Genetics of spondyloarthritis--beyond the MHC

The thiol/disulfide balance is shifted towards oxidation in psoriatic arthritis compared to controls and is associated with higher disease activity

OBJECTIVE

This study was designed to compare thiol/disulfide and ischemia-modified albumin (IMA) levels between psoriatic arthritis (PsA) and healthy controls and evaluate the correlation between these molecules and the disease activity scores used in PsA.

METHODS

A total of 63 PsA patients and 49 healthy volunteers were included in the study. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), modified disease activity score 28 (DAS28), and Bath Ankylosing Spondylitis Functional Index (BASFI) scores were used as disease activity indices for PsA patients. Calculations of native thiol (-SH), disulfide (-SS), and total thiol (-SH+-SS) molecules were made by the automatic spectrophotometric method, and the albumin cobalt binding test was used to measure IMA levels.

RESULTS

In the PsA group, -SS/-SH and -SS/(-SH+-SS) levels were higher and -SH/(-SH+-SS) levels were lower than in controls. In the linear regression analysis, a significant correlation relationship was detected between DAS28-erythrocyte sedimentation rate (ESR) and -SS/(-SH+-SS) (β = 0.795, CI 95%, 0.196-1.395; P = .010), -SH/(-SH+-SS) (β = -0.475, CI 95%, 0.114-0.836; P = .010) and IMA (β = 3.932, CI 95%, 0.859-7.005; P = .013). Additionally, a significant correlation was detected between IMA and BASDAI and BASFI.

CONCLUSION

In PsA, thiol/disulfide homeostasis has shifted in favor of disulfide as an oxidative indicator. Serum thiol/disulfide levels are correlated with PsA disease activity indices.

Enthesitis on Chip - A Model for Studying Acute and Chronic Inflammation of the Enthesis and its Pharmacological Treatment

Enthesitis, the inflammation of the enthesis, which is the point of attachment of tendons and ligaments to bones, is a common musculoskeletal disease. The inflammation often originates from the fibrocartilage region of the enthesis as a consequence of mechanical overuse or -load and consequently tissue damage. During enthesitis, waves of inflammatory cytokines propagate in(to) the fibrocartilage, resulting in detrimental, heterotopic bone formation. Understanding of human enthesitis and its treatment options is limited, also because of lacking in vitro model systems that can closely mimic the pathophysiology of the enthesis and can be used to develop therapies. In this study, an enthes(it)is-on-chip model is developed. On opposite sides of a porous culture membrane separating the chip's two microfluidic compartments, human mesenchymal stromal cells are selectively differentiated into tenocytes and fibrochondrocytes. By introducing an inflammatory cytokine cocktail into the fibrochondrocyte compartment, key aspects of acute and chronic enthesitis, measured as increased expression of inflammatory markers, can be recapitulated. Upon inducing chronic inflammatory conditions, hydroxyapatite deposition, enhanced osteogenic marker expression and reduced secretion of tissue-related extracellular matrix components are observed. Adding the anti-inflammatory drug celecoxib to the fibrochondrocyte compartment mitigates the inflammatory state, demonstrating the potential of the enthesitis-on-chip model for drug testing.

Illuminating the impact of γδ T cells in man and mice in spondylarthritides

Spondylarthritides (SpA) are a group of autoinflammatory diseases affecting the spine, peripheral joints, and entheses, including axial spondyloarthritis (axSpA) and psoriatic arthritis. AxSpA has a multifactorial etiology that involves genetic predispositions, such as HLA-B27 and IL-23R. Although HLA-B27 is strongly associated with axSpA, its role remains unclear. GWAS studies have demonstrated that genetic polymorphisms related to the IL-23 pathway occur throughout the spectrum of SpA, including but not limited to axSpA and PsA. IL-23 promotes the production of IL-17, which drives inflammation and tissue damage. This pathway contributes not only to peripheral enthesitis but also to spinal inflammation. γδ T cells in axSpA express IL-23R and RORγt, crucial for their activation, although specific pathogenic cells and factors remain elusive. Despite drug efficacy in PsA, IL-23R inhibition is ineffective in axSpA. Murine models provide valuable insights into the intricate cellular and molecular interactions that contribute to the development and progression of SpA. Those models are useful tools to elucidate the dynamics of γδ T cell involvement, offering insights into disease mechanisms and potential therapeutic targets. This review aims to illuminate the complex interplay between IL-23 and γδ T cells in SpA pathogenesis, emphasizing their roles in chronic inflammation, tissue damage, and disease heterogeneity.

Dysbiosis in Inflammatory Bowel Disease and Spondyloarthritis: Still a Long Way to Go?

The association between Inflammatory Bowel Disease (IBD) and Spondyloarthritis (SpA) has been known for years, as has the concept that IBD is associated with an altered intestinal bacterial composition, a condition known as "dysbiosis". Recently, a state of intestinal dysbiosis has also been found in SpA. Dysbiosis in the field of IBD has been well characterized so far, as well as in SpA. The aim of this review is to summarize what is known to date and to emphasize the similarities between the microbiota conditions in these two diseases: particularly, an altered distribution in the gut of Enterobacteriaceae, Streptococcus, Haemophilus, Clostridium, Akkermansia, Ruminococcus, Faecalibacterium Prausnitzii, Bacteroides Vulgatus, Dialister Invisus, and Bifidubacterium Adolescentis is common to both IBD and SpA. At the same time, little is known about intestinal dysbiosis in IBD-related SpA. Only a single recent study has found an increase in Escherichia and Shigella abundances and a decrease in Firmicutes, Ruminococcaceae, and Faecalibacterium abundances in an IBD-related SpA group. Based on what has been discovered so far about the altered distribution of bacteria that unite both pathologies, it is appropriate to carry out further studies aiming to improve the understanding of IBD-related SpA for the purpose of developing new therapeutic strategies.

Serum biomarkers and their relationship to axial spondyloarthritis associated with inflammatory bowel diseases

Spondyloarthritis (SpA) constitute a group of chronic inflammatory immune-mediated rheumatic diseases characterized by genetic, clinical, and radiological features. Recent efforts have concentrated on identifying biomarkers linked to axial SpA associated with inflammatory bowel disease (IBD), offering predictive insights into disease onset, activity, and progression. Genetically, the significance of the HLA-B27 antigen is notably diminished in ankylosing spondylitis (AS) associated with IBD, but is heightened in concurrent sacroiliitis. Similarly, certain polymorphisms of endoplasmic reticulum aminopeptidase (ERAP-1) appear to be involved. Carriage of variant NOD2/CARD15 polymorphisms has been demonstrated to correlate with the risk of subclinical intestinal inflammation in AS. Biomarkers indicative of pro-inflammatory activity, including C-reactive protein (CRP) along with erythrocyte sedimentation rate (ESR), are among the consistent predictive biomarkers of disease progression. Nevertheless, these markers are not without limitations and exhibit relatively low sensitivity. Other promising markers encompass IL-6, serum calprotectin (s-CLP), serum amyloid (SAA), as well as biomarkers regulating bone formation such as metalloproteinase-3 (MMP-3) and Dickkopf-related protein 1 (DKK-1). Additional candidate indicators of structural changes in SpA patients include matrix metalloproteinase-3 (MMP-3), vascular endothelial growth factor (VEGF), tenascin C (TNC), and CD74 IgG. Fecal caprotein (f-CLP) levels over long-term follow-up of AS patients have demonstrated predictive value in anticipating the development of IBD. Serologic antibodies characteristic of IBD (ASCA, ANCA) have also been compared; however, results exhibit variability. In this review, we will focus on biomarkers associated with both axial SpA and idiopathic intestinal inflammation, notably enteropathic spondyloarthritis.

Ankylosing spondylitis: acute/subacute vs. chronic iridocyclitis - a bidirectional two-sample Mendelian randomization study

Background

Observational studies found associations between ankylosing spondylitis (AS) and iridocyclitis (IC), but the causality remained unconfirmed.

Methods

We employed two-sample Mendelian randomization (MR) to investigate the bidirectional causal relationships between AS and IC. Single-nucleotide polymorphisms (SNPs) were chosen from the FinnGen database's genome-wide association studies (GWAS) following a rigorous evaluation of the studies' quality. Sensitivity analysis was performed to assess the potential influence of pleiotropy and heterogeneity on the MR findings.

Results

Elevated genetic risk for AS showed positive causal effects on IC and its subtypes (IC, OR = 1.094, 95% CI = 1.035-1.157, P = 0.00156; Acute/Subacute IC, OR = 1.327, 95% CI = 1.266-1.392, P = 8.73×10-32; Chronic IC, OR = 1.454, 95% CI = 1.308-1.618, P = 5.19×10-12). Significant causal association was specifically observed between Acute/Subacute IC and AS (OR = 1.944, 95% CI = 1.316-2.873, P = 8.38×10-4). Sensitivity analysis suggested that horizontal pleiotropy was unlikely to influence the causality, and the leave-one-out analysis confirmed that a single SNP did not drive the observed associations.

Conclusion

Our findings provide new proof of a positive causal relationship between AS and IC in the European population. Notably, it is Acute/Subacute IC, rather than IC as a whole or Chronic IC, that is associated with an elevated risk of AS. These results emphasize the significance of considering AS characteristics in the diagnosis of Acute/Subacute IC.

SpA plus IBD or IBD plus SpA: Does commutative property apply?

The term spondyloarthritis (SpA) encompasses a group of interrelated disorders characterised by the involvement of the musculoskeletal system as well as extra-articular manifestations like acute anterior uveitis, psoriasis and inflammatory bowel diseases (IBD). Likewise, IBD may present with various extra-intestinal manifestations among which those involving the musculoskeletal system, namely peripheral and axial SpA are the most common. The identification of patients with both SpA and IBD is of paramount importance in clinical practice since the coexistence of these two entities has been associated with great disability and decreased quality of life. In order to achieve an early diagnosis of IBD-SpA it is instrumental that rheumatologists seek for gastrointestinal symptoms in SpA patients and likewise that gastroenterologists seek for inflammatory musculoskeletal symptoms in patients with IBD. This narrative review aims at critically appraising the available evidence about SpA occurring in IBD patients versus IBD occurring in patients with SpA and at highlighting similarities and differences between the two scenarios.

Peripheral spondyloarthritis: What have we learned?

The peripheral spondyloarthritis (pSpA) entity remains poorly defined in comparison with axial SpA and psoriatic arthritis, as the clinical symptoms have low specificity, the biological markers are virtually lacking, and dedicated randomized controlled trials in this specific indication remain scarce. In addition, clinical similarities between pSpA and psoriatic arthritis (PsA) have been described, partly explained by a resemblance in the pathophysiology of both entities. Thus, diagnosing pSpA can be challenging because of the overlap with other entities and the absence of a specific test or imaging study that can definitively diagnose the condition. The aim of this review is to summarize the current understanding of pSpA, its epidemiology, physiopathology, clinical diagnosis, and classification criteria. In addition, we present patient-reported outcomes used in pSpA clinical studies, available evidence on therapies, and future directions.

Association Between SPARC Polymorphisms and Ankylosing Spondylitis and Its mRNA and Protein Expression in a Chinese Han Population: A Case-Control Study

Objective

We explore the association of polymorphisms in Secreted protein acidic and rich in cysteine (SPARC) with ankylosing spondylitis (AS) and detect SPARC mRNA and protein expression in a Chinese Han population.

Methods

Nine single-nucleotide polymorphisms (SNPs) of SPARC were genotyped in 768 AS patients and 768 controls by TaqMan genotyping assay. mRNA expression of SPARC was detected by real-time polymerase chain reaction (RT-PCR), and serum level of SPARC protein was detected by ELISA.

Results

The frequency of A allele of rs171121187 was significantly higher in AS patients than in controls (Pc=0.003, odds ratio [OR]=1.45, 95% confidence interval [95% CI] = 1.18-1.77), the AA and AC genotypes increased the risk of AS when compared with CC genotype (Pc=0.003, OR=3.96, 95% CI=1.80-8.75, and Pc=0.003, OR=1.27, 95% CI=1.01-1.61, respectively). The frequency of G allele of rs4958487 was significantly lower in AS than in controls (Pc=0.001, OR=0.60, 95% CI=0.47-0.68), the GG and GA genotypes reduced the risk of AS when compared with AA genotype (Pc=0.005, OR=0.46, 95% CI 0.18-1.14, and Pc=0.005, OR=0.60, 95% CI=0.45-0.79, respectively). The haplotype AA of rs17112187/rs4958487 significantly increased the risk of AS (P=2.31E-5, OR=1.60, 95% CI=1.28-1.98), while haplotype CG decreased the risk of AS (P=5.42E-5, OR=0.55, 95% CI=0.41-0.74). Expression levels of SPARC mRNA were significantly lower in both Peripheral blood mononuclear cells (PBMC) and granulocytes in AS patients than in controls (P=0.008 and P=0.005, respectively). SPARC protein levels were also reduced in AS patients versus the controls (P=0.002).

Conclusion

This study indicates that polymorphisms in SPARC are associated with AS susceptibility, and both mRNA and protein levels of SPARC are decreased in AS patients in a Chinese Han population.

The Risk and Predictors of Malignancies in Ankylosing Spondylitis Patients in Israel-A Retrospective Electronic Data-Based Study

BACKGROUND

Previous studies demonstrated unclear and vast variability in the association between Ankylosing Spondylitis (AS) and the risk of cancer.

OBJECTIVES

To assess the risk of overall and site-specific malignancies for AS patients in Israel, while examining the role of comorbidities and immunomodulatory therapy.

METHODS

We conducted a retrospective electronic data-based study including all AS patients diagnosed between 2002 and 2018, with no history of cancer prior to enrollment, with 5:1 ratio matched-control by age, gender, and place of residence. The odds Ratios (OR) for site-specific malignancies, comparing AS patients and controls, were calculated using logistic regression. Risk factors for malignancies within the AS cohort were evaluated in the same manner.

RESULTS

This study comprised 5825 AS patients and 28,356 matched controls. There was a higher overall risk of cancer in AS patients compared to controls (OR = 1.4, 95% CI 1.24-1.6), specifically for solid malignancies (OR = 1.5, 95% CI 1.3-1.7), CNS (OR = 3.72, 95% CI 1.29-10.7), kidney (OR = 2.06, 95% CI 1.12-3.8), and malignancy of unknown primary (OR = 3.06, 95% CI 2.35-3.98). Regarding predictors for malignancy within AS patients, older age at diagnosis (OR = 1.31, 95%,CI 1.25-2.36), diabetes (OR = 1.52, 95% CI 1.18-1.97), IBD (OR = 2.61, 95% CI 1.75-3.89), and treatment with DMARDs (OR = 2.17, 95% CI 1.65-2.83) were associated with a higher risk of solid malignancies, while NSAIDs treatment alone had a protective effect for solid malignancies (OR = 0.78, 95% CI 0.61-0.99). No significant association was found between anti-TNF therapy and the risk of solid or hematologic malignancies within the AS group.

CONCLUSION

AS is associated with an increased risk of overall and site-specific malignancies, with independently higher risk for older age, comorbidity of DM, IBD, and treatment with DMARDs.

Cytokines in Spondyloarthritis and Inflammatory Bowel Diseases: From Pathogenesis to Therapeutic Implications

Spondyloarthritis and inflammatory bowel diseases are chronic immune disorders of the joints and the gut that often coexist in the same patient, increasing the burden of each disorder, worsening patients' quality of life, and influencing therapeutic strategies. Genetic predisposition, environmental triggers, microbiome features, immune cell trafficking, and soluble factors such as cytokines contribute to the pathogenesis of both articular and intestinal inflammation. Most of the molecular targeted biological therapies developed over the last two decades were based on evidence that specific cytokines may be involved in these immune diseases. Despite pro-inflammatory cytokine pathways sharing the pathogenesis of both articular and gut diseases (i.e., tumor necrosis factor and interleukin-23), several other cytokines (i.e., interleukin-17) may be differently involved in the tissue damage process, depending on the specific disease and the organ involved in inflammation, making difficult the identification of a therapeutic plan that is efficacious for both inflammatory manifestations. In this narrative review, we comprehensively summarize the current knowledge on cytokine involvement in spondyloarthritis and inflammatory bowel diseases, underlining similarities and differences among their pathogenetic pathways; finally, we provide an overview of current and potential future treatment strategies to simultaneously target both articular and gut immune disorders.

Genetic susceptibility to autoimmunity-Current status and challenges

Autoimmune diseases (ADs) often arise from a combination of genetic and environmental triggers that disrupt the immune system's capability to properly tolerate body self-antigens. Familial studies provided the earliest insights into the risk loci of such diseases, while genome-wide association studies (GWAS) significantly broadened the horizons. A drug targeting a prominent pathological pathway can be applied to multiple indications sharing overlapping mechanisms. Advances in genomic technologies used in genetic studies provide critical insights into future research on gene-environment interactions in autoimmunity. This Review summarizes the history and recent advances in the understanding of genetic susceptibility to ADs and related immune disorders, including coronavirus disease 2019 (COVID-19), and their indications for the development of diagnostic or prognostic markers for translational applications.

Analysis of N6-Methyladenosine RNA Methylation Regulators in Diagnosis and Distinct Molecular Subtypes of Ankylosing Spondylitis

The most frequent internal modification in eukaryotic mRNA is N6-methyladenosine (m6A). However, what we know about the m6A regulators in Ankylosing spondylitis (AS) is still limited. In our study, eight distinct m6A regulators were selected utilizing Differentially Expressed Gene (DEG) analysis of the Gene Expression Omnibus GSE73754 dataset for making comparisons between AS (Ankylosing spondylitis) and non-AS patients. The random forest model and the nomogram model were used to screen the eight candidate m6A regulators and evaluate their prediction accuracy for the occurrence of AS. Furthermore, based on the selected m6A regulators, the AS patients were divided into two subgroups, and we applied principal component analysis algorithms to calculate their m6A score and evaluate the m6A patterns. Our findings revealed that patients in cluster A were linked to activated CD4 T cell immunity and activated CD8 T cell immunity. With its major contributions in the area of immunology, our research in m6A patterns may benefit the future diagnosis and treatment strategies of AS.

Identification of diagnostic mRNA biomarkers in whole blood for ankylosing spondylitis using WGCNA and machine learning feature selection

Ankylosing spondylitis (AS) is a common inflammatory spondyloarthritis affecting the spine and sacroiliac joint that finally results in sclerosis of the axial skeleton. Aside from human leukocyte antigen B27, transcriptomic biomarkers in blood for AS diagnosis still remain unknown. Hence, this study aimed to investigate credible AS-specific mRNA biomarkers from the whole blood of AS patients by analyzing an mRNA expression profile (GSE73754) downloaded Gene Expression Omnibus, which includes AS and healthy control blood samples. Weighted gene co-expression network analysis was performed and revealed three mRNA modules associated with AS. By performing gene set enrichment analysis, the functional annotations of these modules revealed immune biological processes that occur in AS. Several feature mRNAs were identified by analyzing the hubs of the protein-protein interaction network, which was based on the intersection between differentially expressed mRNAs and mRNA modules. A machine learning-based feature selection method, SVM-RFE, was used to further screen out 13 key feature mRNAs. After verifying by qPCR, IL17RA, Sqstm1, Picalm, Eif4e, Srrt, Lrrfip1, Synj1 and Cxcr6 were found to be significant for AS diagnosis. Among them, Cxcr6, IL17RA and Lrrfip1 were correlated with severity of AS symptoms. In conclusion, our findings provide a framework for identifying the key mRNAs in whole blood of AS that is conducive for the development of novel diagnostic markers for AS.

The roles of Single Nucleotide Polymorphism (SNP) Endoplasmic Reticulum Aminopeptidase 1 (ERAP 1) gene in axial spondyloarthritis Indonesian adults

Background

Axial Spondyloarthritis (AxSpA) is chronic inflammatory arthritis involving the axial joint whose pathogenesis is related to the SNP ERAP1 gene, HLA B27, and cytokine proinflammatory (IL-17A and IL-23).

Objective

Analyzed the role of SNP gene ERAP1 on disease activity and proinflammatory cytokines.

Methods

This study comprised of two phases including a cross-sectional study and an in-vitro experiment in post-test with a control-group design. Participants underwent a PCR investigation searching for HLA-B27. Disease activities were measured by Ankylosing Spondylitis Disease Activity Score-Erythrocyte Sedimentation Rate (ASDAS-ESR) and modified Stokes Ankylosing Spondylitis Spinal Score (mSASSS). Subjects with HLA-B27 positive underwent PCR ERAP1 gene rs27434, genome-sequencing, and analysis. ELISA sandwich method was used to measure ERAP-1, IL-17, and IL-23 levels with lipopolysaccharide and IFN-γ induction. Analysis using independent t-test, Mann Whitney, and Pearson correlation test with p < 0.05.

Results

The average ASDAS-ESR was 3.33 ± 0.89 and the average mSASSS was 26.53 ± 9.90. In HLA B27 positive group, SNP ERAP1 gene rs 27434 in which alleles A changed to G and A/G with genotypes AA to AG/GG was observed. SNPs of the ERAP1 gene had a correlation on mSASSS (r = 0.553; p < 0.05) and no correlation on ASDAS-ESR (r = 0.232; p = 0.235). There were significant differences observed in the SNP ERAP1 gene on ERAP1 and IL-17A levels in subjects with lipopolysaccharide and IFN-γ induction (p = 0.05) but no significant difference in IL-23 levels (p > 0.05).

Conclusion

The SNP ERAP1 gene affects mSASSS value, ERAP1 levels, and IL-17A levels whereas ASDAS-ESR value and IL-23 level were not associated.

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The SNP ERAP1 gene rs 27434 underwent AA genotype mutations into AG and GG in axial spondyloarthritis (AxSpA).

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Significant correlation of SNP ERAP1 gene on mSASSS score.

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Role of SNP ERAP1 gene on ERAP1 and IL-17A level in Indonesian adults with AxSpA.

Gut dysbiosis associated with worse disease activity and physical function in axial spondyloarthritis

BACKGROUND

Based on clinical and genetic associations, axial spondyloarthritis (axSpA) and inflammatory bowel disease (IBD) are suspected to have a linked pathogenesis. Gut dysbiosis, intrinsic to IBD, has also been observed in axSpA. It is, however, not established to what degree gut dysbiosis is associated with axSpA disease severity. The objective of this study was to compare gut dysbiosis frequency between controls, non-radiographic axial spondyloarthritis (nr-axSpA), and ankylosing spondylitis (AS) patients and investigate whether gut dysbiosis is cross-sectionally associated with axSpA disease activity, physical function, mobility, or pain.

METHODS

Gut dysbiosis was assessed by 16SrRNA analysis of feces from 44/88 nr-axSpA/AS patients (ASAS/mNY criteria) without inflammatory bowel disease (IBD) and 46 controls without IBD or rheumatic disease. The GA-map™ Dysbiosis Test was used, grading gut microbiota aberrations on a 1-5 scale, where ≥3 denotes dysbiosis. Proportions with dysbiosis were compared between the groups. Furthermore, standard axSpA measures of disease activity, function, mobility, and pain were compared between patients (nr-axSpA and AS combined) with and without dysbiosis, univariately, and adjusted for relevant confounders (ANCOVA).

RESULTS

Gut dysbiosis was more frequent in AS than controls (36% versus 17%, p=0.023), while nr-axSpA (25% dysbiosis) did not differ significantly from either AS or controls. Univariately, most axSpA measures were significantly worse in patients with dysbiosis versus those without: ASDAS-CRP between-group difference 0.6 (95% CI 0.2-0.9); BASDAI 1.6 (0.8-2.4); evaluator's global disease activity assessment (Likert scale 0-4) 0.3 (0.1-0.5), BASFI 1.5 (0.6-2.4), and VAS pain (cm) 1.3 (0.4-2.2). Differences remained significant after adjustment for demographics, lifestyle factors, treatments, gut inflammation (fecal calprotectin ≥50 mg/kg), and gut symptoms, except for VAS pain. BASMI and CRP were not associated with dysbiosis.

CONCLUSION

Gut dysbiosis, more frequent in AS patients than controls, is associated with worse axSpA disease activity and physical function, seemingly irrespective of both gut inflammation and treatments. This provides further evidence for an important link between disturbances in gastrointestinal homeostasis and axSpA.

Spondyloarthritis in inflammatory bowel disease cohorts: systematic literature review and critical appraisal of study designs

To critically appraise study designs evaluating spondyloarthritis (SpA) phenotypes in patients with inflammatory bowel disease (IBD). A systematic literature review of PubMed, Ovid, Scopus, Cinahl, Medline, Web of Science, and Cochrane databases was performed. Articles published from January 2000 - March 2020 were included if they evaluated the prevalence/incidence of musculoskeletal disease in cohorts of IBD patients. Most of the 69 included studies were clinic based (54/69, 78%), single center (47/69, 68%) and cross-sectional (60/69, 87%). The median prevalence of axial and peripheral SpA in IBD was 5% (range 1 - 46%) and 16% (range 1 - 43%), respectively. In 38 studies that evaluated axial disease in prospectively enrolled patients, inflammatory back pain was analyzed in 53%. SpA classification criteria were used in 68% and imaging was performed in 76%. In 35 studies that evaluated peripheral disease in prospectively enrolled patients, SpA classification criteria were used in 46%. A physical exam was performed in 74%, and it was performed by a rheumatologist in 54% of studies with a physical exam. Sub-phenotypes of peripheral SpA (mono- or oligo-arthritis, polyarthritis, enthesitis, dactylitis) were variably reported. Seventy-four percent of studies did not mention whether osteoarthritis and fibromyalgia had been assessed or excluded. The spectrum of SpA phenotypes in IBD patients remains incompletely characterized. Future studies should focus on standardizing the variables collected in IBD-SpA cohorts and defining musculoskeletal phenotypes in IBD-SpA in order to better characterize this disease entity and advance the field for clinical and research purposes.

The Potential Role of Genetics, Environmental Factors, and Gut Dysbiosis in the Aberrant Non-Coding RNA Expression to Mediate Inflammation and Osteoclastogenic/Osteogenic Differentiation in Ankylosing Spondylitis

Ankylosing spondylitis (AS) or radiographic axial spondyloarthritis is a chronic immune-mediated rheumatic disorder characterized by the inflammation in the axial skeleton, peripheral joints, and soft tissues (enthesis, fascia, and ligament). In addition, the extra-skeletal complications including anterior uveitis, interstitial lung diseases and aortitis are found. The pathogenesis of AS implicates an intricate interaction among HLA (HLA-B27) and non-HLA loci [endoplasmic reticulum aminopeptidase 1 (ERAP1), and interleukin-23 receptor (IL23R), gut dysbiosis, immune plasticity, and numerous environmental factors (infections, heavy metals, stress, cigarette smoking, etc.) The latter multiple non-genetic factors may exert a powerful stress on epigenetic regulations. These epigenetic regulations of gene expression contain DNA methylation/demethylation, histone modifications and aberrant non-coding RNAs (ncRNAs) expression, leading to inflammation and immune dysfunctions. In the present review, we shall discuss these contributory factors that are involved in AS pathogenesis, especially the aberrant ncRNA expression and its effects on the proinflammatory cytokine productions (TNF-α, IL-17 and IL-23), T cell skewing to Th1/Th17, and osteoclastogenic/osteogenic differentiation. Finally, some potential investigatory approaches are raised for solving the puzzles in AS pathogenesis.

Integrating imaging and biomarker assessment to better define psoriatic arthritis and predict response to biologic therapy

The treatment options for PsA have substantially expanded over the last decade. Approximately 40% of patients will not respond to first-line anti-TNF-α therapies. There is limited data to help clinicians select the most appropriate biologic therapy for PsA patients, including guidance for decisions on biologic therapy switching. In this review we will examine the current understanding of predictors of response to treatment. Imaging technology has evolved to allow us to better study psoriatic disease and define disease activity, including synovitis and enthesitis. Enthesitis is implicated in the pathogenesis, diagnosis and prognosis of PsA. It appears to be a common thread among all of the various PsA clinical presentations. Enthesitis mainly manifests as tenderness, which is difficult to distinguish from FM, chronic pain and mechanically associated enthesopathy, and it might be relevant for understanding the apparent 40% failure of existing therapy. Excess adipose tissue makes if more difficult to detect joint swelling clinically, as many PsA patients have very high BMIs. Integrating imaging and clinical assessment with biomarker analysis could help to deliver stratified medicine in PsA and allow better treatment decision making. This could include which patients require ongoing biologic therapy, which class of biologic therapy that should be, and who alternatively requires management of non-inflammatory disease.

Update on Juvenile Spondyloarthritis

Spondyloarthritis (SpA) is a blanket term encompassing entities such as enthesitis-related arthritis, nonradiographic axial SpA, and ankylosing spondylitis. These diseases share many clinical features, including a predilection for inflammation of the entheses and the sacroiliac joints. The nomenclature is based on the evolution of the classification of the disease and the age of the patient. SpA has a prevalence of approximately 1% of the population of the United States, with 10% to 20% of patients experiencing the onset during childhood. Children with onset of arthritis before age 16 years are classified as having juvenile idiopathic arthritis. Children with enthesitis and/or sacroiliitis are further classified as belonging to the enthesitis-related arthritis subtype of juvenile idiopathic arthritis. The initial manifestations can be subtle and will usually include a peripheral pattern of arthritis and enthesitis. It may take several years for axial disease to develop in children. Except for an association with the human leukocyte antigen (HLA-B27) serotype, there are no laboratory markers for the disease, and the radiographic findings are often negative. A careful clinical evaluation for evidence of inflammation in the entheses and the joints and a search for comorbidities are required. Magnetic resonance imaging facilitates the early detection of sacroiliitis, an important feature that may be clinically silent. Because recent studies indicate that earlier introduction of therapy can help achieve better outcomes, rapid identification and treatment of children with SpA is essential.

Genetic effects of B3GNT2 on ankylosing spondylitis susceptibility and clinical manifestations in Taiwanese

BACKGROUND/PURPOSE

The intergenic SNP rs10865331 at 2p15 was identified as a major risk factor for ankylosing spondylitis (AS) susceptibility in genome-wide association studies (GWAS). B3GNT2 gene regulates polylactosamine synthesis is potentially functionally relevant to AS disease development. We investigated whether SNP rs10865331 and two B3GNT2 SNPs (rs11900673 and rs1136151) are associated with AS susceptibility and disease severity in Taiwanese.

METHODS

Distributions of genotypes, alleles, and haplotypes of three SNPs were compared between 1,472 AS patients and 2,117 healthy blood donors and among AS patients stratified by clinical characteristics.

RESULTS

The intergenic SNP rs10865331 was significantly associated with AS (P_FDR = 1.02E-05) in Taiwanese. In AS patients stratified by positivity of HLA-B27 and syndesmophyte formation, all three B3GNT2 locus SNPs (rs11900673, rs1136151, and rs10865331) were significantly associated with syndesmophyte formation among HLA-B27 positive AS patients. Haplotype analyses revealed that the "CTA" (rs11900673C/rs1136151T/rs10865331A) haplotype was significantly associated with AS susceptibility (Padj = 0.0177) and syndesmophyte formation (Padj = 0.016) in HLA-B27 positive patients. In contrast, "TCG" (rs11900673T/rs1136151C/rs10865331G) haplotype showed protection against AS development (Padj = 0.0005 for HLA-B27 positive and Padj = 0.004 for HLA-B27 negative, respectively) and syndesmophyte formation (Padj = 0.0017) in HLA-B27 positive patients. Furthermore, B3GNT2 mRNA expressions were negatively associated with erythrocyte sedimentation rate (ESR, P = 0.0103), C-reactive protein (CRP, P = 0.0353), Bath ankylosing spondylitis functional index (BASFI, P = 0.0171), and syndesmophyte formation (P = 0.0148).

CONCLUSION

Our data suggest that B3GNT2 gene may contribute to AS development and affect AS severity by interacting with HLA-B27 in Taiwanese.

Incidence of extra-articular manifestations in ankylosing spondylitis, psoriatic arthritis and undifferentiated spondyloarthritis: results from a national register-based cohort study

OBJECTIVES

To estimate the incidence and strength of association of extra-articular manifestations [EAMs, here: anterior uveitis (AU), IBD and psoriasis] in patients with AS, undifferentiated SpA (uSpA) and PsA, compared with controls.

METHODS

Three mutually exclusive cohorts of patients aged 18-69 years with AS (n = 8517), uSpA (n = 10 245) and PsA (n = 22 667) were identified in the Swedish National Patient Register 2001-2015. Age-, sex- and geography-matched controls were identified from the Swedish Population Register. Follow-up began 1 January 2006, or six months after the first SpA diagnosis, whichever occurred later, and ended at the first date of the EAM under study, death, emigration, 70 years of age, and 31 December 2016. Incidence rates (IRs) and incidence rate ratios were calculated for each EAM, and stratified by sex and age.

RESULTS

Incidence rate ratios for incident AU, IBD and psoriasis were significantly increased in AS (20.2, 6.2, 2.5), uSpA (13.6, 5.7, 3.8) and PsA (2.5, 2.3, n.a) vs controls. Men with AS and uSpA had significantly higher IRs per 1000 person-years at risk for incident AU than women with AS (IR 15.8 vs 11.2) and uSpA (IR 10.1 vs 6.0), whereas no such sex difference was demonstrated in PsA or for the other EAMs.

CONCLUSIONS

AU, followed by IBD and psoriasis, is the EAM most strongly associated with AS and uSpA. Among the SpA subtypes, AS and uSpA display a largely similar pattern of EAMs, whereas PsA has a considerably weaker association with AU and IBD.

Ankylosing Spondylitis

The seronegative spondyloarthropathies are a group of autoimmune inflammatory diseases lacking rheumatoid factor or antinuclear antibody in their serum. They include ankylosing spondylitis (AS), reactive arthritis, psoriatic arthritis, spondylitis associated with Crohn's disease and ulcerative colitis, and undifferentiated spondyloarthropathies. Inflammation mostly affects the axial joints, entheses, and extra-articular structures such as uveal tract, gastrointestinal tract, mucocutaneous tissue, and heart. Uveitis is the most common extra-articular manifestation. Spondyloarthropathies, especially AS, have a strong association with the presence of Human Leukocyte Antigen (HLA)-B27 gene. AS happens earlier in HLA-B27 patients and men are more prone to the disease. Uveitis, typically unilateral non-granulomatous acute anterior uveitis, occurs in up to 50% of the patients with AS. HLA-B27 positivity correlates with more frequent flare-ups. Conjunctivitis and scleritis are rare ocular manifestations of AS. To establish the diagnosis of AS, at least one clinical and one radiologic parameter are required for definitive diagnosis. Magnetic resonance imaging (MRI) or bone scan can help early detection of the axial skeleton inflammation. The course of eye and joint involvement are not correlated. Short-term treatment with topical corticosteroids and cycloplegic agents control the uveitis attack. In resistant cases, local or systemic therapy with corticosteroids are recommended. NSAIDs, disease-modifying anti-rheumatic drugs (DMARDs), methotrexate, azathioprine, anti-IL-17A monoclonal antibodies, and TNF-α antagonists are effective treatments for ocular and systemic manifestations of AS. If not treated adequately, uveitis may become recalcitrant and extend posteriorly. Functional impairment due to joint destruction can also occur as a result of under-treatment.

Association of ERAP2 polymorphisms in Colombian HLA-B27+ or HLA-B15+ patients with SpA and its relationship with clinical presentation: axial or peripheral predominance

OBJECTIVE

To determine the association between endoplasmic reticulum aminopeptidase (ERAP)1 and ERAP2 single-nucleotide polymorphisms (SNPs) and human leukocyte antigens (HLA)-B27+ or HLA-B15+ patients with spondyloarthritis (SpA).

METHODS

104 patients with SpA according to Assessment of Spondyloarthritis International Society criteria were included in the study. HLA typing was performed by PCR. The polymorphisms were determined by real-time PCR on genomic DNA using customised probes for SNPs rs27044, rs17482078, rs10050860 and rs30187 in ERAP1, and rs2910686, rs2248374 and rs2549782 in ERAP2.

RESULTS

70 of the104 patients with SpA were HLA-B27+ and 34 were HLA-B15+. The distribution of ERAP1 and ERAP2 SNPs between the HLA-B15+ and HLA-B27+ patients with SpA did not reveal differences. Likewise, no differences in the frequencies of ERAP1 SNP haplotypes and alleles HLA-B15 or HLA-B27 were found. Interestingly, however, the frequencies of three particular haplotypes formed by ERAP2 SNPs rs2549782/rs2248374/rs2910686 varied between HLA-B15+ and HLA-B27+ patients: the ERAP2 SNPs haplotype TGT was more common in HLA-B15+ patients with SpA (OR 2.943, 95% CI 1.264 to 6.585; P=0.009), whereas the ERAP2 SNP haplotypes TGC and CAT were more associated with HLA-B27+ patients with SpA: (OR 4.483, 95% CI 1.524 to 13.187; p=0.003) and (OR 9.014, 95% CI 1.181 to 68.807; p=0.009), respectively.

CONCLUSION

An association was found between HLA-B15+ patients with SpA and haplotype TGT of ERAP2 SNPs. On the other hand, HLA-B27+ patients with SpA were associated with ERAP2 haplotypes TGC and CAT. These associations could be related to the clinical presentation of the disease, specifically with a peripheral or axial predominance, respectively.

Predictors of extra-articular manifestations in axial spondyloarthritis and their influence on TNF-inhibitor prescribing patterns: results from the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis

OBJECTIVES

Extra-articular manifestations (EAMs) are important systemic features of axial spondyloarthritis (axSpA), which may influence the choice of tumour necrosis factor-inhibitor (TNFi). We examined the cumulative incidence and predictors of EAMs and the influence of these on first TNFi choice in a 'real-world' cohort of patients with axSpA.

METHODS

Clinical and patient-reported outcomes of 2420 patients with axSpA from 83 centres were collected by the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis. Lifestyle factors for EAMs (acute anterior uveitis (AAU), inflammatory bowel diseases (IBD), psoriasis) were compared with those without EAMs. Also, the association between pretreatment EAMs and choice of first TNFi (adalimumab, etanercept, certolizumab) was analysed.

RESULTS

AAU was directly associated with human leukocyte antigen (HLA)-B27 (incidence rate ratio (IRR) 1.95, 95% CI 1.40 to 2.73) and inversely associated with ever-smoking (IRR=0.71, 95% CI 0.55 to 0.92). For both psoriasis and IBD, there was an inverse relationship with HLA-B27 (IRR 0.54, 95% CI 0.36 to 0.79 and IRR 0.63, 95% CI 0.43 to 0.91, respectively). A diagnosis of either AAU (OR 3.79, 95% CI 2.11 to 6.80) or IBD (OR 5.50, 95% CI 2.09 to 14.46) was associated with preference for adalimumab versus others. In contrast, a diagnosis of either AAU (OR 0.14, 95% CI 0.06 to 0.33) or IBD (OR 0.17, 95% CI 0.05 to 0.57) was associated with less preference for etanercept over other TNFi.

CONCLUSION

The higher occurrence of AAU and lower occurrence of psoriasis and IBD in HLA-B27-positive patients with axSpA are consistent with current pathophysiology. Patients with previous AAU and IBD are more likely to be prescribed adalimumab and less likely to receive etanercept, consistent with the superior efficacy of monoclonal TNFi for these indications. Future work will determine whether EAMs influence TNFi survival, or effectiveness, and whether this varies between agents.

Insights into the pathogenesis of psoriatic arthritis from genetic studies

Psoriatic arthritis (PsA) is a relatively common inflammatory arthritis, a spondyloarthritis (SpA), that occurs most often in patients with psoriasis, a common immune-mediated inflammatory skin disease. Both psoriasis and PsA are highly heritable. Genetic and recent genomic studies have identified variants associated with psoriasis and PsA, but variants differentiating psoriasis from PsA are few. In this review, we describe recent developments in understanding the genetic burden of PsA, linkage, association and epigenetic studies. Using pathway analysis, we provide further insights into the similarities and differences between PsA and psoriasis, as well as between PsA and other immune-mediated inflammatory diseases, particularly ankylosing spondylitis, another SpA. Environmental factors that may trigger PsA in patients with psoriasis are also reviewed. To further understand the pathogenetic differences between PsA and psoriasis as well as other SpA, larger cohort studies of well-phenotyped subjects with integrated analysis of genomic, epigenomic, transcriptomic, proteomic and metabolomic data using interomic system biology approaches are required.

The gut-joint axis in spondyloarthritis: immunological, microbial, and clinical insights

The strong genetic and clinical overlaps between spondyloarthritis (SpA) and inflammatory bowel disease (IBD) have placed much needed focus on the gut-joint axis of inflammation in SpA, leading to three key hypotheses that attempt to unravel this complex relationship. The arthritogenic peptide hypothesis and the aberrant cellular trafficking hypothesis have been put forth to rationalize the manner by which the innate and adaptive immune systems cooperate and converge during SpA pathogenesis. The bacterial dysbiosis hypothesis discusses how changes in the microbiome lead to architectural and immunological consequences in SpA. These theories are not mutually exclusive, but can provide an explanation as to why subclinical gut inflammation may sometimes precede joint inflammation in SpA patients, thereby implying a causal relationship. Such investigations will be important in informing therapeutic decisions which may be common to both SpA and IBD. However, these hypotheses can also offer insights for a coincident inflammatory relationship between the gut and the joint, particularly when assessing the immunological players involved. Insights from understanding how these systems might affect the gut and joint differently will be equally imperative to address where the therapeutic differences lie between the two diseases. Collectively, this knowledge has practical implications in predicting the likelihood of IBD development in SpA or presence of coincident SpA-IBD, uncovering novel therapeutic targets, and redesigning currently approved treatments. It is evident that a multidisciplinary approach between the rheumatology and gastroenterology fields cannot be ignored, when it comes to the care of SpA patients at risk of IBD or vice versa.

Do geography and ethnicity play a role in juvenile Spondyloarthritis? A multi-center binational retrospective study

BACKGROUND

Observations among Israeli pediatric rheumatologists reveal that pediatric Juvenile Spondyloarthritis (JSpA) may present differently compared to patients from the United States (US). This study is aimed to compare the demographic and clinical variables of Israeli and US JSpA patients upon presentation.

METHODS

We performed a retrospective, cross-sectional, multicenter comparison of JSpA patients among 3 large Israeli pediatric rheumatology centers and a large US pediatric rheumatology center. Patients with diagnosis of Juvenile Ankylosing Spondylitis (JAS) and/or Enthesitis-related Arthritis (ERA) were included. The demographic, clinical and radiologic features were compared.

RESULTS

Overall 87 patients were included (39 Israeli, 48 US patients). Upon presentation, inflammatory back pain, sacroiliac joint tenderness and abnormal modified Schober test, were significantly more prevalent among Israeli patients (59% vs. 35.4, 48.7% vs. 16.7, and 41.2% vs. 21.5%, respectively, all p < 0.05), whereas peripheral arthritis and enthesitis were significantly more prevalent among US patients (43.6% vs. 91.7 and 7.7% vs. 39.6% in Israeli patients vs. US patients, p < 0.05). In addition, 96.7% of the Israeli patients versus 29.7% of the US patients demonstrated sacroiliitis on MRI (p < 0.001, N = 67). Less than one-third of the Israeli patients (32%) were HLA-B27 positive vs. 66.7% of US patients (p = 0.007).

CONCLUSION

Israeli children with JSpA presented almost exclusively with axial disease compared to US patients who were more likely to present with peripheral symptoms. HLA B27 prevalence was significantly lower in the Israeli cohort compared to the US cohort. Further studies are needed to unravel the genetic and possibly environmental factors associated with these findings.

SNP-adjacent super enhancer network mediates enhanced osteogenic differentiation of MSCs in ankylosing spondylitis

Ankylosing spondylitis (AS) is a rheumatic disease with pathological osteogenesis that causes bony ankylosis and even deformity over time. Mesenchymal stem cells (MSCs) are multipotent stem cells that are the main source of osteoblasts. We previously demonstrated that enhanced osteogenic differentiation of MSCs from AS patients (ASMSCs) is related to pathological osteogenesis in AS. However, the more concrete mechanism needs further exploration. Super enhancers (SEs) are dense clusters of stitched enhancers that control cell identity determination and disease development. Single-nucleotide polymorphisms (SNPs) regulate the formation and interaction of SEs and denote genes accounting for AS susceptibility. Via integrative analysis of multiomic data, including histone 3 lysine 27 acetylation (H3K27ac), chromatin immunoprecipitation sequencing (ChIP-seq), SNPs and RNA sequencing (RNA-seq) data, we discovered a transcription network mediated by AS SNP-adjacent SEs (SASEs) in ASMSCs and identified key genes, such as Toll-like receptor 4 (TLR4), interleukin 18 receptor 1 (IL18R1), insulin-like growth factor binding protein 4 (IGFBP4), transportin 1 (TNPO1) and proprotein convertase subtilisin/kexin type 5 (PCSK5), which are pivotal in osteogenesis and AS pathogenesis. The SASE-regulated network modulates the enhanced osteogenic differentiation of ASMSCs by synergistically activating the PI3K-Akt, NF-kappaB and Hippo signaling pathways. Our results emphasize the crucial role of the SASE-regulated network in pathological osteogenesis in AS, and the preferential inhibition of ASMSC osteogenic differentiation by JQ1 indicates that SEs may be attractive targets in future treatment for new bone formation in AS.

Understanding the Pathogenesis of Spondyloarthritis

Spondyloarthritis comprises a group of inflammatory diseases of the joints and spine, with various clinical manifestations. The group includes ankylosing spondylitis, reactive arthritis, psoriatic arthritis, arthritis associated with inflammatory bowel disease, and undifferentiated spondyloarthritis. The exact etiology and pathogenesis of spondyloarthritis are still unknown, but five hypotheses explaining the pathogenesis exist. These hypotheses suggest that spondyloarthritis is caused by arthritogenic peptides, an unfolded protein response, HLA-B*27 homodimer formation, malfunctioning endoplasmic reticulum aminopeptidases, and, last but not least, gut inflammation and dysbiosis. Here we discuss the five hypotheses and the evidence supporting each. In all of these hypotheses, HLA-B*27 plays a central role. It is likely that a combination of these hypotheses, with HLA-B*27 taking center stage, will eventually explain the development of spondyloarthritis in predisposed individuals.

IBD considerations in spondyloarthritis

Spondyloarthritis (SpA) may be regarded a family of auto-inflammatory conditions with inflammation focused on the joints. These form part of a wider family of immune-mediated inflammatory diseases, which include inflammatory bowel diseases (IBD). These conditions share common elements of pathophysiology and it is perhaps unsurprising, therefore, that individuals with SpA frequently manifest gastrointestinal inflammation, to which the physician managing the patient with SpA must be alert. In this article, we review the shared epidemiology and pathophysiology of these conditions, before discussing approaches to diagnosis and management of inflammatory gastrointestinal pathology in patients seen in rheumatology clinics. In particular, we discuss the difference between non-specific gastrointestinal inflammation commonly described in this patient group and the more specific diagnosis of Crohn's disease or ulcerative colitis. We describe the appropriate diagnostic workup for patients suspected of having IBD. In addition, we discuss how a diagnosis of IBD can inform treatment selection, highlighting important differences in treatment choice, drug dosing, monitoring and drug safety for this particular comorbid patient population.

HLA-B27 Negativity Is Associated With Renal Function Decline in Patients With Ankylosing Spondylitis and Secondary IgA Nephropathy

This study aimed to determine the impact of HLA-B27 on clinical phenotype and renal function during follow-up periods in patients with ankylosing spondylitis (AS) and secondary IgA nephropathy (IgAN). This single-center retrospective study included 71 AS patients with secondary IgAN. Renal function decline was defined as a mean eGFR decline of more than 5 mL/min/1.73 m² per year or progression into the dialysis stage. The association between HLA-B27 status and renal function decline was evaluated by univariable and multivariable Cox regression analyses. The results showed that seven (9.85%) of the 71 included patients were HLA-B27-negative. The median follow-up period was 4.0 years. HLA-B27-negative patients showed higher levels of uric acid (UA) than those who were HLA-B27-positive. Pathologically, a higher percentage of globally sclerotic glomeruli was observed in HLA-B27-negative patients. Survival analysis indicated that HLA-B27 negativity was associated with a significantly higher probability of renal function decline than HLA-B27 positivity. This significant association was also found in subgroup analyses of patients with either substantial proteinuria (more than 1.0 g per day) or interstitial fibrosis and tubular atrophy. Multivariable analysis showed that HLA-27 negativity was independently associated with renal function decline (HR 6.58; 95% CI 1.65 to 26.21; p = 0.008). In conclusion, HLA-B27 negativity is associated not only with a higher level of UA and a higher percentage of globally sclerotic glomeruli in AS patients with secondary IgAN but with renal function decline during follow-up periods.

Role of the IL-23 pathway in the pathogenesis and treatment of enthesitis in psoriatic arthritis

INTRODUCTION

Enthesitis is a key feature of spondyloarthritis (SpA). Several studies have underlined the role of interleukin (IL)-23 in SpA development as a crucial cytokine in the pathogenesis of enthesitis.

AREA COVERED

This review summarizes recent evidence of the role of IL-23 in the pathogenesis of and as a target of the treatment of enthesitis. We review the definition, diagnosis and clinical impact of enthesitis and its connection with microbial infections, gut dysbiosis, and mechanical stress. We also review clinical trials and real-life studies of drugs targeting the p19 or p40 subunits of IL-23.

EXPERT OPINION

Novel therapies targeting the p19 or p40 subunit of IL-23 appear to be promising treatment options for patients with enthesitis. Although we are currently unable to identify the best therapeutic window to target IL-23 in SpA disease evolution, the promising ability of this therapy to control the gut-entheseal axis is increasing our knowledge of SpA pathogenesis.

Therapeutic potential of enhancer of zeste homolog 2 in autoimmune diseases

Introduction: Autoimmune diseases (ADs) are idiopathic and heterogeneous disorders with contentious pathophysiology. Great strides have been made in epigenetics and its involvement in ADs. Zeste homolog 2 (EZH2) has sparked extensive interest because of its pleiotropic roles in distinct pathologic contexts.Areas covered: This review summarizes the epigenetic functions and the biological significance of EZH2 in the etiology of rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), type 1 diabetes (T1D), inflammatory bowel disease (IBD), multiple sclerosis (MS), and systemic sclerosis (SSc). A brief recapitulation of the therapeutic potential of EZH2 targeting is provided.Expert opinion: There are questions marks and controversies surrounding the feasibility and safety of EZH2 targeting; it is recommended in RA and SLE, but queried in T1D, IBD, MS, and SSc. Future work should focus on contrast studies, systematic analyses and preclinical studies with optimizing methodologies. Selective research studies conducted in a stage-dependent manner are necessary because of the relapsing-remitting clinical paradigms.

Spondyloarthritis and Outcomes in Pregnancy and Labor: A Nationwide Register-Based Cohort Study

OBJECTIVE

To describe the prevalence of spondyloarthritis (SpA) and subtypes diagnosed prior to delivery in a nationwide population of pregnant women, and to estimate how SpA was associated with adverse pregnancy-related outcomes.

METHODS

Using the Danish Medical Birth Register, we identified 1,199,610 singleton pregnancies (1997-2016). Information on SpA and related subtypes (ankylosing spondylitis, psoriatic arthritis, reactive arthritis, arthritis associated with inflammatory bowel diseases, and undifferentiated SpA) was derived from the Danish National Patient Registry. Odds ratios were calculated using logistic regression models. The analyses were performed with overall SpA as exposure and stratified by subtype.

RESULTS

The overall prevalence of SpA diagnosed prior to delivery was 0.31%, increasing from 0.1% in 1997 to 0.6% in 2016. Comparing women without SpA to women with SpA, the adjusted odds ratios were increased for moderately preterm birth (OR_adj 1.56 [95% confidence interval (95% CI) 1.33-1.83]), very preterm birth (OR_adj 1.47 [95% CI 1.04-2.08]), elective cesarean section (OR_adj 1.44 [95% CI 1.26-1.64]), emergency cesarean section (OR_adj 1.17 [95% CI 1.04-1.33]), and use of epidural (OR_adj 1.11 [95% CI 1.02-1.20]). The odds ratios for small for gestational age birth and preeclampsia were not increased for women with SpA compared to controls. Results were comparable for the subtypes of SpA.

CONCLUSION

Pregnancies in women with SpA were more often complicated by adverse pregnancy outcomes than pregnancies in women without SpA. Clinicians should be aware of this when advising women with SpA in their childbearing years. Future research should focus on investigating causal relations and possible interventions aimed at preventing these outcomes.

Frequencies of the LILRA3 6.7-kb Deletion Are Highly Differentiated Among Han Chinese Subpopulations and Involved in Ankylosing Spondylitis Predisposition

Introduction: Leukocyte immunoglobulin-like receptor A3 (LILRA3) belongs to the LILR family with unique feature of a 6.7-kb deletion variation among individuals. Frequencies of the 6.7-kb deletion vary widely across populations, but so far it has not been carefully investigated among Han Chinese subpopulations. Furthermore, we previously identified the non-deleted (functional) LILRA3 as a novel genetic risk for multiple autoimmune diseases. The current study aimed to investigate (i) whether frequencies of the LILRA3 6.7-kb deletion differ within Han Chinese subpopulations and (ii) whether the functional LILRA3 is a novel genetic risk for ankylosing spondylitis (AS).

Methods: The LILRA3 6.7-kb deletion was genotyped in two independent cohorts, including 1,567 subjects from Shenzhen Hospital and 2,507 subjects from People’s Hospital of Peking University. Frequencies of the 6.7-kb deletion were first investigated in combined healthy cohort according to the Chinese administrative district divisions. Association analyses were performed on whole dataset and subsets according to the geographic regions. Impact of the functional LILRA3 on AS disease activity was evaluated.

Results: Frequencies of LILRA3 6.7-kb deletion were highly differentiated within Han Chinese subpopulations, being gradually decreased from Northeast (80.6%) to South (47.4%). Functional LILRA3 seemed to be a strong genetic risk in susceptibility to AS under almost all the alternative genetic models, if the study subjects were not geographically stratified. However, stratification analysis revealed that the functional LILRA3 was consistently associated with AS susceptibility mainly in Northern Han subgroup under the alternative genetic models, but not in Central and Southern Hans. Functional LILRA3 conferred an increased disease activity in AS patients (P < 0.0001 both for CRP and ESR, and P = 0.003 for BASDAI).

Conclusions: The present study is the first to report that the frequencies of LILRA3 6.7-kb deletion vary among Chinese Hans across geographic regions. The functional LILRA3 is associated with AS susceptibility mainly in Northern Han, but not in Central and Southern Han subgroups. Our finding provides new evidence that LILRA3 is a common genetic risk for multiple autoimmune diseases and highlights the genetic differentiation among different ethnicities, even within the subpopulations of an ethnic group.

Enthesopathy and involvement of synovio-entheseal complex in systemic sclerosis: an ultrasound pilot study

Objectives

SSc is a chronic autoimmune disease characterized by inflammation of the skin and multiple internal organs. Articular involvement is one of the main features of SSc, and typical hallmarks of SpA have been found in SSc patients. The aim of the present study was to estimate the prevalence of entheseal and synovio-entheseal complex (SEC) alterations in a cohort of SSc patients.

Methods

One hundred SSc patients and 25 healthy subjects were included in this cross-sectional study. The enthesis sites of lateral epicondylar common extensor tendons (CET) and the enthesis of the Glasgow Ultrasound Enthesis Scoring System were evaluated. SEC involvement was evaluated only at CET enthesis.

Results

In SSc, the Glasgow Ultrasound Enthesis Scoring System score was significantly higher (median 4.0, interquartile range 2.0–7.0) than in controls (median 1.0, interquartile range 0.0–3.0) (P < 0.0001). CET enthesis of SSc patients showed more frequent US B-mode alterations than that of controls (χ2 = 11.47, P = 0.0007 for size; χ2 = 13.79, P = 0.0002 for cortical irregularity, χ2 = 5.24, P = 0.022 for calcification/enthesophytes). Power Doppler US signal at CET enthesis was significantly more frequent in SSc patients than in healthy controls (χ2 = 9.11, P = 0.0025), as was the concomitant SEC involvement (χ2 = 8.52, P = 0.0035).

Conclusion

These data show that SSc patients frequently present US features of enthesopathy. Moreover, CET enthesopathy was correlated with SEC inflammation, suggesting that entheseal inflammation in SSc may share the same micro-anatomical targets as found in SpA.

Biomarkers in Inflammatory Bowel Disease-Associated Spondyloarthritis: State of the Art and Unmet Needs

Inflammatory bowel disease-associated spondyloarthritis is a systemic disease characterized by the chronic inflammation of both the gastrointestinal tract and the musculoskeletal system. Since inflammatory bowel disease-associated spondyloarthritis has been associated with a significant diagnostic delay, which may lead to poor quality of life and progression of joint damage, efforts to discover new reliable and noninvasive diagnostic biomarkers have been made. We reviewed the state of the art of biomarker research in inflammatory bowel disease-associated spondyloarthritis, showing that to date it has been largely unsatisfactory. Only a few of the biomarkers that have been investigated are likely to enter the clinical practice upon further validation in independent cohorts. The research of new and innovative biomarkers for inflammatory bowel disease-associated spondyloarthritis is warranted.

The role of IL-17A in axial spondyloarthritis and psoriatic arthritis: recent advances and controversies

Although the pathogenic mechanisms underlying axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA) are not fully elucidated, several lines of evidence suggest that immune responses mediated by interleukin 17A (IL-17A) play a pivotal role in both diseases. This is best highlighted by the significant clinical efficacy shown with inhibitors of IL-17A in treating axSpA and PsA. Nevertheless, a number of knowledge gaps exist regarding the role of IL-17A in the pathophysiology of spondyloarthritis in man, including its cellular origin, its precise role in discrete disease processes such enthesitis, bone erosion, and bone formation, and the reasons for the discrepant responses to IL-17A inhibition observed in certain other spondyloarthritis manifestations. In this review, we focus on the latest data from studies investigating the role of IL-17A in ankylosing spondylitis (AS) and PsA that build on existing and emerging scientific knowledge in the field. Key remaining research questions are also highlighted to guide future research.

Ankylosing spondylitis: analysis of gene-gene interactions between IL-12β, JAK2, and STAT3 in Han Chinese and Algerian cohorts

Introduction

Association studies have recently identified the importance of new genetic variants for ankylosing spondylitis (AS) in several populations. Our aim was to confirm associations of variants within genes involved in the IL-23 signalling pathway with AS in two ethnically different populations: Han Chinese and Algerian.

Material and methods

Two case-control studies were performed in separate cohorts: Han Chinese (430 AS patients and 580 controls) and Algerian (130 AS patients and 120 controls). We genotyped four single nucleotide polymorphisms (SNPs): rs3212227 (or +1188A/C) and rs6887695 in IL-12β, rs7857730 in JAK2, and rs2293152 in STAT3, using TaqMan SNP genotyping assays. Gene-gene interaction analyses were also tested by logistic regression and multifactor dimensionality reduction (MDR).

Results

Statistical analysis revealed a difference in allele frequencies between AS patients and controls for rs321222 in the IL-12β gene in both the Han Chinese (p = 0.005) and the Algerian (p = 0.031) cohorts. Two other associations were reported with JAK2 rs7857730 in the Han Chinese (allelic p = 0.014) cohort and STAT3 rs2293152 in the Algerian (allelic p = 0.006) cohort. Moreover, logistic regression analyses showed a number of significant combinations within the two populations, and the gene-gene epistasis effects in AS were also confirmed by MDR.

Conclusions

Our findings have confirmed the association between genes in IL-23 signalling pathway and the pathogenesis of AS. This association was particularly novel in both Han Chinese and Algerian populations with the 3’ untranslated region (3’UTR) variant rs3212227 (or +1188A/C) of IL-12β. The gene-gene interaction models in this pathway may thus increase the risk of AS in these populations.

Extraintestinal manifestations in inflammatory bowel disease - epidemiology, genetics, and pathogenesis

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder, primarily of, but not restricted to the gut. Extraintestinal manifestations (EIMs) are frequently observed and involve the joints, eyes, hepatobiliary tract, and skin. Areas covered: In this review, we discuss classical EIM focusing on epidemiology, genetics, and pathogenesis, highlighting recent advances in the understanding of EIM. We further discuss treatment-induced immunological phenomena, which are increasingly recognized and might challenge IBD-treating physicians in the era of biological treatment. Expert opinion: EIM considerably contributes to morbidity and mortality. Genetic studies have revealed a common genetic background between EIM and IBD and among specific EIM. Identified protein interactions have been shown to cluster in shared biological pathways. However - despite these recent advances - pathogenesis of EIM is at best partially understood. Several pathogenic mechanisms have been proposed such as upregulation of tumor necrosis factor, aberrant lymphocyte homing, and cross-reactive antigen presentation. It still remains unclear whether EIM is a direct result of the inflammatory process in the gut or rather a consequence of a shared genetic background leading to dysfunctional immune responses to environmental stimuli. Exploration and understanding of EIM genetics and pathophysiology will pave the road for better and more efficacious treatment options in the future.

HLA-C*07 in axial spondyloarthritis: data from the German Spondyloarthritis Inception Cohort and the Spondyloarthritis Caught Early cohort

We aimed to assess the mRNA expression of MHC class 1-related molecules in ankylosing spondylitis (AS) patients vs healthy controls (HCs) and, subsequently, if the absence of HLA-C*07 is associated with genetic susceptibility to axial spondyloarthritis (axSpA). HLA-C*07 was assessed in (a) an exploratory cohort of 24 AS patients vs 40 HCs, (b) a confirmatory cohort of 113 AS patients and 83 non-radiographic axSpA patients from the GErman SPondyloarthritis Inception Cohort (GESPIC) vs 134,528 German potential stem cell donors, and (c) an early back pain cohort with 94 early axSpA patients vs 216 chronic back pain (CBP) patients from the SPondyloArthritis Caught Early (SPACE) cohort. In the exploratory cohort, 79% of the AS patients were HLA-C*07 negative compared to 35% of the HCs (p < 0.001). This difference was confirmed in GESPIC with 73% of AS patients being HLA-C*07 negative compared to 50% of the controls (p < 0.0001); 59% of the nr-axSpA patients were HLA-C*07 negative. In the SPACE cohort, 70% of the axSpA patients were HLA-C*07 negative compared to 44% of CBP patients (p < 0.0001); the association between HLA-C*07 negativity and a diagnosis of axSpA was independent from HLA-B*27. In conclusion, the absence of HLA-C*07 is associated with genetic susceptibility to axSpA.

The role of ERAP1 in autoinflammation and autoimmunity

Autoimmune and autoinflammatory diseases affect millions worldwide. These classes of disease involve abnormal immune activation of both the innate and adaptive immune systems. While both classes of disease represent a spectrum of aberrant immune activation, excessive activation of the innate immune system has been considered causal for the inflammation and tissue damage found in autoinflammatory diseases, while excessive activation of the adaptive immune system has been thought to primarily contribute to end-organ symptoms noted in autoimmune diseases. Interestingly, the endoplasmic reticulum aminopeptidase 1 (ERAP1) protein, well known for its aminopeptidase function as a "molecular ruler", trimming peptides prior to their loading onto MHC-I molecules for antigen presentation in the ER, has also been shown to be genetically associated with both autoinflammatory and autoimmune diseases. Indeed, this multifaceted protein has been found to have many functions that affect both the innate and adaptive immune responses. In this review, we summarize these findings, with an attempt to identify the possible ERAP1 dependent mechanisms responsible for the pathogenesis of multiple, ERAP1 associated diseases.

Increased Risk of Hypertension Associated with Spondyloarthritis Disease Duration: Results from the ASAS-COMOSPA Study

OBJECTIVE

Spondyloarthritis (SpA) is associated with a number of cardiovascular (CV) comorbidities. We examined the association of SpA disease duration and delay in diagnosis with CV-related conditions.

METHODS

Using data from the COMOSPA study, the associations between SpA disease duration and CV-related conditions were evaluated in univariable and multivariable logistic regression models. Each model examined 1 CV-related factor as dependent and "SpA disease duration" as a predictor, adjusted for relevant confounders.

RESULTS

Data from 3923 subjects (median SpA disease duration 5.1 yrs, interquartile range 1.3-11.8 yrs) were available for analysis. The main CV-related conditions were hypertension (HTN; 22.4%), ischemic heart disease (2.6%), stroke (1.3%), and diabetes mellitus (5.5%). HTN was associated with SpA disease duration in both univariable and multivariable analysis, with an OR of 1.129 (95% CI 1.072-1.189; p < 0.001) for each 5-year increase in SpA disease duration. Other factors associated with HTN were age, male sex, current body mass index, ever steroid therapy, and ever synthetic disease-modifying antirheumatic drug therapy, but not nonsteroidal antiinflammatory drugs (NSAID). In subgroup analysis, the strongest association of HTN and disease duration was seen in subjects with the axial-only SpA phenotype (OR 1.202, 95% CI 1.053-1.372) but not in those with peripheral-only SpA (OR 0.902, 95% CI 0.760-1.070). The other CV conditions were not associated with SpA disease duration.

CONCLUSION

Duration of SpA disease in the ASAS-COMOSPA cohort is associated with higher odds of HTN, particularly in those with axial disease, but not with other CV-related conditions. The association with HTN does not appear to be related to NSAID exposure.