Epigenetics in the pathogenesis of RA

A bibliometric analysis of miRNAs in rheumatoid arthritis from 2001 to 2022: Research hotspots and trends

BACKGROUND

MicroRNAs (miRNAs) are widely recognized in the pathogenesis of autoimmune disease. As a key regulatory factor, miRNAs have introduced new biomarkers for the early diagnosis of rheumatoid arthritis (RA) and provided a favorable research direction for the development of novel therapeutic targets. This study aimed to explore the hotspots of miRNA research related to RA published from different countries, organizations, and authors.

METHODS

From 2001 to 2022, publications on miRNA related to RA were identified in the Web of Science database. The total and annual number of publishments, citations, impact factor, H-index, productive authors, and involved journals were collected for quantitative and qualitative comparisons.

RESULTS

A total of 29 countries/regions in the world have participated in the research of miRNAs and RA over the past two decades, and China (760, 53.18%) and the United States (233, 16.31%) account for the majority of the total publications. China dominated in total citation (17881) and H-index (62). A total of 507 academic journals have published articles in related fields, and Frontiers in Immunology published the most (53, 3.71%). Chih-hsin Tang of the China Medical University has published the most papers (16, 1.2%). Stanczyk (2008) published the most cited article Altered expression of miRNAs in synovial fibroblasts and synovial tissue in rheumatoid arthritis in Arthritis and Rheumatism, with 660 citations. Inflammation is the high-frequency keyword outside of RA and miRNAs, and related researches have mainly focused on miR-146a and miR-155.

CONCLUSIONS

In the past two decades, extensive and continuous research has been conducted to investigate the role of miRNAs in RA, and miRNAs are widely recognized in the pathogenesis of RA. Related research has mainly focused on miR-146a and miR-155 that have shown promising results as key factors in RA experimental models. Focusing on clinical applications and translational research may be the future research direction and hotspot based on molecular biology basic research and mechanism exploration.

Challenges and promise of targeting miRNA in rheumatic diseases: a computational approach to identify miRNA association with cell types, cytokines, and disease mechanisms

MicroRNAs (miRNAs) are small non-coding RNAs that alter the expression of target genes at the post-transcriptional level, influencing diverse outcomes in metabolism, cell differentiation, proliferation, cell survival, and cell death. Dysregulated miRNA expression is implicated in various rheumatic conditions, including ankylosing spondylitis (AS), gout, juvenile idiopathic arthritis (JIA), osteoarthritis (OA), psoriatic arthritis, rheumatoid arthritis (RA), Sjogren's syndrome, systemic lupus erythematosus (SLE) and systemic sclerosis. For this review, we used an open-source programming language- PowerShell, to scan the massive number of existing primary research publications on PubMed on miRNAs in these nine diseases to identify and count unique co-occurrences of individual miRNAs and the disease name. These counts were used to rank the top seven most relevant immuno-miRs based on their research volume in each rheumatic disease. Individual miRNAs were also screened for publication with the names of immune cells, cytokines, and pathological processes involved in rheumatic diseases. These occurrences were tabulated into matrices to identify hotspots for research relevance. Based on this information, we summarize the basic and clinical findings for the top three miRNAs - miR-146, miR-155, and miR-21 - whose relevance spans across multiple rheumatic diseases. Furthermore, we highlight some unique miRNAs for each disease and why some rheumatic conditions lack research in this emerging epigenetics field. With the overwhelming number of publications on miRNAs in rheumatic diseases, this review serves as a 'relevance finder' to guide researchers in selecting miRNAs based on the compiled existing knowledge of their involvement in disease pathogenesis. This approach applies to other disease contexts with the end goal of developing miRNA-based therapeutics.

Recent developments in the synovial fibroblast pathobiology field in rheumatoid arthritis

PURPOSE OF REVIEW

Synovial fibroblasts are the central cells of connective tissue homeostasis. In rheumatoid arthritis (RA) tissue, synovial fibroblasts are activated because of the proinflammatory environment very early in the disease. Epigenetic alterations in RASF result in a permanently activated stage, and activated RASF are involved in many processes of RA pathophysiology. Therefore, several recent findings of the last 18 months with focus on RASF activation and function are summarized.

RECENT FINDINGS

RASF activation because of a profoundly altered epigenome leads to an invasive phenotype with increased migration, adhesion and invasion into cartilage, which was further characterized in several studies. RASF subtypes and subtype dynamics were evaluated using high-resolution techniques to better understand RASF pathophysiology. Many studies addressing interactions with immune or stromal cell types have been published showing that RASF interact with many different cell types contributing not only to their own activation and pro-inflammatory response but also to the activation of the other cells.

SUMMARY

Highly interesting findings revealing mechanisms of RASF activation and altered functions have been published, RASF subsets further characterized, and interactions with cell types elucidated, which all contribute to a better understanding of the role of RASF in RA development and progression.

Innate immune memory in inflammatory arthritis

The concept of immunological memory was demonstrated in antiquity when protection against re-exposure to pathogens was observed during the plague of Athens. Immunological memory has been linked with the adaptive features of T and B cells; however, in the past decade, evidence has demonstrated that innate immune cells can exhibit memory, a phenomenon called 'innate immune memory' or 'trained immunity'. Innate immune memory is currently being defined and is transforming our understanding of chronic inflammation and autoimmunity. In this Review, we provide an up-to-date overview of the memory-like features of innate immune cells in inflammatory arthritis and the crosstalk between chronic inflammatory milieu and cell reprogramming. Aberrant pro-inflammatory signalling, including cytokines, regulates the metabolic and epigenetic reprogramming of haematopoietic progenitors, leading to exacerbated inflammatory responses and osteoclast differentiation, in turn leading to bone destruction. Moreover, imprinted memory on mature cells including terminally differentiated osteoclasts alters responsiveness to therapies and modifies disease outcomes, commonly manifested by persistent inflammatory flares and relapse following medication withdrawal.

Circulating DNA methylation level of CXCR5 correlates with inflammation in patients with rheumatoid arthritis

OBJECTIVES

To assess the differences in circulating DNA methylation levels of CXCR5 between rheumatoid arthritis (RA) and osteoarthritis (OA) and healthy controls (HC), and the correlation of methylation changes with clinical characteristics of RA patients.

METHODS

Peripheral blood samples were collected from 239 RA patients, 30 patients with OA, and 29 HC. Target region methylation sequencing to the promoter region of CXCR5 was achieved using MethylTarget. The methylation level of cg04537602 and methylation haplotype were compared among the three groups, and the correlation between methylation levels and clinical characteristics of RA patients was performed by Spearman's rank correlation analysis.

RESULTS

The methylation level of cg04537602 was significantly higher in the peripheral blood of RA patients compared with OA patients (p = 1.3 × 10^-3 ) and in the HC group (p = 5.5 × 10^{- 4} ). The sensitivity was enhanced when CXCR5 methylation level combined with rheumatoid factor and anti-cyclic citrullinated peptide with area under curve (AUC) of 0.982 (95% confidence interval 0.970-0.995). The methylation level of cg04537602 in RA was positively correlated with C-reactive protein (CRP) (r = .16, p = .01), and in RA patients aged 60 years and above, cg04537602 methylation levels were positively correlated with CRP (r = .31, p = 4.7 × 10^{- 4} ), tender joint count (r = .21, p = .02), visual analog scales score (r = .21, p = .02), Disease Activity Score in 28 joints (DAS28) using the CRP level DAS28-CRP (r = .27, p = 2.1 × 10^{- 3} ), and DAS28-ESR (r = .22, p = .01). We also observed significant differences of DNA methylation haplotypes in RA patients compared with OA patients and HC, which was consistent with single-loci-based CpG methylation measurement.

CONCLUSION

The methylation level of CXCR5 was significantly higher in RA patients than in OA and HC, and correlated with the level of inflammation in RA patients, our study establishes a link between CXCR5 DNA methylation and clinical features that may help in the diagnosis and disease management of RA patients.

RUNX1 Ameliorates Rheumatoid Arthritis Progression through Epigenetic Inhibition of LRRC15

Leucine-rich repeat containing 15 (LRRC15) has been identified as a contributing factor for cartilage damage in osteoarthritis; however, its involvement in rheumatoid arthritis (RA) and the underlying mechanisms have not been well characterized. The purpose of this study was to explore the function of LRRC15 in RA-associated fibroblast-like synoviocytes (RA-FLS) and in mice with collagen-induced arthritis (CIA) and to dissect the epigenetic mechanisms involved. LRRC15 was overexpressed in the synovial tissues of patients with RA, and LRRC15 overexpression was associated with increased proliferative, migratory, invasive, and angiogenic capacities of RA-FLS and accelerated release of pro-inflammatory cytokines. LRRC15 knockdown significantly inhibited synovial proliferation and reduced bone invasion and destruction in CIA mice. Runt-related transcription factor 1 (RUNX1) transcriptionally represses LRRC15 by binding to core-binding factor subunit beta (CBF-β). Overexpression of RUNX1 significantly inhibited the invasive phenotype of RA-FLS and suppressed the expression of proinflammatory cytokines. Conversely, the effects of RUNX1 were significantly reversed after overexpression of LRRC15 or inhibition of RUNX1-CBF-β interactions. Therefore, we demonstrated that RUNX1-mediated transcriptional repression of LRRC15 inhibited the development of RA, which may have therapeutic effects for RA patients.

Comprehensive overview of microRNA function in rheumatoid arthritis

MicroRNAs (miRNAs), a class of endogenous single-stranded short noncoding RNAs, have emerged as vital epigenetic regulators of both pathological and physiological processes in animals. They direct fundamental cellular pathways and processes by fine-tuning the expression of multiple genes at the posttranscriptional level. Growing evidence suggests that miRNAs are implicated in the onset and development of rheumatoid arthritis (RA). RA is a chronic inflammatory disease that mainly affects synovial joints. This common autoimmune disorder is characterized by a complex and multifaceted pathogenesis, and its morbidity, disability and mortality rates remain consistently high. More in-depth insights into the underlying mechanisms of RA are required to address unmet clinical needs and optimize treatment. Herein, we comprehensively review the deregulated miRNAs and impaired cellular functions in RA to shed light on several aspects of RA pathogenesis, with a focus on excessive inflammation, synovial hyperplasia and progressive joint damage. This review also provides promising targets for innovative therapies of RA. In addition, we discuss the regulatory roles and clinical potential of extracellular miRNAs in RA, highlighting their prospective applications as diagnostic and predictive biomarkers.

Role of DNA dioxygenase Ten-Eleven translocation 3 (TET3) in rheumatoid arthritis progression

Background

Rheumatoid arthritis (RA) patients present with abnormal methylation patterns in their fibroblast-like synoviocytes (FLS). Given that DNA demethylation is critical for producing DNA methylation patterns, we hypothesized that DNA demethylation may facilitate RA progression. Therefore, we designed this study to examine the role of DNA dioxygenase family, Ten-Eleven translocation (TET1/2/3), in the pathological process of RA.

Methods

Synovial tissues and FLS were obtained from patients with RA and Osteoarthritis. K/BxN serum-induced arthritis was induced in Wild-type (WT) and TET3 heterozygous-deficient (TET3^+/−) C57BL/6 mice.

Results

We found that both TET3 and 5-hydroxymethylcytosine (5hmC) were upregulated in synovitis tissues from RA patients and confirmed this upregulation in the cultured FLS derived from synovitis tissues. Tumor necrosis factor α (TNFα) upregulated TET3 and 5hmC levels in cultured FLS, and the stimulated FLS exhibited high cell mobility with increased transcription of cellular migration-related factors such as C-X-C motif chemokine ligand 8 (CXCL8) and C-C motif chemokine ligand 2 (CCL2) in a TET3-dependent manner. In addition, TET3 haploinsufficiency lowered RA progression in a mouse model of serum-induced arthritis.

Conclusions

Based on these findings, we can assume that TET3-mediated DNA demethylation acts as an epigenetic regulator of RA progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02908-5.

Single-cell multimodal analysis identifies common regulatory programs in synovial fibroblasts of rheumatoid arthritis patients and modeled TNF-driven arthritis

Background

Synovial fibroblasts (SFs) are specialized cells of the synovium that provide nutrients and lubricants for the proper function of diarthrodial joints. Recent evidence appreciates the contribution of SF heterogeneity in arthritic pathologies. However, the normal SF profiles and the molecular networks that govern the transition from homeostatic to arthritic SF heterogeneity remain poorly defined.

Methods

We applied a combined analysis of single-cell (sc) transcriptomes and epigenomes (scRNA-seq and scATAC-seq) to SFs derived from naïve and hTNFtg mice (mice that overexpress human TNF, a murine model for rheumatoid arthritis), by employing the Seurat and ArchR packages. To identify the cellular differentiation lineages, we conducted velocity and trajectory analysis by combining state-of-the-art algorithms including scVelo, Slingshot, and PAGA. We integrated the transcriptomic and epigenomic data to infer gene regulatory networks using ArchR and custom-implemented algorithms. We performed a canonical correlation analysis-based integration of murine data with publicly available datasets from SFs of rheumatoid arthritis patients and sought to identify conserved gene regulatory networks by utilizing the SCENIC algorithm in the human arthritic scRNA-seq atlas.

Results

By comparing SFs from healthy and hTNFtg mice, we revealed seven homeostatic and two disease-specific subsets of SFs. In healthy synovium, SFs function towards chondro- and osteogenesis, tissue repair, and immune surveillance. The development of arthritis leads to shrinkage of homeostatic SFs and favors the emergence of SF profiles marked by Dkk3 and Lrrc15 expression, functioning towards enhanced inflammatory responses and matrix catabolic processes. Lineage inference analysis indicated that specific Thy1+ SFs at the root of trajectories lead to the intermediate Thy1+/Dkk3+/Lrrc15+ SF states and culminate in a destructive and inflammatory Thy1− SF identity. We further uncovered epigenetically primed gene programs driving the expansion of these arthritic SFs, regulated by NFkB and new candidates, such as Runx1. Cross-species analysis of human/mouse arthritic SF data determined conserved regulatory and transcriptional networks.

Conclusions

We revealed a dynamic SF landscape from health to arthritis providing a functional genomic blueprint to understand the joint pathophysiology and highlight the fibroblast-oriented therapeutic targets for combating chronic inflammatory and destructive arthritic disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-022-01081-3.

Cytotoxic T Lymphocytes Expressing GPR56 are Up-regulated in the Peripheral Blood of Patients with Active Rheumatoid Arthritis and Reflect Disease Progression

OBJECTIVE

This study aims to elucidate the changes in the percentage of GPR56 and/or granzyme B (GZMB) positive cells in rheumatoid arthritis (RA) CD4 and CD8 T lymphocytes, and to explore their clinical value in diagnosing and reflecting the progression of RA.

METHODS

The percentages of GPR56 and/or GZMB positive cells were analyzed in peripheral blood (PB) and spleen T cells in a collagen-induced arthritis (CIA) model established in DBA/1 mice. The percentages of GPR56+ and/or GZMB+ cells were further analyzed in PBs from RA patients and healthy controls. Correlation analysis was performed between clinical indicators and GPR56+, GZMB+, and GPR56+ GZMB+ T cells. Receiver operating characteristic (ROC) curves were used to evaluate the value of GPR56 and GZMB in differentiating active and stable remitting RA.

RESULTS

GPR56+ levels were increased in CD4 and CD8 T cells in the PB of CIA mice. The percentages of GPR56+ and GZMB+ cells were increased in both CD4 and CD8 T cell subsets in patients with active RA. GPR56+, GZMB+, and GPR56+ GZMB+ cells were positively correlated with rheumatoid factor and DAS28. ROC analysis revealed that AUCs for GPR56+, GZMB+, and GPR56+ GZMB+ cell percentages to distinguish active RA from stable remission RA were 0.7106, 0.6941, 0.7024, with cut-off values of 16.35, 16.40, 14.80 in CD4 + T cells, and 0.8031, 0.8086, 0.8196 with cut-off values 60.25, 62.15, 40.15 in CD8 + T cells, respectively.

CONCLUSIONS

GPR56+ and/or GZMB+ T cells are up-regulated in patients with active RA and reflect their condition. The detection of GPR56 and GZMB is helpful for RA disease assessment.

Identification of Synovial Fibroblast-Associated Neuropeptide Genes and m6A Factors in Rheumatoid Arthritis Using Single-Cell Analysis and Machine Learning

Objectives

Synovial fibroblasts (SFs) play an important role in the development and progression of rheumatoid arthritis (RA). However, the pathogenic mechanism of SFs remains unclear. The objective of this study was to investigate how neuropeptides and N6-methyladenosine (m6A) played an important role in the underlying pathogenic processes of SFs that contribute to the development of RA.

Methods

Single-cell RNA sequencing data were examined using single-cell analysis and machine learning. SF subgroups were identified based on the clustering and annotation results of the single-cell analysis. Moreover, cell–cell communication was used to analyse neuropeptide-related receptor and ligand pairs on the surface of SF cell membranes. Machine learning was used to explore the m6A factors acting on these neuropeptide genes.

Results

NPR3, GHR, BDKRB2, and CALCRL, four neuropeptide genes, were shown to be differently expressed among SF subgroups. Further investigation of receptor–ligand interactions found that NPR3 (in conjunction with NPPC, OSTN, NPPB, and NPPA) and GHR (in conjunction with GH1 and GH2) may have a role in SF interactions. As predicted by machine learning, IGFBP2 and METTL3 were identified as key factors regulating m6A of NPR3 and GHR. The expression levels and enrichment pathways of METTL3 and IGFBP2 were different among SF subgroups.

Conclusions

Single-cell analysis and machine learning efficiently identified neuropeptide genes and m6A factors that perform important regulatory functions in RA. Our strategy may provide a basis for future studies to identify pathogenic cell subpopulations and molecular mechanisms in RA and other diseases.

Functional Interactions Between lncRNAs/circRNAs and miRNAs: Insights Into Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases that affect synovitis, bone, cartilage, and joint. RA leads to bone and cartilage damage and extra-articular disorders. However, the pathogenesis of RA is still unclear, and the lack of effective early diagnosis and treatment causes severe disability, and ultimately, early death. Accumulating evidence revealed that the regulatory network that includes long non-coding RNAs (lncRNAs)/circular RNAs (circRNAs), micro RNAs (miRNAs), and messenger RNAs (mRNA) plays important roles in regulating the pathological and physiological processes in RA. lncRNAs/circRNAs act as the miRNA sponge and competitively bind to miRNA to regulate the expression mRNA in synovial tissue, FLS, and PBMC, participate in the regulation of proliferation, apoptosis, invasion, and inflammatory response. Thereby providing new strategies for its diagnosis and treatment. In this review, we comprehensively summarized the regulatory mechanisms of lncRNA/circRNA-miRNA-mRNA network and the potential roles of non-coding RNAs as biomarkers and therapeutic targets for the diagnosis and treatment of RA.

Relationship of serum copper and HLADR4 tissue typing to disease activity and severity in patients with rheumatoid arthritis: A cross sectional study

Background

Objective

Methods

Results

Conclusions

•

Rheumatoid arthritis is a chronic disease associated with high burden on individuals.

•

Serum copper increases in active disease.

•

Assessment of disease activity helps in treatment and follow up.

•

Positive HLADR4 tissue typing is associated with severe disease and complications.

Potential Role of circRNA-HIPK3/microRNA-124a Crosstalk in the Pathogenesis of Rheumatoid Arthritis

BACKGROUND

Circular RNA-HIPK3 (CircHIPK3) has been shown to be aberrantly expressed in a variety of diseases, contributing to disease initiation and progression. The aim of the present study is to investigate the role of the circHIPK3 RNA/microRNA-124a interaction in the pathogenesis of rheumatoid arthritis (RA).

METHODS

This study included 79 RA patients and 30 control individuals. The patients involved were classified according to the disease activity score (DAS28) into mild (24 patients), moderate (24 patients), and severe (31 patients). Serum samples were collected to estimate the relative gene expression of circHIPK3 RNA and its target gene microRNA-124a by quantitative real time-PCR. Moreover, ELISA was used to detect the serum levels of monocyte chemoattractant protein-1 (MCP-1). Routine laboratory estimation of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and rheumatoid factor (RF) was also done.

RESULTS

In all grades of RA groups, there was a significantly substantial elevation of circHIPK3 RNA gene expression, with subsequent downregulation of miRNA-124a when compared to the control group. CircHIPK3 and microRNA-124a expression have been established to be inversely linked. Also, estimation of serum levels of MCP-1, ESR, CRP, and RF exhibited a significant increase in all grades of RA as compared to the control group.

CONCLUSION

CircHIPK3 and microRNA-124a might be regarded as key players in the pathogenesis of RA. The cross-talk between them appears to be responsible for inducing joint inflammation by increasing MCP-1 production. Targeting circHIPK3 and microRNA-124a, and their downstream adaptor molecules, poses a new challenge for RA therapy.

Epigenome association study for DNA methylation biomarkers in buccal and monocyte cells for female rheumatoid arthritis

Genetics (i.e., mutations) has been assumed to be the major factor in rheumatoid arthritis (RA) etiology, but accounts for a minority of the variance in disease risk for RA. In contrast to genetics, the environment can have dramatic impacts on epigenetics that associate with disease etiology. The current study used buccal cells and purified blood monocytes from two different clinical cohorts involving Caucasian or African American female populations with or without arthritis. The differential DNA methylation regions (DMRs) between the control and RA populations were identified with an epigenome-wide association study. The DMRs (i.e., epimutations) identified in the buccal cells and monocytes were found to be distinct. The DMR associated genes were identified and many have previously been shown to be associated with arthritis. Observations demonstrate DNA methylation epimutation RA biomarkers are cell type specific and similar findings were observed with the two racial background populations. Rheumatoid arthritis susceptibility epigenetic diagnosis appears feasible and may improve the clinical management of RA and allowpreventative medicine considerations.

Study on the alleviation of Fengshi Gutong capsule on rheumatoid arthritis through integrating network pharmacology and experimental exploration

ETHNOPHARMACOLOGICAL RELEVANCE

Fengshi Gutong (FSGT) capsule, a traditional Chinese medicine formula, has effects including warming meridians and dispersing cold, and relieving pain by dredging collaterals. FSGT is generally used for the treatment of rheumatoid arthritis (RA) in clinic in China.

AIM OF THE STUDY

This study aims to investigate the alleviation provided by FSGT capsule on RA in vivo and the engaged mechanism.

MATERIALS AND METHODS

The collagen-induced arthritis (CIA) mouse model was used to evaluate the alleviation of FSGT capsule on RA in vivo. Network pharmacology was used to find the potential involved molecular targets. Western-blot, Real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) were conducted. Wound healing assay was performed in human umbilical vein endothelial cells (HUVECs).

RESULTS

FSGT capsule (300, 900 mg/kg) alleviated RA in CIA mice with no obvious side effects. The results from network pharmacology showed that the top 6 molecular targets involved in the FSGT-provided alleviation on RA were interleukin 6 (IL-6), tumor necrosis factor α (TNFα), C-C motif chemokine 2 (CCL2), vascular endothelial growth factor (VEGF), intercellular cell adhesion molecule-1 (ICAM-1), interleukin 1β (IL-1β), and these results imply the critical participation of inhibiting inflammation or angiogenesis. Next, FSGT capsule decreased the elevated serum contents of rheumatoid factor (RF) and VEGF, and some pro-inflammatory cytokines like TNFα and IL-6. Moreover, FSGT capsule also reduced the elevated protein expression of ICAM1, IL-1β and phosphorylated protein kinase B (Akt) in synovium from CIA mice. Further in vitro results showed that totally 13 compounds from FSGT reduced the enhanced IL-1β and inducible nitric oxide synthase (iNOS) mRNA expression in RAW264.7 macrophages stimulated by lipopolysaccharide (LPS). Meanwhile, 7 compounds from FSGT decreased the VEGF-induced HUVEC migration. Among those compounds, benzoylhypaconine (BHA), pseudoephedrine hydrochloride (PSE), glycyrrhetnic acid (GA), isoliquiritigenin (ISL), quercetin (QUER) and kaempferol (KAE) were found to inhibit both inflammation and angiogenesis in vitro.

CONCLUSION

FSGT capsule ameliorates RA in CIA mice by reducing inflammation, abrogating angiogenesis and relieving pain. Some compounds in FSGT, including BHA, GA, PSE, ISL, QUER and KAE, reduced both inflammation and angiogenesis in vitro, which suggests that those compounds may contribute to the FSGT capsule-provided alleviation on RA.

MicroRNA-26b-5p alleviates murine collagen-induced arthritis by modulating Th17 cell plasticity

Rheumatoid arthritis (RA) is a chronic autoimmune disease, and the abnormal differentiation of IL-17-producing T helper (Th17) cells is an important factor in the pathogenesis. Previous studies have shown that microRNAs (miRNAs, miR) act as key regulators of Th17 cells. However, the effects of miRNAs on Th17 cell differentiation and plasticity in RA are not clear. In this study, not only low miR-26b-5p expression and high IL-17A level were observed in the peripheral blood of RA patients, but also the negative correlation between miR-26b-5p and IL-17A was explored. The changes in collagen-induced arthritis (CIA) mice were consistent with those in RA patients. The results of in vitro experiments showed that miR-26b-5p mainly inhibited the initial differentiation of Th17 cells but did not impact the differentiation of induced-Treg into Th17-like cells. Meanwhile, miR-26b-5p mimics treatment alleviated inflammatory responses and reduced Th17 proportion in CIA mice. These results indicated that miR-26b-5p could alleviate the development of mice CIA by inhibiting the excessive Th17 cells, and that miR-26b-5p could modulate the plasticity of Th17 cell differentiation in RA, mainly block the initial differentiation. This may provide a novel strategy for the clinical treatment of RA.

The complement system drives local inflammatory tissue priming by metabolic reprogramming of synovial fibroblasts

Arthritis typically involves recurrence and progressive worsening at specific predilection sites, but the checkpoints between remission and persistence remain unknown. Here, we defined the molecular and cellular mechanisms of this inflammation-mediated tissue priming. Re-exposure to inflammatory stimuli caused aggravated arthritis in rodent models. Tissue priming developed locally and independently of adaptive immunity. Repeatedly stimulated primed synovial fibroblasts (SFs) exhibited enhanced metabolic activity inducing functional changes with intensified migration, invasiveness and osteoclastogenesis. Meanwhile, human SF from patients with established arthritis displayed a similar primed phenotype. Transcriptomic and epigenomic analyses as well as genetic and pharmacological targeting demonstrated that inflammatory tissue priming relies on intracellular complement C3- and C3a receptor-activation and downstream mammalian target of rapamycin- and hypoxia-inducible factor 1α-mediated metabolic SF invigoration that prevents activation-induced senescence, enhances NLRP3 inflammasome activity, and in consequence sensitizes tissue for inflammation. Our study suggests possibilities for therapeutic intervention abrogating tissue priming without immunosuppression.

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.

The pre-clinical phase of rheumatoid arthritis: From risk factors to prevention of arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease considered as a multistep process spanning from the interaction of genetic (e.g., shared epitope or non-HLA loci), environmental and behavioral risk factors (e.g., smoking) leading to breaking immune tolerance and autoimmune processes such as the production of autoantibodies (e.g., antibodies against citrullinated proteins ACPA or rheumatoid factors, RF), development of the first symptoms without clinical arthritis, and, finally, the manifestation of arthritis. Despite the typical joint involvement in established RA, the pathogenesis of the disease likely begins far from joint structures: in the lungs or periodontium in association with citrullination, intestinal microbiome, or adipose tissue, which supports normal findings in synovial tissue in ACPA+ patients with arthralgia. The presence of ACPA is detectable even years before the first manifestation of RA. The pre-clinical phase of RA is the period preceding clinically apparent RA with ACPA contributing to the symptoms without subclinical inflammation. While the combination of ACPA and RF increases the risk of progression to RA by up to 10 times, increasing numbers of novel autoantibodies are to be investigated to contribute to the increased risk and pathogenesis of RA. With growing knowledge about the course of RA, new aspiration emerges to cure and even prevent RA, shifting the "window of opportunity" to the pre-clinical phases of RA. The clinical definition of individuals at risk of developing RA (clinically suspect arthralgia, CSA) makes it possible to unify these at-risk individuals' clinical characteristics for "preventive" treatment in ongoing clinical trials using mostly biological or conventional synthetic disease-modifying drugs. However, the combination of symptoms, laboratory, and imaging biomarkers may be the best approach to select the correct target at-risk population. The current review aims to explore different phases of RA and discuss the potential of (non)pharmacological intervention aiming to prevent RA.

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.

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.

The Role of Dietary Phenolic Compounds in Epigenetic Modulation Involved in Inflammatory Processes

A better understanding of the interactions between dietary phenolic compounds and the epigenetics of inflammation may impact pathological conditions and their treatment. Phenolic compounds are well-known for their antioxidant, anti-inflammatory, anti-angiogenic, and anti-cancer properties, with potential benefits in the treatment of various human diseases. Emerging studies bring evidence that nutrition may play an essential role in immune system modulation also by altering gene expression. This review discusses epigenetic mechanisms such as DNA methylation, post-translational histone modification, and non-coding microRNA activity that regulate the gene expression of molecules involved in inflammatory processes. Special attention is paid to the molecular basis of NF-κB modulation by dietary phenolic compounds. The regulation of histone acetyltransferase and histone deacetylase activity, which all influence NF-κB signaling, seems to be a crucial mechanism of the epigenetic control of inflammation by phenolic compounds. Moreover, chronic inflammatory processes are reported to be closely connected to the major stages of carcinogenesis and other non-communicable diseases. Therefore, dietary phenolic compounds-targeted epigenetics is becoming an attractive approach for disease prevention and intervention.

Hsa_circ_0088036 promotes the proliferation and migration of fibroblast-like synoviocytes by sponging miR-140-3p and upregulating SIRT 1 expression in rheumatoid arthritis

Circular RNAs (circRNAs) have been demonstrated to play crucial roles in the development and progression of various types of cancers by serving as microRNA sponges to regulate the expression of target genes. Although in-depth studies of circRNAs have been conducted, their functional and pathological significance in autoimmune diseases, including rheumatoid arthritis (RA), remains unclear. Our previous study verified that hsa_circ_0088036 (circ0088036) is significantly elevated in peripheral blood mononuclear cells from patients with RA. The present study aimed to explore the roles of circ0088036 in the pathogenesis of RA. The circ0088036/miR-140-3p/silent information regulator 1 (SIRT 1) axis was predicted by bioinformatics tools. Circ0088036 was found to be aberrantly upregulated in fibroblast-like synoviocytes (FLSs) in RA compared with FLSs in osteoarthritis (OA). Functionally, upregulated circ0088036 promoted the proliferation and migration of RA-FLSs. Mechanistically, circ0088036 acted as a miR-140-3p sponge to upregulate SIRT 1 expression, subsequently promoting RA progression. In conclusion, this study revealed that circ0088036 may play an essential role in promoting synovial pathogenesis via the circ0088036/miR-140-3p/SIRT 1 axis in RA, providing new insight into circRNAs during RA progression.

Update on the Pathomechanism, Diagnosis, and Treatment Options for Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that involves multiple joints bilaterally. It is characterized by an inflammation of the tendon (tenosynovitis) resulting in both cartilage destruction and bone erosion. While until the 1990s RA frequently resulted in disability, inability to work, and increased mortality, newer treatment options have made RA a manageable disease. Here, great progress has been made in the development of disease-modifying anti-rheumatic drugs (DMARDs) which target inflammation and thereby prevent further joint damage. The available DMARDs are subdivided into (1) conventional synthetic DMARDs (methotrexate, hydrochloroquine, and sulfadiazine), (2) targeted synthetic DMARDs (pan-JAK- and JAK1/2-inhibitors), and (3) biologic DMARDs (tumor necrosis factor (TNF)-α inhibitors, TNF-receptor (R) inhibitors, IL-6 inhibitors, IL-6R inhibitors, B cell depleting antibodies, and inhibitors of co-stimulatory molecules). While DMARDs have repeatedly demonstrated the potential to greatly improve disease symptoms and prevent disease progression in RA patients, they are associated with considerable side-effects and high financial costs. This review summarizes our current understanding of the underlying pathomechanism, diagnosis of RA, as well as the mode of action, clinical benefits, and side-effects of the currently available DMARDs.

Rheumatoid Arthritis Patients, Both Newly Diagnosed and Methotrexate Treated, Show More DNA Methylation Differences in CD4+ Memory Than in CD4+ Naïve T Cells

Background: Differences in DNA methylation have been reported in B and T lymphocyte populations, including CD4⁺ T cells, isolated from rheumatoid arthritis (RA) patients when compared to healthy controls. CD4⁺ T cells are a heterogeneous cell type with subpopulations displaying distinct DNA methylation patterns. In this study, we investigated DNA methylation using reduced representation bisulfite sequencing in two CD4⁺ T cell populations (CD4⁺ memory and naïve cells) in three groups: newly diagnosed, disease modifying antirheumatic drugs (DMARD) naïve RA patients (N = 11), methotrexate (MTX) treated RA patients (N = 18), and healthy controls (N = 9) matched for age, gender and smoking status.

Results: Analyses of these data revealed significantly more differentially methylated positions (DMPs) in CD4⁺ memory than in CD4⁺ naïve T cells (904 vs. 19 DMPs) in RA patients compared to controls. The majority of DMPs (72%) identified in newly diagnosed and DMARD naïve RA patients with active disease showed increased DNA methylation (39 DMPs), whereas most DMPs (80%) identified in the MTX treated RA patients in remission displayed decreased DNA methylation (694 DMPs). Interestingly, we also found that about one third of the 101 known RA risk loci overlapped (±500 kb) with the DMPs. Notably, introns of the UBASH3A gene harbor both the lead RA risk SNP and two DMPs in CD4⁺ memory T cells.

Conclusion: Our results suggest that RA associated DNA methylation differences vary between the two T cell subsets, but are also influenced by RA characteristics such as disease activity, disease duration and/or MTX treatment.

Epigenetics in rheumatoid arthritis; fibroblast-like synoviocytes as an emerging paradigm in the pathogenesis of the disease

Rheumatoid arthritis (RA) is characterized by immune dysfunctions and chronic inflammation that mainly affects diarthrodial joints. Genetics has long been surveyed in searching for the etiopathogenesis of the disease and partially clarified the conundrums within this context. Epigenetic alterations, such as DNA methylation, histone modifications, and noncoding RNAs, which have been considered to be involved in RA pathogenesis, likely explain the nongenetic risk factors. Epigenetic modifications may influence RA through fibroblast-like synoviocytes (FLSs). It has been shown that FLSs play an essential role in the onset and exacerbation of RA, and therefore, they may illustrate some aspects of RA pathogenesis. These cells exhibit a unique DNA methylation profile in the early stage of the disease that changes with disease progression. Histone acetylation profile in RA FLSs is disrupted through the imbalance of histone acetyltransferases and histone deacetylase activity. Furthermore, dysregulation of microRNAs (miRNAs) is immense. Most of these miRNAs have shown an aberrant expression in FLSs that are involved in proliferation and cytokine production. Besides, dysregulation of long noncoding RNAs in FLSs has been revealed and attributed to RA pathogenesis. Further investigations are needed to get a better view of epigenetic alterations and their interactions. We also discuss the role of these epigenetic alterations in RA pathogenesis and their therapeutic potential.

EZH2 deficiency attenuates Treg differentiation in rheumatoid arthritis

The chromatin modifier enhancer of zeste homolog 2 (EZH2) methylates lysine 27 of histone H3 (H3K27) and regulates T cell differentiation. However, the potential role of EZH2 in the pathogenesis of rheumatoid arthritis (RA) remains elusive. We analyzed EZH2 expression in PBMC, CD4⁺ T cells, CD19⁺ B cell, and CD14⁺ monocytes from active treatment-naïve RA patients and healthy controls (HC). We also suppressed EZH2 expression using EZH2 inhibitor GSK126 and measured CD4⁺ T cell differentiation, proliferation and apoptosis. We further examined TGFβ-SMAD and RUNX1 signaling pathways in EZH2-suppressed CD4⁺ T cells. Finally, we explored the regulation mechanism of EZH2 by RA synovial fluid and fibroblast-like synoviocyte (FLS) by neutralizing key proinflammatory cytokines. EZH2 expression is lower in PBMC and CD4⁺ T cells from RA patients than those from HC. EZH2 inhibition suppressed regulatory T cells (Tregs) differentiation and FOXP3 transcription, and downregulated RUNX1 and upregulated SMAD7 expression in CD4⁺ T cells. RA synovial fluid and fibroblast-like synoviocytes suppressed EZH2 expression in CD4⁺ T cells, which was partially neutralized by anti-IL17 antibody. Taken together, EZH2 in CD4⁺ T cells from RA patients was attenuated, which suppressed FOXP3 transcription through downregulating RUNX1 and upregulating SMAD7 in CD4⁺ T cells, and ultimately suppressed Tregs differentiation. IL17 in RA synovial fluid might promote downregulation of EZH2 in CD4⁺ T cells. Defective EZH2 in CD4⁺ T cells might contribute to Treg deficiency in RA.

Effects of Treatment with the Hypomethylating Agent 5-aza-2'-deoxycytidine in Murine Type II Collagen-Induced Arthritis

The emerging role of epigenetics in the pathogenesis of autoimmune diseases has recently attracted much interest on the possible use of epigenetic modulators for the prevention and treatment of these diseases. In particular, we and others have shown that drugs that inhibit DNA methylation, such as azacitidine (AZA) and decitabine (DAC), already used for the treatment of acute myeloid leukemia, exert powerful beneficial effects in rodent models of type 1 diabetes, multiple sclerosis, and Guillain Barrè syndrome. Along this line of research, we have presently studied the effects of DAC in a murine model of rheumatoid arthritis induced by type II collagen and have demonstrated that DAC administration was associated with a significant amelioration of the clinical condition, along with in vivo and ex vivo modification of the immunological profile of the so-treated mice, that exhibited a diminished production of Th1 and Th17 pro-inflammatory cytokines and reduction of anti-type II collagen autoantibodies.

Whole Blood Targeted Bisulfite Sequencing and Differential Methylation in the C6ORF10 Gene of Patients with Rheumatoid Arthritis

Objective.

Polymorphisms in human major histocompatibility complex (MHC) are the strongest genetic associations with rheumatoid arthritis (RA). Epigenome-wide methylation studies suggest DNA methylation changes within MHC may contribute to disease susceptibility. We profiled MHC-specific methylated CpG (5′–C–phosphate–G–3′) in autoantibody-positive patients with RA and matched unaffected anticitrullinated protein antibodies–negative first-degree relatives (ACPA−/FDR) from an indigenous North American (INA) population that is known to have prevalent RA.

Methods.

DNA was isolated from whole blood and targeted bisulfite sequencing was used to profile methylated CpG in patients with RA and ACPA−/FDR. Differentially methylated CpG loci (DML) were mapped and gene annotated. Ingenuity pathway analysis (IPA) was used for curating biomolecular networks of mapped genes. Transcript abundance was determined by quantitative (q)PCR.

Results.

We identified 74 uniquely methylated CpG sites within the MHC region that were differentially methylated in patients with RA (p < 0.05), compared to ACPA−/FDR. Of these, 32 DML were located on 22 genes. IPA showed these genes are involved in regulating the nuclear factor–κB complex and processes involved in antigen presentation, and immune cell crosstalk in autoimmunity. Pearson correlation analysis demonstrated a negative association between differentially methylated CpG in the C6ORF10 gene and risk factors associated with RA. Analysis by qPCR confirmed differential abundance of C6ORF10, TNXB, and HCG18 mRNA in patients with RA compared to ACPA−/FDR.

Conclusion.

Our results confirm the presence of differential methylation at specific gene loci within the MHC region of INA patients with RA. These epigenetic signatures may precede disease onset, or alternatively, may be a result of developing RA.

MicroRNAs in rheumatoid arthritis: From pathogenesis to clinical impact

Over the last decade, many epigenetic mechanisms that contribute in the pathogenesis of autoimmune disorders have been revealed. MicroRNAs (miRNAs) are small, non-coding, RNA molecules that bind to messenger RNAs and disrupt the transcription of target genes. Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease in which a plethora of epigenetic changes take place. Current research on RA epigenetics has focused mainly on miRNAs. Genetic variance of some miRNA genes, especially miR-499, might predispose an individual to RA development. Additionally, altered expression of many miRNAs has been discovered in several cells, tissues and body fluids in patients with RA. MiRNAs expression also differs depending on disease's stage and activity. Serum miR-22 and miR-103a might predict RA development in susceptible individuals (pre-RA), while serum miR-16, miR-24, miR-125a and miR-223 levels are altered in early RA (disease duration <12 months) patients compared to established RA or healthy individuals. Moreover, serum miR-223 levels have been associated with RA activity and disease relapse. What is more, serum levels of several miRNAs, including miR-125b and miR-223, could be used to predict response to RA treatment. Finally, miRNA analogs or antagonists have been used as therapeutic regimens in experimental arthritis models and have demonstrated promising results. In conclusion, the research on the miRNA alterations in RA sheds light to several aspects of RA pathogenesis, introduces new biomarkers for RA diagnosis and treatment response prediction and offers the opportunity to discover new, targeted drugs for patients with RA.

[Rheumatoid arthritis]

Rheumatoid arthritis (RA) is a chronic and progressive systemic disease of the connective tissue, which is particularly manifested with destructive alterations to the joints. Inflammatory reactions in the synovium lead to the influx of peripheral inflammatory cells as well as the activation of local cells. Released growth factors, chemokines and especially cytokines play a key role in chronic inflammatory responses. In addition to the central lymphocytes, the T and B cells and their subpopulations, locally resident cells, such as neutrophils, macrophages and fibroblasts as well as cells of bone metabolism are activated by the inflammatory milieu and contribute to and drive inflammation and tissue damage. The destruction of cartilage and bone substance by local tissue cells, synovial fibroblasts and osteoclasts is characteristic for this disease. Untreated, the local inflammatory and destructive processes as well as systemic inflammatory factors lead to progressive and irreversible joint destruction. Cellular and immunological processes in RA are closely interwoven; therefore, besides the general inhibition of immunological processes, specific inhibition of central key molecules can reduce or completely stop the inflammatory destructive processes; however, a high heterogeneity can be observed among RA patients and disease progression. Therefore, an expansion of the therapeutic options is desirable as not all patients are able to equally benefit from the therapeutic treatment. It is important to characterize new molecular mechanisms, which could lead to the development of new therapeutic options. Some of the more recent insights are summarized in this overview.

Pathogenic stromal cells as therapeutic targets in joint inflammation

Knowledge of how the joint functions as an integrated unit in health and disease requires an understanding of the stromal cells populating the joint mesenchyme, including fibroblasts, tissue-resident macrophages and endothelial cells. Knowledge of the physiological and pathological mechanisms that involve joint mesenchymal stromal cells has begun to cast new light on why joint inflammation persists. The shared embryological origins of fibroblasts and endothelial cells might shape the behaviour of these cell types in diseased adult tissues. Cells of mesenchymal origin sustain inflammation in the synovial membrane and tendons by various mechanisms, and the important contribution of newly discovered fibroblast subtypes and their associated crosstalk with endothelial cells, tissue-resident macrophages and leukocytes is beginning to emerge. Knowledge of these mechanisms should help to shape the future therapeutic landscape and emphasizes the requirement for new strategies to address the pathogenic stroma and associated crosstalk between leukocytes and cells of mesenchymal origin.

Synovial tissue biopsy analysis: unlocking the hidden secrets to personalised medicine?

Rheumatoid arthritis is an immune-mediated inflammatory disease of the synovium. Yet we still lack robust tissue-specific (synovial) biomarkers that are able to guide clinical decisions and stratify patients according to their disease subgroup and predicted response to treatment. The EULAR Synovitis Study Group and the OMERACT synovial tissue biopsy (STB) Special Interests Group have undertaken a consensus exercise to identify factors that are important for the standardisation of STB handling and analytical procedures in two situations—clinical practice and translational research.

Regulation of neutrophil pro-inflammatory functions sheds new light on the pathogenesis of rheumatoid arthritis

For more than two centuries now, rheumatoid arthritis (RA) is under investigation intending to discover successful treatment. Despite decades of scientific advances, RA is still representing a challenge for contemporary medicine. Current drug therapies allow to improve significantly the quality of life of RA patients; however, they are still insufficient to reverse tissue injury and are often generating side-effects. The difficulty arises from the considerable fluctuation of the clinical course of RA among patients, making the predictive prognosis difficult. More and more studies underline the profound influence of the neutrophil multifaceted functions in the pathogenesis of RA. This renewed interest in the complexity of neutrophil functions in RA offers new exciting opportunities for valuable therapeutic targets as well as for safe and well-tolerated RA treatments. In this review, we aim to update the recent findings on the multiple facets of neutrophils in RA, in particular their impact in promoting the RA-based inflammation through the release of the cytokine-like S100A8/A9 protein complex, as well as the importance of NETosis in the disease progression and development. Furthermore, we delve into the complex question of neutrophil heterogeneity and plasticity and discuss the emerging role of miRNAs and epigenetic markers influencing the inflammatory response of neutrophils in RA and how they could constitute the starting point for novel attractive targets in RA therapy.

Diagnosis and Management of Rheumatoid Arthritis: A Review

IMPORTANCE

Rheumatoid arthritis (RA) occurs in about 5 per 1000 people and can lead to severe joint damage and disability. Significant progress has been made over the past 2 decades regarding understanding of disease pathophysiology, optimal outcome measures, and effective treatment strategies, including the recognition of the importance of diagnosing and treating RA early.

OBSERVATIONS

Early diagnosis and treatment of RA can avert or substantially slow progression of joint damage in up to 90% of patients, thereby preventing irreversible disability. The development of novel instruments to measure disease activity and identify the presence or absence of remission have facilitated new treatment strategies to arrest RA before joints are damaged irreversibly. Outcomes have been improved by recognizing the benefits of early diagnosis and early therapy with disease-modifying antirheumatic drugs (DMARDs). The treatment target is remission or a state of at least low disease activity, which should be attained within 6 months. Methotrexate is first-line therapy and should be prescribed at an optimal dose of 25 mg weekly and in combination with glucocorticoids; 40% to 50% of patients reach remission or at least low disease activity with this regimen. If this treatment fails, sequential application of targeted therapies, such as biologic agents (eg, tumor necrosis factor [TNF] inhibitors) or Janus kinase inhibitors in combination with methotrexate, have allowed up to 75% of these patients to reach the treatment target over time. New therapies have been developed in response to new pathogenetic findings. The costs of some therapies are considerable, but these costs are decreasing with the advent of biosimilar drugs (drugs essentially identical to the original biologic drugs but usually available at lower cost).

CONCLUSIONS AND RELEVANCE

Scientific advances have improved therapies that prevent progression of irreversible joint damage in up to 90% of patients with RA. Early treatment with methotrexate plus glucocorticoids and subsequently with other DMARDs, such as inhibitors of TNF, IL-6, or Janus kinases, improves outcomes and prevents RA-related disability. A treat-to-target strategy aimed at reducing disease activity by at least 50% within 3 months and achieving remission or low disease activity within 6 months, with sequential drug treatment if needed, can prevent RA-related disability.

DICER1: A Key Player in Rheumatoid Arthritis, at the Crossroads of Cellular Stress, Innate Immunity, and Chronic Inflammation in Aging

Loss-of-function or knockout mouse models have established a fundamental role for the RNAse III enzyme DICER1 in development and tissue morphogenesis and/or homeostasis. These functions are currently assumed to result mainly from the DICER1-dependent biogenesis of microRNAs which exhibit important gene expression regulatory properties. However, non-canonical DICER1 functions have recently emerged. These include interaction with the DNA damage response (DDR) pathway and the processing of cytotoxic non-coding RNAs, suggesting that DICER1 might also participate in the regulation of major cellular processes through miRNA-independent mechanisms. Recent findings indicated that reduced Dicer1 expression, which correlates with worsened symptoms in mouse models of joint inflammation, is also noted in fibroblast-like synoviocytes (FLS) harvested from rheumatoid arthritis (RA) patients, as opposed to FLS cultured from biopsies of osteoarthritic patients. In addition, low DICER1 levels are associated with the establishment of cellular stress and its associated responses, such as cellular senescence. Senescent and/or stressed cells are associated with an inflammatory secretome (cytokines and chemokines), as well as with "find-me" and "eat-me" signals which will attract and activate the innate immune compartment (NK cells, macrophages, and neutrophils) to be eliminated. Failure of this immunosurveillance mechanism and improper restauration of homeostasis could lead to the establishment of a systemic and chronic inflammatory state. In this review, we suggest that reduced DICER1 expression contributes to a vicious cycle during which accumulating inflammation and premature senescence, combined to inadequate innate immunity responses, creates the appropriate conditions for the initiation and/or progression of autoimmune-autoinflammatory diseases, such as RA.

Identification of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome-associated DNA methylation patterns

BACKGROUND

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex condition involving multiple organ systems and characterized by persistent/relapsing debilitating fatigue, immune dysfunction, neurological problems, and other symptoms not curable for at least 6 months. Disruption of DNA methylation patterns has been tied to various immune and neurological diseases; however, its status in ME/CFS remains uncertain. Our study aimed at identifying changes in the DNA methylation patterns that associate with ME/CFS.

METHODS

We extracted genomic DNA from peripheral blood mononuclear cells from 13 ME/CFS study subjects and 12 healthy controls and measured global DNA methylation by ELISA-like method and site-specific methylation status using Illumina MethylationEPIC microarrays. Pyrosequencing validation included 33 ME/CFS cases and 31 controls from two geographically distant cohorts.

RESULTS

Global DNA methylation levels of ME/CFS cases were similar to those of controls. However, microarray-based approach allowed detection of 17,296 differentially methylated CpG sites in 6,368 genes across regulatory elements and within coding regions of genes. Analysis of DNA methylation in promoter regions revealed 307 differentially methylated promoters. Ingenuity pathway analysis indicated that genes associated with differentially methylated promoters participated in at least 15 different pathways mostly related to cell signaling with a strong immune component.

CONCLUSIONS

This is the first study that has explored genome-wide epigenetic changes associated with ME/CFS using the advanced Illumina MethylationEPIC microarrays covering about 850,000 CpG sites in two geographically distant cohorts of ME/CFS cases and matched controls. Our results are aligned with previous studies that indicate a dysregulation of the immune system in ME/CFS. They also suggest a potential role of epigenetic de-regulation in the pathobiology of ME/CFS. We propose screening of larger cohorts of ME/CFS cases to determine the external validity of these epigenetic changes in order to implement them as possible diagnostic markers in clinical setting.

TNF inhibits catecholamine production from induced sympathetic neuron-like cells in rheumatoid arthritis and osteoarthritis in vitro

Synovial adipose stem cells (sASC) can be differentiated into catecholamine-expressing sympathetic neuron-like cells to treat experimental arthritis. However, the pro-inflammatory tumor necrosis factor (TNF) is known to be toxic to catecholaminergic cells (see Parkinson disease), and this may prevent anti-inflammatory effects in inflamed tissue. We hypothesized that TNF exhibits inhibitory effects on human differentiated sympathetic tyrosine hydroxylase-positive (TH+) neuron-like cells. For the first time, iTH+ neuron-like sympathetic cells were generated from sACSs of rheumatoid arthritis (RA) and osteoarthritis (OA) synovial tissue. Compared to untreated controls in both OA and RA, TNF-treated iTH+ cells demonstrated a weaker staining of catecholaminergic markers in cell cultures of RA/OA patients, and the amount of produced noradrenaline was markedly lower. These effects were reversed by etanercept. Exposure of iTH+ cells to synovial fluid of RA patients showed similar inhibitory effects. In mixed synovial cells, significant effects of TNF on catecholamine release were observed only in OA. This study shows that TNF inhibits iTH+ synovial cells leading to the decrease of secreted noradrenaline. This might be a reason why discovered newly appearing TH+ cells in the synovium are not able to develop their possible full anti-inflammatory role in arthritis.

MicroRNA-155-at the Critical Interface of Innate and Adaptive Immunity in Arthritis

MicroRNAs (miRNAs) are small non-coding RNAs that fine-tune the cell response to a changing environment by modulating the cell transcriptome. miR-155 is a multifunctional miRNA enriched in cells of the immune system and is indispensable for the immune response. However, when deregulated, miR-155 contributes to the development of chronic inflammation, autoimmunity, cancer, and fibrosis. Herein, we review the evidence for the pathogenic role of miR-155 in driving aberrant activation of the immune system in rheumatoid arthritis, and its potential as a disease biomarker and therapeutic target.

Synovial fibroblasts in 2017

Stromal cells like synovial fibroblasts gained great interest over the years, since it has become clear that they strongly influence their environment and neighbouring cells. The current review describes the role of synovial fibroblasts as cells of the innate immune system and expands on their involvement in inflammation and cartilage destruction in rheumatoid arthritis (RA). Furthermore, epigenetic changes in RA synovial fibroblasts and studies that focused on the identification of different subsets of synovial fibroblasts are discussed.

Identification of a transitional fibroblast function in very early rheumatoid arthritis

OBJECTIVES

Synovial fibroblasts actively regulate the inflammatory infiltrate by communicating with neighbouring endothelial cells (EC). Surprisingly, little is known about how the development of rheumatoid arthritis (RA) alters these immunomodulatory properties. We examined the effects of phase of RA and disease outcome (resolving vs persistence) on fibroblast crosstalk with EC and regulation of lymphocyte recruitment.

METHODS

Fibroblasts were isolated from patients without synovitis, with resolving arthritis, very early RA (VeRA; symptom ≤12 weeks) and established RA undergoing joint replacement (JRep) surgery. Endothelial-fibroblast cocultures were formed on opposite sides of porous filters. Lymphocyte adhesion from flow, secretion of soluble mediators and interleukin 6 (IL-6) signalling were assessed.

RESULTS

Fibroblasts from non-inflamed and resolving arthritis were immunosuppressive, inhibiting lymphocyte recruitment to cytokine-treated endothelium. This effect was lost very early in the development of RA, such that fibroblasts no longer suppressed recruitment. Changes in IL-6 and transforming growth factor beta 1 (TGF-β₁) signalling appeared critical for the loss of the immunosuppressive phenotype. In the absence of exogenous cytokines, JRep, but not VeRA, fibroblasts activated endothelium to support lymphocyte.

CONCLUSIONS

In RA, fibroblasts undergo two distinct changes in function: first a loss of immunosuppressive responses early in disease development, followed by the later acquisition of a stimulatory phenotype. Fibroblasts exhibit a transitional functional phenotype during the first 3 months of symptoms that contributes to the accumulation of persistent infiltrates. Finally, the role of IL-6 and TGF-β₁ changes from immunosuppressive in resolving arthritis to stimulatory very early in the development of RA. Early interventions targeting 'pathogenic' fibroblasts may be required in order to restore protective regulatory processes.