drugs for RA treatment. Recently, high STAT3 levels have been associated with the upregulation of the scaffold protein NEDD9, which is a regulator of T-cell trafficking and promotes collagen-induced arthritis (CIA). In this study, we aimed to reveal how treatment with JAK inhibitors affects NEDD9 in CD4+ T cells from RA patients. We analyzed NEDD9 expression in CD4+ T cells from 50 patients treated with either baricitinib, tofacitinib, or upadacitinib and performed cell migration assays to assess the potential influence of JAK inhibitor treatment on CD4+ T-cell migration. We observed that treatment with baricitinib and upadacitinib is associated with reduced NEDD9 expression in CD4+ T cells. In contrast, NEDD9 levels were not altered during treatment with tofacitinib. Moreover, treatment with baricitinib was associated with a significantly reduced migratory capacity of effector CD4+ T cells but not with impaired migration of Treg cells. This study reveals previously unknown associations between JAK inhibitor treatment and NEDD9 expression and indicates that JAK inhibitors could reduce effector T-cell migration.

Computational approaches in rheumatic diseases - Deciphering complex spatio-temporal cell interactions

Inflammatory arthritis, including rheumatoid (RA), and psoriatic (PsA) arthritis, are clinically and immunologically heterogeneous diseases with no identified cure. Chronic inflammation of the synovial tissue ushers loss of function of the joint that severely impacts the patient's quality of life, eventually leading to disability and life-threatening comorbidities. The pathogenesis of synovial inflammation is the consequence of compounded immune and stromal cell interactions influenced by genetic and environmental factors. Deciphering the complexity of the synovial cellular landscape has accelerated primarily due to the utilisation of bulk and single cell RNA sequencing. Particularly the capacity to generate cell-cell interaction networks could reveal evidence of previously unappreciated processes leading to disease. However, there is currently a lack of universal nomenclature as a result of varied experimental and technological approaches that discombobulates the study of synovial inflammation. While spatial transcriptomic analysis that combines anatomical information with transcriptomic data of synovial tissue biopsies promises to provide more insights into disease pathogenesis, in vitro functional assays with single-cell resolution will be required to validate current bioinformatic applications. In order to provide a comprehensive approach and translate experimental data to clinical practice, a combination of clinical and molecular data with machine learning has the potential to enhance patient stratification and identify individuals at risk of arthritis that would benefit from early therapeutic intervention. This review aims to provide a comprehensive understanding of the effect of computational approaches in deciphering synovial inflammation pathogenesis and discuss the impact that further experimental and novel computational tools may have on therapeutic target identification and drug development.

hIgD-Fc-Ig fusion protein regulates T cell functions by inhibiting TCR signaling pathway in adjuvant arthritis rats

This study aimed to investigate the effect of hIgD-Fc-Ig on TCR-Lck-Erk activated by IgD in adjuvant arthritis (AA) rats. Wistar rats were divided into the normal, AA model, hIgD-Fc-Ig (1 mg/kg, 3 mg/kg and 9 mg/kg) and Etanercept (3 mg/kg) groups. The overall index of AA rats was measured every 3 days. The pathologic examination of knee joints and the proliferation of the spleen and thymus of AA rats were detected by H&E staining and CCK-8. The blood flow signal of knee joints of experimental rats was examined by US. The articular bone injury was detected by X-ray. The changes in PBMCs and spleen T cell subsets were detected by flow cytometry. The expression of CD3ε, p-Lck, p-Zap70, Ras, and p-Erk in rat spleens was detected by immunofluorescence and WB. Rat spleen T cells or Jurkat cells treated by IgD to observe the effect of hIgD-Fc-Ig on TCR and its downstream protein expression. The results showed that hIgD-Fc-Ig had a therapeutic effect on AA rats by reducing the secondary inflammation, improving pathological changes. hIgD-Fc-Ig can reduce the ratio of Th cells of PBMCs of AA rats, the ratio of Th, Th1, Th17 cells and increase the ratio of Th2, Treg cells of AA rat spleens. hIgD-Fc-Ig could down-regulate the expression of CD3ε, p-Lck, p-Zap70, Ras, p-Erk in vivo or in vitro. In conclusion, hIgD-Fc-Ig could alleviate the symptoms of AA rats and regulate T cells through TCR-Lck-Erk signaling pathway and maybe a new promising biological agent for RA.

The Search for the Pathogenic T Cells in the Joint of Rheumatoid Arthritis: Which T-Cell Subset Drives Autoimmune Inflammation?

Rheumatoid arthritis (RA) is a chronic inflammatory disorder affecting systemic synovial tissues, leading to the destruction of multiple joints. Its etiology is still unknown, but T-cell-mediated autoimmunity has been thought to play critical roles, which is supported by experimental as well as clinical observations. Therefore, efforts have been made to elucidate the functions and antigen specificity of pathogenic autoreactive T cells, which could be a therapeutic target for disease treatment. Historically, T-helper (Th)1 and Th17 cells are hypothesized to be pathogenic T cells in RA joints; however, lines of evidence do not fully support this hypothesis, showing polyfunctionality of the T cells. Recent progress in single-cell analysis technology has led to the discovery of a novel helper T-cell subset, peripheral helper T cells, and attracted attention to the previously unappreciated T-cell subsets, such as cytotoxic CD4 and CD8 T cells, in RA joints. It also enables a comprehensive view of T-cell clonality and function. Furthermore, the antigen specificity of the expanded T-cell clones can be determined. Despite such progress, which T-cell subset drives inflammation is yet known.

Bioinformatics analysis based on crucial genes of endothelial cells in rheumatoid

Objectives: Synovial neovascularization is an early and remarkable event that promotes the development of rheumatoid arthritis (RA) synovial hyperplasia. This study aimed to find potential diagnostic markers and molecular therapeutic targets for RA at the mRNA molecular level. Method: We download the expression profile dataset GSE46687 from the gene expression ontology (GEO) microarray, and used R software to screen out the differentially expressed genes between the normal group and the disease group. Then we performed functional enrichment analysis, used the STRING database to construct a protein-protein interaction (PPI) network, and identify candidate crucial genes, infiltration of the immune cells and targeted molecular drug. Results: Rheumatoid arthritis datasets included 113 differentially expressed genes (DEGs) including 104 upregulated and 9 downregulated DEGs. The enrichment analysis of genes shows that the differential genes are mainly enriched in condensed chromosomes, ribosomal subunits, and oxidative phosphorylation. Through PPI network analysis, seven crucial genes were identified: RPS13, RPL34, RPS29, RPL35, SEC61G, RPL39L, and RPL37A. Finally, we find the potential compound drug for RA. Conclusion: Through this method, the pathogenesis of RA endothelial cells was further explained. It provided new therapeutic targets, but the relationship between these genes and RA needs further research to be validated in the future.

Role of reactive oxygen species and mitochondrial damage in rheumatoid arthritis and targeted drugs

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial inflammation, pannus formation, and bone and cartilage damage. It has a high disability rate. The hypoxic microenvironment of RA joints can cause reactive oxygen species (ROS) accumulation and mitochondrial damage, which not only affect the metabolic processes of immune cells and pathological changes in fibroblastic synovial cells but also upregulate the expression of several inflammatory pathways, ultimately promoting inflammation. Additionally, ROS and mitochondrial damage are involved in angiogenesis and bone destruction, thereby accelerating RA progression. In this review, we highlighted the effects of ROS accumulation and mitochondrial damage on inflammatory response, angiogenesis, bone and cartilage damage in RA. Additionally, we summarized therapies that target ROS or mitochondria to relieve RA symptoms and discuss the gaps in research and existing controversies, hoping to provide new ideas for research in this area and insights for targeted drug development in RA.

The pathogenesis of rheumatoid arthritis

Significant recent progress in understanding rheumatoid arthritis (RA) pathogenesis has led to improved treatment and quality of life. The introduction of targeted-biologic and -synthetic disease modifying anti-rheumatic drugs (DMARDs) has also transformed clinical outcomes. Despite this, RA remains a life-long disease without a cure. Unmet needs include partial response and non-response to treatment in many patients, failure to achieve immune homeostasis or drug free remission, and inability to repair damaged tissues. RA is now recognized as the end of a multi-year prodromal phase in which systemic immune dysregulation, likely beginning in mucosal surfaces, is followed by a symptomatic clinical phase. Inflammation and immune reactivity are primarily localized to the synovium leading to pain and articular damage, but is also associated with a broader series of comorbidities. Here, we review recently described immunologic mechanisms that drive breach of tolerance, chronic synovitis, and remission.

Cellular metabolic adaptations in rheumatoid arthritis and their therapeutic implications

Activation of endothelium and immune cells is fundamental to the initiation of autoimmune diseases such as rheumatoid arthritis (RA), and it results in trans-endothelial cell migration and synovial fibroblast proliferation, leading to joint destruction. In RA, the synovial microvasculature is highly dysregulated, resulting in inefficient oxygen perfusion to the synovium, which, along with the high metabolic demands of activated immune and stromal cells, leads to a profoundly hypoxic microenvironment. In inflamed joints, infiltrating immune cells and synovial resident cells have great requirements for energy and nutrients, and they adapt their metabolic profiles to generate sufficient energy to support their highly activated inflammatory states. This shift in metabolic capacity of synovial cells enables them to produce the essential building blocks to support their proliferation, activation and invasiveness. Furthermore, it results in the accumulation of metabolic intermediates and alteration of redox-sensitive pathways, affecting signalling pathways that further potentiate the inflammatory response. Importantly, the inflamed synovium is a multicellular tissue, with cells differing in their metabolic requirements depending on complex cell-cell interactions, nutrient supply, metabolic intermediates and transcriptional regulation. Therefore, understanding the complex interplay between metabolic and inflammatory pathways in synovial cells in RA will provide insight into the underlying mechanisms of disease pathogenesis.

Inside the Joint of Inflammatory Arthritis Patients: Handling and Processing of Synovial Tissue Biopsies for High Throughput Analysis

Inflammatory arthritis is a chronic systemic autoimmune disease of unknown etiology, which affects the joints. If untreated, these diseases can have a detrimental effect on the patient's quality of life, leading to disabilities, and therefore, exhibit a significant socioeconomic impact and burden. While studies of immune cell populations in arthritis patient's peripheral blood have been informative regarding potential immune cell dysfunction and possible patient stratification, there are considerable limitations in identifying the early events that lead to synovial inflammation. The joint, as the site of inflammation and the local microenvironment, exhibit unique characteristics that contribute to disease pathogenesis. Understanding the contribution of immune and stromal cell interactions within the inflamed joint has been met with several technical challenges. Additionally, the limited availability of synovial tissue biopsies is a key incentive for the utilization of high-throughput techniques in order to maximize information gain. This review aims to provide an overview of key methods and novel techniques that are used in the handling, processing and analysis of synovial tissue biopsies and the potential synergy between these techniques. Herein, we describe the utilization of high dimensionality flow cytometric analysis, single cell RNA sequencing, ex vivo functional assays and non-intrusive metabolic characterization of synovial cells on a single cell level based on fluorescent lifetime imaging microscopy. Additionally, we recommend important points of consideration regarding the effect of different storage and handling techniques on downstream analysis of synovial tissue samples. The introduction of new powerful techniques in the study of synovial tissue inflammation, brings new challenges but importantly, significant opportunities. Implementation of novel approaches will accelerate our path toward understanding of the mechanisms involved in the pathogenesis of inflammatory arthritis and lead to the identification of new avenues of therapeutic intervention.