A genome-wide association study suggests contrasting associations in ACPA-positive versus ACPA-negative rheumatoid arthritis

Patient burden and joint inflammation during development of RA from arthralgia: is it similar in ACPA-positive and ACPA-negative disease?

OBJECTIVES

ACPA-positive and ACPA-negative RA differ in underlying risk factors but have a similar clinical presentation at RA diagnosis. It is unknown what the ACPA-associated differences or similarities are during the symptomatic at-risk stage of RA, i.e. clinically suspect arthralgia (CSA). To deepen insights into these differences/similarities, we compared the course of symptoms/impairments and subclinical joint inflammation in the CSA phase during progression to inflammatory arthritis (IA) or to CSA resolution.

METHODS

A total of 845 CSA patients were followed for a median of 24 months; 136 patients developed IA and an additional 355/505 patients had resolution of CSA according to rheumatologists. Patient burden (pain, morning stiffness, fatigue, functional disabilities, presenteeism) was assessed at baseline and 4, 12 and 24 months and at IA development. Subclinical joint inflammation in the hands and feet was assessed over time with 1.5T MRI. Linear and Poisson mixed models were used.

RESULTS

In both ACPA-positive and ACPA-negative patients, patient burden increased towards IA development and decreased towards CSA resolution. However, patient burden was lower in ACPA-positive vs ACPA-negative disease at all timepoints. Conversely, subclinical joint inflammation tended to increase more rapidly during development of ACPA-positive IA [incidence rate ratio (IRR) 1.52 (95% CI 0.94, 2.47), P = 0.089] and remained higher over time in ACPA-positive CSA patients achieving resolution compared with ACPA-negative patients [IRR 1.52 (95% CI 1.07, 2.15), P = 0.018]. Although correlation coefficients between changes in patient burden and subclinical joint inflammation during progression to IA were weak, they were consistently higher in ACPA-positive than ACPA-negative disease, e.g. ρ = 0.29 vs 0.12 for functional disabilities.

CONCLUSION

During RA development and CSA resolution, ACPA-positive CSA patients have lower patient burden but more subclinical joint inflammation than ACPA-negative CSA patients. These data strengthen the notion that the development of ACPA-positive and ACPA-negative RA is pathophysiologically different and encourage further research on these differences.

Genome-wide investigation of persistence with methotrexate treatment in early rheumatoid arthritis

OBJECTIVES

To investigate the influence of genetic factors on persistence with treatment of early RA with MTX monotherapy.

METHODS

We conducted a genome-wide association study (GWAS) in a sample of 3902 Swedish early-RA patients initiating MTX in DMARD monotherapy as their first-ever DMARD. The outcome, short- and long-term MTX treatment persistence, was defined as remaining on MTX at 1 and at 3 years, respectively, with no additional DMARDs added. As genetic predictors, we investigated individual SNPs, and then calculated a polygenic risk score (PRS) based on SNPs associated with RA risk. The SNP-based heritability of persistence was estimated overall and by RA serostatus.

RESULTS

No individual SNP reached genome-wide significance (P < 5 × 10-8), either for persistence at 1 year or at 3 years. The RA PRS was not significantly associated with MTX treatment persistence at 1 year [relative risk (RR) = 0.98 (0.96-1.01)] or at 3 years [RR = 0.96 (0.93-1.00)]. The heritability of MTX treatment persistence was estimated to be 0.45 (0.15-0.75) at 1 year and 0.14 (0-0.40) at 3 years. The results in seropositive RA were comparable with those in the analysis of RA overall, while heritability estimates and PRS RRs were attenuated towards the null in seronegative RA.

CONCLUSION

Despite being the largest GWAS on an MTX treatment outcome to date, no genome-wide significant associations were detected. The modest heritability observed, coupled with the broad spread of suggestively associated loci, indicate that genetic influence is of polygenic nature. Nevertheless, MTX monotherapy persistence was lower in patients with a greater genetic disposition, per the PRS, towards RA.

Advantages of Chinese herbal medicine in treating rheumatoid arthritis: a focus on its anti-inflammatory and anti-oxidative effects

Oxidative stress is a condition characterized by an imbalance between the oxidative and antioxidant processes within the human body. Rheumatoid arthritis (RA) is significantly influenced by the presence of oxidative stress, which acts as a pivotal factor in its pathogenesis. Elevated levels of mitochondrial reactive oxygen species (ROS) and inflammation have been found to be closely associated in the plasma of patients with RA. The clinical treatment strategies for this disease are mainly chemical drugs, such as nonsteroidal anti-inflammatory drugs (NSAIDs), disease-modifying anti-rheumatic drugs (DMARDs), glucocorticoids (GCs) and biological agents, but it is difficult for patients to accept long-term drug treatment and its side effects. In the theory of traditional Chinese medicine (TCM), RA is thought to be caused by the attack of "wind, cold, damp humor," and herbs with the effect of removing wind and dampness are used to relieve pain. Chinese herbal medicine boasts a rich heritage in effectively attenuating the symptoms of RA, and its global recognition continues to ascend. In particular, RA-relevant anti-inflammatory/anti-oxidative effects of TCM herbs/herbal compounds. The main aim of this review is to make a valuable contribution to the expanding pool of evidence that advocates for the incorporation of Chinese herbal medicine in conventional treatment plans for RA.

Aberrant B cell receptor signaling in circulating naïve and IgA+ memory B cells from newly-diagnosed autoantibody-positive rheumatoid arthritis patients

OBJECTIVE

Altered B cell receptor (BCR) signaling has been implicated in the pathogenesis of rheumatoid arthritis (RA). Here we aimed to identify signaling aberrations in autoantibody-positive and autoantibody-negative RA patients by performing a comprehensive analysis of the BCR signaling cascade in different B cell subsets.

METHODS

We first optimized phosphoflow cytometry for an in-depth analysis of BCR signaling across immunoglobulin isotypes in healthy donors. Subsequently, we compared BCR signaling in circulating B cell subsets from treatment-naïve, newly-diagnosed autoantibody-positive RA and autoantibody-negative RA patients and healthy controls (HCs).

RESULTS

We observed subset-specific phosphorylation patterns of the BCR signalosome in circulating B cells from healthy donors. Compared with HCs, autoantibody-positive RA patients displayed enhanced responses to BCR stimulation for multiple signaling proteins, specifically in naïve and IgA+ memory B cells. Whereas in unstimulated healthy donor B cells, the phosphorylation status of individual signaling proteins showed only limited correlation, BCR stimulation enhanced the interconnectivity in phosphorylation within the BCR signalosome. However, this strong interconnectivity within the BCR signalosome in stimulated B cells from HCs was lost in RA, especially in autoantibody-positive RA patients. Finally, we observed strong correlations between SYK and BTK protein expression, and IgA and IgG anti-citrullinated protein antibody concentrations in serum from autoantibody-positive RA patients.

CONCLUSION

Collectively, the isotype-specific analysis of multiple key components of the BCR signalosome identified aberrant BCR signaling responses in treatment-naïve autoantibody-positive RA patients, particularly in naïve B cells and IgA+ memory B cells. Our findings support differential involvement of dysregulated BCR signaling in the pathogenesis of autoantibody-positive and autoantibody-negative RA.

Determination of the factors associated with antigen-specific CD4+ T-cell responses to BNT162b2 in patients with rheumatoid arthritis

OBJECTIVES

Understanding interpatient variation in CD4+T-cell responses is the bases for understanding the pathogenesis and management of rheumatoid arthritis (RA). We examined immune responses to SARS-CoV-2 vaccine in a cohort of patients with RA and determined factors associated with the responses.

METHODS

Four hundred and thirty-one patients with RA having received two doses of BNT162b2, a messenger RNA-based vaccine for SARS-CoV-2, were included. Vaccine antigen-specific IgG was detected by ELISA, and antigen-specific CD4+T cells were detected by CD154 expression in response to antigenic stimulation. Expression of cytokines was concomitantly detected by intracellular staining. Associations among background variables, antigen-specific antibody production and the CD4+T-cell responses were analysed. Unsupervised hierarchical clustering was performed based on the profiles of antigen-specific cytokine production by CD4+T cells to stratify patients with RA.

RESULTS

Multivariate analysis indicated that ageing negatively affects CD4+T-cell response as well as antibody production. No association was detected between the presence or the levels of rheumatoid factor/anti-cyclic citrullinated peptide antibody and anti-vaccine immune responses. Methotrexate and prednisolone reduced B cell but not T-cell responses. Conventional immunophenotyping by the expression of chemokine receptors was not associated with the actual CD4+T-cell response, except for T helper cells (Th1). Functional immunophenotyping based on the profiles of antigen-specific cytokine production of CD4+T cells stratified patients with RA into three clusters, among which Th1-dominant type less frequently underwent joint surgery.

CONCLUSIONS

Clinical and immunological variables that are associated with antigen-specific CD4 T-cell responses in patients with RA were determined by analysing immune responses against SARS-CoV-2 vaccine.

Porphyromonas gingivalis with collagen immunization induces ACPA-positive rheumatoid arthritis in C3H mice

The pathogenic anti-citrullinated protein antibodies (ACPA) are thought to play a vital role in the initiation and immune maintenance of rheumatoid arthritis (RA). However, it is noteworthy that ACPA is not a salient characteristic of any conventional RA animal model. Porphyromonas gingivalis (Pg) is the first microorganism identified to induce citrullination and a target of autoantibodies in early rheumatoid arthritis (RA). Thus, we employed C3H mice with specific MHC types and combined Pg infection with collagen immunity to develop an animal model of ACPA-positive RA. The resulting model exhibited citrullination characteristics, as well as pathological and immune cell changes. 1) Mice showed a significant increase in ACPA levels, and various organs and tissues exhibited elevated levels of citrullinated protein. 2) The mice experienced heightened pain, inflammation, and bone destruction. 3) The spleen and lymph nodes of the mice showed a significant increase in the proportion of Tfh-GCB cell subpopulations responsible for regulating autoantibody production. In conclusion, the C3H mouse model of Pg infection with collagen immunity demonstrated significant alterations in ACPA levels, citrullinated protein expression, and immune cell subpopulations, which could be a crucial factor leading to increased pain, inflammation, and bone destruction.

Type 3 IP3 receptor: Its structure, functions, and related disease implications

Cell-fate decisions depend on the precise and strict regulation of multiple signaling molecules and transcription factors, especially intracellular Ca2+ homeostasis and dynamics. Type 3 inositol 1,4,5-triphosphate receptor (IP3R3) is an a tetrameric channel that can mediate the release of Ca2+ from the endoplasmic reticulum (ER) in response to extracellular stimuli. The gating of IP3R3 is regulated not only by ligands but also by other interacting proteins. To date, extensive research conducted on the basic structure of IP3R3, as well as its regulation by ligands and interacting proteins, has provided novel perspectives on its biological functions and pathogenic mechanisms. This review aims to discuss recent advancements in the study of IP3R3 and provides a comprehensive overview of the relevant literature pertaining to its structure, biological functions, and pathogenic mechanisms.

Epidemiology and Risk Factors for Rheumatoid Arthritis Development

Rheumatoid arthritis (RA) is a prevalent chronic inflammatory arthritis worldwide, significantly impacting patients and population health. The disease affects women primarily, with a female-to-male ratio of three to one. Its pathogenesis is multifactorial, including genetic and environmental risk factors. Epidemiological studies highlight the link between the environment and genetic susceptibility to RA. The so-called shared epitope is the most significant risk factor that seems to act synergetic with other environmental factors in the disease occurrence. In addition, recent findings suggest a potential role of new substantial environmental factors, such as the observed pollution of the planet's natural resources, on the susceptibility and progression of the disease. This review summarises the most decisive evidence on epidemiology and genetic, environmental, and lifestyle risk factors for RA. It shows that studying genetic and environmental factors in correlation could lead to prevention strategies that may impact the natural history of the disease.

Citrullination of myelin basic protein induces a Th17-cell response in healthy individuals and enhances the presentation of MBP85-99 in patients with multiple sclerosis

The post-translational modification citrullination has been proposed to play a role in the pathogenesis of multiple sclerosis (MS). Myelin basic protein (MBP) is a candidate autoantigen which is citrullinated to a minor extent under physiological conditions and hypercitrullinated in MS. We examined immune cell responses elicited by hypercitrullinated MBP (citMBP) in cultures of mononuclear cells from 18 patients with MS and 42 healthy donors (HDs). The immunodominant peptide of MBP, MBP85-99, containing citrulline in position 99, outcompeted the binding of native MBP85-99 to HLA-DR15, which is strongly linked to MS. Moreover, using the monoclonal antibody MK16 as probe, we observed that B cells and monocytes from HLA-DR15+ patients with MS presented MBP85-99 more efficiently after challenge with citMBP than with native MBP. Both citMBP and native MBP induced proliferation of CD4+ T cells from patients with MS as well as TNF-α production by their B cells and CD4+ T cells, and citrullination of MBP tended to enhance TNF-α secretion by CD4+ T cells from HLA-DR15+ patients. Unlike native MBP, citMBP induced differentiation into Th17 cells in cultures from HDs, while neither form of MBP induced Th17-cell differentiation in cultures from patients with MS. These data suggest a role for citrullination in the breach of tolerance to MBP in healthy individuals and in maintenance of the autoimmune response to MBP in patients with MS.

Overview of Rheumatoid Arthritis and Scientific Understanding of the Disease

Rheumatoid arthritis (RA), a chronic inflammatory autoimmune disorder, is characterised by persistent synovial inflammation, erosion of bones and cartilage, leading to joint destruction. Clinical manifestations are morning stiffness, pain in shoulder, neck and pelvic girdle, loss of mobility with fever, fatigue, malaise, loss of body weight, and development of rheumatoid nodules. Environmental and genetic factors are important contributors in its susceptibility. Association between RA and diet, cigarette smoking, hormones, alcohol, microbiota, infection, and coffee have also been reported. To diagnose patients with RA, American college of rheumatology (ACR, 2010) criteria, developed by European league against rheumatism (EULAR). Inflammation produced in RA patients is due to cell-mediated immune response. The rheumatoid synovium consists of a large number of CD4+ T cells suggesting pathogenic nature of T cells in this disorder. B-cells may also participate in the pathogenesis by several means such as autoantibodies, by instigation of T-cells through expression of co-stimulatory molecules, by generating pro-inflammatory and anti-inflammatory cytokines and by organisation of other inflammatory cells. The conventional management of RA usually focuses over reducing pain and limiting the disability by medical therapies which include a number of classes of agents such as non-steroidal anti-inflammatory drugs (NSAIDs), non-biological and biological agents, disease-modifying anti rheumatic drugs (DMARDs), immunosuppressants, and corticosteroids. However, only proper rehabilitation can promote the objective to achieve the joint functionality and ease of motion which improves independence as well as quality of life in patient suffering from Rheumatoid Arthritis.

Tutorial: a statistical genetics guide to identifying HLA alleles driving complex disease

The human leukocyte antigen (HLA) locus is associated with more complex diseases than any other locus in the human genome. In many diseases, HLA explains more heritability than all other known loci combined. In silico HLA imputation methods enable rapid and accurate estimation of HLA alleles in the millions of individuals that are already genotyped on microarrays. HLA imputation has been used to define causal variation in autoimmune diseases, such as type I diabetes, and in human immunodeficiency virus infection control. However, there are few guidelines on performing HLA imputation, association testing, and fine mapping. Here, we present a comprehensive tutorial to impute HLA alleles from genotype data. We provide detailed guidance on performing standard quality control measures for input genotyping data and describe options to impute HLA alleles and amino acids either locally or using the web-based Michigan Imputation Server, which hosts a multi-ancestry HLA imputation reference panel. We also offer best practice recommendations to conduct association tests to define the alleles, amino acids, and haplotypes that affect human traits. Along with the pipeline, we provide a step-by-step online guide with scripts and available software ( https://github.com/immunogenomics/HLA_analyses_tutorial ). This tutorial will be broadly applicable to large-scale genotyping data and will contribute to defining the role of HLA in human diseases across global populations.

A genome-wide cross-trait analysis identifies genomic correlation, pleiotropic loci, and causal relationship between sex hormone-binding globulin and rheumatoid arthritis

BACKGROUND

Our study aims to investigate an intrinsic link underlying sex hormone-binding globulin (SHBG) and rheumatoid arthritis (RA), which remains inconclusive in observational settings.

METHODS

Summary statistics were collected from the largest GWAS(s) on SHBG adjusted for BMI (SHBGadjBMI; Noverall = 368,929; Nmen = 180,094; Nwomen = 188,908), crude SHBG (Noverall = 370,125; Nmen = 180,726; Nwomen = 189,473), and RA (Ncase = 22,350; Ncontrol = 74,823). A genome-wide cross-trait design was performed to quantify global and local genetic correlation, identify pleiotropic loci, and infer a causal relationship.

RESULTS

Among the overall population, a significant global genetic correlation was observed for SHBGadjBMI and RA ([Formula: see text] = 0.11, P = 1.0 × 10-4) which was further supported by local signal (1q25.2). A total of 18 independent pleiotropic SNPs were identified, of which three were highly likely causal variants and four were found to have effects on both traits through gene expression mediation. A putative causal association of SHBGadjBMI on RA was demonstrated (OR = 1.20, 95% CI = 1.01-1.43) without evidence of reverse causality (OR = 0.999, 95% CI = 0.997-1.000). Sex-specific analyses revealed distinct shared genetic regions (men: 1q32.1-q32.2 and 5p13.1; women: 1q25.2 and 22q11.21-q11.22) and diverse pleiotropic SNPs (16 in men and 18 in women, nearly half were sex-specific) underlying SHBGadjBMI and RA, demonstrating biological disparities between sexes. Replacing SHBGadjBMI with crude SHBG, a largely similar yet less significant pattern of results was observed.

CONCLUSION

Our cross-trait analysis suggests an intrinsic, as well as a sex-specific, link underlying SHBG and RA, providing novel insights into disease etiology.

Effects of Human Leukocyte Antigen DRB1 Genetic Polymorphism on Anti-Cyclic Citrullinated Peptide (ANTI-CCP) and Rheumatoid Factor (RF) Expression in Rheumatoid Arthritis (RA) Patients

Rheumatoid arthritis (RA) is a systemic disease characterized by non-infectious inflammation of the joints and surrounding tissues, which can cause severe health problems, affect the patient's daily life, and even cause death. RA can be clinically diagnosed by the occurrence of blood serological markers, rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibody (anti-CCP). However, about 20% of RA patients exhibit negative results for both markers, which makes RA diagnosis difficult and, therefore, may delay the effective treatment. Previous studies found some evidence that human leukocyte antigen (HLA)-related genes might be the susceptibility genes for RA and their polymorphisms might contribute to varieties of susceptibility and disease severity. This study aimed for the genetic polymorphisms of the RA patient genome and their effects on the RA patient's serological makers, RF and anti-CCP. A total of 4580 patients' electronic medical records from 1992 to 2020 were retrieved from the China Medical University Hospital database. The most representative single-nucleotide polymorphisms (SNPs) were identified through a genome-wide association study (GWAS) followed by enzyme-linked immunosorbent assay (ELISA) validation using the blood from 30 additional RA patients. The results showed significant changes at the position of chromosome 6 with rs9270481 being the most significant locus, which indicated the location of the HLA-DRB1 gene. Further, patients with the CC genotype at this locus were more likely to exhibit negative results for RF and anti-CCP than those with the TT genotype. The C allele was also more likely to be associated with negative results for RF and anti-CCP. The results demonstrated that a genetic polymorphism at rs9270481 affected the expression of RF and anti-CCP in RA patients, which might indicate the necessity to develop a personalized treatment plan for each individual patient based on the genetic profile.

Anti-citrullinated protein antibodies as biomarkers in rheumatoid arthritis

INTRODUCTION

The serological biomarker anti-citrullinated protein antibodies (ACPAs) may have several functions but is especially important for the diagnosis of rheumatoid arthritis (RA) along with clinical symptoms.

AREAS COVERED

This review provides an overview of ACPAs, which are useful in RA diagnostics and may improve our understanding of disease etiology. PubMed was searched with combinations of words related to antibodies recognizing epitopes containing the post-translationally modified amino acid citrulline in combination with rheumatoid arthritis; cyclic citrullinated peptide, CCP, anti-CCP, anti-citrullinated protein antibodies, ACPA, citrullination, peptide/protein arginine deiminase, PAD, filaggrin, vimentin, keratin, collagen, perinuclear factor, EBNA1, EBNA2, and others. From this search, we made a qualitative extract of publications relevant to the discovery, characterization, and clinical use of these antibodies in relation to RA. We highlight significant findings and identify areas for improvement.

EXPERT OPINION

ACPAs have high diagnostic sensitivity and specificity for RA and recognize citrullinated epitopes from several proteins. The best-performing single epitope originates from Epstein-Barr Virus nuclear antigen 2 and contains a central Cit-Gly motif, which is recognized by ACPAS when located in a flexible peptide structure. In addition, ACPAs may also have prognostic value, especially in relation to early treatment, although ACPAs' main function is to aid in the diagnosis of RA.

Sex differences in the genetics of sarcoidosis across European and African ancestry populations

Background

Sex differences in the susceptibility of sarcoidosis are unknown. The study aims to identify sex-dependent genetic variations in two clinical sarcoidosis phenotypes: Löfgren's syndrome (LS) and non-Löfgren's syndrome (non-LS).

Methods

A meta-analysis of genome-wide association studies was conducted on Europeans and African Americans, totaling 10,103 individuals from three population-based cohorts, Sweden (n = 3,843), Germany (n = 3,342), and the United States (n = 2,918), followed by an SNP lookup in the UK Biobank (UKB, n = 387,945). A genome-wide association study based on Immunochip data consisting of 141,000 single nucleotide polymorphisms (SNPs) was conducted in the sex groups. The association test was based on logistic regression using the additive model in LS and non-LS sex groups independently. Additionally, gene-based analysis, gene expression, expression quantitative trait loci (eQTL) mapping, and pathway analysis were performed to discover functionally relevant mechanisms related to sarcoidosis and biological sex.

Results

We identified sex-dependent genetic variations in LS and non-LS sex groups. Genetic findings in LS sex groups were explicitly located in the extended Major Histocompatibility Complex (xMHC). In non-LS, genetic differences in the sex groups were primarily located in the MHC class II subregion and ANXA11. Gene-based analysis and eQTL enrichment revealed distinct sex-specific gene expression patterns in various tissues and immune cell types. In LS sex groups, a pathway map related to antigen presentation machinery by IFN-gamma. In non-LS, pathway maps related to immune response lectin-induced complement pathway in males and related to maturation and migration of dendritic cells in skin sensitization in females were identified.

Conclusion

Our findings provide new evidence for a sex bias underlying sarcoidosis genetic architecture, particularly in clinical phenotypes LS and non-LS. Biological sex likely plays a role in disease mechanisms in sarcoidosis.

Patients with ACPA-positive and ACPA-negative rheumatoid arthritis show different serological autoantibody repertoires and autoantibody associations with disease activity

Patients with rheumatoid arthritis (RA) can test either positive or negative for circulating anti-citrullinated protein antibodies (ACPA) and are thereby categorized as ACPA-positive (ACPA+) or ACPA-negative (ACPA-), respectively. In this study, we aimed to elucidate a broader range of serological autoantibodies that could further explain immunological differences between patients with ACPA+ RA and ACPA- RA. On serum collected from adult patients with ACPA+ RA (n = 32), ACPA- RA (n = 30), and matched healthy controls (n = 30), we used a highly multiplex autoantibody profiling assay to screen for over 1600 IgG autoantibodies that target full-length, correctly folded, native human proteins. We identified differences in serum autoantibodies between patients with ACPA+ RA and ACPA- RA compared with healthy controls. Specifically, we found 22 and 19 autoantibodies with significantly higher abundances in ACPA+ RA patients and ACPA- RA patients, respectively. Among these two sets of autoantibodies, only one autoantibody (anti-GTF2A2) was common in both comparisons; this provides further evidence of immunological differences between these two RA subgroups despite sharing similar symptoms. On the other hand, we identified 30 and 25 autoantibodies with lower abundances in ACPA+ RA and ACPA- RA, respectively, of which 8 autoantibodies were common in both comparisons; we report for the first time that the depletion of certain autoantibodies may be linked to this autoimmune disease. Functional enrichment analysis of the protein antigens targeted by these autoantibodies showed an over-representation of a range of essential biological processes, including programmed cell death, metabolism, and signal transduction. Lastly, we found that autoantibodies correlate with Clinical Disease Activity Index, but associate differently depending on patients' ACPA status. In all, we present candidate autoantibody biomarker signatures associated with ACPA status and disease activity in RA, providing a promising avenue for patient stratification and diagnostics.

Signaling pathways in rheumatoid arthritis: implications for targeted therapy

Rheumatoid arthritis (RA) is an incurable systemic autoimmune disease. Disease progression leads to joint deformity and associated loss of function, which significantly impacts the quality of life for sufferers and adds to losses in the labor force. In the past few decades, RA has attracted increased attention from researchers, the abnormal signaling pathways in RA are a very important research field in the diagnosis and treatment of RA, which provides important evidence for understanding this complex disease and developing novel RA-linked intervention targets. The current review intends to provide a comprehensive overview of RA, including a general introduction to the disease, historical events, epidemiology, risk factors, and pathological process, highlight the primary research progress of the disease and various signaling pathways and molecular mechanisms, including genetic factors, epigenetic factors, summarize the most recent developments in identifying novel signaling pathways in RA and new inhibitors for treating RA. therapeutic interventions including approved drugs, clinical drugs, pre-clinical drugs, and cutting-edge therapeutic technologies. These developments will hopefully drive progress in new strategically targeted therapies and hope to provide novel ideas for RA treatment options in the future.

Added value of multiple autoantibody testing for predicting progression to inflammatory arthritis in at-risk individuals

BACKGROUND

Predicting progression to clinical arthritis in individuals at-risk of developing rheumatoid arthritis is a prerequisite to developing stratification groups for prevention strategies. Selecting accurate predictive criteria is the critical step to define the population at-risk. While positivity for anti-citrullinated protein antibodies (ACPA) remains the main recruitment biomarker, positivity for other autoantibodies (AutoAbs) identified before the onset of symptoms, may provide additional predictive accuracy for stratification.

OBJECTIVE

To perform a multiple AutoAbs analysis for both the prediction and the time of progression to inflammatory arthritis (IA).

METHODS

392 individuals were recruited based on a new musculoskeletal complaint and positivity for ACPA or rheumatoid factor (RF). ELISAs were performed for ACPA, RF, anti-nuclear Ab, anti-carbamylated protein (anti-CarP) and anti-collagen AutoAbs. Logistic and COX regression were used for analysis.

RESULTS

Progression to IA was observed in 125/392 (32%) of cases, of which 78 progressed within 12 months. The AutoAbs ACPA, RF, anti-CarP were individually associated with progression (p<0.0001) and improved prediction when combined with demographic/clinical data (Accuracy >77%; area under the curve (AUC) >0.789), compared with prediction using only demographic/clinical data (72.9%, AUC=0.760). Multiple AutoAbs testing provided added value, with +6.4% accuracy for number of positive AutoAbs (AUC=0.852); +5.4% accuracy for AutoAbs levels (ACPA/anti-CarP, AUC=0.832); and +6.2% accuracy for risk-groups based on high/low levels (ACPA/RF/anti-CarP, AUC=0.837). Time to imminent progression was best predicted using ACPA/anti-CarP levels (AUC=0.779), while the number of positive AutoAbs was/status/risk were as good (AUC=0.778).

CONCLUSION

We confirm added value of multiple AutoAbs testing for identifying progressors to clinical disease, allowing more specific stratification for intervention studies.

Diversity and Clonality of T Cell Receptor Repertoire and Antigen Specificities in Small Joints of Early Rheumatoid Arthritis

OBJECTIVE

CD4+ T cells are implicated in rheumatoid arthritis (RA) pathology from the strong association between RA and certain HLA class II gene variants. This study was undertaken to examine the synovial T cell receptor (TCR) repertoire, T cell phenotypes, and T cell specificities in small joints of RA patients at time of diagnosis before therapeutic intervention.

METHODS

Sixteen patients, of whom 11 patients were anti-citrullinated protein antibody (ACPA)-positive and 5 patients were ACPA-, underwent ultrasound-guided synovial biopsy of a small joint (n = 13) or arthroscopic synovial biopsy of a large joint (n = 3), followed by direct sorting of single T cells for paired sequencing of the αβ TCR together with flow cytometry analysis. TCRs from expanded CD4+ T cell clones of 4 patients carrying an HLA-DRB1*04:01 allele were artificially reexpressed to study antigen specificity.

RESULTS

T cell analysis demonstrated CD4+ dominance and the presence of peripheral helper T-like cells in both patient groups. We identified >4,000 unique TCR sequences, as well as 225 clonal expansions. Additionally, T cells with double α-chains were a recurring feature. We identified a biased gene usage of the V_β chain segment TRBV20-1 in CD4+ cells from ACPA+ patients. In vitro stimulation of T cell lines expressing selected TCRs with an extensive panel of citrullinated and viral peptides identified several different virus-specific TCRs (e.g., human cytomegalovirus and human herpesvirus 2). Still, the majority of clones remained orphans with unknown specificity.

CONCLUSION

Minimally invasive biopsies of the RA synovium allow for single-cell TCR sequencing and phenotyping. Clonally expanded, viral-reactive T cells account for part of the diverse CD4+ T cell repertoire. TRBV20-1 bias in ACPA+ patients suggests recognition of common antigens.

Latest models for the discovery and development of rheumatoid arthritis drugs

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic autoimmune disease that reduces the quality of life. The current speed of development of therapeutic agents against RA is not satisfactory. Models on which initial experiments are conducted do not fully reflect human pathogenesis. Overcoming this oversimplification might be a crucial step to accelerate studies on RA treatment.

AREAS COVERED

The current approaches to produce novel models or to improve currently available models for the development of RA drugs have been discussed. Advantages and drawbacks of two- and three-dimensional cell cultures and animal models have been described based on recently published results of the studies. Moreover, approaches such as tissue engineering or organ-on-a-chip have been reviewed.

EXPERT OPINION

The cell cultures and animal models used to date appear to be of limited value due to the complexity of the processes involved in RA. Current models in RA research should take into account the heterogeneity of patients in terms of disease subtypes, course, and activity. Several advanced models and tools using human cells and tissues have been developed, including three-dimensional tissues, liquid bioreactors, and more complex joint-on-a-chip devices. This may increase knowledge of the molecular mechanisms leading to disease development, to help identify new biomarkers for early detection, and to develop preventive strategies and more effective treatments.

Multi-ancestry genome-wide association analyses identify novel genetic mechanisms in rheumatoid arthritis

Rheumatoid arthritis (RA) is a highly heritable complex disease with unknown etiology. Multi-ancestry genetic research of RA promises to improve power to detect genetic signals, fine-mapping resolution and performances of polygenic risk scores (PRS). Here, we present a large-scale genome-wide association study (GWAS) of RA, which includes 276,020 samples from five ancestral groups. We conducted a multi-ancestry meta-analysis and identified 124 loci (P < 5 × 10-8), of which 34 are novel. Candidate genes at the novel loci suggest essential roles of the immune system (for example, TNIP2 and TNFRSF11A) and joint tissues (for example, WISP1) in RA etiology. Multi-ancestry fine-mapping identified putatively causal variants with biological insights (for example, LEF1). Moreover, PRS based on multi-ancestry GWAS outperformed PRS based on single-ancestry GWAS and had comparable performance between populations of European and East Asian ancestries. Our study provides several insights into the etiology of RA and improves the genetic predictability of RA.

Sustained DMARD-free remission in rheumatoid arthritis - about concepts and moving towards practice

Sustained DMARD-free remission (SDFR) is the best possible outcome in RA. It is characterized by sustained absence of clinical arthritis, which is accompanied by resolution of symptoms and restoration of normal physical functioning. Therefore it's the best proxy for cure in RA. The mechanisms underlying SDFR-development are yet unidentified. Hypothetically, there are two possible scenarios. The first hypothesis is based on the concept of regaining immune-tolerance, which implies that RA-patients are similar at diagnosis and that disease-processes during the disease-course shift into a favorable direction, resulting in regaining a state in which arthritis is persistently absent. This could imply that SDFR is theoretically achievable for all RA-patients. The alternative hypothesis is that RA-patients who achieve SDFR are intrinsically different from those who cannot. This would imply that DMARD-cessation could be restricted to a subgroup of RA-patients. Since the 1990s, DMARD-discontinuation and SDFR have been increasingly studied as long-term-outcome in RA. In this review, we describe hitherto results of clinical, genetic, serological, histological and imaging studies and looked for arguments for the first or second hypothesis in both auto-antibody-positive and auto-antibody-negative RA. In auto-antibody-negative RA, SDFR is presumably restricted to a subgroup of patients with high serological-markers of inflammation at diagnosis and a rapid and sustained decrease in inflammation after treatment-start. Identifying these RA-patients could be helpful in realizing personalized-medicine. In auto-antibody-positive RA, only few patients achieve SDFR and no definite conclusions can be drawn, but data could suggest that SDFR-patients might be a subgroup with relatively low inflammation from disease-presentation onwards.

Nonalcoholic fatty liver disease in inflammatory arthritis: Relationship with cardiovascular risk

Liver disease is one of the most important causes of morbidity and mortality worldwide whose prevalence is dramatically increasing. The first sign of hepatic damage is inflammation which could be accompanied by the accumulation of fat called non-alcoholic fatty liver disease (NAFLD), causing damage in the hepatocytes. This stage can progress to fibrosis where the accumulation of fibrotic tissue replaces healthy tissue reducing liver function. The next stage is cirrhosis, a late phase of fibrosis where a high percentage of liver tissue has been replaced by fibrotic tissue and liver functionality is substantially impaired. There is a close interplay of cardiovascular disease (CVD) and hepatic alterations, where different mechanisms mediating this relation between the liver and systemic vasculature have been described. In chronic inflammatory diseases such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA), in which the CVD risk is high, hepatic alterations seem to be more prevalent compared to the general population and other rheumatic disorders. The pathogenic mechanisms involved in the development of this comorbidity are still unraveled, although chronic inflammation, autoimmunity, treatments, and metabolic deregulation seem to have an important role. In this review, we will discuss the involvement of liver disease in the cardiovascular risk associated with inflammatory arthritis, the pathogenic mechanisms, and the recognized factors involved. Likewise, monitoring of the liver disease risk in routine clinical practice through both, classical and novel techniques and indexes will be exposed. Finally, we will examine the latest controversies that have been raised about the effects of the current therapies used to control the inflammation in RA and PsA, in the liver damage of those patients, such as methotrexate, leflunomide or biologics.

ACPA-negative rheumatoid arthritis: From immune mechanisms to clinical translation

The presence of anti-citrullinated protein autoantibodies (ACPA) is a hallmark feature of rheumatoid arthritis (RA), which causes chronic joint destruction and systemic inflammation. Based on ACPA status, RA patients can be sub-grouped into two major subsets: ACPA-positive RA (ACPA⁺ RA) and ACPA-negative RA (ACPA^– RA). Accumulating evidence have suggested that ACPA⁺ RA and ACPA^– RA are two distinct disease entities with different underlying pathophysiology. In contrast to the well-characterized pathogenic mechanisms of ACPA⁺ RA, the etiology of ACPA^– RA remains largely unknown. In this review, we summarized current knowledge about the primary drivers of ACPA^– RA, particularly focusing on the serological, cellular, and molecular aspects of immune mechanisms. A better understanding of the immunopathogenesis in ACPA^– RA will help in designing more precisely targeting strategies, and paving the road to personalized treatment. In addition, identification of novel biomarkers in ACPA^– RA will substantially promote early treatment and improve the outcomes.

Disease mechanisms in preclinical rheumatoid arthritis: A narrative review

In the last decades, the concept of preclinical rheumatoid arthritis (RA) has become established. In fact, the discovery that disease mechanisms start years before the onset of clinical RA has been one of the major recent insights in the understanding of RA pathogenesis. In accordance with the complex nature of the disease, preclinical events extend over several sequential phases. In a genetically predisposed host, environmental factors will further increase susceptibility for incident RA. In the initial steps of preclinical disease, immune disturbance mechanisms take place outside the joint compartment, namely in mucosal surfaces, such as the lung, gums or gut. Herein, the persistent immunologic response to altered antigens will lead to breach of tolerance and trigger autoimmunity. In a second phase, the immune response matures and is amplified at a systemic level, with epitope spreading and widening of the autoantibody repertoire. Finally, the synovial and bone compartment are targeted by specific autoantibodies against modified antigens, initiating a local inflammatory response that will eventually culminate in clinically evident synovitis. In this review, we discuss the elaborate disease mechanisms in place during preclinical RA, providing a broad perspective in the light of current evidence.

Genetic Polymorphism of PTPN22 in Autoimmune Diseases: A Comprehensive Review

It is known that the etiology and clinical outcomes of autoimmune diseases are associated with a combination of genetic and environmental factors. In the case of the genetic factor, the SNPs of the PTPN22 gene have shown strong associations with several diseases. The recent exploding numbers of genetic studies have made it possible to find these associations rapidly, and a variety of autoimmune diseases were found to be associated with PTPN22 polymorphisms. Proteins encoded by PTPN22 play a key role in the adaptative and immune systems by regulating both T and B cells. Gene variants, particularly SNPs, have been shown to significantly disrupt several immune functions. In this review, we summarize the mechanism of how PTPN22 and its genetic variants are involved in the pathophysiology of autoimmune diseases. In addition, we sum up the findings of studies reporting the genetic association of PTPN22 with different types of diseases, including type 1 diabetes mellitus, systemic lupus erythematosus, juvenile idiopathic arthritis, and several other diseases. By understanding these findings comprehensively, we can explain the complex etiology of autoimmunity and help to determine the criteria of disease diagnosis and prognosis, as well as medication developments.

Multiomics analysis of rheumatoid arthritis yields sequence variants that have large effects on risk of the seropositive subset

OBJECTIVES

To find causal genes for rheumatoid arthritis (RA) and its seropositive (RF and/or ACPA positive) and seronegative subsets.

METHODS

We performed a genome-wide association study (GWAS) of 31 313 RA cases (68% seropositive) and ~1 million controls from Northwestern Europe. We searched for causal genes outside the HLA-locus through effect on coding, mRNA expression in several tissues and/or levels of plasma proteins (SomaScan) and did network analysis (Qiagen).

RESULTS

We found 25 sequence variants for RA overall, 33 for seropositive and 2 for seronegative RA, altogether 37 sequence variants at 34 non-HLA loci, of which 15 are novel. Genomic, transcriptomic and proteomic analysis of these yielded 25 causal genes in seropositive RA and additional two overall. Most encode proteins in the network of interferon-alpha/beta and IL-12/23 that signal through the JAK/STAT-pathway. Highlighting those with largest effect on seropositive RA, a rare missense variant in STAT4 (rs140675301-A) that is independent of reported non-coding STAT4-variants, increases the risk of seropositive RA 2.27-fold (p=2.1×10^-9), more than the rs2476601-A missense variant in PTPN22 (OR=1.59, p=1.3×10^-160). STAT4 rs140675301-A replaces hydrophilic glutamic acid with hydrophobic valine (Glu128Val) in a conserved, surface-exposed loop. A stop-mutation (rs76428106-C) in FLT3 increases seropositive RA risk (OR=1.35, p=6.6×10^-11). Independent missense variants in TYK2 (rs34536443-C, rs12720356-C, rs35018800-A, latter two novel) associate with decreased risk of seropositive RA (ORs=0.63-0.87, p=10^-9-10^-27) and decreased plasma levels of interferon-alpha/beta receptor 1 that signals through TYK2/JAK1/STAT4.

CONCLUSION

Sequence variants pointing to causal genes in the JAK/STAT pathway have largest effect on seropositive RA, while associations with seronegative RA remain scarce.

Integrated single cell and spatial transcriptomics reveal autoreactive differentiated B cells in joints of early rheumatoid arthritis

B cells play a significant role in established Rheumatoid Arthritis (RA). However, it is unclear to what extent differentiated B cells are present in joint tissue already at the onset of disease. Here, we studied synovial biopsies (n = 8) captured from untreated patients at time of diagnosis. 3414 index-sorted B cells underwent RNA sequencing and paired tissue pieces were subjected to spatial transcriptomics (n = 4). We performed extensive bioinformatics analyses to dissect the local B cell composition. Select plasma cell immunoglobulin sequences were expressed as monoclonal antibodies and tested by ELISA. Memory and plasma cells were found irrespective of autoantibody status of the patients. Double negative memory B cells were prominent, but did not display a distinct transcriptional profile. The tissue architecture implicate both local B cell maturation via T cell help and plasma cell survival niches with a strong CXCL12–CXCR4 axis. The immunoglobulin sequence analyses revealed clonality between the memory B and plasma cell pools further supporting local maturation. One of the plasma cell-derived antibodies displayed citrulline autoreactivity, demonstrating local autoreactive plasma cell differentiation in joint biopsies captured from untreated early RA. Hence, plasma cell niches are not a consequence of chronic inflammation, but are already present at the time of diagnosis.

Single cell sequencing identifies clonally expanded synovial CD4+ TPH cells expressing GPR56 in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease affecting synovial joints where different CD4⁺ T cell subsets may contribute to pathology. Here, we perform single cell sequencing on synovial CD4⁺ T cells from anti-citrullinated protein antibodies (ACPA)+ and ACPA- RA patients and identify two peripheral helper T cell (T_PH) states and a cytotoxic CD4⁺ T cell subset. We show that the adhesion G-protein coupled receptor 56 (GPR56) delineates synovial CXCL13^high T_PH CD4⁺ T cells expressing LAG-3 and the tissue-resident memory receptors CXCR6 and CD69. In ACPA- SF, T_PH cells display lower levels of GPR56 and LAG-3. Further, most expanded T cell clones in the joint are within CXCL13^high T_PH CD4⁺ T cells. Finally, RNA-velocity analyses suggest a common differentiation pathway between the two T_PH clusters and effector CD4⁺ T cells. Our study provides comprehensive immunoprofiling of the synovial CD4⁺ T cell subsets in ACPA+ and ACPA- RA.

Antibodies against citrullinated proteins (ACPA) can divide rheumatoid arthritis patients but the difference in immune phenotype is not clear. Here the authors characterise T peripheral helper cells in arthritic joints comparing ACPA+ and ACPA- patients showing changes in immune cell phenotype and surface molecules.

The Impact of Seropositivity on Systemic Bone Loss in Rheumatoid Arthritis-A 3-Year Interim Analysis of a Longitudinal Observational Cohort Study

Objective

To explore the impact of seropositivity on systemic bone loss in rheumatoid arthritis (RA).

Methods

We conducted an interim analysis of the RA registry. Patients were examined with dual-energy X-ray absorptiometry at baseline and again 3 years later. Participants were grouped into seropositive (SPRA) and seronegative (SNRA) based on the presence or absence of rheumatoid factor (RF) and/or anti-cyclic citrullinated peptide antibodies (ACPA). After matching (1:2) for age and sex, SNRA and SPRA patients were divided into groups A and B. Each matched group (A or B) was further subdivided according to the number of antibodies present (0, group I; 1, group II; 2, group III). Multiple ordinary least squares regression was used with the dependent variables to develop a model to predict bone mineral density (BMD) change.

Results

A total of 477 participants who completed a 3-year observation period were included. After matching, 312 participants were enrolled (group A, 104; group B, 208). Three years later, group B had significant BMD reduction in the femoral neck (FN) (p < 0.001), total hip (TH) (p = 0.001), and first through fourth lumbar vertebrae (L1–4) (p = 0.006), while group A had bone loss only at FN (p = 0.002). Groups I, II, and III included 104, 52, and 156 participants, respectively. Compared to baseline, BMD decreased significantly at FN (p = 0.002) in group I, FN (p < 0.001) in group II, and FN (p < 0.001), TH (p = 0.002), and L1–4 (p = 0.016) in group III. In terms of regression-adjusted percent change in BMD, more significantly negative changes were found at all measured sites in group B (p < 0.001, all) and at TH and L1–4 within groups I-III (p for trend < 0.001 and < 0.001, respectively). Regardless of antibodies, anti-osteoporotic therapy can preserve bone density in RA patients.

Conclusion

After 3 years, SPRA patients lost more bone density than SNRA patients. More attention should be paid to SPRA patients, especially those with double-positive antibodies, including a vigorous evaluation of BMD and fracture risk. Anti-osteoporotic therapy can prevent BMD loss irrespective of autoantibodies.

Mucosal Gene Transcript Signatures in Treatment Naïve Inflammatory Bowel Disease: A Comparative Analysis of Disease to Symptomatic and Healthy Controls in the European IBD-Character Cohort

Background

Studies of the mucosal transcriptomic landscape have given new insight into the pathogenesis of inflammatory bowel disease (IBD). Recently, the predictive biomarker potential of gene expression signatures has been explored. To further investigate the mucosal gene expression in IBD, we recruited a cohort of treatment naïve patients and compared them to both symptomatic and healthy controls.

Methods

Altogether, 323 subjects were included: Crohn’s disease (N = 75), ulcerative colitis (N = 87) and IBD unclassified (N = 3). Additionally, there were two control groups: symptomatic controls (N = 131) and healthy controls (N = 27). Mucosal biopsies were collected during ileocolonoscopy and gene expression in inflamed and non-inflamed mucosa was explored. Gene expression profiling was performed using Agilent G3 Human Gene Expression 860K v3 One-Color microarray. We recorded information about treatment escalation to anti-TNF agents or surgery, and anti-TNF response, to explore predictive opportunities of the mucosal transcriptome.

Results

Gene expression profiles in symptomatic controls in whom IBD had been excluded resembled that of IBD patients and diverged from that of healthy controls. In non-inflamed Crohn’s disease and ulcerative colitis, gene set enrichment analysis revealed dysregulation of pathways involved in basic cellular biological processes. Mitochondria-associated pathways were dysregulated both in non-inflamed and inflamed Crohn’s disease and ulcerative colitis (>2.6 normalized enrichment scores <−1.8). Gene expression signatures of Crohn’s disease and ulcerative colitis did not predict time for treatment escalation (p = 0.175). No significant association was found between gene expression signatures and anti-TNF response.

Conclusion

Non-inflamed samples are probably superior to inflamed samples when exploring gene expression signatures in IBD and might reveal underlying mechanisms central for disease initiation. The gene expression signatures of the control groups were related to if they were symptomatic or not, which may have important implications for future study designs.

SLAMF6 is associated with the susceptibility and severity of rheumatoid arthritis in the Chinese population

OBJECTIVES

A recently published genome-wide association study identified six novel loci associated with rheumatoid arthritis (RA) in Korean population. We aimed to investigate whether these newly reported RA-risk loci are associated with RA in the Chinese population and to further characterize the functional role of the susceptible gene.

METHODS

The susceptible variants of RA were genotyped in 600 RA patients and 800 healthy controls, including rs148363003 of SLAMF6, rs117605225 of CXCL13, rs360136 of SWAP70, rs111597524 of NFKBIA, rs194757 of ZFP36L1 and rs1547233 of LINC00158. Synovial tissues were collected from the knee joint of 50 RA patients and 40 controls without osteoarthritis for the gene expression analysis. Inter-group comparisons were performed with the Chi-square test for genotyping data or with Student's t-test for gene expression analysis.

RESULT

For rs148363003 of SLAMF6, RA patients were observed to have a significantly lower frequency of genotype CC (4.5% vs. 0.9%, p = 0.004) as compared with the controls. The frequency of allele C was remarkably higher in the patients than in the controls (11.5% vs. 8.0%, p = 0.002), with an odds ratio of 1.49 (95% CI = 1.16-1.92). There was no significant difference between the patients and the controls regarding genotype or allele frequency of the other 5 variants. The mRNA expression of SLAMF6 was 1.6 folds higher in the RA patients than in the controls. Moreover, SLAMF6 expression was 1.5 folds higher in patients with genotype CC than in the patients with genotype TT.

CONCLUSIONS

SLAMF6 was associated with both the susceptibility and severity of RA in the Chinese population. Moreover, rs148363003 could be a functional variant regulating the tissue expression of SLAMF6 in RA patients. It is advisable to conduct further functional analysis for a comprehensive knowledge on the contribution of this variant to the development of RA.

Etiology and Risk Factors for Rheumatoid Arthritis: A State-of-the-Art Review

Rheumatoid arthritis (RA) is the most common systemic inflammatory rheumatic disease. It is associated with significant burden at the patient and societal level. Extensive efforts have been devoted to identifying a potential cause for the development of RA. Epidemiological studies have thoroughly investigated the association of several factors with the risk and course of RA. Although a precise etiology remains elusive, the current understanding is that RA is a multifactorial disease, wherein complex interactions between host and environmental factors determine the overall risk of disease susceptibility, persistence and severity. Risk factors related to the host that have been associated with RA development may be divided into genetic; epigenetic; hormonal, reproductive and neuroendocrine; and comorbid host factors. In turn, environmental risk factors include smoking and other airborne exposures; microbiota and infectious agents; diet; and socioeconomic factors. In the present narrative review, aimed at clinicians and researchers in the field of RA, we provide a state-of-the-art overview of the current knowledge on this topic, focusing on recent progresses that have improved our comprehension of disease risk and development.

Methotrexate Treatment of Newly Diagnosed RA Patients Is Associated With DNA Methylation Differences at Genes Relevant for Disease Pathogenesis and Pharmacological Action

Background

Methotrexate (MTX) is the first line treatment of rheumatoid arthritis (RA), and methylation changes in bulk T cells have been reported after treatment with MTX. We have investigated cell-type specific DNA methylation changes across the genome in naïve and memory CD4⁺ T cells before and after MTX treatment of RA patients. DNA methylation profiles of newly diagnosed RA patients (N=9) were assessed by reduced representation bisulfite sequencing.

Results

We found that MTX treatment significantly influenced DNA methylation levels at multiple CpG sites in both cell populations. Interestingly, we identified differentially methylated sites annotated to two genes; TRIM15 and SORC2, previously reported to predict treatment outcome in RA patients when measured in bulk T cells. Furthermore, several of the genes, including STAT3, annotated to the significant CpG sites are relevant for RA susceptibility or the action of MTX.

Conclusion

We detected CpG sites that were associated with MTX treatment in CD4⁺ naïve and memory T cells isolated from RA patients. Several of these sites overlap genetic regions previously associated with RA risk and MTX treatment outcome.

The current status of anti-citrullinated protein antibodies and citrullinated protein-reactive B cells in the pathogenesis of rheumatoid arthritis

Anti-citrullinated protein antibodies are a hallmark of rheumatoid arthritis. It is widely acknowledged that the presence of ACPAs is the result of the interaction of genes, the environment and epigenetic modifications. The mechanism by which the factors, especially citrullination and ACPA glycosylation, affect ACPAs is still unclear. In this article, we review the presence of the ACPAs in RA and their relationship with clinical manifestations. The pathogenicity of ACPAs and B cells in RA was also summarized. A growing body of evidence has shown that ACPA-positive patients have more serious bone erosion and destruction and poor clinical prognosis than ACPA-negative patients. Recently, with the direct study of citrullinated protein-reactive B cells, their role in the development of rheumatoid arthritis has been further understood. It indicates that further understanding of the mechanism of ACPAs and CP-reactive B cells would beneficial in the prevention and treatment of RA.

The Genetic, Environmental, and Immunopathological Complexity of Autoantibody-Negative Rheumatoid Arthritis

Differences in clinical presentation, response to treatment, and long-term outcomes between autoantibody-positive and -negative rheumatoid arthritis (RA) highlight the need for a better comprehension of the immunopathogenic events underlying the two disease subtypes. Whilst the drivers and perpetuators of autoimmunity in autoantibody-positive RA have started to be disclosed, autoantibody-negative RA remains puzzling, also due its wide phenotypic heterogeneity and its possible misdiagnosis. Genetic susceptibility appears to mostly rely on class I HLA genes and a number of yet unidentified non-HLA loci. On the background of such variable genetic predisposition, multiple exogeneous, endogenous, and stochastic factors, some of which are not shared with autoantibody-positive RA, contribute to the onset of the inflammatory cascade. In a proportion of the patients, the immunopathology of synovitis, at least in the initial stages, appears largely myeloid driven, with abundant production of proinflammatory cytokines and only minor involvement of cells of the adaptive immune system. Better understanding of the complexity of autoantibody-negative RA is still needed in order to open new avenues for targeted intervention and improve clinical outcomes.

Possibilities for personalised medicine in rheumatoid arthritis: hype or hope

Knowledge of pathophysiology of rheumatoid arthritis (RA) has improved over the past decades, which resulted in new treatment options and strategies that led to better clinical outcomes. At the same time, we have come to understand that RA is a heterogeneous disease on a clinical as well as a pathophysiological level. Despite this heterogeneity, current management recommendations still adopt a ‘one-size-fits-all’ treatment approach, where ideally individualised treatment, or personalised medicine, is preferred. The first step towards personalised medicine in RA would be to designate different treatment strategies to distinct clinical or molecular phenotypes of patients. This viewpoint discusses current evidence and elaborates on future possibilities for personalised medicine in RA.

Assessment of fingolimod versus dimethyl fumarate for the treatment of multiple sclerosis; a 24-month follow-up study

BACKGROUND

Oral treatment of multiple sclerosis (MS) using disease-modifying therapies (DMTs) is a challenge worldwide. Fingolimod (FTY) and dimethyl fumarate (DMF) are two approved agents for oral treatment of MS with remarkable efficacy for relapse control and deceleration of disability progression. Therefore, the current study was done to compare disability control, lesions in magnetic resonance imaging (MRI), and adverse effects between the patients treated with FTY and DMF.

METHODS

This randomized clinical trial (IR.MUI.REC.1396.3.786) was conducted on 60 patients who were randomly divided into two groups of treatment with 0.5 mg daily dose of FTY (n = 30) and 240 mg dose of DMF twice daily (n = 30). Disability of patients was assessed using the expanded disability status scale (EDSS) within 6 weeks, 12, and 24 months following treatment initiation and MRI was performed for all the patients prior to study initiation and within 24 months. Obtained data were compared between two study groups.

RESULTS

There was no significant difference between two treatment groups based on EDSS scores, brain lesions in MRI, and newly formed plaques (P>0.05). Skin and gastrointestinal-related complaints were the most common adverse effects of DMF while the increase in liver enzyme level and thrombocytopenia were the most common complications of FTY, respectively (P-value = 0.22).

CONCLUSION

According to our findings, within 24-month follow-up, DMF was neither superior nor inferior to FTY comparing MRI lesions, EDSS scores, and adverse effects. Although, further evaluations with larger sample size are recommended.

CD3D, GZMK, and KLRB1 Are Potential Markers for Early Diagnosis of Rheumatoid Arthritis, Especially in Anti-Citrullinated Protein Antibody-Negative Patients

Early diagnosis and monitoring of rheumatoid arthritis (RA) progress are critical for effective treatment. In clinic, the detection of rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA) are usually combined to diagnose early RA. However, the poor specificity of RF and high heterogeneity of ACPA make the early diagnosis of RA still challenging. Bioinformatics analysis based on high-throughput omics is an emerging method to identify novel and effective biomarkers, which has been widely used in many diseases. Herein, utilizing an integrated strategy based on expression correlation analysis and weighted gene coexpression network analysis (WGCNA), we identified 76 RA-trait different expression genes (DEGs). Combined with protein-protein interaction (PPI) network construction and clustering, new hub genes associated in RA synovia, CD3D, GZMK, and KLRB1, were identified. We verified the specificity of these genes in the synovium of RA patients through three external datasets. We also observed high sensitivity and specificity of them for ACPA-negative patients. CD3D, GZMK, and KLRB1 are potentially key mediators of RA pathogenesis and markers for RA diagnosis.

A review of liquid biopsy as a tool to assess epigenetic, cfDNA and miRNA variability as methotrexate response predictors in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a common autoimmune inflammatory disease affecting 0.5-1% of adults worldwide. Achieving long term remission or low disease activity is possible through early diagnosis, rapid initiation of disease modifying anti-rheumatic drugs (DMARDs) and implementation of a treat to target approach. Initial DMARD therapy usually involves methotrexate (MTX), either alone or in combination with other agents, however 40% of RA patients do not respond adequately, putting them at risk of disease progression and unnecessary exposure to MTX related adverse effects. Early predictors of MTX response would therefore enable a more personalized treatment strategy, ensuring timely access to MTX for those likely to respond and importantly, early initiation of alternative treatment for those in which MTX is unlikely to be efficacious. Predicting response to treatment will most likely require consideration of the clinical characteristics of the patient and interrogation of a number of factors including genetic, epigenetic, cell free DNA (cfDNA) and microRNA (miRNA), all of which can be investigated through blood derived liquid biopsies. This review will summarize the existing literature examining the use of epigenetic factors, cfDNA and miRNA as response predictors among RA patients treated with MTX.

Technological readiness and implementation of genomic-driven precision medicine for complex diseases

The fields of human genetics and genomics have generated considerable knowledge about the mechanistic basis of many diseases. Genomic approaches to diagnosis, prognostication, prevention and treatment - genomic-driven precision medicine (GDPM) - may help optimize medical practice. Here, we provide a comprehensive review of GDPM of complex diseases across major medical specialties. We focus on technological readiness: how rapidly a test can be implemented into health care. Although these areas of medicine are diverse, key similarities exist across almost all areas. Many medical areas have, within their standards of care, at least one GDPM test for a genetic variant of strong effect that aids the identification/diagnosis of a more homogeneous subset within a larger disease group or identifies a subset with different therapeutic requirements. However, for almost all complex diseases, the majority of patients do not carry established single-gene mutations with large effects. Thus, research is underway that seeks to determine the polygenic basis of many complex diseases. Nevertheless, most complex diseases are caused by the interplay of genetic, behavioural and environmental risk factors, which will likely necessitate models for prediction and diagnosis that incorporate genetic and non-genetic data.

Single-cell sequencing of immune cells from anticitrullinated peptide antibody positive and negative rheumatoid arthritis

The presence or absence of anti-citrullinated peptide antibodies (ACPA) and associated disparities in patients with rheumatoid arthritis (RA) implies disease heterogeneity with unknown diverse immunopathological mechanisms. Here we profile CD45⁺ hematopoietic cells from peripheral blood or synovial tissues from both ACPA+ and ACPA- RA patients by single-cell RNA sequencing and identify subsets of immune cells that contribute to the pathogenesis of RA subtypes. We find several synovial immune cell abnormalities, including up-regulation of CCL13, CCL18 and MMP3 in myeloid cell subsets of ACPA- RA compared with ACPA+ RA. Also evident is a lack of HLA-DRB5 expression and lower expression of cytotoxic and exhaustion related genes in the synovial tissues of patients with ACPA- RA. Furthermore, the HLA-DR15 haplotype (DRB1/DRB5) conveys an increased risk of developing active disease in ACPA+ RA in a large cohort of patients with treatment-naive RA. Immunohistochemical staining shows increased infiltration of CCL13 and CCL18-expressing immune cells in synovial tissues of ACPA- RA. Collectively, our data provide evidence of the differential involvement of cellular and molecular pathways involved in the pathogenesis of seropositive and seronegative RA subtypes and reveal the importance of precision therapy based on ACPA status.

Patients with rheumatoid arthritis are commonly stratified by ACPA serology, with positivity being associated with more severe disease and joint destruction. Here the authors present a single cell RNA sequencing resource comparing peripheral blood and synovial tissue cells from patients with ACPA+ versus ACPA- rheumatoid arthritis.

A Comprehensive Evaluation of the Relationship Between Different IgG and IgA Anti-Modified Protein Autoantibodies in Rheumatoid Arthritis

Seropositive rheumatoid arthritis (RA) is characterized by the presence of rheumatoid factor (RF) and anti-citrullinated protein autoantibodies (ACPA) with different fine-specificities. Yet, other serum anti-modified protein autoantibodies (AMPA), e.g. anti-carbamylated (Carb), -acetylated (KAc), and malondialdehyde acetaldehyde (MAA) modified protein antibodies, have been described. In this comprehensive study, we analyze 30 different IgG and IgA AMPA reactivities to Cit, Carb, KAc, and MAA antigens detected by ELISA and autoantigen arrays in N=1985 newly diagnosed RA patients. Association with patient characteristics such as smoking and disease activity were explored. Carb and KAc reactivities by different assays were primarily seen in patients also positive for anti-citrulline reactivity. Modified vimentin (mod-Vim) peptides were used for direct comparison of different AMPA reactivities, revealing that IgA AMPA recognizing mod-Vim was mainly detected in subsets of patients with high IgG anti-Cit-Vim levels and a history of smoking. IgG reactivity to acetylation was mainly detected in a subset of patients with Cit and Carb reactivity. Anti-acetylated histone reactivity was RA-specific and associated with high anti-CCP2 IgG levels, multiple ACPA fine-specificities, and smoking status. This reactivity was also found to be present in CCP2+ RA-risk individuals without arthritis. Our data further demonstrate that IgG autoreactivity to MAA was increased in RA compared to controls with highest levels in CCP2+ RA, but was not RA-specific, and showed low correlation with other AMPA. Anti-MAA was instead associated with disease activity and was not significantly increased in CCP2+ individuals at risk of RA. Notably, RA patients could be subdivided into four different subsets based on their AMPA IgG and IgA reactivity profiles. Our serology results were complemented by screening of monoclonal antibodies derived from single B cells from RA patients for the same antigens as the RA cohort. Certain CCP2+ clones had Carb or Carb+KAc+ multireactivity, while such reactivities were not found in CCP2- clones. We conclude that autoantibodies exhibiting different patterns of ACPA fine-specificities as well as Carb and KAc reactivity are present in RA and may be derived from multireactive B-cell clones. Carb and KAc could be considered reactivities within the "Cit-umbrella" similar to ACPA fine-specificities, while MAA reactivity is distinctly different.

Understanding interactions between risk factors, and assessing the utility of the additive and multiplicative models through simulations

Understanding the genetic background of complex diseases requires the expansion of studies beyond univariate associations. Therefore, it is important to use interaction assessments of risk factors in order to discover whether, and how genetic risk variants act together on disease development. The principle of interaction analysis is to explore the magnitude of the combined effect of risk factors on disease causation. In this study, we use simulations to investigate different scenarios of causation to show how the magnitude of the effect of two risk factors interact. We mainly focus on the two most commonly used interaction models, the additive and multiplicative risk scales, since there is often confusion regarding their use and interpretation. Our results show that the combined effect is multiplicative when two risk factors are involved in the same chain of events, an interaction called synergism. Synergism is often described as a deviation from additivity, which is a broader term. Our results also confirm that it is often relevant to estimate additive effect relationships, because they correspond to independent risk factors at low disease prevalence. Importantly, we evaluate the threshold of more than two required risk factors for disease causation, called the multifactorial threshold model. We found a simple mathematical relationship (square root) between the threshold and an additive-to-multiplicative linear effect scale (AMLES), where 0 corresponds to an additive effect and 1 to a multiplicative. We propose AMLES as a metric that could be used to test different effects relationships at the same time, given that it can simultaneously reveal additive, multiplicative and intermediate risk effects relationships. Finally, the utility of our simulation study was demonstrated using real data by analyzing and interpreting gene-gene interaction odds ratios from a rheumatoid arthritis case-control cohort.

ACPA Status Correlates with Differential Immune Profile in Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a progressive erosive autoimmune disease that affects 1% of the world population. Anti-citrullinated protein autoantibodies (ACPA) are routinely used for the diagnosis of RA, however 20–30% of patients are ACPA negative. ACPA status is a delineator of RA disease endotypes with similar clinical manifestation but potentially different pathophysiology. Profiling of key peripheral blood and synovial tissue immune populations including B cells, T follicular helper (Tfh) cells and CD4 T cell proinflammatory cytokine responses could elucidate the underlying immunological mechanisms involved and inform a treat to target approach for both ACPA-positive and ACPA-negative RA. Detailed high dimensionality flow cytometric analysis with supervised and unsupervised algorithm analysis revealed unique RA patient peripheral blood B cell and Tfh cell profiles. Synovial tissue single cell analysis of B cell subpopulation distribution was similar between ACPA− and ACPA+ RA patients, highlighting a key role for specific B cell subsets in both disease endotypes. Interestingly, synovial tissue single cell analysis of CD4 T cell proinflammatory cytokine production was markedly different between ACPA− and APCA+ RA patients. RNAseq analysis of RA patient synovial tissue highlighted disease endotype specific gene signatures. ACPA status associates with unique immune profile signatures that reinforce the need for a treat to target approach for both endotypes of RA.

Adult-Onset Anti-Citrullinated Peptide Antibody-Negative Destructive Rheumatoid Arthritis Is Characterized by a Disease-Specific CD8+ T Lymphocyte Signature

Rheumatoid arthritis (RA) is a complex autoimmune disease targeting synovial joints. Traditionally, RA is divided into seropositive (SP) and seronegative (SN) disease forms, the latter consisting of an array of unrelated diseases with joint involvement. Recently, we described a severe form of SN-RA that associates with characteristic joint destruction. Here, we sought biological characteristics to differentiate this rare but aggressive anti-citrullinated peptide antibody-negative destructive RA (CND-RA) from early seropositive (SP-RA) and seronegative rheumatoid arthritis (SN-RA). We also aimed to study cytotoxic CD8+ lymphocytes in autoimmune arthritis. CND-RA, SP-RA and SN-RA were compared to healthy controls to reveal differences in T-cell receptor beta (TCRβ) repertoire, cytokine levels and autoantibody repertoires. Whole-exome sequencing (WES) followed by single-cell RNA-sequencing (sc-RNA-seq) was performed to study somatic mutations in a clonally expanded CD8+ lymphocyte population in an index patient. A unique TCRβ signature was detected in CND-RA patients. In addition, CND-RA patients expressed higher levels of the bone destruction-associated TNFSF14 cytokine. Blood IgG repertoire from CND-RA patients recognized fewer endogenous proteins than SP-RA patients’ repertoires. Using WES, we detected a stable mutation profile in the clonally expanded CD8+ T-cell population characterized by cytotoxic gene expression signature discovered by sc-RNA-sequencing. Our results identify CND-RA as an independent RA subset and reveal a CND-RA specific TCR signature in the CD8+ lymphocytes. Improved classification of seronegative RA patients underlines the heterogeneity of RA and also, facilitates development of improved therapeutic options for the treatment resistant patients.

Modulation of TCR Signaling by Tyrosine Phosphatases: From Autoimmunity to Immunotherapy

Early TCR signaling is dependent on rapid phosphorylation and dephosphorylation of multiple signaling and adaptor proteins, leading to T cell activation. This process is tightly regulated by an intricate web of interactions between kinases and phosphatases. A number of tyrosine phosphatases have been shown to modulate T cell responses and thus alter T cell fate by negatively regulating early TCR signaling. Mutations in some of these enzymes are associated with enhanced predisposition to autoimmunity in humans, and mouse models deficient in orthologous genes often show T cell hyper-activation. Therefore, phosphatases are emerging as potential targets in situations where it is desirable to enhance T cell responses, such as immune responses to tumors. In this review, we summarize the current knowledge about tyrosine phosphatases that regulate early TCR signaling and discuss their involvement in autoimmunity and their potential as targets for tumor immunotherapy.

Increased expression of CXCL2 in ACPA-positive rheumatoid arthritis and its role in osteoclastogenesis

Anti-citrullinated protein/peptide antibodies (ACPA) play important roles in the pathogenesis of rheumatoid arthritis (RA). ACPA-positive (ACPA⁺ ) and ACPA-negative (ACPA^- ) RA were suggested to be different disease subsets, with distinct differences in genetic variation and clinical outcomes. The aims of the present study were to compare gene expression profiles in ACPA⁺ and ACPA^- RA, and to identify novel candidate gene signatures that might serve as therapeutic targets. Comprehensive transcriptome analysis of peripheral blood mononuclear cells (PBMCs) from ACPA⁺ and ACPA^- RA patients and healthy controls was performed via RNA sequencing. A validation cohort was used to further investigate differentially expressed genes via polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). Spearman's correlation test was used to evaluate the correlation of differentially expressed genes and the clinical and laboratory data of the patients. The role of differentially expressed genes in osteoclastogenesis was further investigated. Expression of C-X-C motif chemokine ligand 2 (CXCL2) was significantly increased in ACPA⁺ RA than in ACPA^- RA, which was validated in PBMCs and serum. CXCL2 promoted the migration of CD14⁺ monocytes and increased osteoclastogenesis in RA patients. RAW264.7 macrophages were used to investigate specific mechanisms, and the results suggested that CXCL2 stimulated osteoclastogenesis via extracellular receptor kinase (ERK) mitogen-activated protein kinase (MAPK) and nuclear factor kappa B pathways. In conclusion, CXCL2 was highly expressed in ACPA⁺ RA than in ACPA^- RA. CXCL2 promoted osteoclastogenesis and was related to bone erosion in RA, which suggests that the blockade of CXCL2 might be a novel strategy for the treatment of RA.

TREAT Early Arthralgia to Reverse or Limit Impending Exacerbation to Rheumatoid arthritis (TREAT EARLIER): a randomized, double-blind, placebo-controlled clinical trial protocol

BACKGROUND

We present a study protocol for a randomized, double-blind, placebo-controlled trial that investigates the hypothesis if intervention in the symptomatic phase preceding clinical arthritis (clinically suspect arthralgia (CSA)) is effective in preventing progression from subclinical inflammation to clinically apparent persistent arthritis. Currently, rheumatoid arthritis (RA) can be recognized and diagnosed when arthritis (joint swelling) has become detectable at physical examination. Importantly, at this time, the immune processes have already matured, chronicity is established, and patients require long-standing treatment with disease-modifying anti-rheumatic drugs. The TREAT EARLIER trial studies the hypothesis that intervention in the symptomatic phase preceding clinical arthritis is more often successful in permanent disease modification because of less matured underlying disease processes.

METHODS

A two-level definition to identify patients that are prone to develop RA is used. First, patients should have CSA and recent-onset arthralgia (< 1 year) that is suspect to progress to RA according to the expertise of the treating rheumatologist. Second, patients need to have subclinical inflammation of the hand or foot joints at 1.5 T MRI. The trial aims to recruit 230 participants from secondary care hospital settings across the south-west region of The Netherlands. Intervention will be randomly assigned and includes a single-dose of intramuscular 120 mg methylprednisolon followed by methotrexate (increasing dose to 25 mg/week orally) or placebo (both; injection and tablets) over the course of 1 year. Thereafter, participants are followed for another year. The primary endpoint is the development of clinically detectable arthritis, either fulfilling the 2010 criteria for RA or unclassified clinical arthritis of ≥ 2 joints, which persists for at least 2 weeks. DMARD-free status is a co-primary endpoint. The patient-reported outcomes functioning, along with workability and symptoms, are key secondary endpoints. Participants, caregivers (including those assessing the endpoints), and scientific staff are all blinded to the group assignment.

DISCUSSION

This proof-of-concept study is the logical consequence of pre-work on the identification of patients with CSA with MRI-detected subclinical joint inflammation. It will test the hypothesis whether intervention in patients in this early phase with the cornerstone treatment of classified RA (methotrexate) hampers the development of persistent RA and reduce the disease burden of RA.

TRIAL REGISTRATION

Dutch Trial Register NL4599 (NTR4853). Registered on 20 October 2014.