Epigenetic control in rheumatoid arthritis synovial fibroblasts

Involvement of Epithelial-Mesenchymal Transition (EMT) in Autoimmune Diseases

Epithelial-mesenchymal transition (EMT) is a complex reversible biological process characterized by the loss of epithelial features and the acquisition of mesenchymal features. EMT was initially described in developmental processes and was further associated with pathological conditions including metastatic cascade arising in neoplastic progression and organ fibrosis. Fibrosis is delineated by an excessive number of myofibroblasts, resulting in exuberant production of extracellular matrix (ECM) proteins, thereby compromising organ function and ultimately leading to its failure. It is now well acknowledged that a significant number of myofibroblasts result from the conversion of epithelial cells via EMT. Over the past two decades, evidence has accrued linking fibrosis to many chronic autoimmune and inflammatory diseases, including systemic sclerosis (SSc), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), and inflammatory bowel diseases (IBD). In addition, chronic inflammatory states observed in most autoimmune and inflammatory diseases can act as a potent trigger of EMT, leading to the development of a pathological fibrotic state. In the present review, we aim to describe the current state of knowledge regarding the contribution of EMT to the pathophysiological processes of various rheumatic conditions.

Quantitative investigation of the effects of DNA modifications and protein mutations on MeCP2-MBD-DNA interactions

DNA methylation as an important epigenetic marker, has gained attention for the significance of three oxidative modifications (hydroxymethyl-C (hmC), formyl-C (fC), and carboxyl-C (caC)). Mutations occurring in the methyl-CpG-binding domain (MBD) of MeCP2 result in Rett. However, uncertainties persist regarding DNA modification and MBD mutation-induced interaction changes. Here, molecular dynamics simulations were used to investigate the underlying mechanisms behind changes due to different modifications of DNA and MBD mutations. Alanine scanning combined with the interaction entropy method was employed to accurately evaluate the binding free energy. The results show that MBD has the strongest binding ability for mCDNA, followed by caC, hmC, and fCDNA, with the weakest binding ability observed for CDNA. Further analysis revealed that mC modification induces DNA bending, causing residues R91 and R162 closer to the DNA. This proximity enhances van der Waals and electrostatic interactions. Conversely, the caC/hmC and fC modifications lead to two loop regions (near K112 and K130) closer to DNA, respectively. Furthermore, DNA modifications promote the formation of stable hydrogen bond networks, however mutations in the MBD significantly reduce the binding free energy. This study provides detailed insight into the effects of DNA modifications and MBD mutations on binding ability. It emphasizes the necessity for research and development of targeted Rett compounds that induce conformational compatibility between MBD and DNA, enhancing the stability and strength of their interactions.

Saliva microRNA Profile in Children with and without Severe SARS-CoV-2 Infection

Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) may impair immune modulating host microRNAs, causing severe disease. Our objectives were to determine the salivary miRNA profile in children with SARS-CoV-2 infection at presentation and compare the expression in those with and without severe outcomes. Children <18 years with SARS-CoV-2 infection evaluated at two hospitals between March 2021 and February 2022 were prospectively enrolled. Severe outcomes included respiratory failure, shock or death. Saliva microRNAs were quantified with RNA sequencing. Data on 197 infected children (severe = 45) were analyzed. Of the known human miRNAs, 1606 (60%) were measured and compared across saliva samples. There were 43 miRNAs with ≥2-fold difference between severe and non-severe cases (adjusted p-value < 0.05). The majority (31/43) were downregulated in severe cases. The largest between-group differences involved miR-4495, miR-296-5p, miR-548ao-3p and miR-1273c. These microRNAs displayed enrichment for 32 gene ontology pathways including viral processing and transforming growth factor beta and Fc-gamma receptor signaling. In conclusion, salivary miRNA levels are perturbed in children with severe COVID-19, with the majority of miRNAs being down regulated. Further studies are required to validate and determine the utility of salivary miRNAs as biomarkers of severe COVID-19.

Characterizing crosstalk in epigenetic signaling to understand disease physiology

Epigenetics, the inheritance of genomic information independent of DNA sequence, controls the interpretation of extracellular and intracellular signals in cell homeostasis, proliferation and differentiation. On the chromatin level, signal transduction leads to changes in epigenetic marks, such as histone post-translational modifications (PTMs), DNA methylation and chromatin accessibility to regulate gene expression. Crosstalk between different epigenetic mechanisms, such as that between histone PTMs and DNA methylation, leads to an intricate network of chromatin-binding proteins where pre-existing epigenetic marks promote or inhibit the writing of new marks. The recent technical advances in mass spectrometry (MS) -based proteomic methods and in genome-wide DNA sequencing approaches have broadened our understanding of epigenetic networks greatly. However, further development and wider application of these methods is vital in developing treatments for disorders and pathologies that are driven by epigenetic dysregulation.

Advances in experimental models of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by persistent articular inflammation and joint damage. RA was first described over 200 years ago; however, its etiology and pathophysiology remain insufficiently understood. The current treatment of RA is mainly empirical or based on the current understanding of etiology with limited efficacy and/or substantial side effects. Thus, the development of safer and more potent therapeutics, validated and optimized in experimental models, is urgently required. To improve the transition from bench to bedside, researchers must carefully select the appropriate experimental models as well as draw the right conclusions. Here, we summarize the establishment, pathological features, potential mechanisms, advantages, and limitations of the currently available RA models. The aim of the review is to help researchers better understand available RA models; discuss future trends in RA model development, which can help highlight new translational and human-based avenues in RA research.

The Role of Podoplanin in the Immune System and Inflammation

Podoplanin is a small cell-surface mucin-like glycoprotein that participates in multiple physiological and pathological processes. Podoplanin exerts an important function in the immune response and is upregulated in fibroblasts, macrophages, T helper cells, and epithelial cells during inflammation. Herein, we summarize the latest knowledge on the functional expression of podoplanin in the immune system and review the contribution of podoplanin to several inflammatory diseases. Furthermore, we discuss podoplanin as a novel therapeutic target for various inflammatory diseases.

Sp1 S-Sulfhydration Induced by Hydrogen Sulfide Inhibits Inflammation via HDAC6/MyD88/NF-κB Signaling Pathway in Adjuvant-Induced Arthritis

Histone deacetylase 6 (HDAC6) acts as a regulator of the nuclear factor kappa-B (NF-κB) signaling pathway by deacetylating the non-histone protein myeloid differentiation primary response 88 (MyD88) at lysine residues, which is an adapter protein for the Toll-like receptor (TLR) and interleukin (IL)-1β receptor. Over-activated immune responses, induced by infiltrated immune cells, excessively trigger the NF-κB signaling pathway in other effector cells and contribute to the development of rheumatoid arthritis (RA). It has also been reported that HDAC6 can promote the activation of the NF-κB signaling pathway. In the present study, we showed that HDAC6 protein level was increased in the synovium tissues of adjuvant-induced arthritis rats. In addition, hydrogen sulfide (H₂S) donor S-propargyl-cysteine (SPRC) can inhibit HDAC6 expression and alleviate inflammatory response in vivo. In vitro study revealed that HDAC6 overexpression activated the NF-κB signaling pathway by deacetylating MyD88. Meanwhile, sodium hydrosulfide (NaHS) or HDAC6 inhibitor tubastatin A (tubA) suppressed the pro-inflammatory function of HDAC6. Furthermore, the reduced expression of HDAC6 appeared to result from transcriptional inhibition by S-sulfhydrating specificity protein 1 (Sp1), which is a transcription factor of HDAC6. Our results demonstrate that Sp1 can regulate HDAC6 expression, and S-sulfhydration of Sp1 by antioxidant molecular H₂S ameliorates RA progression via the HDAC6/MyD88/NF-κB signaling pathway.

YAP/TAZ: Key Players for Rheumatoid Arthritis Severity by Driving Fibroblast Like Synoviocytes Phenotype and Fibro-Inflammatory Response

Objective

The role of YAP/TAZ, two transcriptional co-activators involved in several cancers, was investigated in rheumatoid arthritis (RA).

Methods

Fibroblast like synoviocytes (FLS) from patients with RA or osteoarthritis were cultured in 2D or into 3D synovial organoids. Arthritis rat model (n=28) and colitis mouse model (n=21) were used. YAP/TAZ transcriptional activity was inhibited by verteporfin (VP). Multiple techniques were used to assess gene and/or protein expression and/or localization, cell phenotype (invasion, proliferation, apoptosis), bone erosion, and synovial stiffness.

Results

YAP/TAZ were transcriptionally active in arthritis (19-fold increase for CTGF expression, a YAP target gene, in RA vs. OA organoids; p<0.05). Stiff support of culture or pro-inflammatory cytokines further enhanced YAP/TAZ transcriptional activity in RA FLS. Inhibiting YAP/TAZ transcriptional activity with VP restored a common phenotype in RA FLS with a decrease in apoptosis resistance, proliferation, invasion, and inflammatory response. Consequently, VP blunted hyperplasic lining layer formation in RA synovial organoids. In vivo, VP treatment strongly reduced arthritis severity (mean arthritic index at 3.1 in arthritic group vs. 2.0 in VP treated group; p<0.01) by restoring synovial homeostasis and decreasing systemic inflammation. YAP/TAZ transcriptional activity also enhanced synovial membrane stiffening in vivo, thus creating a vicious loop with the maintenance of YAP/TAZ activation over time in FLS. YAP/TAZ inhibition was also effective in another inflammatory model of mouse colitis.

Conclusion

Our work reveals that YAP/TAZ were critical factors during arthritis. Thus, their transcriptional inhibition could be relevant to treat inflammatory related diseases.

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.

Penta-acetyl Geniposide Suppresses Migration, Invasion, and Inflammation of TNF-α-Stimulated Rheumatoid Arthritis Fibroblast-Like Synoviocytes Involving Wnt/β-Catenin Signaling Pathway

We previously reported that penta-acetyl geniposide ((Ac)5GP, an active derivative of geniposide) showed anti-arthritic effect on adjuvant-induced arthritis (AIA) rats by promoting the apoptosis of AIA fibroblast-like synoviocyte (FLS). This study aimed to demonstrate the effects of (Ac)5GP on migration, invasion, and inflammation of TNF-α-stimulated rheumatoid arthritis (RA) FLS (MH7A cell) and to explore the involved mechanisms. MTT assay was used to determine the applied non-cytotoxic doses of (Ac)5GP (12.5, 25, 50 μM) in vitro. Results of wound-healing, transwell, and phalloidin staining assays indicated that (Ac)5GP reduced the migration, invasion, and F-actin cytoskeletal reorganization of TNF-α-stimulated MH7A. Results of ELISA and western blot assays confirmed that (Ac)5GP reduced TNF-α-induced production of pro-inflammatory cytokines (like IL-1β, IL-6, IL-8) and matrix metalloproteinases (MMPs, such as MMP-2 and MMP-9). Moreover, (Ac)5GP inhibited TNF-α-induced activation of Wnt/β-catenin pathway, evidenced by reducing the protein levels of Wnt1, p-GSK-3β (Ser9), and β-catenin and preventing β-catenin nuclear translocation. Importantly, the combination of XAV939 (an inhibitor of Wnt/β-catenin) promoted the actions of (Ac)5GP on TNF-α-induced migration, invasion, and inflammation, further revealing the involvement of Wnt/β-catenin pathway underlying the therapeutic effects of (Ac)5GP on TNF-α-stimulated MH7A. In vivo, (Ac)5GP relieved the progression and severity of rat collagen-induced arthritis, related to reducing the levels of IL-1β, IL-6, IL-8, MMP-2, and MMP-9 as well as inhibiting Wnt/β-catenin pathway in synovial tissues. Collectively, (Ac)5GP could suppress TNF-α-induced migration, invasion, and inflammation in RA FLS involving Wnt/β-catenin pathway and (Ac)5GP might be as a candidate agent for RA treatment.

Nanotechnology as a promising platform for rheumatoid arthritis management: Diagnosis, treatment, and treatment monitoring

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that develops in about 5 per 1000 people. Over the past years, substantial progresses in knowledge of the disease's pathophysiology, effective diagnosis methods, early detection, and efficient treatment strategies have been made. Notably, nanotechnology has emerged as a game-changer in the efficacious management of many diseases, especially for RA. Joint replacement, photothermal therapy (PTT), photodynamic therapy (PDT), RA diagnosis, and treatment monitoring are nano-based avenues in RA management. Here, we present a brief overview of the pathogenesis of RA, risk factors, conventional diagnostic methods and treatment approaches, and then discuss the role of nanomedicine in RA diagnosis, treatment, and treatment monitoring with an emphasis on functional characteristics distinctive from other RA therapeutics.

Network Pharmacology-Based Analysis on the Curative Effect of Kunxian Capsules against Rheumatoid Arthritis

Kunxian capsules (KCs), a Chinese patent medicine, have been clinically proven to be effective in the treatment of rheumatoid arthritis (RA). However, the chemical profile of KC remains to be characterized, and the mechanism underlying the protective effect against RA is yet to be elucidated. Here, a network pharmacology-based approach was adopted, integrated with the chemical profiling of KC by UHPLC-Q-TOF/MS. As a result, a total of 67 compounds have been identified from KC extract, among which 43 were authenticated by comparison to the mass spectrum of standard chemicals. ADME behaviors of the chemical constituents of KC were predicted, resulting in 35 putative active ingredients. Through target prediction of both active ingredients of KC and RA and PPI analysis, core targets were screened out, followed by biological process and related pathway enrichment. Then, a TCM-herb-ingredient-target-pathway network was constructed and a multicomponent, multitarget, and multipathway synergistic mechanism was proposed, providing an information basis for further investigation. The active pharmaceutical ingredients included mainly terpenoids (such as triptolide and celastrol), sesquiterpene pyridines (such as wilforgine and wilforine), and flavonoids (such as icariin, epimedin A, B, and C, and 2″-O-rhamnosylicariside II).

Upregulating miR-27a-3p inhibits cell proliferation and inflammation of rheumatoid arthritis synovial fibroblasts through targeting toll-like receptor 5

Rheumatoid arthritis (RA) is a serious chronic inflammatory disease and synovial fibroblasts (SFs) serve a vital role in the pathogenesis and progression of RA. Current studies have demonstrated that dysregulation of microRNAs is involved in RA etiopathogenesis. The present study aimed to investigate the role of microRNA (miR)-27a-3p in RASFs, as well as its molecular mechanism. RASFs were isolated from synovial tissues from patients with RA. Expression of miR-27a-3p and toll-like receptor 5 (TLR5) was detected using reverse transcription-quantitative polymerase chain reaction and western blotting. Cell proliferation, apoptosis and inflammatory response were measured with MTT assay, flow cytometry and ELISA kits, respectively. The target binding between miR-27a-3p and TLR5 was predicted on DIANA TOOLS software, and confirmed by dual-luciferase reporter assay and Biotin-coupled miRNA pull-down assay. Expression of miR-27a-3p was downregulated and TLR5 was upregulated in synovial tissues and RASFs isolated from patients with RA. Functionally, upregulating miR-27a-3p may promote the apoptosis rate of RASFs and suppress cell proliferation and secretions of interleukin (IL)-1β, IL-6 and tumor necrosis factor-α. TLR5 was validated as a downstream target for miR-27a-3p in RASFs, and its expression was negatively regulated by miR-27a-3p. Silencing TLR5 in RASFs may exert similar effects to miR-27a-3p-overexpression; whereas, restoring TLR5 counteracted the suppression of miR-27a-3p-overexpression on RASF proliferation and inflammation, as well as the promotion on apoptosis. miR-27a-3p upregulation may suppress RA progression by inhibiting RASFs proliferation and inflammation through targeting TLR5.

Fibroblast-like Synoviocytes-derived Exosomal PCGEM1 Accelerates IL-1β-induced Apoptosis and Cartilage Matrix Degradation by miR-142-5p/RUNX2 in Chondrocytes

Background: Long non-coding RNA (lncRNA) prostate cancer gene expression marker 1 (PCGEM1) has been revealed to participate in the pathogenesis of osteoarthritis (OA). However, the molecular mechanism of PCGEM1 regulating OA progression has not been fully elucidated.Methods: Fibroblast-like synoviocytes (FLSs) were isolated from synovium tissues of OA patients (OA-FLSs) and trauma donors (Normal-FLSs). The size and morphology of the isolated exosomes were analyzed by transmission electron microscopy and nanoparticle tracking analysis. Protein levels were analyzed by western blotting. Expression levels of PCGEM1, microRNA-142-5p (miR-142-5p), runt-related transcription factor 2 (RUNX2) mRNA, and OA related genes were assessed by qRT-PCR. Cell proliferation, viability, and apoptosis were evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide or flow cytometry assays. The relationship between miR-142-5p and PCGEM1 or RUNX2 was verified by dual-luciferase reporter and/or RNA pull down assays.Results: PCGEM1 was overexpressed in OA cartilages and exosomes from OA-FLSs. Exosomal PCGEM1 from OA-FLSs facilitated IL-1β-induced apoptosis and cartilage matrix degradation in chondrocytes. MiR-142-5p was downregulated while RUNX2 was upregulated in OA cartilages. Exosomal PCGEM1 from OA-FLSs regulated RUNX2 expression by sponging miR-142-5p in IL-1β-induced chondrocytes. MiR-142-5p inhibitor offset exosomal PCGEM1 knockdown-mediated effects on the apoptosis and cartilage matrix degradation of IL-1β-induced chondrocytes. RUNX2 overexpression counteracted the suppressive effect of miR-142-5p mimic on apoptosis and cartilage matrix degradation of IL-1β-induced chondrocytes.Conclusion: Exosomal PCGEM1 from OA-FLSs facilitated IL-1β-induced apoptosis and cartilage matrix degradation in chondrocytes by sequestering miR-142-5p and upregulating RUNX2, which offered new insights into the pathogenesis of OA.

Lentivirus-Mediated Overexpression or Silencing of Aquaporin 1 Affects the Proliferation, Migration and Invasion of TNF-α-Stimulated Rheumatoid Arthritis Fibroblast-Like Synoviocytes by Wnt/β-Catenin Signaling Pathway

Introduction

Previous studies have confirmed the pathologic role of synovial aquaporin 1 (AQP1) in rheumatoid arthritis (RA), but its associations with the abnormal biologic behaviors of fibroblast-like synoviocytes (FLS) remain unclear. Herein, we examined the roles of AQP1 in the proliferation, migration and invasion of TNF-α-stimulated RA FLS (MH7A cells) and explored the underlying mechanisms.

Materials and Methods

Lentivirus-mediated AQP1 overexpression or silencing MH7A cells was constructed. Assays of MTT, flow cytometry (PI staining and Annexin V-PE/7-AAD staining), TMRM staining, wound-healing, transwell and phalloidin staining were performed to detect cell proliferation, cycle distribution, apoptosis, migration and invasion. The involvement of Wnt/β-catenin pathway was revealed by Western blot and β-catenin immunofluorescence staining.

Results

AQP1 overexpression promoted cell proliferation of TNF-α-stimulated MH7A by facilitating transformation from G0/G1 to S phase and inhibiting cell apoptosis (ie, reduced apoptosis rates, raised mitochondrial membrane potential, increased Bcl-2 protein level and decreased levels of Bax and cleaved caspase 3 protein). Also, AQP1 overexpression increased the migration index as well as the numbers of migrated and invasive cells. Furthermore, AQP1 overexpression promoted the activation of Wnt/β-catenin pathway, and XAV939, an inhibitor of Wnt/β-catenin, canceled the above effects of AQP1 overexpression on MH7A cells. As expected, AQP1 silencing exhibited the opposite effects on TNF-α-stimulated MH7A cells, which could be reversed by LiCl, an activator of Wnt/β-catenin.

Conclusion

AQP1 can affect the proliferation, migration and invasion of MH7A cells by Wnt/β-catenin signaling pathway, and AQP1 can be as a crucial determiner that can regulate RA FLS biologic behaviors.

Loss of microRNA-147 function alleviates synovial inflammation through ZNF148 in rheumatoid and experimental arthritis

MicroRNA-147 (miR-147) had been previously found induced in synoviocytes by inflammatory stimuli derived from T cells in experimental arthritis. This study was designed to verify whether loss of its function might alleviate inflammatory events in joints of experimental and rheumatoid arthritis (RA). Dark Agouti (DA) rats were injected intradermally with pristane to induce arthritis, and rno-miR-147 antagomir was locally administrated into individual ankle compared with negative control or rno-miR-155-5p antagomir (potential positive control). Arthritis onset, macroscopic severity, and pathological changes were monitored. While in vitro, gain or loss function of hsa-miR-147b-3p/hsa-miR-155-5p and ZNF148 was achieved in human synovial fibroblast cell line SW982 and RA synovial fibroblasts (RASF). The expression of miRNAs and mRNAs was detected by using RT-quantitative PCR, and protein expression was detected by using Western blotting. Anti-miR-147 therapy could alleviate the severity, especially for the synovitis and joint destruction in experimental arthritis. Gain of hsa-miR-147b-3p/hsa-miR-155-5p function in TNF-α stimulated SW982 and RASF cells could upregulate, in contrast, loss of hsa-miR-147b-3p/hsa-miR-155-5p function could downregulate the gene expression of TNF-α, IL-6, MMP3, and MMP13. Hence, such alteration could participate in synovial inflammation and joint destruction. RNAi of ZNF148, a miR-147's target, increased gene expression of TNF-α, IL-6, MMP3, and MMP13 in SW982 and RASF cells. Also, mRNA sequencing data showed that hsa-miR-147b-3p mimic and ZNF148 siRNA commonly regulated the gene expression of CCL3 and DEPTOR as well as some arthritis and inflammation-related pathways. Taken together, miR-147b-3p contributes to synovial inflammation through repressing ZNF148 in RA and experimental arthritis.

Cell-specific epigenetic drivers of pathogenesis in rheumatoid arthritis

Rheumatoid arthritis is a complex, inflammatory autoimmune disease, which is characterized by pain, swelling and joint damage driven by the altered behavior of a number of different cell types such as synovial fibroblasts macrophages and lymphocytes. The mechanism underlying pathogenesis is unclear but increasing evidence points to altered epigenetic regulation within these cell types which promotes the activated destructive behavior that underlies disease pathogenesis. This review summarizes the key epigenetic modifications in the most important cells types in rheumatoid arthritis, which are associated with disease activity. We also discuss emerging avenues of research focusing on readers of epigenetic markers which may serve to be potential therapeutic targets.

Location, location, location: how the tissue microenvironment affects inflammation in RA

Current treatments for rheumatoid arthritis (RA) do not work well for a large proportion of patients, or at all in some individuals, and cannot cure or prevent this disease. One major obstacle to developing better drugs is a lack of complete understanding of how inflammatory joint disease arises and progresses. Emerging evidence indicates an important role for the tissue microenvironment in the pathogenesis of RA. Each tissue is made up of cells surrounded and supported by a unique extracellular matrix (ECM). These complex molecular networks define tissue architecture and provide environmental signals that programme site-specific cell behaviour. In the synovium, a main site of disease activity in RA, positional and disease stage-specific cellular diversity exist. Improved understanding of the architecture of the synovium from gross anatomy to the single-cell level, in parallel with evidence demonstrating how the synovial ECM is vital for synovial homeostasis and how dysregulated signals from the ECM promote chronic inflammation and tissue destruction in the RA joint, has opened up new ways of thinking about the pathogenesis of RA. These new ideas provide novel therapeutic approaches for patients with difficult-to-treat disease and could also be used in disease prevention.

Metabolic Reprogramming of Fibroblasts as Therapeutic Target in Rheumatoid Arthritis and Cancer: Deciphering Key Mechanisms Using Computational Systems Biology Approaches

Fibroblasts, the most abundant cells in the connective tissue, are key modulators of the extracellular matrix (ECM) composition. These spindle-shaped cells are capable of synthesizing various extracellular matrix proteins and collagen. They also provide the structural framework (stroma) for tissues and play a pivotal role in the wound healing process. While they are maintainers of the ECM turnover and regulate several physiological processes, they can also undergo transformations responding to certain stimuli and display aggressive phenotypes that contribute to disease pathophysiology. In this review, we focus on the metabolic pathways of glucose and highlight metabolic reprogramming as a critical event that contributes to the transition of fibroblasts from quiescent to activated and aggressive cells. We also cover the emerging evidence that allows us to draw parallels between fibroblasts in autoimmune disorders and more specifically in rheumatoid arthritis and cancer. We link the metabolic changes of fibroblasts to the toxic environment created by the disease condition and discuss how targeting of metabolic reprogramming could be employed in the treatment of such diseases. Lastly, we discuss Systems Biology approaches, and more specifically, computational modeling, as a means to elucidate pathogenetic mechanisms and accelerate the identification of novel therapeutic targets.

Metformin inhibits inflammation and bone destruction in collagen-induced arthritis in rats

Background

Metformin (MF) is a widely used biguanide oral hypoglycemic agent, which has obvious anti-inflammatory and immunomodulatory effects. However, the mechanism of MF on rheumatoid arthritis (RA) remains uncertain. In this study, we investigated the therapeutic effects of MF on collagen-induced arthritis (CIA).

Methods

CIA was induced in rats by intradermal injection of a mixture of bovine type II collagen and incomplete Freund's adjuvant (IFA) on day 0 and day 7 through the base of the tail. Intraperitoneal injection of MF (100 mg/kg) was given every 3 days, from day 14 for 3 weeks. The effects of MF on arthritis-induced systemic inflammation and synovitis were studied by pathological analysis of the knee joint and serological examination of peripheral blood in CIA rats. The bone protection effect of MF was studied by microscopic computed tomography (micro-CT) and histological analysis of the knee joint. The effects of MF on chondrocytes in CIA rats were studied by detecting the relevant pro-apoptotic mediators in the chondrocytes.

Results

After administration of MF in CIA rats, systemic inflammation and synovitis caused by arthritis were significantly suppressed. Histomorphometry and micro-CT analysis of the knee joint revealed that MF can protect bone by inhibiting the changes of trabecular bone in CIA rats. Histological analysis of the knee joint found that MF can inhibit osteoclast formation and degradation of the cartilage layer matrix. Detection of the relevant pro-apoptotic mediators in chondrocytes revealed that MF can significantly inhibit the apoptosis of chondrocytes in CIA rats.

Conclusions

Our study showed that MF can inhibit systemic inflammation and synovitis and plays a role in bone protection by inhibiting cartilage layer matrix degradation, osteoclast formation, and chondrocyte apoptosis.

Role of Adiponectin in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic chronic inflammatory autoimmune joint disease, characterized by progressive articular damage and joint dysfunction. One of the symptoms of this disease is persistent inflammatory infiltration of the synovial membrane, the principle site of inflammation in RA. In the affected conditions, the cells of the synovial membrane, fibroblast-like synoviocytes and macrophage-like synovial cells, produce enzymes degrading cartilage and underlining bone tissue, as well as cytokines increasing the infiltration of immune cells. In patients with RA, higher levels of adiponectin are measured in the serum and synovial fluid. Adiponectin, a secretory product that is mainly white adipose tissue, is a multifunctional protein with dual anti-inflammatory and pro-inflammatory properties. Several studies underline the fact that adiponectin can play an important pro-inflammatory role in the pathophysiology of RA via stimulating the secretion of inflammatory mediators. This narrative review is devoted to the presentation of recent knowledge on the role played by one of the adipokines produced by adipose tissue—adiponectin—in the pathogenesis of rheumatoid arthritis.

Engineered nanoparticle-induced epigenetic changes: An important consideration in nanomedicine

Engineered nanoparticles (ENPs) are now being applied across a range of disciplines, and as a result numerous studies have now assessed ENP-related bioeffects. Among them, ENP-induced epigenetic changes including DNA methylation, histone modifications, and miRNA-mediated regulation of gene expression have recently attracted attention. In this review, we describe the diversity of ENP-induced epigenetic changes, focusing on their interplay with related functional biological events, especially oxidative stress, MAPK pathway activation, and inflammation. In doing so, we highlight the underlying mechanisms and biological effects of ENP-induced epigenetic changes. We also summarize how high-throughput technologies have helped to uncover ENP-induced epigenetic changes. Finally, we discuss future perspectives and the challenges related to ENP-induced epigenetic changes that still need to be addressed.

Overexpression of Aquaporin 1 in Synovium Aggravates Rat Collagen-Induced Arthritis Through Regulating β-Catenin Signaling: An in vivo and in vitro Study

Introduction

Previous studies have confirmed that aquaporin 1 (AQP1) is up-regulated in synovium of rheumatoid arthritis (RA), but its exact pathogenic mechanisms in RA are unclear. This study revealed the pathogenic role of AQP1 in rat collagen-induced arthritis (CIA) and the underlying mechanisms related to β-catenin signaling.

Materials and Methods

Secondary paw swelling and pathological changes of ankle joints were used to evaluate the severity of rat CIA. Synovial AQP1 and β-catenin expression were measured by immunohistochemistry (IHC) and Western blot assay. AQP1 siRNA was applied to knockdown AQP1 in cultured CIA fibroblast-like synoviocyte (FLS). Assays of MTT, PCNA immunofluorescence and transwell were performed to detect cell proliferation, migration and invasion. The protein levels of β-catenin pathway members and ratio of TOP/FOP luciferase activity were also measured.

Results

In vivo, we revealed that synovial AQP1 and β-catenin expressions in CIA rats were higher than normal rats, and synovial AQP1 expression of CIA rats increased in parallel with secondary paw swelling and total pathological score on joint damage. Correlation analysis of IHC results indicated that synovial AQP1 expression positively correlated with β-catenin expression in CIA rat. In vitro, AQP1 siRNA apparently reduced the proliferation, migration and invasion of CIA FLS by inhibiting β-catenin signaling pathway. As an activator of β-catenin signaling, lithium chloride (an inhibitor of GSK-3β) reversed the inhibitory effects of AQP1 siRNA on the cultured CIA FLS.

Conclusion

We concluded that the overexpression of synovial AQP1 aggravated rat CIA by promoting the activation of FLS through β-catenin signaling pathway.

NR1D1 modulates synovial inflammation and bone destruction in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial hyperplasia, pannus formation, and cartilage and bone destruction. Nuclear receptor subfamily 1 group D member 1 (NR1D1) functions as a transcriptional repressor and plays a vital role in inflammatory reactions. However, whether NR1D1 is involved in synovial inflammation and joint destruction during the pathogenesis of RA is unknown. In this study, we found that NR1D1 expression was increased in synovial tissues from patients with RA and decreased in RA Fibroblast-like synoviocytes (FLSs) stimulated with IL-1β in vitro. We showed that NR1D1 activation decreased the expression of proinflammatory cytokines and matrix metalloproteinases (MMPs), while NR1D1 silencing exerted the opposite effect. Furthermore, NR1D1 activation reduced reactive oxygen species (ROS) generation and increased the production of nuclear transcription factor E2-related factor 2 (Nrf2)-associated enzymes. Mitogen-activated protein kinase (MAPK) and nuclear factor κB (NF-κB) pathways were blocked by the NR1D1 agonist SR9009 but activated by NR1D1 silencing. NR1D1 activation also inhibited M1 macrophage polarization and suppressed osteoclastogenesis and osteoclast-related genes expression. Treatment with NR1D1 agonist SR9009 in collagen-induced arthritis (CIA) mouse significantly suppressed the hyperplasia of synovial, infiltration of inflammatory cell and destruction of cartilage and bone. Our findings demonstrate an important role for NR1D1 in RA and suggest its therapeutic potential.

Recent discoveries in dendritic cell tolerance-inducing pharmacological molecules

Dendritic cells (DCs) represent one of the most important biological tools for cellular immunotherapy purposes. There are an increasing number of phase I and II studies, where regulatory or tolerogenic DCs (TolDCs) are utilized as negative vaccines, with the aim of inducing tolerogenic outcomes in patients with various autoimmune or chronic-inflammatory diseases, as well as in transplant settings. The induction of tolerogenic properties in DCs can be achieved by altering their activation state toward expression of immunosuppressive elements and/or by achieving resistance to maturation, which leads to insufficient co-stimulatory signal delivery and inability to efficiently present antigens. In the past, one of the most efficient ways to induce DC tolerance has been the application of selected pharmacological agents which actively induce a tolerogenic transcription program or inhibit major pro-inflammatory transcription factors such as Nf-κB. Important examples include immunosuppressants such as different corticosteroids, vitamin D₃, rapamycin and others. The quality of TolDCs induced by different approaches is becoming a vital issue and recent evidence suggests substantial heterogeneity between variously-generated TolDCs as evidenced by their transcriptomic profile and function. The possibility of various "flavors" of TolDCs encourages future research in discovery of Tol-DC inducing agents to enrich various ways of DC manipulation. This would enable a broader range of tools to manipulate DC toward specific characteristics desirable in different disease settings. In recent years, several novel small molecules have been identified with the capacity to promote DC tolerogenic characteristics. In this review, we will present and discuss these novel findings and also highlight novel understandings of tolerogenic mechanisms by which DC tolerogenicity is induced by already established agents.

Collagens and DNA methyltransferases in mare endometrosis

Inflammation and fibroproliferative diseases may be modulated by epigenetic changes. Therefore, we suggest that epigenetic mechanisms could be involved in equine endometrosis pathogenesis. DNA methylation is one of the methods to evaluate epigenetics, through the transcription of methyltransferases (DNMT1, DNMT3A, DNMT3B). The correlation between DNMTs and collagen (COL) transcripts was assessed for the different Kenney and Doig's (Current Therapy in Theriogenology. Philadelphia: WB Saunders; 1986) endometrium categories. Endometrial biopsies were randomly collected from cyclic mares. Histological classification (category I, n = 13; II A, n = 17; II B, n = 12; and III, n = 7) and evaluation of COL1A2, COL3A1 and DNMTs transcripts by qPCR, were performed. Data were analysed by one-way analysis of variance (ANOVA), Kruskal-Wallis test and Pearson correlation. As mares aged, there was an increase in endometrium fibrosis (p < .01), and in DNMT1 mRNA (p < .001). Considering DNMT3B transcripts for each category, there was an increase with fibrosis (p < .05). No changes were observed for DNMT1 and DNMT3A transcripts. However, DNMT3A mRNA levels were the highest in all categories (p < .01). In category I endometrium, a positive correlation was observed for transcripts of all DNMTs in both COLs (p < .01). In category IIA, this correlation was also maintained for all DNMTs transcripts in COL1A2 (p < .05), but only for DNMT3B in COL3A1 (p < .05). In category IIB, there was a positive correlation between DNMT3B and COL3A1 (p < .05). In category III, a positive correlation was only observed between DNMT3B and COL3A1 (p < .05). Our results suggest that there is a disturbance in COLs and DNMTs correlation during fibrosis.

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.

The evolution in our understanding of the genetics of rheumatoid arthritis and the impact on novel drug discovery

Introduction: Rheumatoid arthritis (RA) is an autoimmune disease that is characterized by chronic inflammation of the joints and affects 1% of the population. Polymorphisms of genes that encode proteins that primarily participate in inflammation may influence RA occurrence or become useful biomarkers for certain types of anti-rheumatic treatment.Areas covered: The authors summarize the recent progress in our understanding of the genetics of RA. In the last few years, multiple variants of genes that are associated with RA risk have been identified. The development of new technologies and the detection of new potential therapeutic targets that contribute to novel drug discovery are also described.Expert opinion: There is still the need to search for new genes which may be a potential target for RA therapy. The challenge is to develop appropriate strategies for achieving insight into the molecular pathways involved in RA pathogenesis. Understanding the genetics, immunogenetics, epigenetics and immunology of RA could help to identify new targets for RA therapy. The development of new technologies has enabled the detection of a number of new genes, particularly genes associated with proinflammatory cytokines and chemokines, B- and T-cell activation pathways, signal transducers and transcriptional activators, which might be potential therapeutic targets in RA.

miR-449a inhibits cell proliferation, migration, and inflammation by regulating high-mobility group box protein 1 and forms a mutual inhibition loop with Yin Yang 1 in rheumatoid arthritis fibroblast-like synoviocytes

Background

We previously found that high-mobility group box protein 1 (HMGB1) promoted cell proliferation, migration, invasion, and autophagy in rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS), but little is known about its regulatory mechanism. The aim of this study was to investigate the regulatory mechanism of HMGB1 at the posttranscription level.

Methods

Real-time qPCR, CCK-8 cell proliferation assay, transwell cell migration assay, enzyme-linked immunosorbent assay (ELISA), and western blotting were used in this study. The targeting relationship between miRNA and mRNA was presented by the luciferase reporter assay.

Results

MiR-449a was downregulated in RA synovial tissue and inhibited RA-FLS proliferation, migration, and IL-6 production. MiR-449a directly targeted HMGB1 and inhibited its expression. Yin Yang 1(YY1) negatively regulated miR-449a expression and formed a mutual inhibition loop in RA-FLS. MiR-449a inhibited TNFα-mediated HMGB1 and YY1 overexpression and IL-6 production.

Conclusions

Our results reveal the regulatory mechanism of HMGB1 in RA and demonstrate that miR-449a is a crucial molecule in RA pathogenesis and a suitable candidate for miRNA replacement therapies in RA.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1920-0) contains supplementary material, which is available to authorized users.

Expression and function of miR-155 in rat synovial fibroblast model of rheumatoid arthritis

Rheumatoid arthritis (RA) is a common autoimmune disease characterized by joint synovial inflammation and is a challenge for researchers and clinicians. MicroRNAs (miRNAs/miRs) represent a group of small non-coding RNA molecules that post-transcriptionally regulate mRNA expression and are involved in various diseases, including cancer, autoimmune and metabolic diseases, as well as neurological disorders. In the present study, various experiments were performed to investigate the effects and underlying mechanism of miR-155 in RA using rat synoviocytes induced by lipopolysaccharide (LPS) to model rheumatoid arthritis. It was revealed that synovial fibroblasts exhibited significantly higher miR-155 mRNA levels than the control group. Compared with the RA group, the viability of synovial fibroblasts was significantly decreased in the miR-155 mimics + RA group, but markedly increased in the miR-155 inhibitor + RA group. Compared with that in the RA + NC mimic or RA + NC inhibitor groups, the apoptosis of synovial fibroblasts increased significantly in the miR-155 mimics + RA group, but was significantly decreased in the miR-155 inhibitor + RA group. The miR-155 mimics + RA group exhibited higher expression levels of β-catenin, matrix metalloproteinase 7 and cyclin D1 compared with the miR-155 inhibitor + RA group, and the glycogen synthase kinase protein levels was lower compared with the miR-155 inhibitor + RA group. In brief, it was inferred that the Wnt signaling pathway is involved in the miR-155-associated inhibition of RA synovial fibroblast viability and induction of cell apoptosis. Inhibition of miR-155 may be an effective treatment for RA through regulation of the Wnt signaling pathway to reduce cell apoptosis and enhance cell viability.

Synthesis of NSC 106084 and NSC 14778 and evaluation of their DNMT inhibitory activity

DNA methylation is an epigenetic modification that is performed by DNA methyltransferases (DNMTs) and that leads to the transfer of a methyl group from S-adenosylmethionine (SAM) to the C5 position of cytosine. This transformation results in hypermethylation and silencing of genes such as tumor suppressor genes. Aberrant DNA methylation has been associated with the development of many diseases, including cancer. Inhibition of DNMTs promotes the demethylation and reactivation of epigenetically silenced genes. NSC 106084 and 14778 have been reported to inhibit DNMTs in the micromolar range. We report herein the synthesis of NSC 106084 and 14778 and the evaluation of their DNMT inhibitory activity. Our results indicate that while commercial NSC 14778 is moderately active against DNMT1, 3A/3L and 3B/3L, resynthesized NSC 14778 is inactive under our assay conditions. Resynthesized 106084 was also found to be inactive.

Dihydromyricetin Inhibits Inflammation of Fibroblast-Like Synoviocytes through Regulation of Nuclear Factor-κB Signaling in Rats with Collagen-Induced Arthritis

Dihydromyricetin (DMY), the main flavonoid of Ampelopsis grossedentata, has potent anti-inflammatory activity. However, the effect of DMY on chronic autoimmune arthritis remains undefined. In this study, we investigated the therapeutic effects of DMY on collagen-induced arthritis (CIA). Wistar rats were immunized with bovine type II collagen to establish CIA and were then administered DMY intraperitoneally (5, 25, and 50 mg/kg) every other day for 5 weeks. Paw swelling, clinical scoring, and histologic analysis were assessed to determine the therapeutic effects of DMY on the development of arthritis in CIA rats. The results showed that treatment with DMY significantly reduced erythema and swelling in the paws of CIA rats. Pathologic analysis of the knee joints and peripheral blood cytokine assay results confirmed the antiarthritic effects of DMY on synovitis and inflammation. Fibroblast-like synoviocytes (FLSs) were isolated from the synovium of CIA rats and treated with 10 ng/ml interleukin (IL)-1β DMY significantly inhibited the proliferation, migration, and inflammation of IL-1β-induced FLSs, whereas it significantly increased IL-1β-induced FLS apoptosis in a dose-dependent manner (6.25-25 μM). Moreover, DMY suppressed phosphorylation of IκB kinase (IKK) and inhibitor of NF-κB α and subsequently reduced the IL-1β-induced nucleus translocation of NF-κB in FLSs. Through a molecular docking assay, we demonstrated that DMY could directly bind to the Thr9 and Asp88 residues in IKKα and the Asp95, Asn142, and Gln167 residues in IKKβ These findings demonstrate that DMY could alleviate inflammation in CIA rats and attenuate IL-1β-induced activities in FLSs through suppression of NF-κB signaling.

Induction of chronic destructive arthritis in SCID mice by arthritogenic fibroblast-like synoviocytes derived from mice with antigen-induced arthritis

Background

Fibroblast-like synoviocytes (FLSs) from patients with rheumatoid arthritis (RA) are autonomously activated to maintain inflammation and joint destruction in co-transplantation models. To elucidate inducing mechanisms involved in this altered behavior, the arthritogenic potential of FLSs from murine antigen-induced arthritis (AIA) were investigated in a transfer model.

Methods

FLSs were isolated, expanded in vitro, and transferred into knee joint cavities of severe combined immunodeficient (SCID) mice. Their arthritogenic capacity was assessed by monitoring joint swelling and evaluation of histological parameters 70 to 100 days after transfer.

Results

FLSs from AIA mice were able to transfer arthritis into recipient SCID mice. FLS transfer induced a chronic arthritis with recruitment of inflammatory cells and marked cartilage destruction. Long-lasting inflammation was not required for imprinting of arthritogenicity in FLSs since cells isolated from acute arthritic joints were fully competent to transfer arthritis. We also observed arthritogenic potential in FLSs isolated from contralateral non-arthritic joints in our monoarticular arthritis model.

Conclusions

We show that the transformation of FLSs into arthritogenic cells occurs early in arthritis development. This challenges current hypotheses on the role of these cells in arthritis pathogenesis and opens up the way for further mechanistic studies.

Involvement of miR-126 in autoimmune disorders

BACKGROUND

Micro-RNA represent a great family of small non-condign ribonucleic acid molecules; in particular microRNA-126 is an important member of this family and is expressed in many human cells such as cardiomyocytes, endothelial and lung cells. Some studies have shown the implication of miR-126 in cancer, but recently significant progresses have also been made in determining the role of miR-126 regulating immune-related diseases; probably, in a near future, they could potentially serve as diagnostic biomarkers or therapeutic targets.

OBJECTIVE

The purpose of this review is to investigate the role of miR-126 in autoimmune diseases, so as to offer innovative therapies.

RESULTS

According literature, it was concluded that miRNAs, especially miR-126, are involved in many pathologies and that their expression levels increase in autoimmune diseases because they interfere with the transcription of the proteins involved. Since microRNAs can be detected from several biological sources, they may be attractive as potential biomarkers for the diagnosis, prognosis, disease activity and severity of various diseases. In fact, once confirmed the involvement of miR-126 in autoimmune diseases, it was speculated that it could be used as a promising biomarker. These discovers implicate that miR-126 have a central role in many pathways leading to the development and sustain of autoimmune diseases. Its key role make this microRNA a potential therapeutic target in autoimmunity.

CONCLUSION

Although miR-126 relevant role in several immune-related diseases, further studies are needed to clear its molecular mechanisms; the final step of these novel researches could be the blockage or the prevention of the diseases onset by creating of new targeted therapy.

Down-regulation of miR-10a-5p promotes proliferation and restricts apoptosis via targeting T-box transcription factor 5 in inflamed synoviocytes

Synoviocytes from rheumatoid arthritis (RA) patients share certain features with tumor cells, such as over proliferation and invasion. Anomalous microRNA (miRNA) expression may participate in the pathogenesis of RA in different ways. The objective of the present study was to observe the role of miR-10a-5p targeting T-box transcription factor 5 (TBX5) gene on synoviocyte proliferation and apoptosis in RA. Human synovial sarcoma cell line, SW982 cells stimulating with interleukin-1β (IL-1β) were transfected with miR-10a-5p mimic and siRNA of TBX5. The real-time quantitative polymerase chain reaction (RT-qPCR) and Western blotting analysis were used to evaluate the expression level of miR-10a-5p and TBX5 in SW982 cells respectively. Further, the proliferation and apoptosis of SW982 cells after treatment were determined by cell counting kit (CCK-8) and flow cytometry analysis respectively. We found that the miR-10a-5p showed down-regulated while TBX5 showed up-regulated expression in synoviocytes after stimulation with IL-1β. The miR-10a-5p mimic treatment showed a decline in cell proliferation while the increased rate of cell apoptosis as compared with control. Moreover, knockdown of TBX5 favored the apoptosis and reduced the cell proliferation as compared with control group. We conclude that down-regulation of miR-10a-5p promotes proliferation and restricts apoptosis via targeting TBX5 in inflamed synoviocytes.

Comorbid TNF-mediated heart valve disease and chronic polyarthritis share common mesenchymal cell-mediated aetiopathogenesis

Objectives

Patients with rheumatoid arthritis and spondyloarthritisshow higher mortality rates, mainly caused by cardiac comorbidities. The TghuTNF (Tg197) arthritis model develops tumour necrosis factor (TNF)-driven and mesenchymalsynovial fibroblast (SF)-dependent polyarthritis. Here, we investigate whether this model develops, similarly to human patients, comorbid heart pathology and explore cellular and molecular mechanisms linking arthritis to cardiac comorbidities.

Methods

Histopathological analysis and echocardiographic evaluation of cardiac function were performed in the Tg197 model. Valve interstitial cells (VICs) were targeted by mice carrying the ColVI-Cretransgene. Tg197 ColVI-Cre Tnfr1^fl/fl and Tg197 ColVI-Cre Tnfr1^cneo/cneo mutant mice were used to explore the role of mesenchymal TNF signalling in the development of heart valve disease. Pathogenic VICs and SFs were further analysed by comparative RNA-sequencing analysis.

Results

Tg197 mice develop left-sided heart valve disease, characterised by valvular fibrosis with minimal signs of inflammation. Thickened valve areas consist almost entirely of hyperproliferative ColVI-expressing mesenchymal VICs. Development of pathology results in valve stenosis and left ventricular dysfunction, accompanied by arrhythmic episodes and, occasionally, valvular regurgitation. TNF dependency of the pathology was indicated by disease modulation following pharmacological inhibition or mesenchymal-specific genetic ablation or activation of TNF/TNFR1 signalling. Tg197-derived VICs exhibited an activated phenotype ex vivo, reminiscent of the activated pathogenic phenotype of Tg197-derived SFs. Significant functional similarities between SFs and VICs were revealed by RNA-seq analysis, demonstrating common cellular mechanisms underlying TNF-mediated arthritides and cardiac comorbidities.

Conclusions

Comorbidheart valve disease and chronic polyarthritis are efficiently modelled in the Tg197 arthritis model and share common TNF/TNFR1-mediated, mesenchymal cell-specific aetiopathogenic mechanisms.

Fibroblast heterogeneity: implications for human disease

Fibroblasts synthesize the extracellular matrix of connective tissue and play an essential role in maintaining the structural integrity of most tissues. Researchers have long suspected that fibroblasts exhibit functional specialization according to their organ of origin, body site, and spatial location. In recent years, a number of approaches have revealed the existence of fibroblast subtypes in mice. Here, we discuss fibroblast heterogeneity with a focus on the mammalian dermis, which has proven an accessible and tractable system for the dissection of these relationships. We begin by considering differences in fibroblast identity according to anatomical site of origin. Subsequently, we discuss new results relating to the existence of multiple fibroblast subtypes within the mouse dermis. We consider the developmental origin of fibroblasts and how this influences heterogeneity and lineage restriction. We discuss the mechanisms by which fibroblast heterogeneity arises, including intrinsic specification by transcriptional regulatory networks and epigenetic factors in combination with extrinsic effects of the spatial context within tissue. Finally, we discuss how fibroblast heterogeneity may provide insights into pathological states including wound healing, fibrotic diseases, and aging. Our evolving understanding suggests that ex vivo expansion or in vivo inhibition of specific fibroblast subtypes may have important therapeutic applications.

Down-regulation of miR-10a-5p in synoviocytes contributes to TBX5-controlled joint inflammation

MicroRNAs are considered to play critical roles in the pathogenesis of human inflammatory arthritis, including rheumatoid arthritis (RA). The purpose of this study was to determine the relationship between miR‐10a‐5p and TBX5 in synoviocytes and evaluate their contribution to joint inflammation. The expression of miR‐10a‐5p and TBX5 in the synovium of RA and human synovial sarcoma cell line SW982 stimulated by IL‐1β was determined by RT‐qPCR and Western blotting. The direct interaction between miR‐10a‐5p and TBX5 3′UTR was determined by dual‐luciferase reporter assay in HeLa cells. Mimics and inhibitors of miR‐10a‐5p were transfected into SW982 cells. TBX5 was overexpressed by plasmid transfection or knocked down by RNAi. Proinflammatory cytokines and TLR3 and MMP13 expressions were determined by RT‐qPCR and Western blotting. Down‐regulated expression of miR‐10a‐5p and up‐regulation of TBX5 in human patients with RA were found compared to patients with OA. IL‐1β could reduce miR‐10a‐5p and increase TBX5 expression in SW982 cells in vitro. The direct target relationship between miR‐10a‐5p and 3′UTR of TBX5 was confirmed by luciferase reporter assay. Alterations of miR‐10‐5p after transfection with its mimic and inhibitor caused the related depression and re‐expression of TBX5 and inflammatory factors in SW982 cells. Overexpression of TBX5 after pCMV3‐TBX5 plasmid transfection significantly promoted the production of TLR3, MMP13 and various inflammatory cytokines, while this effect was rescued after knocking down of TBX5 with its specific siRNA. We conclude that miR‐10a‐5p in a relation with TBX5 regulates joint inflammation in arthritis, which would serve as a diagnostic and therapeutic target for RA treatment.

Epigenetic modifying enzyme expression in asthmatic airway epithelial cells and fibroblasts

BACKGROUND

Recognition of the airway epithelium as a central mediator in the pathogenesis of asthma has necessitated greater understanding of the aberrant cellular mechanisms of the epithelium in asthma. The architecture of chromatin is integral to the regulation of gene expression and is determined by modifications to the surrounding histones and DNA. The acetylation, methylation, phosphorylation, and ubiquitination of histone tail residues has the potential to greatly alter the accessibility of DNA to the cells transcriptional machinery. DNA methylation can also interrupt binding of transcription factors and recruit chromatin remodelers resulting in general gene silencing. Although previous studies have found numerous irregularities in the expression of genes involved in asthma, the contribution of epigenetic regulation of these genes is less well known. We propose that the gene expression of epigenetic modifying enzymes is cell-specific and influenced by asthma status in tissues derived from the airways.

METHODS

Airway epithelial cells (AECs) isolated by pronase digestion or endobronchial brushings and airway fibroblasts obtained by outgrowth technique from healthy and asthmatic donors were maintained in monolayer culture. RNA was analyzed for the expression of 82 epigenetic enzymes across 5 families of epigenetic modifying enzymes. Western blot and immunohistochemistry were also used to examine expression of 3 genes.

RESULTS

Between AECs and airway fibroblasts, we identified cell-specific gene expression in each of the families of epigenetic modifying enzymes; specifically 24 of the 82 genes analyzed showed differential expression. We found that 6 histone modifiers in AECs and one in fibroblasts were differentially expressed in cells from asthmatic compared to healthy donors however, not all passed correction. In addition, we identified a corresponding increase in Aurora Kinase A (AURKA) protein expression in epithelial cells from asthmatics compared to those from non-asthmatics.

CONCLUSIONS

In summary, we have identified cell-specific variation in gene expression in each of the families of epigenetic modifying enzymes in airway epithelial cells and airway fibroblasts. These data provide insight into the cell-specific variation in epigenetic regulation which may be relevant to cell fate and function, and disease susceptibility.

Differentially Methylated DNA Regions in Monozygotic Twin Pairs Discordant for Rheumatoid Arthritis: An Epigenome-Wide Study

Objectives

In an explorative epigenome-wide association study (EWAS) to search for gene independent, differentially methylated DNA positions and regions (DMRs) associated with rheumatoid arthritis (RA) by studying monozygotic (MZ) twin pairs discordant for RA.

Methods

Genomic DNA was isolated from whole blood samples from 28 MZ twin pairs discordant for RA. DNA methylation was measured using the HumanMethylation450 BeadChips. Smoking, anti-cyclic citrullinated peptide antibodies, and immunosuppressive treatment were included as covariates. Pathway analysis was performed using GREAT.

Results

Smoking was significantly associated with hypomethylation of a DMR overlapping the promoter region of the RNF5 and the AGPAT1, which are implicated in inflammation and autoimmunity, whereas DMARD treatment induced hypermethylation of the same region. Additionally, the promotor region of both S100A6 and EFCAB4B were hypomethylated, and both genes have previously been associated with RA. We replicated several candidate genes identified in a previous EWAS in treatment-naïve RA singletons. Gene-set analysis indicated the involvement of immunologic signatures and cancer-related pathways in RA.

Conclusion

We identified several differentially methylated regions associated with RA, which may represent environmental effects or consequences of the disease and plausible biological pathways pertinent to the pathogenesis of RA.

MicroRNA-27a Inhibits Cell Migration and Invasion of Fibroblast-Like Synoviocytes by Targeting Follistatin-Like Protein 1 in Rheumatoid Arthritis

Fibroblast-like synoviocytes (FLS) with aberrant expression of microRNA (miRNA) are critical pathogenic regulators in rheumatoid arthritis (RA). Previous studies have found that overexpression or silencing of miRNA can contribute to the development of miRNA-based therapeutics in arthritis models. In this study, we explored the effects of miR-27a on cell migration and invasion in cultured FLS from RA patients. We found that miR-27a was markedly downregulated in the serum, synovial tissue, and FLS of RA patients. Meanwhile, the expression of follistatin-like protein 1 (FSTL1) was upregulated, which suggests that FSTL1 plays a key role in RA development. The results of a Transwell assay showed that miR-27a inhibited FLS migration and invasion. However, miR-27a inhibition promoted the migration and invasion of FLS. In addition, the down-regulated expression of matrix metalloproteinases (MMP2, MMP9, and MMP13) and Rho family proteins (Rac1, Cdc42, and RhoA) was detected after treatment with miR-27a in RA-FLS by quantitative reverse transcription-PCR and western blot analysis. Then, a luciferase reporter assay validated that miR-27a targeted the 3-untranslated region (3'-UTR) of FSTL1. Moreover, miR-27a caused a significant decrease of FSTL1. In addition, the expression of TLR4 and NFκB was inhibited by miR-27a but increased by FSTL1 overexpression. In conclusion, we found that miR-27a inhibited cell migration and invasion of RA-FLS by targeting FSTL1 and restraining the TLR4/NFκB pathway.

Role of epigenetics in modulation of immune response at the junction of host-pathogen interaction and danger molecule signaling

Epigenetic mechanisms have rapidly and controversially emerged as silent modulators of host defenses that can lead to a more prominent immune response and shape the course of inflammation in the host. Thus, the epigenetics can both drive the production of specific inflammatory mediators and control the magnitude of the host response. The epigenetic actions that are predominantly shown to modulate the host defense against microbial pathogens are DNA methylation, histone modification and the activity of non-coding RNAs. There is also growing evidence that opportunistic chronic pathogens, such as Porphyromonas gingivalis, as a microbial host subversion strategy, can epigenetically interfere with the host DNA machinery for successful colonization. Similarly, the novel involvement of small molecule 'danger signals', which are released by stressed or infected cells, at the center of host-pathogen interplay and epigenetics is developing. In this review, we systematically examine the latest knowledge within the field of epigenetics in the context of host-derived danger molecule and purinergic signaling, with a particular focus on host microbial defenses and infection-driven chronic inflammation.

The histone demethylase inhibitor GSK-J4 limits inflammation through the induction of a tolerogenic phenotype on DCs

As it has been established that demethylation of lysine 27 of histone H3 by the lysine-specific demethylase JMJD3 increases immune responses and thus elicits inflammation, we hypothesize that inhibition of JMJD3 may attenuate autoimmune disorders. We found that in vivo administration of GSK-J4, a selective inhibitor of JMJD3 and UTX, ameliorates the severity of experimental autoimmune encephalomyelitis (EAE). In vitro experiments revealed that the anti-inflammatory effect of GSK-J4 was exerted through an effect on dendritic cells (DCs), promoting a tolerogenic profile characterized by reduced expression of costimulatory molecules CD80/CD86, an increased expression of tolerogenic molecules CD103 and TGF-β1, and reduced secretion of proinflammatory cytokines IL-6, IFN-γ, and TNF. Adoptive transfer of GSK-J4-treated DCs into EAE mice reduced the clinical manifestation of the disease and decreased the extent of inflammatory CD4+ T cells infiltrating the central nervous system. Notably, Treg generation, stability, and suppressive activity were all exacerbated by GSK-J4-treated DCs without affecting Th1 and Th17 cell production. Our data show that GSK-J4-mediated modulation of inflammation is achieved by a direct effect on DCs and that systemic treatment with GSK-J4 or adoptive transfer of GSK-J4-treated DCs ex vivo may be promising approaches for the treatment of inflammatory and autoimmune disorders.