Genetics of ankylosing spondylitis

Functional genomics implicates natural killer cells in the pathogenesis of ankylosing spondylitis

Objective

Multiple lines of evidence indicate that ankylosing spondylitis (AS) is a lymphocyte-driven disease. However, which lymphocyte populations are critical in AS pathogenesis is not known. In this study, we aimed to identify the key cell types mediating the genetic risk in AS using an unbiased functional genomics approach.

Methods

We integrated genome-wide association study (GWAS) data with epigenomic and transcriptomic datasets of human immune cells. To quantify enrichment of cell type-specific open chromatin or gene expression in AS risk loci, we used three published methods that have successfully identified relevant cell types in other diseases. We performed co-localization analyses between GWAS risk loci and genetic variants associated with gene expression (eQTL) to find putative target genes.

Results

Natural killer (NK) cell-specific open chromatin regions are significantly enriched in heritability for AS, compared to other immune cell types such as T cells, B cells, and monocytes. This finding was consistent between two AS GWAS. Using RNA-seq data, we validated that genes in AS risk loci are enriched in NK cell-specific gene expression. Using the human Space-Time Gut Cell Atlas, we also found significant upregulation of AS-associated genes predominantly in NK cells. Co-localization analysis revealed four AS risk loci affecting regulation of candidate target genes in NK cells: two known loci, ERAP1 and TNFRSF1A, and two under-studied loci, ENTR1 (aka SDCCAG3) and B3GNT2.

Conclusion

Our findings suggest that NK cells may play a crucial role in AS development and highlight four putative target genes for functional follow-up in NK cells.

The Association Between Epidermal Growth Factor rs3756261 A/G Gene Polymorphism and the Risk of Ankylosing Spondylitis in a Chinese Han Population

Background

Epidermal growth factor (EGF) is a potent pro-angiogenic molecule promoting the angiogenic phenotype of ankylosing spondylitis (AS). Studies demonstrated that EGF rs3756261 polymorphism was associated with the risk of inflammatory diseases, but not including AS.

Methods

To investigate the association between EGF rs3756261 polymorphism and the risk of AS, we genotyped the EGF rs3756261 polymorphism in 208 patients with AS and 412 controls in a Chinese Han population using a custom-by-design 48-Plex SNP scanTM Kit. The serum EGF levels were measured using an enzyme-linked immunosorbent assay in 208 AS patients and 412 controls.

Results

Our data indicated that EGF rs3756261 polymorphism was associated with an increased risk of AS in the Chinese Han population. Stratified analyses indicated that the EGF rs3756261 polymorphism elevated the risk of AS among the males, smokers, drinkers and those aged <30 years. In addition, the EGF rs3756261 polymorphism was related to increased CRP and HLA-B27 levels in AS patients. Next, we found that the average serum levels of EGF were significantly higher in AS patients compared with controls. Meanwhile, EGF serum levels were significantly higher in AG genotype carriers when compared with AA genotype carriers in AS patients.

Conclusion

In conclusion, this study indicated that EGF rs3756261 polymorphism was associated with the risk of AS and EGF serum levels in a Chinese Han population.

Aryl hydrocarbon receptor gene expression in ankylosing spondylitis and its correlation with interleukin-17, RAR-related orphan receptor gamma t expression, and disease activity indices

Objectives

Considering the role of T helper (Th)17 cells in the pathogenesis of ankylosing spondylitis (AS), the aim of this study was to determine the correlation between aryl hydrocarbon receptor (AHR) gene expression and the expression of Th17-related genes including interleukin (IL)-17 and RAR-related orphan receptor gamma t (RORγt) transcription factor.

Patients and methods

Thirty patients with AS (26 males, 4 females; mean age: 36.1±8.1 years) and 30 age- and sex-matched healthy individuals (26 males, 4 females; mean age: 36.2±14.6 years) were recruited for the case-control study between June 2021 and January 2022. Ribonucleic acid (RNA) was extracted from peripheral blood cells and expression levels of AHR, IL-17, RORγt, and AHR repressor (AHRR) genes were evaluated using real-time polymerase chain reaction technique. The serum level of IL-17 was evaluated with enzyme-linked immunosorbent assay.

Results

The results showed a nonsignificant elevation of AHR, IL-17, and RORγt gene expression in the patient group compared to the control. There was a direct correlation between AHR gene expression and IL-17 and RORγt genes and a negative correlation between AHR and AHRR expression. Moreover, AHR gene expression showed a weak correlation with disease activity indices, including Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Functional Index, Bath Ankylosing Spondylitis Metrology Index, Bath Ankylosing Spondylitis Global Score, and Ankylosing Spondylitis Quality of Life. Moreover, the serum level of IL-17 was higher in AS patients compared to the healthy group (p=0.02).

Conclusion

Upregulated expression of the AHR gene in ankylosing spondylitis and its correlation with IL-17 and ROR-γ t gene expression suggests that it could be a potential diagnostic and therapeutic target for AS.

A Review of Laboratory Practices Using the HLA-B27 Survey by the College of American Pathologists: How Important Is Allele-Level Typing?

CONTEXT.—

Ankylosing spondylitis (AS) is an autoimmune disorder with a strong genetic risk, especially with HLA-B27. Clinical testing for HLA-B27 has been used to help diagnose patients with signs and symptoms of AS. Testing methods used by clinical laboratories for HLA-B27 fall into the broad categories of serologic/antibody- or molecular-based methods and have evolved over time. The College of American Pathologists (CAP) offers a proficiency testing survey for HLA-B27.

OBJECTIVE.—

To analyze HLA-B27 testing trends and their performance in the past decade, using the proficiency testing survey data submitted to CAP.

DESIGN.—

We analyzed the HLA-B27 CAP proficiency testing data from 2010 to 2020 for the method used, participant concordance, and error rates. Results from case scenarios to understand evolving scientific data around HLA-B27 risk alleles were also analyzed.

RESULTS.—

Antibody-based flow cytometry is the most common method, though it has decreased from 60% in 2010 to 52% in 2020, with a corresponding increase in molecular methods. Among the molecular methods, real-time polymerase chain reaction has increased from 2% to 15%. Flow cytometry had the highest error rate (5.33%), and sequence-specific oligonucleotide (0%) is the most accurate (0%). Results of case scenarios demonstrated that most participants understood that allele-level HLA-B27 typing results inform clinical interpretation, for example HLA-B*27:06 is not associated with AS.

CONCLUSIONS.—

These data demonstrated the changing trends for HLA-B27 testing during the past decade. HLA-B27 allelic typing provides a better understanding of AS association. This is possible by testing for the second field with methods like next-generation sequencing.

Antigen-specific immune reactions by expanded CD8+ T cell clones from HLA-B*27-positive patients with spondyloarthritis

Spondyloarthritis (SpA) is a chronic inflammatory disease that is tightly linked to HLA-B*27 but the pathophysiological basis of this link is still unknown. It is discussed whether either the instability of HLA-B*27 molecules triggers predominantly innate immune reactions or yet unknown antigenic peptides presented by HLA-B*27 induce adaptive autoimmune reactions by CD8⁺ T cells. To analyze the pathogenesis of SpA, we here investigated the T cell receptor (TCR) usage and whole transcriptomes of CD8⁺ single cells from synovial fluid of HLA-B*27-positive SpA patients and HLA-B*27-negative controls. In HLA-B*27-positive patients, we confirmed preferential expression of several TCR β-chain families, found even more restricted usage of particular TCR α-chains, assigned matching TCR αβ-chain pairs with homologous CDR3-sequences, and detected identical TCR-chains in different patients. Gene expression analyses by single cell mRNAseq revealed that genes specific for the tissue resident memory phenotype, exhaustion, and apoptosis were particularly highly expressed in expanded clonotypes from HLA-B*27-positive SpA patients. Together, several independent lines of evidence argue in favor of an (auto)antigenic peptide related pathogenesis.

Single Cell Transcriptome and Surface Epitope Analysis of Ankylosing Spondylitis Facilitates Disease Classification by Machine Learning

Ankylosing spondylitis (AS) is an immune-mediated inflammatory disorder that primarily affects the axial skeleton, especially the sacroiliac joints and spine. This results in chronic back pain and, in extreme cases, ankylosis of the spine. Despite its debilitating effects, the pathogenesis of AS remains to be further elucidated. This study used single cell CITE-seq technology to analyze peripheral blood mononuclear cells (PBMCs) in AS and in healthy controls. We identified a number of molecular features associated with AS. CD52 was found to be overexpressed in both RNA and surface protein expression across several cell types in patients with AS. CD16+ monocytes overexpressed TNFSF10 and IL-18Rα in AS, while CD8+ TEM cells and natural killer cells overexpressed genes linked with cytotoxicity, including GZMH, GZMB, and NKG7. Tregs underexpressed CD39 in AS, suggesting reduced functionality. We identified an overrepresented NK cell subset in AS that overexpressed CD16, CD161, and CD38, as well as cytotoxic genes and pathways. Finally, we developed machine learning models derived from CITE-seq data for the classification of AS and achieved an Area Under the Receiver Operating Characteristic (AUROC) curve of > 0.95. In summary, CITE-seq identification of AS-associated genes and surface proteins in specific cell subsets informs our understanding of pathogenesis and potential new therapeutic targets, while providing new approaches for diagnosis via machine learning.

Mechanism of Hip Arthropathy in Ankylosing Spondylitis: Abnormal Myeloperoxidase and Phagosome

Background

The pathogenesis of Ankylosing spondylitis (AS) has not been elucidated, especially involving hip joint disease. The purpose of this study was to analyze the proteome of diseased hip in AS and to identify key protein biomarkers.

Material and Methods

We used label-free quantification combined with liquid chromatography mass spectrometry (LC–MS/MS) to screen for differentially expressed proteins in hip ligament samples between AS and No-AS groups. Key protein was screened by Bioinformatics methods. and verified by in vitro experiments.

Results

There were 3,755 identified proteins, of which 92.916% were quantified. A total of 193 DEPs (49 upregulated proteins and 144 downregulated proteins) were identified according to P < 0.01 and Log|FC| > 1. DEPs were mainly involved in cell compartment, including the vacuolar lumen, azurophil granule, primary lysosome, etc. The main KEGG pathway included Phagosome, Glycerophospholipid metabolism, Lysine degradation, Pentose phosphate pathway. Myeloperoxidase (MPO) was identified as a key protein involved in Phagosome pathway. The experiment of siRNA interfering with cells further confirmed that the upregulated MPO may promote the inflammatory response of fibroblasts.

Conclusions

The overexpression of MPO may contribute to the autoimmune inflammatory response of AS-affected hip joint through the phagosome pathway.

Predominant frequency of HLA-B*27 in patients with ankylosing spondylitis in southeastern China

OBJECTIVES

This study was to investigate the polymorphism and distribution of alleles of HLA-B*27 in patients with ankylosing spondylitis (AS) in Han population of southeastern China.

METHODS

A total of 89 peripheral blood samples from southeastern Chinese Han patients with AS that diagnosed according to Modified New York criteria were subtyped using the high-resolution PCR-SSP.Exon 2-3 of HLA-B*27 gene was amplified and sequenced to further confirm the HLA-B*27 subtype.

RESULTS

The frequency of HLA-B*27 was 99.87% in AS patients. Three subtypes, HLA-B*2704, HLA-B*2705, and HLA-B*2706 were identified. The frequencies for these three alleles were HLA-B*2704 in 84/88 (95.46%), HLA-B*2705 in 3/88(3.41%), and HLA-B*2706 in 1/88 (1.13%) of the HLA-B*27 positive patients, respectively.

CONCLUSIONS

Our study shows that HLA-B*2704 has an overwhelming frequency in southeastern Chinese Han AS patients. A combined analysis including previous studies of HLA-B*27-subtype distributions in Chinese Han populations showed that HLA-B*2704 may originate from the southern Han and then migrate and spread to the northern areas, and HLA-B*2705 show the opposite result.

Serum IL-6 and TNF-α Levels Are Correlated with Disease Severity in Patients with Ankylosing Spondylitis

OBJECTIVE

Previous studies have shown that a number of cytokines participate in the regulation of ankylosing spondylitis (AS). To investigate the potential role of interleukin (IL)-6 and tumor necrosis factor- α (TNF-α) in AS pathogenesis, this study examined the serum levels of IL-6 and TNF-α in patients with AS and its clinical association with disease activity.

MATERIALS AND METHODS

The serum concentrations of IL-6 and TNF-α from 80 patients with AS and 46 healthy control patients (HCs) were examined by electrochemiluminescence immunoassay. The correlations between the serum IL-6 and TNF-α levels and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), computed tomography (CT) imaging-based classification, and laboratory indicators were analyzed using the Spearman correlation test.

RESULTS

Compared to HCs, patients with AS showed higher levels of IL-6 and TNF-α. There was also a positive correlation between the serum IL-6 and TNF-α levels and the BASDAI, the progression of AS, and the CT imaging-based classification. The serum levels of IL-6 correlated closely with C-reactive protein and the erythrocyte sedimentation rate. More important, patients with AS with hip joint involvement exhibited a significant elevation of serum levels of TNF-α, and higher IL-6 was detected in patients with the involvement of joints other than the hip and sacroiliac joints.

CONCLUSION

The serum levels of IL-6 and TNF-α can function as important indicators for auxiliary diagnosis and disease activity evaluation of AS.

Association of Protective HLA-A With HLA-B∗27 Positive Ankylosing Spondylitis

Objectives

To further elucidate the role of the MHC in ankylosing spondylitis by typing 17 genes, searching for HLA-B^∗27 independent associations and assessing the impact of sex on this male biased disease.

Methods

High-confidence two-field resolution genotyping was performed on 310 cases and 2196 controls using an n-1 concordance method. Protein-coding variants were called from next-generation sequencing reads using up to four software programs and the consensus result recorded. Logistic regression tests were applied to the dataset as a whole, and also in stratified sets based on sex or HLA-B^∗27 status. The amino acids driving association were also examined.

Results

Twenty-five HLA protein-coding variants were significantly associated to disease in the population. Three novel protective associations were found in a HLA-B^∗27 positive population, HLA-A^∗24:02 (OR = 0.4, CI = 0.2–0.7), and HLA-A amino acids Leu95 and Gln156. We identified a key set of seven loci that were common to both sexes, and robust to change in sample size. Stratifying by sex uncovered three novel risk variants restricted to the female population (HLA-DQA1^∗04.01, -DQB1^∗04:02, -DRB1^∗08:01; OR = 2.4–3.1). We also uncovered a set of neutral variants in the female population, which in turn conferred strong effects in the male set, highlighting how population composition can lead to the masking of true associations.

Conclusion

Population stratification allowed for a nuanced investigation into the tightly linked MHC region, revealing novel HLA-B^∗27 signals as well as replicating previous HLA-B^∗27 dependent results. This dissection of signals may help to elucidate sex biased disease predisposition and clinical progression.

Allele frequency spectrum of known ankylosing spondylitis associated variants in a Swedish population

Objective: The genetic predisposition to ankylosing spondylitis (AS) has been most widely studied in cohorts with European ancestry. However, within Europe, disease prevalence is higher in Sweden. Given this, we aimed to characterize known AS susceptibility variants in a homogeneous Swedish data set, assessing reproducibility and direction of effect.Method: The power to detect association within an existing Swedish targeted sequencing study (381 controls; 310 AS cases) was examined, and a set of published associations (n = 151) was intersected with available genotypes. Association to disease was calculated using logistic regression accounting for population structure, and HLA-B27 status was determined with direct polymerase chain reaction genotyping.Results: The cases were found to be 92.3% HLA-B27 positive, with the data set showing ≥ 80% predictive power to replicate associations, with odds ratios ≥ 1.6 over a range of allele frequencies (0.1-0.7). Thirty-four markers, representing 23 gene loci, were available for investigation. The replicated variants tagged MICA and IL23R loci (p < 1.47 × 10^-3), with variable direction of effect noted for gene loci IL1R1 and MST1.Conclusion: The Swedish data set successfully replicated both major histocompatibility complex (MHC) and non-MHC loci, and revealed a different replication pattern compared to discovery data sets. This was possibly due to population demographics, including HLA-B27 frequency and measured comorbidities.

Comparison of Next-Generation Sequencing-Based Human Leukocyte Antigen Typing with Clinical Flow Cytometry and Allele-Specific PCR Melting Assays for HLA-B27 Genotyping

BACKGROUND

Due to the strong association between ankylosing spondylitis and Human Leukocyte Antigen (HLA)-B27, accurate identification of HLA-B27 is important in the diagnosis of patients with suspected spondyloarthritides. For this study, we compared a high-resolution HLA-B typing method to the clinical flow cytometry and allele-specific PCR melting assays to determine clinical benefits of high-resolution testing.

METHODS

Residual clinical samples submitted for HLA-B27 testing by flow cytometry were tested by single-locus HLA-B genotyping using next-generation sequencing (NGS), and PCR with melting curve analysis, currently used as a reflex test for indeterminate flow cytometry results.

RESULTS

Fifty out of the 51 samples (98%) positive by flow cytometry confirmed as HLA-B27 positive by PCR melting assay and by NGS. The sample that did not confirm was genotyped as HLA-B*07:02. All the samples negative by flow cytometry were confirmed as HLA-B27 negative by both PCR melting assay and NGS. For the group that was indeterminate by flow cytometry, 84.5% (n = 49) typed as positive for HLA-B27, while 15.5% (n = 9) were negative for HLA-B27 but positive for HLA-B*07:02. NGS was the only method able to distinguish between pathogenic and nonpathogenic HLA-B27 variants, in contrast to the flow cytometry or the PCR melting assays.

CONCLUSIONS

Single-locus NGS is superior to flow cytometry and PCR melting assay for the unambiguous identification of HLA-B27 variants, and uniquely able to distinguish between pathogenic and nonpathogenic B27 alleles. Due to its high accuracy, it may be a feasible superior alternative to flow cytometry and traditional molecular methods for clinical HLA-B27 testing.

Value-Based Healthcare in Rheumatology: Axial Spondyloarthritis and Beyond

PURPOSE OF REVIEW

This review examines axial spondyloarthritis (axSpA) and the wider field of rheumatology through a value-based healthcare (VBHC) lens. VBHC is focused on ensuring patients receive high quality care to improve outcomes and reduce unnecessary costs.

RECENT FINDINGS

There are many opportunities to apply the principles of VBHC in axSpA. These include the appropriate utilization of diagnostic investigations, such as HLA-B27 and magnetic resonance imaging, assessing outcomes meaningful to patients, and optimizing care pathways. Multidisciplinary care may improve value, and reduced specialist review and medication tapering may be appropriate. Increasing the value of the care we provide to patients can occur across domains and directly and indirectly improves patient outcomes. Taking the time to integrate principles of VBHC into our practice will allow us to justifiably gain and maintain access to diagnostic and therapeutic advances for the benefit of all our patients.

Osteoimmunological insights into the pathogenesis of ankylosing spondylitis

Ankylosing spondylitis (AS) is inflammatory arthritis predominantly affecting the spine, which is involved in the disorders of both immune and skeletal systems. The exact pathogenesis of AS is not fully understood. Osteoimmunology is a new subject of study in inflammatory arthritis, in particular the pathogenic events involved in the cross-regulation of both skeletal and immune systems. In this review, we discuss osteoimmunological and pathological changes of AS in the spine that are characterized by altered osteogenesis and osteolytic bone destruction, accompanied by the changes of the immune system. It was revealed that bone cells like mesenchymal stem cells, osteoblast, and osteoclast in crossing talking with immune cells such as T cells, B cells coregulate to the pathogenesis of AS. Further, an array of cytokines and molecules expressed by both skeletal and immune systems contribute to these complex interplays. Understanding the cellular and molecular mechanisms underlying the pathogenesis of AS will lay a foundation for the exploration of the potential new treatment to AS.

BMP2 variants in the risk of ankylosing spondylitis

The purpose of the study was to explore the genetic effects of bone morphogenetic protein (BMP2) polymorphisms on the susceptibility to ankylosing spondylitis (AS) in Chinese Han population. The case-control study included 120 AS cases and 110 healthy controls. Hardy-Weinberg equilibrium test was performed in control group. BMP2 rs235768 and rs3178250 polymorphisms were analyzed by polymerase chain reaction and direct sequencing. Additionally, the χ²  test was used to estimate association strength between BMP2 genetic polymorphisms and AS susceptibility, and the results were assessed via odds ratio (OR) with the corresponding 95% confidence interval (95%CI). Results adjustment was performed using logistic regression analysis. AA, AT, TT genotype and A, T allele frequencies of BMP2 rs235768 polymorphism presented no significant differences between case and control groups (P > .05 for all). TC genotype of rs3178250 polymorphism showed significantly higher in case group than that in control group (P = .048). After adjusting, TC genotype was a risk factor for AS (OR = 2.095; 95%CI = 1.086-4.038; P = .027). BMP2 rs3178250 polymorphism may increase individual susceptibility to AS in Chinese Han population.

Clinical utility of next generation sequencing based HLA typing for disease association and pharmacogenetic testing

HLA associations have been linked to many diseases and are important for risk assessment of drug hypersensitivity reactions. The increasing number of HLA alleles discovered generated a list of ambiguities that cannot be resolved with the current clinical assays, which commonly include sequence-specific oligonucleotide probe (SSOP) genotyping, and real-time PCR with melting curve analysis. HLA typing by next-generation sequencing (NGS) has recently been adopted by clinical laboratories for transplantation testing, as it provides unambiguous and cost-effective HLA typing. The goal of this study was to evaluate the feasibility of using NGS-based HLA-B and DQ genotyping for clinical HLA disease association testing, and provide direct comparison with the currently used clinical tests, including SSOP genotyping, and real-time PCR with melting curve analysis. While the real-time PCR method is easy and inexpensive to perform, ambiguities are rapidly increasing as more and more HLA alleles are discovered. SSOP genotyping identifies the alleles present but limitations include ambiguities and underreporting less common alleles. Our data show that HLA typing by NGS is superior to the existing clinical methods for identifying HLA alleles associated with disease or drug hypersensitivity, and offers a viable approach for high volume clinical diagnostic laboratories.

Modulation of inflammatory response and gut microbiota in ankylosing spondylitis mouse model by bioactive peptide IQW

AIMS

Ankylosing spondylitis (AS) is a widespread and chronic inflammatory autoimmune disease of unknown provenance. Naturally occurring peptides and proteins have shown significant promise as modulators of immune responses. Thus, the aims of this study were to assess the protective effects of the bioactive peptide IQW (Ile-Gln-Trp) with respect to inflammatory indicators, gut microbiota and oxidative stress, and to examine the potential mechanisms of these effects.

METHODS AND RESULTS

A mouse model was prepared by four injections of human proteoglycan extract (2 mg) in dimethyldioctadecylammonium solution (2 mg) over an interval of 2 weeks. Enzyme-linked immunosorbent assay results for the markers of oxidative stress and inflammation in the AS mice revealed increased concentrations of malondialdehyde, IL-6, IL-1β and TNF-α, along with decreased concentrations of catalase (CAT), glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD). Treatment with IQW was found to decrease the concentrations of IL-6, IL-1β and TNF-α, and increase the concentrations of CAT, GSH-PX and SOD. Moreover the quantification of the microbiota via 16s rRNA sequencing revealed a reduced microbial diversity in the AS mice, while a significantly increased microbial diversity was displayed by those treated with IQW. Whereas, there was a significant reduction in the relative abundance of Bacteroidetes and an increased relative abundance of Verrucomicrobia in AS mice, this was reversed following the IQW treatment.

CONCLUSIONS

The results demonstrated that IQW exerts a beneficial influence in AS by delaying progression of the disease, reducing the arthritic grade of intervertebral joints, altering the concentrations of cytokines and modulating the microbial diversity and composition.

SIGNIFICANCE AND IMPACT OF THE STUDY

Oral IQW treatment might represent a new approach to mitigate the onset and development of AS.

Identification of RELN variant p.(Ser2486Gly) in an Iranian family with ankylosing spondylitis; the first association of RELN and AS

Ankylosing spondylitis (AS) is a common complex inflammatory disease; however, up to now distinct genes with monogenic pattern have not been reported for this disease. In the present study, we report a large Iranian family with several affected members with AS. DNAs of the three affected and two healthy cases were chosen for performing whole-exome sequencing (WES). After several filtering steps, candidate variants in the following genes were detected: RELN, DNMT1, TAF4β, MUC16, DLG2, and FAM208. However, segregation analysis confirmed the association of only one variant, c.7456A>G; p.(Ser2486Gly) in the RELN gene with AS in this family. In addition, in silico predictions supported the probable pathogenicity of this variant. In this study, for the first time, we report a novel variant in the RELN gene, c.7456A>G; p.(Ser2486Gly), which completely co-segregates with AS. This association suggests potential insights into the pathophysiological bases of AS and it could broaden horizons toward new therapeutic strategies.

Cardiac conduction disturbances in patients with ankylosing spondylitis: results from a 5-year follow-up cohort study

Objectives

To describe electrocardiographic (ECG) development in patients with ankylosing spondylitis (AS) and identify associations between baseline characteristics and cardiac conduction disturbances (CCD) at 5-year follow-up.

Methods

In a longitudinal cohort study, 172 patients (54% men, mean age (SD) of 50 (13) years at baseline) with AS underwent ECG, physical examination, questionnaires and laboratory testing at baseline and at 5-year follow-up. Descriptive statistics and univariate and age- and sex-adjusted logistic regression analyses were used. CCD included both atrioventricular and intraventricular blocks.

Results

Twenty-three of the 172 patients (13.4%) had a CCD at follow-up. Eight patients had developed a new CCD and eight had normalised their ECG. In the age- and sex-adjusted analyses, CCD at baseline (OR 24.8, 95% CI 7.3 to 84.5), male sex (OR 6.4, 95% CI 2.0 to 20.8), history of anterior uveitis (OR 4.4, 95% CI 1.3 to 14.5), higher ASDAS-CRP (OR 2.3, 95% CI 1.3 to 4.0), greater waist circumference (OR 1.3, 95% CI 1.1 to 1.6, per 5 cm), and medication with antiplatelets (OR 7.0, 95% CI 1.5 to 31.8) and beta-blockers (OR 3.4, 95% CI 1.0 to 11.5) were associated with a CCD at follow-up. Higher age and longer symptom duration were highly correlated and were both associated with a CCD at follow-up.

Conclusions

The presence of CCD in AS is in part dynamic and associated with both AS and non-AS characteristics. Our results suggest that patients especially prone to present with CCDs are older men with a previous CCD, longer symptom duration, higher AS disease activity, a history of anterior uveitis and medication reflecting cardiovascular disease.

Advances in nanomedicine for the treatment of ankylosing spondylitis

Ankylosing spondylitis (AS) is a complex disease characterized by inflammation and ankylosis primarily at the cartilage-bone interface. The disease is more common in young males and risk factors include both genetic and environmental. While the pathogenesis of AS is not completely understood, it is thought to be an immune-mediated disease involving inflammatory cellular infiltrates, and human leukocyte antigen-B27. Currently, there is no specific diagnostic technique available for this disease; therefore conventional diagnostic approaches such as clinical symptoms, laboratory tests and imaging techniques are used. There are various review papers that have been published on conventional treatment approaches, and in this review work, we focus on the more promising nanomedicine-based treatment modalities to move this field forward.

Disease Activity and Patient-Reported Health Measures in Relation to Cytokine Levels in Ankylosing Spondylitis

INTRODUCTION

Ankylosing spondylitis (AS) is a lifelong condition where spinal inflammation causes chronic back pain and restriction of spinal function. While proinflammatory cytokines participate in the disease process, their relation with disease activity, spinal function, and quality of life is less well understood.

METHODS

Cross-sectional study of serum levels of four inflammatory cytokines (IL-6, TNF, IL-23, and IL-17A) in AS patients not on biologics. Disease characteristics and simultaneous spinal function tests and patient-reported health measures (Bath Functional Index (BASFI), Dougados Functional Index (DFI), Modified Health Assessment Questionnaire (MHAQ), and routine laboratory parameters were recorded. The composite ASDAS-CRP score was used to classify disease activity as absent, low, or high.

RESULTS

In 164 AS patients (age 46 years, 70.1% males, 90.9% HLAB27 positive, ASDAS-CRP 1.8), disease activity was classified as inactive in 14%, low in 54%, and high in 31%. ASDAS-CRP correlated well with MHAQ, DFI, BASFI, and spinal mobility across patients with low and high disease activity (all p < 0.05). Cytokine levels did not correlate with ASDAS-CRP, ESR, BASFI, or spinal mobility scores and were comparable between patients with no, low, or high disease activity regardless of gender or disease duration (all p > 0.2).

CONCLUSIONS

A large proportion of AS not on biologics have active disease far into the disease course. This impacts negatively on quality of life, work ability, and spinal mobility. Serum cytokine levels are poor markers for these central disease features in AS management.

FUNDING

Abbott Norway AS and Arthritis Foundation of Western Australia.

IL-38: A New Player in Inflammatory Autoimmune Disorders

Interleukin (IL)-38, a newly discovered IL-1 family cytokine, is expressed in several tissues and secreted by various cells. IL-38 has recently been reported to exert an anti-inflammatory function by binding to several receptors, including interleukin-36 receptor (IL-36R), interleukin-1 receptor accessory protein-like 1 (IL-1RAPL1), and interleukin-1 receptor 1 (IL-1R1) to block binding with other pro-inflammatory cytokines and inhibit subsequent signaling pathways; thereby regulating the differentiation and function of T cells, peripheral blood mononuclear cells, macrophages, and dendritic cells. Inflammatory autoimmune diseases, which are common immune-mediated inflammatory syndromes, are characterized by an imbalance between T helper cells (Ths), especially Th1s and Th17s, and regulatory T cells (Tregs). Recent findings have shown that abnormal expression of IL-38 in inflammatory autoimmune diseases, such as rheumatoid arthritis, psoriatic arthritis, systemic lupus erythematosus, primary Sjogren's syndrome, psoriasis, inflammatory bowel disease, hidradenitis suppurativa, ankylosing spondylitis, and glaucoma, involves Th1s, Th17s, and Tregs. In this review, the expression, regulation, and biological function of IL-38 are discussed, as are the roles of IL-38 in various inflammatory autoimmune disorders. Current data support that the IL-38/IL-36R and/or IL-38/IL-1RAPL1 axis primarily play an anti-inflammatory role in the development and resolution of inflammatory autoimmune diseases and indicate a possible therapeutic benefit of IL-38 in these diseases.

Association study of copy number variation in BMP8A gene with the risk of ankylosing spondylitis in Iranian population

BACKGROUND

Copy number variation (CNV) of DNA segments has been considered as an important component of genetic variation, affecting the quality and quantity of gene expression. Bone morphogenic protein 8A (BMP8A) has been reported to function in bone formation. With respect to the bone and joint complications in ankylosing spondylitis (AS), this investigation aimed to study the role of BMP8A gene CNV in impressing the gene expression as well as the disease risk.

METHODS

A total of 900 individuals, including 450 patients with AS and 450 healthy controls were enrolled. The copy numbers of BMP8A gene were detected by TaqMan real-time polymerase chain reaction (PCR) method. BMP8A messenger RNA (mRNA) transcript level in peripheral blood mononuclear cells (PBMCs) was also measured by SYBR Green real-time gene expression PCR method.

RESULTS

No significant association of BMP8A copy number was detected with the risk of AS. BMP8A mRNA expression level was significantly downregulated in patients compared with controls. mRNA expression level of BMP8A in both AS patients with and without syndesmophyte was significantly lower than the healthy control group. There was no correlation between the mRNA expression level of BMP8A and both demographic and clinical data of the patients.

CONCLUSIONS

Although BMP8A gene expression was downregulated in patients with AS, its copy number could not affect the transcript level of BMP8A gene in PBMCs and was not associated with susceptibility to AS in Iranian population. BMP8a may take into account as an indicator of bone formation process in AS, but it seems that mechanisms other than CNV may regulate this protein.

The antiquity of the spondyloarthritides: Presentation of one of the oldest Neolithic cases in Western Europe

In humans, little is yet known about the origins of the inflammatory rheumatisms of the spondyloarthritides group, especially regarding the period of their emergence. However, a better knowledge of their history would help to clarify their aetiology. We report a paleopathological case of European origin, dated from the late Neolithic (3621-3023 cal BC), consisting of an isolated vertebral block combining erosion, ossification and severe anterior and posterior ankylosis. The lesional presentation is very suggestive of a severe form of axial spondyloarthritis. This specimen and some other rare cases from the same period found in Western Europe suggest that these diseases appeared, in this geographical region, in evolving groups of humans as part of the demographic and epidemiological transition that constituted the Neolithic period. The emergence of infectious agents and the profound dietary changes that occurred during this period of human history may have favoured the appearance of the spondyloarthritides.

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.

Ankylosing Spondylitis: A Trade Off of HLA-B27, ERAP, and Pathogen Interconnections? Focus on Sardinia

The frequency of HLA-B27 in patients with Ankylosing Spondylitis (AS) is over 85%. There are more than 170 recognized HLA-B27 alleles but the majority of them is not sufficiently represented for genetic association studies. So far only two alleles, the HLA-B^*2706 in Asia and the HLA-B^*2709 in Sardinia, have not been found to be associated with AS. The highly homogenous genetic structure of the Sardinian population has favored the search of relevant variants for disease-association studies. Moreover, malaria, once endemic in the island, has been shown to have contributed to shape the native population genome affecting the relative allele frequency of relevant genes. In Sardinia, the prevalence of HLA-B^*2709, which differs from the strongly AS-associated B^*2705 prototype for one amino acid (His/Asp116) in the F pocket of the peptide binding groove, is around 20% of all HLA-B27 alleles. We have previously hypothesized that malaria could have contributed to the establishment of this allele in Sardinia. Based on our recent findings, in this perspective article we speculate that the Endoplasmic Reticulum Amino Peptidases, ERAP1 and 2, associated with AS and involved in antigen presentation, underwent co-selection by malaria. These genes, besides shaping the immunopeptidome of HLA-class I molecules, have other biological functions that could also be involved in the immunosurveillance against malaria.

Association of TNF, IL12, and IL23 gene polymorphisms and psoriatic arthritis: meta-analysis

BACKGROUND

Psoriatic arthritis (PsA) is a chronic skin and joint condition that considerably affects patient quality of life. Several studies have demonstrated different associations of genetic polymorphisms in the pathogenic process of PsA. Therefore, we conducted a meta-analysis to estimate the effect of polymorphisms in the cytokines TNF, IL12B, IL23A, and IL23R on PsA risk.

METHODS

We screened 1,097 abstracts and identified 14 relevant studies published between January 2007 and December 2017. A systematic search was conducted in PubMed, Web of Knowledge and Scopus databases. Meta-analyses were performed for the comparisons of alleles and multiple genetic models.

RESULTS

Among the cytokines studied, we found 17 polymorphisms that were the most investigated. The association to PsA was observed in the presence of polymorphisms: TNF-238 G > A (rs361525), -308 G > A (rs1800629), and -857 C > T (rs1799724); IL12B C > G (rs6887695) and A > C (rs3212227); IL23A A > G (rs2066808) and IL23R G > A (rs11209026).

CONCLUSION

Our findings suggest that these variant cytokine genes may strongly influence the immunological response of PsA.

RUNX3 and T-Bet in Immunopathogenesis of Ankylosing Spondylitis-Novel Targets for Therapy?

Susceptibility to ankylosing spondylitis (AS) is polygenic with more than 100 genes identified to date. These include HLA-B27 and the aminopeptidases (ERAP1, ERAP2, and LNPEPS), which are involved in antigen processing and presentation to T-cells, and several genes (IL23R, IL6R, STAT3, JAK2, IL1R1/2, IL12B, and IL7R) involved in IL23 driven pathways of inflammation. AS is also strongly associated with polymorphisms in two transcription factors, RUNX3 and T-bet (encoded by TBX21), which are important in T-cell development and function. The influence of these genes on the pathogenesis of AS and their potential for identifying drug targets is discussed here.

Genetics and Functional Genomics of Spondyloarthritis

Spondyloarthritis (SpA) is a chronic inflammatory disorder with high heritability but with complex genetics. It encompasses several entities that share common clinical features. Most of the genetic studies in SpA have been restricted to ankylosing spondylitis (AS), the prototypical form of SpA. However, there is growing evidence of shared genetic background between all the SpA subtypes and also with some other immune-mediated diseases. The most important part of SpA heritability comes from the HLA-B27 allele in the major histocompatibility complex (MHC) that explains around 25% of the attributable heredity. Several other loci outside of the MHC have been shown to be involved in the disease. However, all these non-MHC loci explain only a small additional fraction of disease predisposition. Thus, a substantial fraction of SpA genetic basis remains poorly understood. Gene expression profiling is a complementary approach to elucidate the underlying mechanisms and pathways that drive the disease. Several expression profiling studies have been undertaken in SpA. However, results have been quite disappointing with little overlap between the studies largely due to the small sample sizes, resulting in limited power to discover small effects. In this review, we summarize current knowledge on genetic findings concerning SpA and we describe strategic approaches for identification of additional variants, with a focus on rare variants in familial forms. We also provide an overview of gene expression studies in SpA and discuss the possibilities offered by high-throughput RNA sequencing technologies, in particular in sorted cells. Finally, issues in establishing molecular mechanisms underlying genetic association hits and potential translational applications will be addressed.

IL-1A gene variation in relation to cytokine levels and clinical characteristics in ankylosing spondylitis

Objective

Variations in the IL-1 alpha (IL-A) gene increase the risk for ankylosing spondylitis (AS), but the pathway underlying this association is not fully understood. As IL-1A is primarily a regulatory cytokine, we investigated the influence of IL-1A gene variation on disease severity and cytokine expression in AS.

Methods

This was a cross sectional study of tumor necrosis factor inhibitors (TNFi)-naïve AS patients (n=334, 90% B27 +, age 45 years) fulfilling the modified New York criteria. We recorded demographics, clinical findings, spinal mobility, Bath AS Functional Index (BASFI), and routine lab findings. IL-1A genotyping for three AS-associated single nucleotide polymorphism (SNP; rs2856836, rs17561 and rs1894399) was performed using Taqman RT-PCR, with TNF, IL-6, IL-17A, and IL-23 levels measured using ELISA. Genotypic associations included logistic regression analysis for genotype (codominant model) and global haplotype (threshold 5%) associations with cytokine levels and clinical features.

Results

The three variants were in near complete linkage disequilibrium and formed two only common haplotypes (ACC 67%, GAT 33%). The levels for TNF, IL-6, IL-17A, IL-23, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were similar across genotypes and haplotypes (all p-values >0.4) as were the measures for spinal mobility and BASFI. The TAQ haplotype showed a borderline significant trend with reduced heart disease and mortality during follow-up.

Conclusion

IL-1A gene cluster variations do not have an impact on the clinical disease measures or cytokine levels in AS, suggesting that IL-1A has no direct role in AS.

Translating GWAS in rheumatic disease: approaches to establishing mechanism and function for genetic associations with ankylosing spondylitis

Ankylosing spondylitis (AS) is a highly heritable chronic inflammatory arthritis characterized by osteoproliferation, fusion of affected joints and systemic manifestations. Many disease associations for AS have been reported through genome-wide association studies; however, identifying modulated genes and functional mechanism remains challenging. This review summarizes current genetic associations involving AS and describes strategic approaches for functional follow-up of disease-associated variants. Fine mapping using methods leveraging Bayesian approaches are outlined. Evidence highlighting the importance of context specificity for regulatory variants is reviewed, noting current evidence in AS for the relevant cell and tissue type to conduct such analyses. Technological advances for understanding the regulatory landscape within which functional variants may act are discussed using exemplars. Approaches include defining regulatory elements based on chromatin accessibility, effects of variants on genes at a distance through evidence of physical interactions (chromatin conformation capture), expression quantitative trait loci mapping and single-cell methodologies. Opportunities for mechanistic studies to investigate the function of specific variants, regulatory elements and genes enabled by genome editing using clustered regularly interspaced short palindromic repeats/Cas9 are also described. Further progress in our understanding of the genetics of AS through functional genomic and epigenomic approaches offers new opportunities to understand mechanism and develop innovative treatments.

Downregulation of lncRNA TUG1 is involved in ankylosing spondylitis and is related to disease activity and course of treatment

Long non-coding RNA taurine-upregulated gene 1 (lncRNA TUG1) promotes osteosarcoma, while its involvement in other bone diseases, such as ankylosing spondylitis (AS) is unknown. Expression of TUG1 in serum and open sacroiliac biopsies of AS patents and healthy controls was detected by real-time quantitative PCR (qRT-PCR). Ankylosing spondylitis disease activity score (ASDAS) system was used to evaluate disease activity. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic value of lncRNA TUG1 for AS. Chi-square test was performed to analyze the correlations between TUG1 expression and patients' clinicopathological data. Patients were divided into 2 groups (high and low expression groups) according to the median expression level of TUG1 and were followed-up for 5 years after discharge. Treatment courses and rehospitalization rate were compared between two groups. It was observed that TUG1 expression level was significantly lower in AS patients than in healthy controls in both serum and biopsies. Reduced expression level of TUG1 distinguished AS patients from controls. LncRNA TUG1 expression was significantly correlated with patients' smoking habits, disease activity, and course of disease. Patients in high expression group showed longer hospitalization time and higher rehospitalization rate. We therefore conclude that expression of lncRNA TUG1 was inhibited in AS patients and downregulation of lncRNA TUG1 is related to higher disease activity, longer course of treatment and higher rehospitalization rate.

The clinical utility of human leucocyte antigen B27 in axial spondyloarthritis

The association between HLA-B27 and AS was first established in the early 1970s. Since then, our understanding of this disease has changed, such that we now recognize AS to be the extreme of the clinical phenotype within a disease spectrum known as axial SpA (axSpA). Recent advances in therapeutic options have driven the need for earlier diagnosis and many screening strategies have been proposed to facilitate this. In parallel, our understanding of axSpA genetics, and especially the contribution of HLA-B27, has expanded. In this article we will present and discuss the evidence supporting the use of HLA-B27 in clinical practice. We will briefly summarize the evolution of the concept of axSpA, the prevalence of HLA-B27 and axSpA and the potential role of HLA-B27 in the aetiopathogenesis of axSpA and focus on the utility of HLA-B27 in everyday clinical practice.

Protective Effects of Sinomenine Against Ankylosing Spondylitis and the Underlying Molecular Mechanisms

BACKGROUND This study aimed to investigate the effect and underlying molecular mechanism of sinomenine (SIN) on ankylosing spondylitis (AS). MATERIAL AND METHODS To study the potential role of SIN in the pathogenesis of AS, an AS mouse model was established and mice were treated with different concentrations of SIN (10, 30, and 50 mg/kg, administered intraperitoneally). Markers of inflammation and oxidative stress were determined by ELISA assay. Western blot analysis and qRT-PCR were used to quantify the levels of related proteins and gene mRNA expression. RESULTS The results suggest that AS mice has higher levels of TNF-α, IL-1β, and IL-6 (p<0.01 for all), and lower levels of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX) (p<0.01 for all). SIN treatment reduced the level of TNF-α, IL-1β, and IL-6 in a dose-dependent manner, and the levels of SOD, CAT, and GSH-PX were dose-dependently increased (p<0.05 for all). The results also revealed that NF-κBp65 expression decreased, while the level of IkB increased, in a dose-dependent manner, after SIN treatment in AS mice (p<0.05 for all). The level of p-p38 was dose-dependently reduced in AS mice by SIN treatment (p<0.05). Moreover, SIN inhibited Cox-2 expression in AS mice in a dose-dependent manner (p<0.05). CONCLUSIONS SIN has a beneficial role in AS through suppressing inflammatory mediators and by down-regulating oxidative stress via inhibiting the MAPKp38/NF-kB pathway and Cox-2 expression.

HLA-B*27 subtypes and their implications in the pathogenesis of ankylosing spondylitis

Ankylosing spondylitis (AS) is a highly heritable kind of arthritis that affects the vertebral column. AS risk has been associated strongly with Human leukocyte antigen (HLA)-B*27. In fact, some HLA-B*27 subtypes have been associated with the increased disease risk, although some specific subtypes have not shown such associations. It is supposed that HLA-B*27 plays a major role in the etiopathogenesis of the disease. However, the difference in pathogenic outcomes of HLA-B*27 certain subtypes needs to be clarified. The purpose of this review article is to overview on the detailed implications of the HLA-B*27 subtypes in the etiopathogenesis of AS. Moreover, the role of ERAP1 in AS and its epistasis with HLA-B*27 have been reviewed.

Genetics in TNF-TNFR pathway: A complex network causing spondyloarthritis and conditioning response to anti-TNFα therapy

Objectives

We investigated whether polymorphisms (SNPs) in the promoter region of TNFA, or in the autoinflammatory TNFRSF1A and MEFV genes, concur with HLA-B27 in enhancing the risk of Spondyloarthritis (SpA) and/or in predicting the response to anti-TNFα treatment.

Methods

373 controls and 137 SpA (82 with Psoriatic Arthritis-PsA and 55 with Ankylosing Spondylitis- AS; 98/137 under TNFα inhibitor therapy) from the Veneto Region (Italy) were studied. TNFA polymorphisms (-1031T>C;-857C>T;-376G>A;-308G>A;-238G>A) and HLA-B27 were assayed by RT-PCR. Direct sequencing of MEFV (exons 2,3,5 and 10) and TNFRSF1A (exons 2,3,4 and 6) genes were performed.

Results

HLA-B27 was associated with AS (χ² = 120.1; p = 0.000). Only the TNFA -1031T>C was singly associated with SpA, and the haplotype C/G, resulting from -1031T>C/-308G>A combination, was significantly associated with a reduced risk of SpA (OR: 0.67, CI: 0.46–0.97; p = 0.035). Two SNPs were identified in TNFRSF1A, the R92Q (Minor allele frequency-MAF = 0.034) and c.625+10A>G (MAF = 0.479). None of them was associated with SpA (p>0.05). The TNFRSF1A c.625+10 G allele was associated with late response to anti-TNFα therapy (p = 0.031). Twenty-one SNPs were identified in MEFV gene, 10 with a known potential functional significance. Variant alleles were extremely rare in our population (MAF<0.025) except for R202Q (MAF = 0.27). None was associated with SpA diagnosis (p>0.05).

Conclusion

TNFRSF1A and MEFV gene SNPs are not associated with SpA in the North-East of Italy. AS risk appears to depend not only on HLA-B27, but also on the protective TNFA haplotype -1031C/-308G. The TNFRSF1A c.625+10A>G impacts on the response to anti-TNFα therapy.

Regulation of Cytokine Production by the Unfolded Protein Response; Implications for Infection and Autoimmunity

Protein folding in the endoplasmic reticulum (ER) is an essential cell function. To safeguard this process in the face of environmental threats and internal stressors, cells mount an evolutionarily conserved response known as the unfolded protein response (UPR). Invading pathogens induce cellular stress that impacts protein folding, thus the UPR is well situated to sense danger and contribute to immune responses. Cytokines (inflammatory cytokines and interferons) critically mediate host defense against pathogens, but when aberrantly produced, may also drive pathologic inflammation. The UPR influences cytokine production on multiple levels, from stimulation of pattern recognition receptors, to modulation of inflammatory signaling pathways, and the regulation of cytokine transcription factors. This review will focus on the mechanisms underlying cytokine regulation by the UPR, and the repercussions of this relationship for infection and autoimmune/autoinflammatory diseases. Interrogation of viral and bacterial infections has revealed increasing numbers of examples where pathogens induce or modulate the UPR and implicated UPR-modulated cytokines in host response. The flip side of this coin, the UPR/ER stress responses have been increasingly recognized in a variety of autoimmune and inflammatory diseases. Examples include monogenic disorders of ER function, diseases linked to misfolding protein (HLA-B27 and spondyloarthritis), diseases directly implicating UPR and autophagy genes (inflammatory bowel disease), and autoimmune diseases targeting highly secretory cells (e.g., diabetes). Given the burgeoning interest in pharmacologically targeting the UPR, greater discernment is needed regarding how the UPR regulates cytokine production during specific infections and autoimmune processes, and the relative place of this interaction in pathogenesis.

IL23R gene variants in relation to IL17A levels and clinical phenotype in patients with ankylosing spondylitis

Background

IL23 receptor (IL23R) binding by IL23 is required for the maturation of CD4⁺ cells into Th17 cells and subsequent generation of IL17A and TNF. As IL23R variations contribute to AS susceptibility, we investigated the effect of IL23R variants on cytokine levels and disease measures in an AS cohort.

Methods

This was a cross-sectional study of AS patients (n = 334, 90% B27⁺, age 45 years). IL23R genotyping for three non-synonymous single-nucleotide polymorphisms (rs11209026, protective allele A; rs10489629, protective allele A; and rs11209032, risk allele A) was done by Taqman RT-PCR. IL23, IL17A, TNF and IL6 concentrations were determined by sandwich ELISA. Genotypic associations were analysed with non-parametric methods.

Results

Twenty-two AS patients (6.6%) carried the protective rs11209026 A allele, whereas 206 (61.7%) carried the rs11209032A risk allele (P = 0.03). Two patients homozygous for rs11209026A had late onset, no co-morbidity and undetectable cytokine levels. IL23R genotypes and five common haplotypes were unrelated with age at onset, BASFI or co-morbidity (all P >0.2). There was no overall difference in the concentration of IL17A (184 vs 233 pg/ml, P > 0.2) or IL23 (276 vs 262 pg/ml, P > 0.4) between AS patients and controls, but a global haplotype association (P = 0.01) was observed for IL23 concentrations.

Conclusion

Homozygosity for rs11209026A is rare in AS patients, but may ameliorate the clinical presentation. IL17A and IL23 levels are similar in controls and AS patients. IL23R variants influence IL23 levels but not IL17A levels in AS patients, suggesting that IL23R impacts more on cell types other than Th17 cells.

Association of polymorphisms in TNF and GRN genes with ankylosing spondylitis in a Chinese Han population

The aim of this study is to investigate the association of the polymorphisms in tumor necrosis factor (TNF) and granulin (GRN) with ankylosing spondylitis (AS) in a Chinese Han population. Five single nucleotide polymorphisms (SNPs) covering TNF and six SNPs covering GRN were investigated in 861 Chinese Han AS patients and 864 healthy controls. For rs1799964, the C allele was linked to reduced risk of AS (p < 0.0001, OR = 0.60, 95% CI = 0.50-0.71). The carriers of the C/C homozygote showed a significantly lower risk of AS compared with the TT homozygote and the C/T heterozygote under the recessive model (p < 0.0001, OR = 0.23, 95% CI = 0.12-0.45). For rs1800629, the A allele was also linked to reduced risk of AS (p < 0.0001, OR = 0.54, 95% CI = 0.39-0.74). For rs1800630, the A allele was also linked to reduced risk of AS (p < 0.0001, OR = 0.59, 95% CI = 0.48-0.72). The carriers of the A/A homozygote showed a significantly lower risk of AS compared with the C/C homozygote and the A/C heterozygote under the recessive model (p < 0.0001, OR = 0.18, 95% CI = 0.07-0.47). For rs769178, the T allele was linked to increased risk of AS (p < 0.0001, OR = 2.59, 95% CI = 2.18-3.09). The carriers of the T/T homozygote showed a significantly higher risk of AS compared with the GG homozygote and the G/T heterozygote under the recessive model (p < 0.0001, OR = 3.34, 95 %CI = 1.95-5.72). There was no significant difference between the AS patients and the controls in the genotype or allele frequencies of rs361525. For GRN, there was no significant difference between the AS patients and the controls in the genotype or allele frequencies of rs25646, rs3760365, rs3785817, rs4792939, rs5848, rs850713 (p > 0.05). This study indicates that polymorphisms in TNF are related to AS, but polymorphisms in GRN are not related to AS susceptibility in a Chinese Han population.

Osteoimmunology: The Conceptual Framework Unifying the Immune and Skeletal Systems

The immune and skeletal systems share a variety of molecules, including cytokines, chemokines, hormones, receptors, and transcription factors. Bone cells interact with immune cells under physiological and pathological conditions. Osteoimmunology was created as a new interdisciplinary field in large part to highlight the shared molecules and reciprocal interactions between the two systems in both heath and disease. Receptor activator of NF-κB ligand (RANKL) plays an essential role not only in the development of immune organs and bones, but also in autoimmune diseases affecting bone, thus effectively comprising the molecule that links the two systems. Here we review the function, gene regulation, and signal transduction of osteoimmune molecules, including RANKL, in the context of osteoclastogenesis as well as multiple other regulatory functions. Osteoimmunology has become indispensable for understanding the pathogenesis of a number of diseases such as rheumatoid arthritis (RA). We review the various osteoimmune pathologies, including the bone destruction in RA, in which pathogenic helper T cell subsets [such as IL-17-expressing helper T (Th17) cells] induce bone erosion through aberrant RANKL expression. We also focus on cellular interactions and the identification of the communication factors in the bone marrow, discussing the contribution of bone cells to the maintenance and regulation of hematopoietic stem and progenitors cells. Thus the time has come for a basic reappraisal of the framework for understanding both the immune and bone systems. The concept of a unified osteoimmune system will be absolutely indispensable for basic and translational approaches to diseases related to bone and/or the immune system.

Bioinformatics analysis of genetic variants of endoplasmic reticulum aminopeptidase 1 in ankylosing spondylitis

According to the results of the first genome-wide association study of ankylosing spondylitis (AS), endoplasmic reticulum aminopeptidase 1 (ERAP1) may serve an important role. However, a number of case-control studies have not been able to replicate this result using the same genetic markers. In the present study, the role of common genetic variants of ERAP1 in AS was investigated using two-stage bioinformatics analysis. In the first stage, a classical meta-analysis was performed to assess AS susceptibility markers in ERAP1 using data from available published case-control association studies. The summary odds ratios for 10 single nucleotide polymorphisms (SNPs) were observed to be statistically significant in different studies. In the second stage, the functional effects of these genetic ERAP1 variants were investigated using prediction tools and structural analyses. The K528R (rs30187) substitution SNP in ERAP1 was termed as likely damaging by PolyPhen-2 software, was observed to be located close to the entrance of the substrate pocket, and was predicted to contribute to reduced ERAP1 aminopeptidase activity. In addition, the R725Q (rs17482078) SNP, which was an additional potentially damaging substitution, was suggested to decrease the enzymatic activity of ERAP1, as this substitution may lead to the loss of two hydrogen bonds between R725 and D766 and affect the stability of the C-terminus of ERAP1. In conclusion, the results of the two-stage bioinformatics analysis supported the hypothesis that ERAP1 may present an important susceptibility gene for AS. In addition, the results revealed that two functional SNPs (rs30187 and rs17482078) demonstrated the potential to decrease the enzymatic activity of ERAP1 by affecting its protein structure. Further protein structure-guided studies of the specificity and activity of these ERAP1 variants are therefore warranted.

Association between the autophagy-related gene ULK1 and ankylosing spondylitis susceptibility in the Chinese Han population: a case-control study

PURPOSE

Ankylosing spondylitis (AS), inflammatory bowel disease and Crohn's disease (CD) often coexist in the same patient and these diseases have remarkably strong overlaps in genetic association. The association between Unc51like kinase 1 (ULK1) gene polymorphisms and CD has been reported, and the aim of the current study was to investigate whether ULK1 polymorphisms are also associated with susceptibility to AS in the Chinese Han population.

METHODS

Five tagging single nucleotide polymorphisms in the ULK1 gene (rs9652059, rs11616018, rs12303764, rs4964879 and rs7300908) were genotyped by the improved multiplex ligase detection reaction method in a cohort of patients with AS (n=649) and controls (n=628). Various genetic models were performed and haplotypes were constructed after linkage disequilibrium analysis.

RESULTS

A statistically significant difference was found in the dominant model of the rs9652059 polymorphism (OR (95% CI) = 0.796 (0.638 to 0.994), χ² = 4.064, p= 0.044). Haplotypes were conducted between rs9652059 and rs11616018, rs11616018 and rs4964879, rs9652059 and rs4964879 based on D' ≥0.9 and r² ≥ 0.6. Ht5 (rs9652059^C-rs4964879^G) haplotype was associated with AS (OR (95% CI) = 0.834 (0.706 to 0.985), χ²=4.555, p= 0.0328) and other two haplotypes were marginally correlated with AS (ht2 (rs9652059^C-rs11616018^T): OR (95% CI) = 0.846 (0.717 to 1.000), χ²= 3.864, p= 0.0493); ht3 (rs9652059^T-rs11616018^T): OR (95% CI) = 1.440 (0.999 to 2.076), χ² = 3.849, p = 0.0498).

CONCLUSIONS

Our findings suggest that rs9652059 variation (C→T) could increase AS susceptibility and haplotypes of rs9652059^C-rs4964879^G, rs9652059^C-rs11616018^T and rs9652059^T-rs11616018^T may be associatd with AS.

The genetics revolution in rheumatology: large scale genomic arrays and genetic mapping

Susceptibility to rheumatic diseases, such as osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, juvenile idiopathic arthritis and psoriatic arthritis, includes a large genetic component. Understanding how an individual's genetic background influences disease onset and outcome can lead to a better understanding of disease biology, improved diagnosis and treatment, and, ultimately, to disease prevention or cure. The past decade has seen great progress in the identification of genetic variants that influence the risk of rheumatic diseases. The challenging task of unravelling the function of these variants is ongoing. In this Review, the major insights from genetic studies, gained from advances in technology, bioinformatics and study design, are discussed in the context of rheumatic disease. In addition, pivotal genetic studies in the main rheumatic diseases are highlighted, with insights into how these studies have changed the way we view these conditions in terms of disease overlap, pathways of disease and potential new therapeutic targets. Finally, the limitations of genetic studies, gaps in our knowledge and ways in which current genetic knowledge can be fully translated into clinical benefit are examined.

Ankylosing spondylitis: beyond genome-wide association studies

PURPOSE OF REVIEW

This article discusses genomic investigations in ankylosing spondylitis (AS) beyond genome-wide association (GWA) studies, but prior to this, genetic variants achieving genome-wide significance will be summarized highlighting key pathways contributing to disease pathogenesis.

RECENT FINDINGS

Evidence suggests that disease pathogenesis is attributed to a complex interplay of genetic, environmental and immunological factors. GWA studies have greatly enhanced our understanding of AS pathogenesis by illuminating distinct immunomodulatory pathways affecting innate and acquired immunity, most notably the interleukin-23/interleukin-17 pathway. However, despite the wealth of new information gleaned from such studies, a fraction of the heritability (24.4%) has been explained. This review will focus on investigations beyond GWA studies including copy number variants, gene expression profiling, including microRNA (miRNA), epigenetics, rare variants and gene-gene interactions.

SUMMARY

To address the 'missing heritability' and advance beyond GWA studies, a concerted effort involving rethinking of study design and implementation of newer technologies will be required. The coming of age of next-generation sequencing and advancements in epigenetic and miRNA technologies, combined with familial-focused investigations using well-characterized cohorts, is likely to reveal some of the hidden genomic mysteries associated with AS.

Macrophage Polarization and Bone Formation: A review

The contribution of inflammation to bone loss is well documented in arthritis and other diseases with an emphasis on how inflammatory cytokines promote osteoclastogenesis. Macrophages are the major producers of cytokines in inflammation, and the factors they produce depend upon their activation state or polarization. In recent years, it has become apparent that macrophages are also capable of interacting with osteoblasts and their mesenchymal precursors. This interaction provides growth and differentiation factors from one cell that act on the other and visa versa-a concept akin to the requirement for a feeder layer to grow hemopoietic cells or the coupling that occurs between osteoblasts and osteoclasts to maintain bone homeostasis. Alternatively, activated macrophages are the most likely candidates to promote bone formation and have also been implicated in the tissue repair process in other tissues. In bone, a number of factors, including oncostatin M, have been shown to promote osteoblast formation both in vitro and in vivo. This review discusses the different cell types involved, cellular mediators, and how this can be used to direct new bone anabolic approaches.