J. Claude Bennett, MD: Scholar, Physician, and Leader.

Dr Claude Bennett provided local, national, and international leadership in rheumatology when it was developing as a subspecialty of internal medicine. His early contributions included work in helping to understand at the molecular level how antibodies are formed. Under his leadership, UAB grew into a nationally respected institution known for its high-quality clinical care, impactful research, and outstanding training programs. His many contributions have had a lasting effect on the fields of rheumatology, medicine, and immunology. Throughout his career, he served as a role model and was widely respected for his wise advice and superb mentorship.

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.

Peripheral blood mononuclear cells are hypomethylated in active rheumatoid arthritis and methylation correlates with disease activity.

OBJECTIVE: Epigenetic modifications are dynamic and influence cellular disease activity. The aim of this study was to investigate global DNA methylation in peripheral blood mononuclear cells (PBMCs) of RA patients to clarify whether global DNA methylation pattern testing might be useful in monitoring disease activity as well as the response to therapeutics. METHODS: Flow cytometric measurement of 5-methyl-cytosine (5'-mC) was established using the cell line U937. In the subsequent prospective study, 62 blood samples were investigated, including 17 healthy donors and 45 RA patients at baseline and after 3 months of treatment with methotrexate, the IL-6 receptor inhibitor sarilumab, and Janus kinase inhibitors. Methylation status was assessed with an anti-5'-mC antibody and analysed in PBMCs and CD4+, CD8+, CD14+ and CD19+ subsets. Signal intensities of 5'-mC were correlated with 28-joint DASs with ESR and CRP (DAS28-ESR and DAS28-CRP). RESULTS: Compared with healthy individuals, PBMCs of RA patients showed a significant global DNA hypomethylation. Signal intensities of 5'-mC correlated with transcription levels of DNMT1, DNMT3B and MTR genes involved in methylation processes. Using flow cytometry, significant good correlations and linear regression values were achieved in RA patients between global methylation levels and DAS28-ESR values for PBMCs (r = -0.55, P = 0.002), lymphocytes (r = -0.57, P = 0.001), CD4+ (r = -0.57, P = 0.001), CD8+ (r = -0.54, P = 0.001), CD14+ (r = -0.49, P = 0.008) and CD19+ (r = -0.52, P = 0.004) cells. CONCLUSIONS: The degree of global DNA methylation was found to be associated with disease activity. Based on this novel approach, the degree of global methylation is a promising biomarker for therapy monitoring and the prediction of therapy outcome in inflammatory diseases.

Nicotine Changes the microRNA Profile to Regulate the FOXO Memory Program of CD8+ T Cells in Rheumatoid Arthritis.

Objective: Smoking suppresses PD-1 expression in patients with rheumatoid arthritis (RA). In this study, we assess if smoking changed the epigenetic control over CD8+ T cell memory formation through a microRNA (miR) dependent mechanism. Methods: Phenotypes of CD8+ T cells from smokers and non-smokers, RA and healthy, were analyzed by flow cytometry. A microarray analysis was used to screen for differences in miR expression. Sorted CD8+ cells were in vitro stimulated with nicotine and analyzed for transcription of miRs and genes related to memory programming by qPCR. Results: CD27+CD107a-CD8+ T cells, defining a naïve-memory population, had low expression of PD-1. Additionally, the CD27+ population was more frequent in smokers (p = 0.0089). Smokers were recognized by differential expression of eight miRs. Let-7c-5p, let-7d-5p and let-7e-5p, miR-92a-3p, miR-150-5p, and miR-181-5p were up regulated, while miR-3196 and miR-4723-5p were down regulated. These miRs were predicted to target proteins within the FOXO-signaling pathway involved in CD8+ memory programming. Furthermore, miR-92a-3p was differentially expressed in CD8+ cells with naïve-memory predominance. Nicotine exposure of CD8+ cells induced the expression of miR-150-5p and miR-181a-5p in the naïve-memory cells in vitro. Additionally, nicotine exposure inverted the ratio between mRNAs of proteins in the FOXO pathway and their targeting miRs. Conclusions: Smokers have a high prevalence of CD8+ T cells with a naïve-memory phenotype. These cells express a miR profile that interacts with the memory programming conducted through the FOXO pathway.

Cardiovascular Safety of Tocilizumab Versus Etanercept in Rheumatoid Arthritis: A Randomized Controlled Trial.

OBJECTIVE: To assess the risk of major adverse cardiovascular events (MACE) in patients with rheumatoid arthritis (RA) treated with tocilizumab compared to those treated with the tumor necrosis factor inhibitor etanercept. METHODS: This randomized, open-label, parallel-group trial enrolled patients with active seropositive RA (n = 3,080) who had an inadequate response to conventional synthetic disease-modifying antirheumatic drugs and who had at least 1 cardiovascular (CV) risk factor. Patients were randomly assigned 1:1 to receive open-label tocilizumab at 8 mg/kg/month or etanercept at 50 mg/week. All patients were followed up for a mean of 3.2 years. The primary end point was comparison of time to first occurrence of MACE. The trial was powered to exclude a relative hazard ratio for MACE of 1.8 or higher in the tocilizumab group compared to the etanercept group. RESULTS: By week 4 of treatment, the serum low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglyceride levels were a median 11.1%, 5.7%, and 13.6% higher, respectively, in patients receiving tocilizumab compared to those receiving etanercept (each P < 0.001). During follow-up, 83 MACE occurred in the tocilizumab group compared to 78 MACE in the etanercept group. The estimated hazard ratio for occurrence of MACE in the tocilizumab group relative to the etanercept group was 1.05 (95% confidence interval 0.77-1.43). Results were similar in sensitivity analyses and in the on-treatment population analysis. Adverse events occurred more frequently in the tocilizumab group, including serious infection and gastrointestinal perforation. CONCLUSION: The results of this trial, which provide insights into the CV safety of tocilizumab as compared to etanercept, ruled out a risk for occurrence of MACE of 1.43 or higher in patients treated with tocilizumab. This result should be interpreted in the context of the clinical efficacy and non-CV safety of tocilizumab.

Molecular Characterization of Human Lymph Node Stromal Cells During the Earliest Phases of Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is a progressive, destructive autoimmune arthritis. Break of tolerance and formation of autoantibodies occur years before arthritis. Adaptive immunity is initiated in lymphoid tissue where lymph node stromal cells (LNSCs) play a crucial role in shaping the immune response and maintaining peripheral tolerance. Here we performed the first epigenomic characterization of LNSCs during health and early RA, by analyzing their transcriptome and DNA methylome in LNSCs isolated from lymph node needle biopsies obtained from healthy controls (HC), autoantibody positive RA-risk individuals and patients with established RA. Of interest, LNSCs from RA-risk individuals and RA patients revealed a common significantly differential expressed gene signature compared with HC LNSCs. Pathway analysis of this common signature showed, among others, significant enrichment of pathways affecting the extracellular matrix (ECM), cholesterol biosynthesis and immune system. In a gel contraction assay LNSCs from RA-risk individuals and RA patients showed impaired collagen contraction compared to healthy LNSCs. In RA LNSCs a significant enrichment was observed for genes involved in cytokine signaling, hemostasis and packaging of telomere ends. In contrast, in RA-risk LNSCs pathways in cancer (cell cycle related genes) were differentially expressed compared with HC, which could be validated in vitro using a proliferation assay, which indicated a slower proliferation rate. DNA methylation analyses revealed common and specific differentially methylated CpG sites (DMS) in LNSC from RA patients and RA-risk individuals compared with HC. Intriguingly, shared DMS were all associated with antigen processing and presentation. This data point toward alterations in cytoskeleton and antigen-processing and presentation in LNSC from RA-risk individuals and RA patients. Further studies are required to investigate the consequence of this LNSC abnormality on LNSC-mediated immunomodulation.

Narcolepsy - clinical spectrum, aetiopathophysiology, diagnosis and treatment.

Narcolepsy is a rare brain disorder that reflects a selective loss or dysfunction of orexin (also known as hypocretin) neurons of the lateral hypothalamus. Narcolepsy type 1 (NT1) is characterized by excessive daytime sleepiness and cataplexy, accompanied by sleep-wake symptoms, such as hallucinations, sleep paralysis and disturbed sleep. Diagnosis is based on these clinical features and supported by biomarkers: evidence of rapid eye movement sleep periods soon after sleep onset; cerebrospinal fluid orexin deficiency; and positivity for HLA-DQB1*06:02. Symptomatic treatment with stimulant and anticataplectic drugs is usually efficacious. This Review focuses on our current understanding of how genetic, environmental and immune-related factors contribute to a prominent (but not isolated) orexin signalling deficiency in patients with NT1. Data supporting the view of NT1 as a hypothalamic disorder affecting not only sleep-wake but also motor, psychiatric, emotional, cognitive, metabolic and autonomic functions are presented, along with uncertainties concerning the 'narcoleptic borderland', including narcolepsy type 2 (NT2). The limitations of current diagnostic criteria for narcolepsy are discussed, and a possible new classification system incorporating the borderland conditions is presented. Finally, advances and obstacles in the symptomatic and causal treatment of narcolepsy are reviewed.

TET1 is an important transcriptional activator of TNFα expression in macrophages.

Activation of macrophages and overexpression of TNFα is associated with the pathogenesis of chronic inflammatory diseases. However, the mechanisms leading to TNFα overexpression are still unknown. 5-methylocytosine (5-mC) is an epigenetic modification that is associated with silenced genes. Recent studies showed that it is converted to 5-hydroxylmethylocytosine (5-hmC) and reactivates gene expression through the action of the family of Ten-Eleven-Translocation (TET1-3) enzymes. In this study, we show that 5-hmC levels are increased globally and specifically in the TNFα promoter during the differentiation of monocytes to macrophages. In addition, the levels of 5-hmC are increased upon LPS stimulation of macrophages. Furthermore, CRIPSR stable knockout of TET1 decreases the expression of TNFα and other pro-inflammatory cytokines. In conclusion, we showed that TET1 contributes to the activation of macrophages possibly through regulation of 5-hydroxymethylation in the promoter of pro-inflammatory cytokine genes. The TET1 enzyme could be a promising therapeutic target to inhibit the persistent inflammation caused by macrophages in chronic inflammatory diseases.

Adipokine expression in systemic sclerosis lung and gastrointestinal organ involvement.

OBJECTIVES: The immunomodulatory properties of adipokines have previously been reported in autoimmune disorders. Less is known about the role of adipokines in systemic sclerosis (SSc). Lung and gastrointestinal tract are frequently involved in SSc; therefore, these organs were analyzed for adipokine expression as well as pulmonary samples of patients suffering from idiopathic pulmonary fibrosis (IPF) as comparison. METHODS: Gastric samples (antrum, corpus) of SSc were analyzed immunohistochemically for adiponectin, resistin and visfatin compared with non-SSc related gastritis. Inflammatory cells were quantified in gastric samples and correlated with adipokine expression. Lung samples of SSc, IPF and healthy controls were also analyzed. Protein levels of lung tissue lysates and bronchoalveolar lavages (BAL) in minor fibrotic stages were measured by ELISA. RESULTS: Lung sections of donor parenchyma showed significantly stronger adiponectin signals as IPF and SSc (donor vs. IPF: p < 0.0001). In SSc and IPF, resistin and visfatin were increased within immune cell infiltrates, but overall no difference in expression for resistin or visfatin compared to controls was observed. In BAL and lung protein lysates of early stages of fibrosis, adiponectin and visfatin were not reduced in IPF and SSc compared to controls. In gastric samples collected by standard endoscopic gastric biopsy, adiponectin was also significantly reduced in SSc- compared to non-SSc gastritis (p = 0.049) while resistin and visfatin were comparable although deeper fibrotic layers were not included in the respective samples. Adiponectin-positive tissues showed higher amounts of CD4+ but not CD8+ T cells. Controls showed no correlation between CD4+ T cells and resistin, whereas SSc showed significantly more CD4+ T cells in resistin-negative tissues. CONCLUSION: Adipokines are expressed in gastric and lung samples of patients with SSc and in lung samples affected by IPF. Prominently, adiponectin levels were reduced in fibrotic SSc gastritic tissue as well as in IPF and SSc lung tissue. Consequently, adiponectin expression seems to be associated with fibrotic progression in the context of SSc and IPF.

PU.1 controls fibroblast polarization and tissue fibrosis.

Fibroblasts are polymorphic cells with pleiotropic roles in organ morphogenesis, tissue homeostasis and immune responses. In fibrotic diseases, fibroblasts synthesize abundant amounts of extracellular matrix, which induces scarring and organ failure. By contrast, a hallmark feature of fibroblasts in arthritis is degradation of the extracellular matrix because of the release of metalloproteinases and degrading enzymes, and subsequent tissue destruction. The mechanisms that drive these functionally opposing pro-fibrotic and pro-inflammatory phenotypes of fibroblasts remain unknown. Here we identify the transcription factor PU.1 as an essential regulator of the pro-fibrotic gene expression program. The interplay between transcriptional and post-transcriptional mechanisms that normally control the expression of PU.1 expression is perturbed in various fibrotic diseases, resulting in the upregulation of PU.1, induction of fibrosis-associated gene sets and a phenotypic switch in extracellular matrix-producing pro-fibrotic fibroblasts. By contrast, pharmacological and genetic inactivation of PU.1 disrupts the fibrotic network and enables reprogramming of fibrotic fibroblasts into resting fibroblasts, leading to regression of fibrosis in several organs.

Osteogenic differentiation of fibroblast-like synovial cells in rheumatoid arthritis is induced by microRNA-218 through a ROBO/Slit pathway.

BACKGROUND: Fibroblast-like synovial cells (FLS) have multilineage differentiation potential including osteoblasts. We aimed to investigate the role of microRNAs during the osteogenic differentiation of rheumatoid arthritis (RA)-FLS. METHODS: RA-FLS were differentiated in osteogenic medium for 21 days. Osteogenic differentiation was evaluated by alkaline phosphatase (ALP) staining and Alizarin Red staining. MicroRNA (miRNA) array analysis was performed to investigate the differentially expressed miRNAs during osteogenic differentiation. Expression of miR-218-5p (miR-218) during the osteogenic differentiation was determined by quantitative real-time PCR. Transfections with an miR-218 precursor and inhibitor were used to confirm the targets of miR-218 and to analyze the ability of miR-218 to induce osteogenic differentiation. Secreted Dickkopf-1 (DKK1) from FLS transfected with miR-218 precursor/inhibitor or roundabout 1 (ROBO1) knockdown FLS established using ROBO1-small interfering RNA (siRNA) were measured by ELISA. RESULTS: The miRNA array revealed that 12 miRNAs were upregulated and 24 miRNAs were downregulated after osteogenic differentiation. We observed that the level of miR-218 rose in the early phase of osteogenic differentiation and then decreased. Pro-inflammatory cytokines modified the expression of miR-218. The induction of miR-218 in RA-FLS decreased ROBO1 expression, and promoted osteogenic differentiation. Both the overexpression of miR-218 and the knockdown of ROBO1 in RA-FLS decreased DKK1 secretion. CONCLUSION: We identified miR-218 as a crucial inducer of the osteogenic differentiation of RA-FLS. MiR-218 modulates the osteogenic differentiation of RA-FLS through the ROBO1/DKK-1 axis. The induction of the osteogenic differentiation of proliferating RA-FLS through the provision of miR-218 into RA-FLS or by boosting the cellular reservoir of miR-218 might thus become a therapeutic strategy for RA.

Endogenous Galectin-9 Suppresses Apoptosis in Human Rheumatoid Arthritis Synovial Fibroblasts.

Galectin-9 (Gal9) has been postulated to have anti-inflammatory properties based on the ability of exogenous Gal9 to induce apoptosis in synovial fibroblasts in animal models of rheumatoid arthritis (RA). Here we aimed to assess the potential role of endogenous Galectins, including Gal9, in the inflammatory pathology of the RA synovium in humans. Firstly expression of Galectins 1-9 was determined in synovial fibroblasts (RASF) and dermal fibroblasts (DF) isolated from RA patients, the latter representing a non-inflamed site. We then further challenged the cells with pro-inflammatory TLR agonists and cytokines and assessed Galectin expression. Gal9 was found to be differentially and abundantly expressed in RASF compared to DF. Agonists of TLR3 and TLR4, along with IFNgamma were also found to induce Gal9 expression in RASF. siRNA was then used to knock-down Gal9 expression in RASF and the effects of this on apoptosis and cell viability were assessed. Increased apoptosis was observed in RASF following Gal9 knock-down. We conclude that, unlike exogenous Gal9, endogenous Gal9 is protective against apoptosis and enhances synovial fibroblast viability suggesting that its role in RA is both pathogenic and pro-inflammatory.

Evaluating the bromodomain protein BRD1 as a therapeutic target in rheumatoid arthritis.

Targeting epigenetic reader proteins by small molecule inhibitors represents a new therapeutic concept in autoimmune diseases such as rheumatoid arthritis (RA). Although inhibitors targeting bromodomain protein 1 (BRD1) are in development, the function of BRD1 has hardly been studied. We investigated the therapeutic potential of BRD1 inhibition in joint-resident cells in RA, synovial fibroblasts (SF) and macrophages. The proliferation of SF was decreased upon BRD1 silencing, accompanied by the downregulation of genes involved in cell cycle regulation. Silencing of BRD1 in SF decreased the basal expression of MMP1 but increased TNF-α- and LPS-induced levels of MMP3, IL6 and IL8. In monocyte-derived macrophages (MDM), silencing of BRD1 decreased the LPS-induced expression of TNF-α, but did not significantly affect basal and the TNF-α- and LPS-induced expression of IL6 and IL8. Our data point to a cell type- and a stimulus-specific function of BRD1. Inhibiting BRD1 could have potential beneficial effects in RA via decreasing the proliferation of SF. Anti-inflammatory effects were limited and only observed in MDM.

Analysis of early changes in DNA methylation in synovial fibroblasts of RA patients before diagnosis.

DNA methylation is an important epigenetic modification that is known to be altered in rheumatoid arthritis synovial fibroblasts (RASF). Here, we compared the status of promoter DNA methylation of SF from patients with very early RA with SF from patients with resolving arthritis, fully established RA and from non-arthritic patients. DNA was hybridized to Infinium Human methylation 450k and 850k arrays and differential methylated genes and pathways were identified. We could identify a significant number of CpG sites that differed between the SF of different disease stages, showing that epigenetic changes in SF occur early in RA development. Principal component analysis confirmed that the different groups of SF were separated according to their DNA methylation state. Furthermore, pathway analysis showed that important functional pathways were altered in both very early and late RASF. By focusing our analysis on CpG sites in CpG islands within promoters, we identified genes that have significant hypermethylated promoters in very early RASF. Our data show that changes in DNA methylation differ in RASF compared to other forms of arthritis and occur at a very early, clinically yet unspecific stage of disease. The identified differential methylated genes might become valuable prognostic biomarkers for RA development.

TLR3 Ligand Poly(I:C) Exerts Distinct Actions in Synovial Fibroblasts When Delivered by Extracellular Vesicles.

Extracellular vesicles (EV) can modulate the responses of cells to toll-like receptor (TLR) ligation; conversely, TLR ligands such as double-stranded RNA (dsRNA) can enhance the release of EV and influence of the composition and functions of EV cargos. Inflamed synovial joints in rheumatoid arthritis (RA) are rich in EV and extracellular RNA; besides, RNA released from necrotic synovial fluid cells can activate the TLR3 signaling in synovial fibroblasts (SFs) from patients with RA. Since EV occur prominently in synovial joints in RA and may contribute to the pathogenesis, we questioned whether EV can interact with dsRNA, a TLR3 ligand, and modify its actions in arthritis. We have used as model the effects on RA SFs, of EV released from monocyte U937 cells and peripheral blood mononuclear cells upon stimulation with Poly(I:C), a synthetic analog of dsRNA. We show that EV released from unstimulated cells and Poly(I:C)-stimulated U937 cells [Poly(I:C) EV] differ in size but bind similar amounts of Annexin V and express comparable levels of MAC-1, the receptor for dsRNA, on the vesicular membranes. Specifically, Poly(I:C) EV contain or associate with Poly(I:C) and at least partially protect Poly(I:C) from RNAse III degradation. Poly(I:C) EV shuttle Poly(I:C) to SFs and reproduce the proinflammatory and antiviral gene responses of SFs to direct stimulation with Poly(I:C). Poly(I:C) EV, however, halt the death receptor-induced apoptosis in SFs, thereby inverting the proapoptotic nature of Poly(I:C). These prosurvival effects sharply contrast with the high toxicity of cationic liposome-delivered Poly(I:C) and may reflect the route of Poly(I:C) delivery via EV or the fine-tuning of Poly(I:C) actions by molecular cargo in EV. The demonstration that EV may safeguard extracellular dsRNA and allow dsRNA to exert antiapoptotic effects on SFs highlights the potential of EV to amplify the pathogenicity of dsRNA in arthritis beyond inflammation (by concurrently enhancing the expansion of the invasive synovial stroma).

Interleukin-36 receptor mediates the crosstalk between plasma cells and synovial fibroblasts.

The IL-1 family member IL-36α has proinflammatory and pathogenic properties in psoriasis. IL-36α binds to the IL-36 receptor leading to nuclear factor kappa B/mitogen activated protein kinase mediated cytokine release. The IL-36R antagonist prevents recruitment of IL-1 receptor accessory protein and therefore IL-36-dependent cell activation. In inflamed human tissue, we previously could show that resident B cells and plasma cells (PC) express IL-36α. Further, fibroblast-like synoviocytes (FLS) produced proinflammatory cytokines upon IL-36α-stimulation. We hypothesize an IL-36-specific crosstalk between B cells/PCs and FLS permitting a proinflammatory B cell niche. Here, we firstly demonstrated that B cell lines and B cells from healthy donors express IL-36α and stimulation increased IL-36α in B cells and primary plasmablasts/PCs. Moreover, FLS respond specifically to IL-36α by proliferation and production of matrix metalloproteinases via p38/HSP27 signaling. Importantly, IL-36R-deficiency abrogated IL-36α-induced production of inflammatory mediators in FLS and changed the intrinsic FLS-phenotype. Using an in vitro co-culture system, we could show that IL-36R-deficient FLS had a limited capacity to support PC survival compared to wild-type FLS. Hence, we demonstrated an IL-36R-dependent crosstalk between B cells/PCs and FLS. Our data support the concept of initiation and maintenance of a proinflammatory niche by B cells in the joints.

Association between circulating miRNAs and spinal involvement in patients with axial spondyloarthritis.

OBJECTIVES: Dysregulation of miRNAs and their target genes contributes to the pathophysiology of autoimmune diseases. Circulating miRNAs may serve as diagnostic/prognostic biomarkers. We aimed to investigate the association between circulating miRNAs, disease activity and spinal involvement in patients with axial spondyloarthritis (AxSpA). METHODS: Total RNA was isolated from the plasma of patients with non-radiographic (nr)AxSpA, patients with ankylosing spondylitis (AS) and healthy controls (HC) via phenol-chloroform extraction. A total of 760 miRNAs were analysed with TaqMan® Low Density Arrays, and the expression of 21 miRNAs was assessed using single assays. RESULTS: Comprehensive analysis demonstrated the differential expression of miRNAs among patients with progressive spinal disease. Of the 21 miRNAs selected according to their expression patterns, the levels of miR-625-3p were significantly different between nr-AxSpA patients and HCs. We found no correlation between miRNA levels and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) in nr-AxSpA patients. Selected miRNAs, such as miR-29a-3p, miR-146a-5p or miR-222-3p with an established role in extracellular matrix formation and inflammation were associated with spinal changes and/or disease activity assessed by BASDAI in AS patients, including miR-625-3p reflecting disease activity in AS with spinal involvement. CONCLUSIONS: Our data indicate that circulating miRNAs play a role in the pathogenesis of AxSpA and are also suggestive of their potential as biomarkers of disease progression. We hypothesize that differential systemic levels of miRNA expression reflect miRNA dysregulation at sites of spinal inflammation or bone formation where these molecules contribute to the development of pathophysiological features typical of AxSpA.

The epigenetic architecture at gene promoters determines cell type-specific LPS tolerance.

Synovial fibroblasts (SF) drive inflammation and joint destruction in chronic arthritis. Here we show that SF possess a distinct type of LPS tolerance compared to macrophages and other types of fibroblasts. In SF and dermal fibroblasts, genes that were non-tolerizable after repeated LPS stimulation included pro-inflammatory cytokines, chemokines and matrix metalloproteinases, whereas anti-viral genes were tolerizable. In macrophages, all measured genes were tolerizable, whereas in gingival and foreskin fibroblasts these genes were non-tolerizable. Repeated stimulation of SF with LPS resulted in loss of activating histone marks only in promoters of tolerizable genes. The epigenetic landscape at promoters of tolerizable genes was similar in unstimulated SF and monocytes, whereas the basal configuration of histone marks profoundly differed in genes that were non-tolerizable in SF only. Our data suggest that the epigenetic configuration at gene promoters regulates cell-specific LPS-induced responses and primes SF to sustain their inflammatory response in chronic arthritis.