Epigenetic Changes in the Pathogenesis of Rheumatoid Arthritis

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.

Paternal inflammatory arthritis is associated with a higher risk of miscarriage: results of a large multicenter study (iFAME-Fertility)

Objectives

Paternal preconception health is recognized as an important contributor to pregnancy outcomes. Nonetheless, pregnancy outcomes of partners of men with inflammatory arthritis (IA) have never been studied. Our objective was to describe the pregnancy outcomes of partners of men diagnosed with IA.

Methods

We performed a multicentre cross-sectional retrospective study conducted in the Netherlands. Men with IA who were over 40 years old that reported at least one positive pregnancy test were included. To analyse the impact of IA on pregnancy outcomes, pregnancies were classified into two groups: pregnancies conceived after the diagnosis of IA and before the diagnosis of IA.

Results

In total, 408 male participants diagnosed with IA reported 897 singleton pregnancies that resulted in 794 live births. Pregnancies conceived after the diagnosis of IA had higher rate of miscarriage (12.27 vs 7.53%, P = <0.05). This increased risk was still present after adjusting for confounders [OR 2.03 (95% CI 1.12, 3.69) P = 0.015].

Conclusions

This is the largest study to describe the pregnancy outcomes of partners of men diagnosed with IA and the first to demonstrate that paternal IA is associated with a higher risk of miscarriage. Notwithstanding, the overall rate of miscarriage reported in our study could be comparable to previously reported population estimates.

Stromal cell regulation of inflammatory responses

In the last fifteen years it has become apparent that tissue-resident mesenchymal cells such as fibroblasts, which are the structural elements of all organs, play a cardinal role in the pathology of immune-mediated inflammatory diseases. We now know that all fibroblasts originate from universal pan-organ cellular ancestors and that they are diversified into more specific subsets according to the functional needs of their home tissue-and its activation state. In arthritis, a plethora of activated joint-resident and migrating fibroblast types have been recently described that are central for pathogenesis and persistence of inflammatory joint-disease. Here we provide a current overview on the multiple inflammatory and immune-related functions of fibroblasts and how they could be curbed to induce long-lasting abatement of disease.

Epigenetic Regulation (Including Micro-RNAs, DNA Methylation and Histone Modifications) of Rheumatoid Arthritis: A Systematic Review

The inflammatory reaction in rheumatoid arthritis (RA) is controlled by major epigenetic modifications that modulate the phenotype of synovial and immune cells. The aim of this work was to perform a systematic review focusing on miR expression, DNA methylation and histone modifications in RA. We demonstrated that, in human samples, the expressions of miR-155, miR-146a and miR-150 were significantly decreased while the expression of miR-410-3p was significantly increased in the RA group. Moreover, miR-146a significantly decreased pro-autoimmune IL-17 cytokine expression in RA. In a murine model, miR-34a inhibition can ameliorate the arthritis score. However, this evidence remain critically insufficient to support current therapeutic applications in RA patients.

Epigenetic drug development for autoimmune and inflammatory diseases

ES-62 is the major secreted protein of the parasitic filarial nematode, Acanthocheilonema viteae. The molecule exists as a large tetramer (MW, ~240kD), which possesses immunomodulatory properties by virtue of multiple phosphorylcholine (PC) moieties attached to N-type glycans. By suppressing inflammatory immune responses, ES-62 can prevent disease development in certain mouse models of allergic and autoimmune conditions, including joint pathology in collagen-induced arthritis (CIA), a model of rheumatoid arthritis (RA). Such protection is associated with functional suppression of "pathogenic" hyper-responsive synovial fibroblasts (SFs), which exhibit an aggressive inflammatory and bone-damaging phenotype induced by their epigenetic rewiring in response to the inflammatory microenvironment of the arthritic joint. Critically, exposure to ES-62 in vivo induces a stably-imprinted CIA-SF phenotype that exhibits functional responses more typical of healthy, Naïve-SFs. Consistent with this, ES-62 "rewiring" of SFs away from the hyper-responsive phenotype is associated with suppression of ERK activation, STAT3 activation and miR-155 upregulation, signals widely associated with SF pathogenesis. Surprisingly however, DNA methylome analysis of Naïve-, CIA- and ES-62-CIA-SF cohorts reveals that rather than simply preventing pathogenic rewiring of SFs, ES-62 induces further changes in DNA methylation under the inflammatory conditions pertaining in the inflamed joint, including targeting genes associated with ciliogenesis, to programme a novel "resolving" CIA-SF phenotype. In addition to introducing a previously unsuspected aspect of ES-62's mechanism of action, such unique behaviour signposts the potential for developing DNA methylation signatures predictive of pathogenesis and its resolution and hence, candidate mechanisms by which novel therapeutic interventions could prevent SFs from perpetuating joint inflammation and destruction in RA. Pertinent to these translational aspects of ES-62-behavior, small molecule analogues (SMAs) based on ES-62's active PC-moieties mimic the rewiring of SFs as well as the protection against joint disease in CIA afforded by the parasitic worm product.

Recent Advances in Understanding the Pathogenesis of Rheumatoid Arthritis: New Treatment Strategies

Rheumatoid arthritis (RA) is considered a chronic systemic, multi-factorial, inflammatory, and progressive autoimmune disease affecting many people worldwide. While patients show very individual courses of disease, with RA focusing on the musculoskeletal system, joints are often severely affected, leading to local inflammation, cartilage destruction, and bone erosion. To prevent joint damage and physical disability as one of many symptoms of RA, early diagnosis is critical. Auto-antibodies play a pivotal clinical role in patients with systemic RA. As biomarkers, they could help to make a more efficient diagnosis, prognosis, and treatment decision. Besides auto-antibodies, several other factors are involved in the progression of RA, such as epigenetic alterations, post-translational modifications, glycosylation, autophagy, and T-cells. Understanding the interplay between these factors would contribute to a deeper insight into the causes, mechanisms, progression, and treatment of the disease. In this review, the latest RA research findings are discussed to better understand the pathogenesis, and finally, treatment strategies for RA therapy are presented, including both conventional approaches and new methods that have been developed in recent years or are currently under investigation.

Toward a New Paradigm for Targeted Natriuretic Peptide Enhancement in Heart Failure

The natriuretic peptide system (NPS) plays a fundamental role in maintaining cardiorenal homeostasis, and its potent filling pressure-regulated diuretic and vasodilatory effects constitute a beneficial compensatory mechanism in heart failure (HF). Leveraging the NPS for therapeutic benefit in HF has been the subject of intense investigation during the last three decades and has ultimately reached widespread clinical use in the form of angiotensin receptor-neprilysin inhibition (ARNi). NPS enhancement via ARNi confers beneficial effects on mortality and hospitalization in HF, but inhibition of neprilysin leads to the accumulation of a number of other vasoactive peptides in the circulation, often resulting in hypotension and raising potential concerns over long-term adverse effects. Moreover, ARNi is less effective in the large group of HF patients with preserved ejection fraction. Alternative approaches for therapeutic augmentation of the NPS with increased specificity and efficacy are therefore warranted, and are now becoming feasible particularly with recent development of RNA therapeutics. In this review, the current state-of-the-art in terms of experimental and clinical strategies for NPS augmentation and their implementation will be reviewed and discussed.

Ten Years of EWAS

Epigenome-wide association study (EWAS) has been applied to analyze DNA methylation variation in complex diseases for a decade, and epigenome as a research target has gradually become a hot topic of current studies. The DNA methylation microarrays, next-generation, and third-generation sequencing technologies have prepared a high-quality platform for EWAS. Here, the progress of EWAS research is reviewed, its contributions to clinical applications, and mainly describe the achievements of four typical diseases. Finally, the challenges encountered by EWAS and make bold predictions for its future development are presented.

Impact of Posttranslational Modification in Pathogenesis of Rheumatoid Arthritis: Focusing on Citrullination, Carbamylation, and Acetylation

Rheumatoid arthritis (RA) is caused by prolonged periodic interactions between genetic, environmental, and immunologic factors. Posttranslational modifications (PTMs) such as citrullination, carbamylation, and acetylation are correlated with the pathogenesis of RA. PTM and cell death mechanisms such as apoptosis, autophagy, NETosis, leukotoxic hypercitrullination (LTH), and necrosis are related to each other and induce autoantigenicity. Certain microbial infections, such as those caused by Porphyromonasgingivalis, Aggregatibacter actinomycetemcomitans, and Prevotella copri, can induce autoantigens in RA. Anti-modified protein antibodies (AMPA) containing anti-citrullinated protein/peptide antibodies (ACPAs), anti-carbamylated protein (anti-CarP) antibodies, and anti-acetylated protein antibodies (AAPAs) play a role in pathogenesis as well as in prediction, diagnosis, and prognosis. Interestingly, smoking is correlated with both PTMs and AMPAs in the development of RA. However, there is lack of evidence that smoking induces the generation of AMPAs.

Network Pharmacology and Molecular Docking-Based Prediction of the Mechanism of Qianghuo Shengshi Decoction against Rheumatoid Arthritis

Qianghuo Shengshi decoction (QHSSD) is a classical Chinese medicine formula, which is used in clinical practice for the treatment of rheumatoid arthritis (RA) in China. However, the pharmacological mechanism of QHSSD on RA has remained unclear by now. We collected and screened active compounds and its potential targets by the pharmacology platform of Chinese herbal medicines. In addition, the therapeutic targets of RA were obtained and selected from databases. Network construction analyzed that 128 active compounds may act on 87 candidate targets and identified a total of 18 hub targets. GO annotation and KEGG enrichment investigated that the action mechanism underlying the treatment of RA by QHSSD might be involved in cell proliferation, angiogenesis, anti-inflammation, and antioxidation. Finally, molecular docking verification showed that TP53, VEGFA, TNF, EGFR, and NOS3 may be related to the RA treatment and molecular dynamics simulation showed the stability of protein-ligand interactions. In this work, QHSSD might exert therapeutic effect through a multicomponent, multitarget, and multipathway in RA from a holistic aspect, which provides basis for its mechanism of action and subsequent experiments.

Analysis of the Composition and Anti-Rheumatoid Arthritis Mechanism of Qintengtongbi Decoction Based on Network Pharmacology

Qintengtongbi Decoction (QTTBD) is a traditional prescription for rheumatoid arthritis (RA) treatment in Ruikang Hospital Affiliated to Guangxi University of Chinese Medicine, Nanning, southern China's Guangxi Zhuang Autonomous Region. However, there is not yet any analysis on its active compounds or action mechanism for treating RA. Moreover, the prescription has not been investigated from the perspective of network pharmacology. Therefore, this study aimed to analyze the compounds QTTBD and their potential pharmacological effects and the mechanism by which they treat RA via an integrated network pharmacology approach. With the aid of the relevant database tools and research indices, 188 compounds and 272 related drug targets genes/proteins were collected from QTTBD through the compound-target network, and 175 common gene targets between the QTTBD and RA were obtained by Venn 2.1. Finally, the top 10 gene targets and pathways were identified through the protein–protein interaction network, gene ontology, and KEGG pathway analysis: the gene targets include AKT1, IL6, TP53, VEGFA, MAPK3, TNF, CASP3, JUN, EGF, and EGFR; the pathways include oxytocin signaling pathway, amphetamine addiction, graft-versus-host disease, ovarian steroidogenesis, cGMP-PKG signaling pathway, Rap1 signaling pathway, allograft rejection, cytokine–cytokine receptor interaction, regulation of lipolysis in adipocytes and inflammatory mediator regulation of transient receptor potential channels. Therefore, it is concluded that a network pharmacology-based approach can help reveal and clarify the anti-RA role of QTTBD, and provide a scientific basis for further research into the mechanism.

KP-10/Gpr54 attenuates rheumatic arthritis through inactivating NF-κB and MAPK signaling in macrophages

Rheumatoid arthritis (RA) is an autoimmune disease mainly characterized as chronic inflammation of joint. Both genetic and environmental factors play important roles in RA progression. G protein-coupled receptor 54 (GPR54) and Kisspeptins (KPs), the natural GRP54 ligands encoded by Kiss-1 gene are known to play important roles in immune regulation but the precise role of KP-10/GPR54 in RA remains elusive. Kiss1/Gpr54 expression was determined by immunohistochemistry on protein and real-time PCR on RNA from isolated RA-patient synovial tissue and PBMC. Collagen-induced arthritis (CIA) mouse models were used to investigate the effect of KP-10/Gpr54 on the rheumatic arthritis severity in the mice. The signaling pathway involved in KP-10/GPR54 was assessed by western blot and immunofluorescence.In the present study, we demonstrated that GPR54 upregulation in bone marrow-derived macrophages (BMDM) was associated with the severity of RA. In addition, Gpr54-/- increased the inflammatory cytokines induced by lipopolysaccharide (LPS) in BMDM and diseased severity of CIA (n = 10), while KP-10 reduced the LPS-induced inflammatory cytokines in vitro and ameliorated the CIA symptoms in vivo. Furthermore, we demonstrated that KP-10/GPR54 binds to PP2A-C to suppressed LPS induced NF-κB and MAPK signaling in BMDM. All these findings suggest that KP-10/GPR54 may be a novel therapeutic target for the diagnosis and treatment of RA.

Cell-Free DNA in Rheumatoid Arthritis

Endogenous DNA derived from the nuclei or mitochondria is released into the bloodstream following cell damage or death. Extracellular DNA, called cell-free DNA (cfDNA), is associated with various pathological conditions. Recently, multiple aspects of cfDNA have been assessed, including cfDNA levels, integrity, methylation, and mutations. Rheumatoid arthritis (RA) is the most common form of autoimmune arthritis, and treatment of RA has highly varied outcomes. cfDNA in patients with RA is elevated in peripheral blood and synovial fluid and is associated with disease activity. Profiling of cfDNA in patients with RA may then be utilized in various aspects of clinical practice, such as the prediction of prognosis and treatment responses; monitoring disease state; and as a diagnostic marker. In this review, we discuss cfDNA in patients with RA, particularly the sources of cfDNA and the correlation of cfDNA with RA pathogenesis. We also highlight the potential of analyzing cfDNA profiles to guide individualized treatment approaches for RA.

Emerging epigenetic targets in rheumatoid arthritis

Rheumatoid arthritis is a complex disorder that is characterized by irreversible and progressive destructions of joints, but its exact etiology remains mainly unknown. The occurrence and the progression of the disease entirely depend on environmental and genetic factors. In recent years, various epigenetic changes involving DNA methylation, histone modification, miRNA, X-chromosome inactivation, bromodomain, sirtuin, and many others were identified that were found to be linked to the activation and the aggressive phenotype in rheumatoid arthritis. Epigenetics is found to be one of the root causes, which brings changes in the heritable phenotype and is not determined by changes in the DNA sequences and understanding these epigenetic mechanisms and the pathogenesis of the disease can help in understanding the disease and various other possible ways for its control and/or prevention. The various epigenetic modification occurring are reversible and can be modulated by drugs, diet, and environmental factors. This article focuses on various epigenetic factors involved in the pathogenesis of rheumatoid arthritis. Further, various epigenetic therapies that might be successful in inhibiting these epigenetic modifications are summarized. Several therapeutic agents alter the epigenetic modifications occurring in various diseases and many of the epigenetic therapies are under pre-clinical and clinical trial. However, exploring these epigenetic prognostic biomarkers would give a broader perspective and provide more ideas and knowledge regarding the process and pathways through which the diseases occur, and also combining various therapeutic agents would show more beneficial and synergistic effects.

Tuning Monocytes and Macrophages for Personalized Therapy and Diagnostic Challenge in Rheumatoid Arthritis

Monocytes/macrophages play a central role in chronic inflammatory disorders, including rheumatoid arthritis (RA). Activation of these cells results in the production of various mediators responsible for inflammation and RA pathogenesis. On the other hand, the depletion of macrophages using specific antibodies or chemical agents can prevent their synovial tissue infiltration and subsequently attenuates inflammation. Their plasticity is a major feature that helps the switch from a pro-inflammatory phenotype (M1) to an anti-inflammatory state (M2). Therefore, understanding the precise strategy targeting pro-inflammatory monocytes/macrophages should be a powerful way of inhibiting chronic inflammation and bone erosion. In this review, we demonstrate potential consequences of different epigenetic regulations on inflammatory cytokines production by monocytes. In addition, we present unique profiles of monocytes/macrophages contributing to identification of new biomarkers of disease activity or predicting treatment response in RA. We also outline novel approaches of tuning monocytes/macrophages by biologic drugs, small molecules or by other therapeutic modalities to reduce arthritis. Finally, the importance of cellular heterogeneity of monocytes/macrophages is highlighted by single-cell technologies, which leads to the design of cell-specific therapeutic protocols for personalized medicine in RA in the future.

Fibroblast pathology in inflammatory joint disease

Rheumatoid arthritis is an immune-mediated inflammatory disease in which fibroblasts contribute to both joint damage and inflammation. Fibroblasts are a major cell constituent of the lining of the joint cavity called the synovial membrane. Under resting conditions, fibroblasts have an important role in maintaining joint homeostasis, producing extracellular matrix and joint lubricants. In contrast, during joint inflammation, fibroblasts contribute to disease pathology by producing pathogenic levels of inflammatory mediators that drive the recruitment and retention of inflammatory cells within the joint. Recent advances in single-cell profiling techniques have transformed our ability to examine fibroblast biology, leading to the identification of specific fibroblast subsets, defining a previously underappreciated heterogeneity of disease-associated fibroblast populations. These studies are challenging the previously held dogma that fibroblasts are homogeneous and are providing unique insights into their role in inflammatory joint pathology. In this review, we discuss the recent advances in our understanding of how fibroblast heterogeneity contributes to joint pathology in rheumatoid arthritis. Finally, we address how these insights could lead to the development of novel therapies that directly target selective populations of fibroblasts in the future.

Treatment of Rheumatoid Arthritis with Gene Therapy Applications: Biosafety and Bioethical Considerations

Rheumatoid Arthritis (RA) is an autoimmune and inflammatory disease that affects the synovium (lining that surrounds the joints), causing the immune system to attack its own healthy tissues. Treatment options, to the current day, have serious limitations and merely offer short-term alleviation to the pain. Using a theoretical exercise based on literature, a new potentially viable therapy has been proposed. The new therapy focusses on a long-term treatment of RA based on gene therapy, which is only active when inflammation of the joint occurs. This treatment will prevent side effects of systemic application of drugs. Furthermore, the benefits of this treatment for the patient from a socio-economic perspective has been discussed, focusing on the quality of life of the patent and lower costs for the society.

Therapeutic potential of targeted-gold nanospheres on collagen-induced arthritis in rats

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that causes functional disability due to bone destruction and severe joint pain. Current anti-rheumatic treatments develop severe complications and do not provide complete remission. Gold nanoparticles (AuNPs) have garnered attention because of their unique physical and chemical properties. In this study, we have evaluated the therapeutic effects of gold nanospheres (AuNSs) with two different ligands (targeted-nanoparticles) against collagen-induced arthritis (CIA) and compared the outcomes with conventional methotrexate (MTX) and biological (infliximab) treatments. Clinical evaluation was performed by radiographic and histological examinations. The bioaccumulation of AuNSs in vital organs was assessed. The mechanistic studies targeting pro-inflammatory/anti-inflammatory and angiogenic mediators' expressions were performed. Radiographic examination showed that the targeted AuNSs reduced joint space narrowing and bone erosion. Moreover, histopathological examination of rat ankle joints demonstrated that targeted AuNSs reduce bone and cartilage degeneration/inflammation. Gold nanospheres-conjugated with nucleus localized peptide (nuclear membrane-targeted) (AuNSs@NLS) has resolved bone destruction and inflammation compared to gold nanospheres-conjugated at polyethylene glycol (AuNSs@PEG). Although the AuNSs accumulated in different organs in both cases, they did not induce any toxicity or tissue damage. The two different targeted AuNSs significantly suppress inflammatory and angiogenic mediators' expression and induced anti-inflammatory cytokine production, but the AuNSs@NLS had superior therapeutic efficacy. In conclusion, these results suggested that nuclear membrane-targeted AuNSs effectively attenuated arthritis progression without systemic side effects.

The p53 status in rheumatoid arthritis with focus on fibroblast-like synoviocytes

P53 is a transcription factor that regulates many signaling pathways like apoptosis, cell cycle, DNA repair, and cellular stress responses. P53 is involved in inflammatory responses through the regulation of inflammatory signaling pathways, induction of cytokines, and matrix metalloproteinase expression. Also, p53 regulates immune responses through modulating Toll-like receptors expression and innate and adaptive immune cell differentiation and maturation. P53 is a modulator of the apoptosis and proliferation processes through regulating multiple anti and pro-apoptotic genes. Rheumatoid arthritis (RA) is categorized as an invasive inflammatory autoimmune disease with irreversible deformity of joints and bone resorption. Different immune and non-immune cells contribute to RA pathogenesis. Fibroblast-like synoviocytes (FLSs) have been recently introduced as a key player in the pathogenesis of RA. These cells in RA synovium produce inflammatory cytokines and matrix metalloproteinases which results in synovitis and joint destruction. Besides, hyper proliferation and apoptosis resistance of FLSs lead to synovial hyperplasia and bone and cartilage destruction. Given the critical role of p53 in inflammation, apoptosis, and cell proliferation, lack of p53 function (due to mutation or low expression) exerts a prominent role for this gene in the pathogenesis of RA. This review focuses on the role of p53 in different mechanisms and cells (specially FLSs) that involved in RA pathogenesis.

Epigenetic Contribution and Genomic Imprinting Dlk1-Dio3 miRNAs in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease that afflicts multiple organs, especially kidneys and joints. In addition to genetic predisposition, it is now evident that DNA methylation and microRNAs (miRNAs), the two major epigenetic modifications, are critically involved in the pathogenesis of SLE. DNA methylation regulates promoter accessibility and gene expression at the transcriptional level by adding a methyl group to 5' cytosine within a CpG dinucleotide. Extensive evidence now supports the importance of DNA hypomethylation in SLE etiology. miRNAs are small, non-protein coding RNAs that play a critical role in the regulation of genome expression. Various studies have identified the signature lupus-related miRNAs and their functional contribution to lupus incidence and progression. In this review, the mutual interaction between DNA methylation and miRNAs regulation in SLE is discussed. Some lupus-associated miRNAs regulate DNA methylation status by targeting the DNA methylation enzymes or methylation pathway-related proteins. On the other hand, DNA hyper- and hypo-methylation are linked with dysregulated miRNAs expression in lupus. Further, we specifically discuss the genetic imprinting Dlk1-Dio3 miRNAs that are subjected to DNA methylation regulation and are dysregulated in several autoimmune diseases, including SLE.

Novel Insights Into Rheumatoid Arthritis Through Characterization of Concordant Changes in DNA Methylation and Gene Expression in Synovial Biopsies of Patients With Differing Numbers of Swollen Joints

In this study, we sought to characterize synovial tissue obtained from individuals with arthralgia and disease-specific auto-antibodies and patients with established rheumatoid arthritis (RA), by applying an integrative multi-omics approach where we investigated differences at the level of DNA methylation and gene expression in relation to disease pathogenesis. We performed concurrent whole-genome bisulphite sequencing and RNA-Sequencing on synovial tissue obtained from the knee and ankle from 4 auto-antibody positive arthralgia patients and thirteen RA patients. Through multi-omics factor analysis we observed that the latent factor explaining the variance in gene expression and DNA methylation was associated with Swollen Joint Count 66 (SJC66), with patients with SJC66 of 9 or more displaying separation from the rest. Interrogating these observed differences revealed activation of the immune response as well as dysregulation of cell adhesion pathways at the level of both DNA methylation and gene expression. We observed differences for 59 genes in particular at the level of both transcript expression and DNA methylation. Our results highlight the utility of genome-wide multi-omics profiling of synovial samples for improved understanding of changes associated with disease spread in arthralgia and RA patients, and point to novel candidate targets for the treatment of the disease.

Overexpression of circ_0021739 in Peripheral Blood Mononuclear Cells in Women with Postmenopausal Osteoporosis Is Associated with Reduced Expression of microRNA-194-5p in Osteoclasts

BACKGROUND Postmenopausal osteoporosis, a common disease among elderly women, is linked to estrogen deficiency, mechanical loading, and genotype. Circular RNAs (circRNAs) are formed through reverse splicing of the splice donor at the 3' end and the splice accepter at the 5' end in pre-mRNA and have been shown to be involved in the development of multiple diseases. Based on their high sequence conservation and stability, circRNAs may be useful biomarkers in different diseases. However, the roles of circRNAs in postmenopausal osteoporosis remain incompletely understood. MATERIAL AND METHODS Fifty-three postmenopausal women were assigned to either the postmenopausal osteoporosis group (n=28) or the control group (n=25). Reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR) analysis was performed to determine the differential expression of circRNAs between the 2 groups. Receiver-operating characteristic (ROC) curve analysis was conducted to evaluate the clinical diagnostic value of circRNA. Prediction of the binding sites between circRNA and miRNAs was conducted using miRanda and RNAhybrid. The function of the circRNA in osteoclastogenesis was determined by circRNA overexpression followed by tartrate-resistant acid phosphatase staining and RT-qPCR analysis. RESULTS Among 4 circRNAs previously identified by RNA-sequencing analysis as differentially expressed in patients with postmenopausal osteoporosis, only hsa_circ_0021739 showed a significant difference in expression between the groups and was downregulated in patients with postmenopausal osteoporosis. The hsa_circ_0021739 expression level was determined to be correlated with the lumbar vertebra, femur, and forearm T-scores. Overexpression of hsa_circ_0021739 decreased the level of hsa-miR-502-5p and inhibited the differentiation of osteoclasts. CONCLUSIONS The circRNA hsa_circ_0021739 is a potential blood biomarker for postmenopausal osteoporosis. In addition, hsa-miR-502-5p is a likely target of hsa_circ_0021739, which acts to regulate the differentiation of osteoclasts.

Chromatin accessibility landscapes of immune cells in rheumatoid arthritis nominate monocytes in disease pathogenesis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease that involves a variety of cell types. However, how the epigenetic dysregulations of peripheral immune cells contribute to the pathogenesis of RA still remains largely unclear.

RESULTS

Here, we analysed the genome-wide active DNA regulatory elements of four major immune cells, namely monocytes, B cells, CD4⁺ T cells and CD8⁺ T cells, in peripheral blood of RA patients, osteoarthritis (OA) patients and healthy donors using Assay of Transposase Accessible Chromatin with sequencing (ATAC-seq). We found a strong RA-associated chromatin dysregulation signature in monocytes, but no other examined cell types. Moreover, we found that serum C-reactive protein (CRP) can induce the RA-associated chromatin dysregulation in monocytes via in vitro experiments. And the extent of this dysregulation was regulated through the transcription factor FRA2.

CONCLUSIONS

Together, our study revealed a CRP-induced pathogenic chromatin dysregulation signature in monocytes from RA patients and predicted the responsible signalling pathway as potential therapeutic targets for the disease.

The Immunomodulatory and Anti-Inflammatory Effect of Curcumin on Immune Cell Populations, Cytokines, and In Vivo Models of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a widespread chronic autoimmune disorder affecting the joints, causing irreversible cartilage, synovium, and bone degradation. During the course of the disease, many immune and joint cells are activated, causing inflammation. Immune cells including macrophages, lymphocytes, neutrophils, mast cells, natural killer cells, innate lymphoid cells, as well as synovial tissue cells, like fibroblast-like synoviocytes, chondrocytes, and osteoclasts secrete different proinflammatory factors, including many cytokines, angiogenesis-stimulating molecules and others. Recent studies reveal that curcumin, a natural dietary anti-inflammatory compound, can modulate the response of the cells engaging in RA course. This review comprises detailed data about the pathogenesis and inflammation process in rheumatoid arthritis and demonstrates scientific investigations about the molecular interactions between curcumin and immune cells responsible for rheumatoid arthritis development to discuss this herbal drug’s immunoregulatory role in RA treatment.

A Review on Rheumatoid Arthritis Interventions and Current Developments

Rheumatoid arthritis is a chronic autoimmune disorder characterized by inflammation, swelling, and joint destruction primarily affecting the peripheral joints. In recent years, RA has become an alarming concern affecting more than 1.5% of the population worldwide. The majority of the drugs in clinical trials for rheumatoid arthritis are immunomodulatory. The development of novel drugs for RA is impending and scientists are exploring new strategies through various innovative approaches for RA drug development. Treat-to-target and window of opportunity hypothesis are the new approaches that are used to treat, improve outcomes, and prevent long-term use of ineffective therapy, respectively. Novel therapeutic agents (e.g. GM-CSF inhibitors, Matrix metalloproteinase inhibitors) and delivery systems (e.g., Liposomes, Superparamagnetic iron oxide nano particles (SPIONs)) are under investigation for more target based therapy with reduced side effects and toxicity. The new drug discovery and repositioning of previously FDA-approved drugs are also being considered for chronic inflammatory disorder. The review encompasses a vast array of information, including genetics, etiology, clinical symptoms, current treatment, and newer therapeutics approaches, focused on the development of RA interventions. The introduction of the bioinformatics-based approach in RA has also been significantly discussed in the review. This review provides a general understanding of the challenges and uncertainties in the treatment of RA and summarizes the evolving scenario as well as innovative approaches taken into consideration for drug development in rheumatoid arthritis.

m6A RNA Methylation in Systemic Autoimmune Diseases-A New Target for Epigenetic-Based Therapy?

The general background of autoimmune diseases is a combination of genetic, epigenetic and environmental factors, that lead to defective immune reactions. This erroneous immune cell activation results in an excessive production of autoantibodies and prolonged inflammation. During recent years epigenetic mechanisms have been extensively studied as potential culprits of autoreactivity. Alike DNA and proteins, also RNA molecules are subjected to an extensive repertoire of chemical modifications. N6-methyladenosine is the most prevalent form of internal mRNA modification in eukaryotic cells and attracts increasing attention due to its contribution to human health and disease. Even though m6A is confirmed as an essential player in immune response, little is known about its role in autoimmunity. Only few data have been published up to date in the field of RNA methylome. Moreover, only selected autoimmune diseases have been studied in respect of m6A role in their pathogenesis. In this review, I attempt to present all available research data regarding m6A alterations in autoimmune disorders and appraise its role as a potential target for epigenetic-based therapies.

Study of miRNA interactome in active rheumatoid arthritis patients reveals key pathogenic roles of dysbiosis in the infection-immune network

OBJECTIVES

To characterize serum microRNA (miR) and the miR interactome of active RA patients in RA aetiology and pathogenesis.

METHODS

The differentially expressed miRs (DEmiRs) in serum of naïve active RA patients (NARAPs, n = 9, into three pools) vs healthy controls (HCs, n = 15, into five pools) were identified with Agilent human miR microarray analysis. Candidate driver genes in epigenetic and pathogenic signalling pathway modules for RA were analysed using miRTarBase and a molecular complex detection algorithm. The interactome of these DEmiRs in RA pathogenesis were further characterized with gene ontology and Kyoto Encyclopaedia of Genes and Genomes.

RESULTS

Three upregulated DEmiRs (hsa-miR-187-5p, -4532, -4516) and eight downregulated DEmiRs (hsa-miR-125a-3p, -575, -191-3p, -6865-3p, -197-3p, -6886-3p, -1237-3p, -4436b-5p) were identified in NARAPs. Interactomic analysis from heterogeneous experimentally validated sources yielded 1719 miR-target interactions containing 5.67% strong and 94.33% less strong experimental evidence. Gene ontology and Kyoto Encyclopaedia of Genes and Genomes analyses allocated the upregulated DEmiRs in the infection modules and the downregulated DEmiRs in the immune signalling pathways. Specifically, these DEmiRs revealed the significant contributions of the intestinal microbiome dysbiosis in the infection-inflammation-immune network for activation of T cells, immune pathways of IL-17, Toll-like receptor, TNF, Janus kinase-signal transducer and activator of transcription, osteoclast cell differentiation pathway and IgA production to the active RA pathogenesis.

CONCLUSIONS

Our experiment-based interactomic study of DEmiRs in serum of NARAPs revealed novel clinically relevant miRs interactomes in the infection-inflammation-immune network of RA. These results provide valuable resources for understanding the integrated function of the miR network in RA pathogenesis and the application of circulating miRs as biomarkers for early aetiologic RA diagnosis.

Nutrition and Rheumatoid Arthritis in the 'Omics' Era

Modern high-throughput 'omics' science tools (including genomics, transcriptomics, proteomics, metabolomics and microbiomics) are currently being applied to nutritional sciences to unravel the fundamental processes of health effects ascribed to particular nutrients in humans and to contribute to more precise nutritional advice. Diet and food components are key environmental factors that interact with the genome, transcriptome, proteome, metabolome and the microbiota, and this life-long interplay defines health and diseases state of the individual. Rheumatoid arthritis (RA) is a chronic autoimmune disease featured by a systemic immune-inflammatory response, in genetically susceptible individuals exposed to environmental triggers, including diet. In recent years increasing evidences suggested that nutritional factors and gut microbiome have a central role in RA risk and progression. The aim of this review is to summarize the main and most recent applications of 'omics' technologies in human nutrition and in RA research, examining the possible influences of some nutrients and nutritional patterns on RA pathogenesis, following a nutrigenomics approach. The opportunities and challenges of novel 'omics technologies' in the exploration of new avenues in RA and nutritional research to prevent and manage RA will be also discussed.

Insights Into the Involvement of Circular RNAs in Autoimmune Diseases

Circular RNAs (circRNAs) are single-stranded, endogenous, non-coding RNA (ncRNA) molecules formed by the backsplicing of messenger RNA (mRNA) precursors and have covalently closed circular structures without 5′-end caps and 3′-end polyadenylation [poly(A)] tails. CircRNAs are characterized by abundant species, stable structures, conserved sequences, cell- or tissue-specific expression, and widespread and stable presence in many organisms. Therefore, circRNAs can be used as biomarkers for the prediction, diagnosis, and treatment of a variety of diseases. Autoimmune diseases (AIDs) are caused by defects in immune tolerance or abnormal immune regulation, which leads to damage to host organs. Due to the complexity of the pathophysiological processes of AIDs, clinical therapeutics have been suboptimal. The emergence of circRNAs sheds new light on the treatment of AIDs. In particular, circRNAs mainly participate in the occurrence and development of AIDs by sponging targets. This review systematically explains the formation, function, mechanism, and characteristics of circRNAs in the context of AIDs. With a deeper understanding of the pathophysiological functions of circRNAs in the pathogenesis of AIDs, circRNAs may become reasonable, accurate, and effective biomarkers for the diagnosis and treatment of AIDs in the future.

Anti-nociceptive effect of Portulaca oleracea L. ethanol extracts attenuated zymosan-induced mouse joint inflammation via inhibition of Nrf2 expression

The aim of this study was to explore the effects of ethanol extracts from Portulaca oleracea L. (ePO) on joint inflammation and to explain the underlying mechanisms. A joint inflammation mouse model was constructed by injecting zymosan, and the Von Frey method was employed and the joint thickness measured. The numbers of leukocytes, neutrophils, and monocytes were counted in the joint cavity and the infiltration of inflammatory cells was assessed by joint histopathological analysis. The mRNA levels of inflammatory cytokines were determined by quantitative RT-PCR and their secretion levels were determined by specific ELISAs. Pre-treatment with ePO inhibited articular mechanical hyperalgesia and edema and ameliorated the recruitment of mononuclear neutrophils and leukocytes. In addition, pre-treatment with ePO improved pathological alternations in the joint tissues by reducing the number of inflammatory cells. Pre-treatment with ePO regulated the nuclear factor erythroid 2-related factor 2 (Nrf2)-related proteins and thereby inhibited oxidative stress. In addition, ePO inhibited NLR family pyrin domain containing 3 (NLRP3) inflammasome-related genes (NLRP3, ASC, pro-caspase-1 and pro-IL-1ß), modulated inflammatory cytokines and the activation of NF-κB. ePO attenuated zymosan-induced joint inflammation by regulating oxidative stress, NLRP3 inflammasome, and NF-κB.

Marine-Derived Biologically Active Compounds for the Potential Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease with a prevalence rate of up to 1% and is significantly considered a common worldwide public health concern. Commercially, several traditional formulations are available to treat RA to some extent. However, these synthetic compounds exert toxicity and considerable side effects even at lower therapeutic concentrations. Considering the above-mentioned critiques, research is underway around the world in finding and exploiting potential alternatives. For instance, marine-derived biologically active compounds have gained much interest and are thus being extensively utilized to confront the confines of in practice counterparts, which have become ineffective for 21st-century medical settings. The utilization of naturally available bioactive compounds and their derivatives can minimize these synthetic compounds' problems to treat RA. Several marine-derived compounds exhibit anti-inflammatory and antioxidant properties and can be effectively used for therapeutic purposes against RA. The results of several studies ensured that the extraction of biologically active compounds from marine sources could provide a new and safe source for drug development against RA. Finally, current challenges, gaps, and future perspectives have been included in this review.

Persistent inflammatory and non-inflammatory mechanisms in refractory rheumatoid arthritis

Despite nearly three decades of advances in the management of rheumatoid arthritis (RA), a substantial minority of patients are exposed to multiple DMARDs without necessarily benefitting from them; a group of patients variously designated as having 'difficult to treat', 'treatment-resistant' or 'refractory' RA. This Review of refractory RA focuses on two types of patients: those for whom multiple targeted therapies lack efficacy and who have persistent inflammatory pathology, which we designate as persistent inflammatory refractory RA (PIRRA); and those with supposed refractory RA who have continued disease activity that is predominantly independent of objective evidence of inflammation, which we designate as non-inflammatory refractory RA (NIRRA). These two types of disease are not mutually exclusive, but identifying those individuals with predominant PIRRA or NIRRA is important, as it informs distinct treatment and management approaches. This Review outlines the clinical differences between PIRRA and NIRRA, the genetic and epigenetic mechanisms and immune pathways that might contribute to the immunopathogenesis of recalcitrant synovitis in PIRRA, and a possible basis for non-inflammatory symptomatology in NIRRA. Future approaches towards the definition of refractory RA and the application of single-cell and integrated omics technologies to the identification of refractory RA endotypes are also discussed.

Analysis of miRNA Expression in Patients with Rheumatoid Arthritis during Olokizumab Treatment

Rheumatoid arthritis (RA) is the most common autoimmune disease worldwide. Epigenetic alternations of microRNAs (miRNAs) can contribute to its pathogenesis and progression. As the first line therapy with DMARDs is not always successful, other drugs and therapeutic targets should be applied. This study aims to measure the expression level of plasma miRNAs in RA patients treated with olokizumab and to evaluate their potential as prognostic biomarkers. The expression of 9 miRNAs was quantified in 103 RA patients before treatment and at weeks 12 and 24 of olokizumab therapy by reverse transcription-polymerase chain reaction (RT-PCR) assay and analyzed in groups of responders and non-responders. Almost all miRNAs changed their expression during therapy. The ROC curve analysis of the most prominent of them together with consequent univariate and multivariate regression analysis revealed statistically significant associations with the olokizumab therapy efficiency scores for miR-26b, miR-29, miR-451, and miR-522. Therefore, these miRNAs might be a potential therapeutic response biomarker.

Latin American Genes: The Great Forgotten in Rheumatoid Arthritis

The successful implementation of personalized medicine will rely on the integration of information obtained at the level of populations with the specific biological, genetic, and clinical characteristics of an individual. However, because genome-wide association studies tend to focus on populations of European descent, there is a wide gap to bridge between Caucasian and non-Caucasian populations before personalized medicine can be fully implemented, and rheumatoid arthritis (RA) is not an exception. In this review, we discuss advances in our understanding of genetic determinants of RA risk among global populations, with a focus on the Latin American population. Geographically restricted genetic diversity may have important implications for health and disease that will remain unknown until genetic association studies have been extended to include Latin American and other currently under-represented ancestries. The next few years will witness many breakthroughs in personalized medicine, including applications for common diseases and risk stratification instruments for targeted prevention/intervention strategies. Not all of these applications may be extrapolated from the Caucasian experience to Latin American or other under-represented populations.

Epigenetics, pregnancy and autoimmune rheumatic diseases

Autoimmune rheumatic diseases (ARDs) are chronic conditions with a striking female predominance, frequently affecting women of childbearing age. Sex hormones and gender dimorphism of immune response are major determinants in the multifactorial pathogenesis of ARDs, with significant implications throughout reproductive life. Particularly, pregnancy represents a challenging condition in the context of autoimmunity, baring profound hormonal and immunologic changes, which are responsible for the bi-directional interaction between ARDs outcome and pregnancy course. In the latest years epigenetics has proven to be an important player in ARDs pathogenesis, finely modulating major immune functions and variably tuning the significant gender effects in autoimmunity. Additionally, epigenetics is a recognised influencer of the physiological dynamic modifications occurring during pregnancy. Still, there is currently little evidence on the pregnancy-related epigenetic modulation of immune response in ARDs patients. This review aims to overview the current knowledge of the role of epigenetics in the context of autoimmunity, as well as during physiologic and pathologic pregnancy, discussing under-regarded aspects in the interplay between ARDs and pregnancy pathology. The outline of a new ongoing European project will be presented.

Prediction of Self-Perception of Patient in Rheumatoid Arthritis With the Key RNAs Expression Profiles

Self-perception in patients is their self-response to sensory stimuli. It is an important aspect of the existence and quality of life among patients. However, the inherent relationship between self-perception and the cellular activity at the molecular level is elusive. In this study, we aimed to explore the association of self-perception with RNA expression profile in patients with rheumatoid arthritis (RA) through computational analysis. We recruited 30 patients clinically diagnosed with RA and to age- and sex-matched controls without previous clinical history. In total, 5 self-perception measures and 30 RNA expression measures were derived from RA patients and control groups. A correlation analysis based on Spearman correlation and Logistic-regression methods was adopted to assess the correlation between self-perception and RNA expression. Quantitative analysis revealed that RA patients with poor self-perception were closely associated with RNAs expression, In addition, 3 key molecules including AC019117.2, LINC00638, and hsa_circ_0003972 could be used to predict self-perception changes in RA patients. Herein, our results will provide new insights in RA diagnosis however, the underlying mechanisms need to be further explored.

Genetic Polymorphisms Associated with Rheumatoid Arthritis Development and Antirheumatic Therapy Response

Rheumatoid arthritis (RA) is the most common inflammatory arthropathy worldwide. Possible manifestations of RA can be represented by a wide variability of symptoms, clinical forms, and course options. This multifactorial disease is triggered by a genetic predisposition and environmental factors. Both clinical and genealogical studies have demonstrated disease case accumulation in families. Revealing the impact of candidate gene missense variants on the disease course elucidates understanding of RA molecular pathogenesis. A multivariate genomewide association study (GWAS) based analysis identified the genes and signalling pathways involved in the pathogenesis of the disease. However, these identified RA candidate gene variants only explain 30% of familial disease cases. The genetic causes for a significant proportion of familial RA have not been determined until now. Therefore, it is important to identify RA risk groups in different populations, as well as the possible prognostic value of some genetic variants for disease development, progression, and treatment. Our review has two purposes. First, to summarise the data on RA candidate genes and the increased disease risk associated with these alleles in various populations. Second, to describe how the genetic variants can be used in the selection of drugs for the treatment of RA.

Removable prostheses improve OHRQL and satisfaction of elderly people with rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that affects joint tissues and causes severe physical and functional impairments on quality of life due to muscular and articular pain. The involvement of temporomandibular joint in RA interferes with mouth opening and masticatory process. However, no studies addressed the impact of RA on oral health-related quality of life (OHRQoL) and satisfaction with prostheses use in elderly people. Aim: This study assessed the impact of oral rehabilitation with conventional dentures on the OHRQoL and prostheses satisfaction in elderly patients with RA, associated or not with temporomandibular disorder (TMD). Methods: Forty-five elderly were enrolled and divided into three groups: (1) RA and TMD (n=15, experimental), (2) RA without TMD (n=15, experimental), and (3) without RA and without TMD (n=15, control). The OHRQoL and the prostheses satisfaction were evaluated before and after new oral rehabilitation with partial and/or complete dentures. The OHRQoL and prosthesis satisfaction were assessed and verified through OHIP-14 questionnaire and visual analogue scale, respectively. Results: TMD group exhibited the worst mean values (P<0.05) for all OHIP-14 domains before insertion of new dentures. Group 2 showed worst means (P<0.05) compared to controls for functional limitation and physical pain domains of the OHIP-14, but not in the general score. Patients showed better outcomes of satisfaction with prostheses use only after the new rehabilitation. Conclusion: The use of new and well-fitted dentures improves all domains of OHRQoL in patients with RA and TMD and all groups were satisfied with prostheses use after the new rehabilitation with conventional dentures.

Prediction of triptolide targets in rheumatoid arthritis using network pharmacology and molecular docking

Network pharmacology is a novel approach that uses bioinformatics to predict and identify multiple drug targets and interactions in disease. Here, we used network pharmacology to investigate the mechanism by which triptolide acts in rheumatoid arthritis (RA). We first searched public databases for genes and proteins known to be associated with RA, as well as those predicted to be targets of triptolide, and then used Ingenuity Pathway Analysis (IPA) to identify enriched gene pathways and networks. Networks and pathways that overlapped between RA-associated proteins and triptolide target proteins were then used to predict candidate protein targets of triptolide in RA. The following proteins were found to occur in both RA-associated networks and triptolide target networks: CD274, RELA, MCL1, MAPK8, CXCL8, STAT1, STAT3, c-JUN, JNK, c-Fos, NF-κB, and TNF-α. Docking studies suggested that triptolide can fit in the binding pocket of the six top candidate triptolide target proteins (CD274, RELA, MCL1, MAPK8, CXCL8 and STAT1). The overlapping pathways were activation of Th1 and Th2 cells, macrophages, fibroblasts and endothelial cells in RA, while the overlapping networks were involved in cellular movement, hematological system development and function, immune cell trafficking, cell-to-cell signaling and interaction, inflammatory response, cellular function and maintenance, and cell death and survival. These results show that network pharmacology can be used to generate hypotheses about how triptolide exerts therapeutic effects in RA. Network pharmacology may be a useful method for characterizing multi-target drugs in complex diseases.

AA, Lukashev AN. Emerging Concepts and Challenges in Rheumatoid Arthritis Gene Therapy

Rheumatoid arthritis (RA) is a systemic inflammatory joint disease affecting about 1% of the population worldwide. Current treatment approaches do not ensure a cure for every patient. Moreover, classical regimens are based on nontargeted systemic immune suppression and have significant side effects. Biological treatment has advanced considerably but efficacy and specificity issues remain. Gene therapy is one of the potential future directions for RA therapy, which is rapidly developing. Several gene therapy trials done so far have been of moderate success, but experimental and genetics studies have yielded novel targets. As a result, the arsenal of gene therapy tools keeps growing. Currently, both viral and nonviral delivery systems are used for RA therapy. Herein, we review recent approaches for RA gene therapy.

Citrullinated Peptide Epitope Targets Therapeutic Nanoparticles to Human Neutrophils

Multiple drugs have been proposed for reducing harsh symptoms of human rheumatic diseases. However, a targeted therapy with mild to no side effects is still missing. In this study, we have prepared and tested a series of therapeutic nanoparticles for specific targeting of human neutrophils associated with rheumatoid arthritis. In doing this, a series of citrullinated peptide epitopes derived from human proteins, fibrinogen, vimentin, and histone 3, were screened with regard to specific recognition of neutrophils. The most potent epitope proved to be a mutated fragment of an alpha chain in human fibrinogen. Next, a straightforward synthetic strategy was developed for nanoparticles decorated with this citrullinated peptide epitope and an antisense oligonucleotide targeting disease associated microRNA miR-125b-5p. Our study shows that the nanoparticles specifically recognize neutrophils and knock down miR-125b-5p, with no apparent toxicity to human cells. In contrast to organic dendrimers, chitosan-hyaluronic acid formulations do not activate human innate immune response. Our data proves that the strategy we report herein is effective in developing peptide epitopes for decorating delivery vehicles bearing biological drugs, targeted to a specific cell type.

DNA Methylation as a Future Therapeutic and Diagnostic Target in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a long-term autoimmune disease of unknown etiology that leads to progressive joint destruction and ultimately to disability. RA affects as much as 1% of the population worldwide. To date, RA is not a curable disease, and the mechanisms responsible for RA development have not yet been well understood. The development of more effective treatments and improvements in the early diagnosis of RA is direly needed to increase patients' functional capacity and their quality of life. As opposed to genetic mutation, epigenetic changes, such as DNA methylation, are reversible, making them good therapeutic candidates, modulating the immune response or aggressive synovial fibroblasts (FLS-fibroblast-like synoviocytes) activity when it is necessary. It has been suggested that DNA methylation might contribute to RA development, however, with insufficient and conflicting results. Besides, recent studies have shown that circulating cell-free methylated DNA (ccfDNA) in blood offers a very convenient, non-invasive, and repeatable "liquid biopsy", thus providing a reliable template for assessing molecular markers of various diseases, including RA. Thus, epigenetic therapies controlling autoimmunity and systemic inflammation may find wider implications for the diagnosis and management of RA. In this review, we highlight current challenges associated with the treatment of RA and other autoimmune diseases and discuss how targeting DNA methylation may improve diagnostic, prognostic, and therapeutic approaches.