Genetics of ankylosing spondylitis--insights into pathogenesis

Elevated serum IL-36γ levels in patients with ankylosing spondylitis and its association with disease activity

Ankylosing spondylitis (AS) is a chronic autoimmune disease. The purpose of this study was to investigate the levels of serum IL-36γ in AS patients and their association with AS. The study enrolled 131 subjects, including 45 with active AS, 46 with inactive AS, and 40 healthy controls (HCs). The basic clinical information of each participant was obtained through physical examination and relevant clinical medical records. Serum IL-36γ levels were detected through an enzyme-linked immunosorbent assay. Serum IL-36γ levels in the active AS group were significantly higher than those in the HC group (94.72 vs. 65.76 pg/mL, P = 0.0087). The serum IL-36γ concentration in the inactive AS group was increased as compared to that in the HC group (100.90 vs. 65.76 pg/mL, P = 0.0138). Correlation analysis indicated that serum IL-36γ was positively correlated with glutamyl transferase in the active AS group (P = 0.0172), while serum IL-36γ was positively correlated with uric acid in the inactive AS group (P = 0.0151). The area under the curve (AUC) for IL-36γ was 0.6824 (P = 0.0009), and the AUC for IL-36γ combined with the erythrocyte sedimentation rate and C-reactive protein levels was 0.8102 (P < 0.0001), according to receiver operating characteristic curve analysis. This study found that serum IL-36γ levels were elevated in AS patients and correlated with disease activity. Our results suggest that IL-36γ may be involved in the progression of AS disease and is a potential biomarker for AS.

Haplotype Analysis Reveals Pleiotropic Disease Associations in the HLA Region

The human leukocyte antigen (HLA) region plays an important role in human health through involvement in immune cell recognition and maturation. While genetic variation in the HLA region is associated with many diseases, the pleiotropic patterns of these associations have not been systematically investigated. Here, we developed a haplotype approach to investigate disease associations phenome-wide for 412,181 Finnish individuals and 2,459 traits. Across the 1,035 diseases with a GWAS association, we found a 17-fold average per-SNP enrichment of hits in the HLA region. Altogether, we identified 7,649 HLA associations across 647 traits, including 1,750 associations uncovered by haplotype analysis. We find some haplotypes show trade-offs between diseases, while others consistently increase risk across traits, indicating a complex pleiotropic landscape involving a range of diseases. This study highlights the extensive impact of HLA variation on disease risk, and underscores the importance of classical and non-classical genes, as well as non-coding variation.

Treatment controversies in spondyloarthritis and psoriatic arthritis: focus on biologics and targeted therapies

INTRODUCTION

There are several treatment controversies that have emerged in spondyloarthritis and psoriatic arthritis. These are related to the nature of the conditions as well as to the use of medications.

AREAS COVERED

This review, which included a search of PubMed database as well as the references within the articles provides an overview of the nature of spondyloarthritis, controversy over the inclusion of psoriatic arthritis (PsA) as a peripheral spondyloarthritis, and a summary of current treatments for both PsA and axial spondyloarthritis (axSpA), with special emphasis on targeted therapy. The review highlights the differences in response to certain medications, particularly biologic therapy and summarizes the randomized controlled trials in psoriatic arthritis and axial spondyloarthritis providing data about the responses in table format.

EXPERT OPINION

There is a need for better outcome measures in axSpA. Currently, the measures are subjective. Imaging may be more appropriate but there is a need for research into the reliability and responsiveness of imaging techniques. In PsA, there may also be better response measures and research into the reliability and responsiveness of available measures is underway. There is also a need for novel therapies as well as biomarkers for response in both diseases.

Causal associations between both psoriasis and psoriatic arthritis and multiple autoimmune diseases: a bidirectional two-sample Mendelian randomization study

Background

Numerous observational studies have identified associations between both psoriasis (PsO) and psoriatic arthritis (PsA), and autoimmune diseases (AIDs); however, the causality of these associations remains undetermined.

Methods

We conducted a bidirectional two-sample Mendelian Randomization study to identify causal associations and directions between both PsO and PsA and AIDs, such as systemic lupus erythematosus (SLE), Crohn's disease (CD), ulcerative colitis (UC), multiple sclerosis (MS), uveitis, bullous pemphigoid (BP), Hashimoto's thyroiditis (HT), rheumatoid arthritis (RA), vitiligo, and ankylosing spondylitis (AS). The causal inferences were drawn by integrating results from four regression models: Inverse Variance Weighting (IVW), MR-Egger, Weighted Median, and Maximum Likelihood. Furthermore, we performed sensitivity analyses to confirm the reliability of our findings.

Results

The results showed that CD [IVW odds ratio (ORIVW), 1.11; 95% confidence interval (CI), 1.06-1.17; P = 8.40E-06], vitiligo (ORIVW, 1.16; 95% CI, 1.05-1.28; P = 2.45E-03) were risk factors for PsO, while BP may reduce the incidence of PsO (ORIVW, 0.91; 95% CI, 0.87-0.96; P = 1.26E-04). CD (ORIVW, 1.07; 95% CI, 1.02-1.12; P = 0.01), HT (ORIVW, 1.23; 95% CI, 1.08-1.40; P = 1.43E-03), RA (ORIVW, 1.11; 95% CI, 1.02-1.21, P = 2.05E-02), AS (ORIVW, 2.18; 95% CI, 1.46-3.27; P = 1.55E-04), SLE (ORIVW, 1.04; 95% CI, 1.01-1.08; P = 1.07E-02) and vitiligo (ORIVW, 1.27; 95% CI, 1.14-1.42; P = 2.67E-05) were risk factors for PsA. Sensitivity analyses had validated the reliability of the results.

Conclusions

Our study provides evidence for potential causal relationships between certain AIDs and both PsO and PsA. Specifically, CD and vitiligo may increase the risk of developing PsO, while CD, HT, SLE, RA, AS, and vitiligo may elevate the risk for PsA. Additionally, it is crucial to closely monitor the condition of PsO patients with specific AIDs, as they have a higher likelihood of developing PsA than those without AIDs. Moving forward, greater attention should be paid to PsA and further exploration of other PsO subtypes is warranted.

Risk of disease flare in spondyloarthritis patients after tapering tumor necrosis factor inhibitors: A meta-analysis and literature review

BACKGROUND

Tumor necrosis factor inhibitors (TNFis) have shown dramatic benefit in patients with spondyloarthritis (SpA). Tapering of TNFi medication may be considered in patients with sustained low disease activity because continued use of TNFis at standard doses may increase the risk of side effects including infections and impose an economic burden. However, the optimal TNFi tapering strategy for SpA patients with inactive disease has not been established. In the present study, we investigated whether tapering TNFi doses is associated with similar risk of disease flare to maintaining SpA patients on TNFis at the standard dosage.

METHODS

The MEDLINE, Embase, and Cochrane databases were systemically searched to retrieve randomized control trials (RCTs) and observational studies published prior to August 2023, that compared disease flare in SpA (including axial SpA [axSpA], psoriatic arthritis [PsA], and SpA with IBD) patients who received standard TNFi doses and those who received a tapered dose of TNFi. Odds ratios (ORs) and 95% confidence intervals (CIs) were directly retrieved or calculated, and meta-analyses were performed. Bias was assessed using funnel plots with Begg and Mazumdar rank correlation / Egger's regression method.

RESULTS

Among 2,237 SpA patients in the 12 studies (9 RCTs and 3 observational studies) retrieved, 1,301 received the standard TNFi dose, while 936 SpA patients underwent TNFi tapering. Of these, 216 (16.6%) standard-dose TNFi and 217 (23.2%) TNF-tapering patients experienced disease flares. The pooled OR for disease flare in TNFi-tapering patients was 1.601 (95% CI 1.276 - 2.008) compared with the standard-dose patients. The funnel plot showed no publication bias.

CONCLUSIONS

The strategy of TNFi tapering was associated with a significantly increased risk of disease flare compared to maintaining SpA patients at the standard TNF dose. Further studies are needed to determine which patients can safely undergo tapering of TNFi and to develop safe tapering strategies.

Effective diagnosis of sacroiliitis in children: evaluating magnetic resonance imaging with the Canadian scoring system

OBJECTIVES

To reveal the differences by comparing the magnetic resonance imaging (MRI) findings of patients with clinically symptomatic sacroiliitis with those undergoing sacroiliac imaging for other reasons using the Canadian Spondyloarthritis Research Consortium-Sacroiliac Inflammatory Scoring System (SPARCC-SIS).

METHODS

In this retrospective single-center study, sacroiliac MRIs performed between 2017 and 2023 were evaluated from the database. The SPARCC-SIS scoring system is used to evaluate and grade the inflammation of the sacroiliac joints. Mild inflammation is indicated by a score below 24, moderate by a score of 24-48, and severe by a score above 49. Additionally, structural defects of the sacroiliac joint, such as erosion, sclerosis, and ankylosis, were observed. After MRI evaluation, clinically symptomatic (group 1) and non-symptomatic (group 2) patients were divided into two groups. The clinical and laboratory findings of the patients and MRI findings were compared. The patient's age, gender, clinical information from hospital records, acute phase reactants (APRs), and the presence of the Human Leukocyte Antigen (HLA-B27) gene (if applicable) were thoroughly recorded.

RESULTS

One hundred thirty-six children who performed sacroiliac MRI for any indication were included in the study. The APRs positivity, presence of HLA-B27, and SPARCC scoring system were significantly higher in 24 patients with clinical sacroiliitis (group 1) than in 112 patients without sacroiliitis (group 2). In our study, the most common MRI findings in children were bone marrow edema, capsulitis, synovitis, and erosion, while chronic structural changes such as sclerosis and ankylosing were rare.

CONCLUSION

In this study, the SPARCC scoring method, which shows the severity of sacroiliac joint inflammation, correlates with the clinical diagnosis of sacroiliitis. In cases with suspected sacroiliitis, except for extraordinary reasons, it can be evaluated with MRI without contrast material and can be graded to guide the clinician in treatment and approach.

The Mechanism of "Treating Different Diseases with the Same Treatment" by Qiangji Jianpi Decoction in Ankylosing Spondylitis Combined with Inflammatory Bowel Disease: A Comprehensive Analysis of Multiple Methods

Background

Ankylosing spondylitis (AS) and inflammatory bowel disease (IBD) are prevalent autoimmune disorders that often co-occur, posing significant treatment challenges. This investigation adopts a multidisciplinary strategy, integrating bioinformatics, network pharmacology, molecular docking, and Mendelian randomization, to elucidate the relationship between AS and IBD and to investigate the potential mechanisms of traditional Chinese medicine formulations, represented by Qiangji Jianpi (QJJP) decoction, in treating these comorbid conditions.

Methods

We utilized databases to pinpoint common targets among AS, IBD, and QJJP decoction's active compounds through intersection analysis. Through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, we mapped a network in Cytoscape, isolating critical targets. Molecular docking with AutoDock validated the affinity between targets and compounds. ROC analysis and dataset validation assessed diagnostic performance, while Gene Set Enrichment Analysis (GSEA) offered pathway insights. Mendelian randomization explored the AS-IBD causal relationship.

Results

Screening identified 105 targets for QJJP decoction, 414 for AS, and 2420 for IBD, with 85 overlapping. These targets predominantly participate in organismal responses and DNA transcription factor binding, with a significant cellular presence in the endoplasmic reticulum and vesicle lumen. Molecular docking, facilitated by Cytoscape, confirmed IL1A, IFNG, TGFB1, and EDN1 as critical targets, with IFNG demonstrating diagnostic potential through GEO dataset validation. The integration of GSEA with network pharmacology highlighted the therapeutic significance of the relaxin, osteoclast differentiation, HIF-1, and AGE-RAGE signaling pathways in QJJP decoction's action. Mendelian randomization analysis indicated a positive causal relationship between IBD and AS, pinpointing rs2193041 as a key SNP influencing IFNG.

Conclusion

Based on the principle of "treating different diseases with the same method" in traditional Chinese medicine theory, we explored the intricate mechanisms through which QJJP decoction addresses AS and IBD comorbidity. Our research spotlighted the pivotal role of the IFNG gene. IFNG emerges not only as a key therapeutic target but also assumes significance as a potential diagnostic biomarker through its genetic underpinnings. This investigation establishes a solid base for subsequent experimental inquiries. Our findings introduce novel approaches for incorporating traditional Chinese medicine into the treatment of AS-IBD comorbidity, setting the stage for groundbreaking research directions.

miRNAs dysregulation in ankylosing spondylitis: A review of implications for disease mechanisms, and diagnostic markers

Epigenetic processes, including non-coding RNA, histone modifications, and DNA methylation, play a vital role in connecting the environment to the development of a disorder, especially when there is a favorable genetic background. Ankylosing Spondylitis (AS) is a chronic type of spinal arthritis that highlights the significance of epigenetics in diseases related to autoimmunity and inflammation. MicroRNAs (miRNAs) are small non-coding RNAs that are involved in both normal and aberrant pathological and physiological gene expression. This study focuses on the pathophysiological pathways to clarify the role of miRNAs in AS. We have conducted a thorough investigation of the involvement of miRNAs in several processes, including inflammation, the production of new bone, T-cell activity, and the regulation of pathways such as BMP, Wnt, and TGFβ signaling. Undoubtedly, miRNAs play a crucial role in enhancing our comprehension of the pathophysiology of AS, and their promise as a therapeutic strategy is quickly expanding.

A review of long non-coding RNAs in ankylosing spondylitis: pathogenesis, clinical assessment, and therapeutic targets

Ankylosing spondylitis (AS) is a chronic immune-mediated type of inflammatory arthritis characterized by inflammation, bone erosion, and stiffness of the spine and sacroiliac joints. Despite great efforts put into the investigation of the disease, the pathogenesis of AS remains unclear, posing challenges in identifying ideal targets for diagnosis and treatment. To enhance our understanding of AS, an increasing number of studies have been conducted. Some of these studies reveal that long non-coding RNAs (lncRNAs) play crucial roles in the etiology of AS. Some certain lncRNAs influence the development of AS by regulating inflammatory responses, autophagy, apoptosis, and adipogenesis, as well as the proliferation and differentiation of cells. Additionally, some lncRNAs demonstrate potential as biomarkers, aiding in monitoring disease progression and predicting prognosis. In this review, we summarize recent studies concerning lncRNAs in AS to elucidate the underlying mechanisms in which lncRNAs are involved and their potential values as biomarkers for disease assessment and druggable targets for therapy.

Programmed cell death 10 can be used as a potential biomarker for ankylosing spondylitis diagnosis and treatment

STUDY DESIGN

Diagnostic study.

OBJECTIVE

Programmed cell death 10 (PDCD10) is a new versatile molecule involved in signal transduction regulation in angiogenesis and tumors. The potential of using it as a biomarker for the diagnosis of ankylosing spondylitis (AS) is still unknown.

SETTING

University laboratory in Gannan Medical University, China.

METHODS

Expression of PDCD10 was analyzed using clinical samples of patients with AS and Gene Expression Omnibus (GEO) data GDS5231. To explore its function, PDCD10 was upregulated and downregulated in synovial cells. Spearman analysis was used to study the association between PDCD10 and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS). The Receiver operating characteristic (ROC) curve was applied to evaluate the sensitivity and specificity of PDCD10.

RESULTS

Expression of PDCD10 was upregulated in patients with AS and it is capable of promoting the calcification of synovial cells. A positive association between PDCD10 and the BASDAI and the mSASSS was observed. The area under the ROC curve (AUC) of PDCD10 was 82% with a 95% confidence interval of [0.772, 0.868].

CONCLUSIONS

PDCD10 is upregulated in patients with AS and it can promote the calcification of synovial cells in vitro. PDCD10 is positively associated with outcome parameters of AS. ROC analysis of PDCD10 suggests that it can be used as a biomarker for the diagnosis and treatment of AS.

Serum proteome analysis identifies a potential biomarker for axial psoriatic arthritis

BACKGROUND

To identify potential serum biomarkers for differentiating between axial psoriatic arthritis (axPsA) and peripheral psoriatic arthritis (pPsA).

METHODS

Serum samples were collected from patients with PsA to create a biomarker discovery cohort and a verification cohort. Patients with PsA were classified into axial or peripheral subtypes based on imaging criteria. Untargeted proteomics technology was used in the discovery phase to screen for biomarkers, and candidate biomarkers were evaluated using enzyme-linked immunosorbent assay (ELISA) in the verification phase.

RESULTS

We identified 45 significantly differentially expressed proteins (DEPs) between axPsA (n = 20) and pPsA (n = 20) with liquid chromatography-mass spectrometry. Among these DEPs, serum pigment epithelium-derived factor (PEDF) was identified as a candidate biomarker using the Boruta algorithm and lasso regression. Results of ELISA further confirmed that the level of serum PEDF expression was significantly higher in axPsA (n = 37) than in pPsA (n = 51) at the verification cohort (37.9 ± 10.1 vs. 30.5 ± 8.9 μg/mL, p < 0.001). Receiver operating characteristics analysis showed that PEDF had an area under the curve (AUC) of 0.72. Serum PEDF was positively correlated with body mass index and C-reactive protein. Additionally, there was a tendency towards a positive correlation between PEDF and the Bath Ankylosing Spondylitis Disease Activity Index.

CONCLUSIONS

This study provided a comprehensive characterization of the proteome in axPsA and pPsA and identified a candidate biomarker, PEDF, that may contribute to early diagnosis for axPsA.

Advanced Progress of Histone Deacetylases in Rheumatic Diseases

Rheumatic disease is a disease which is not yet fully clarified to etiology and also involved in a local pathological injury or systemic disease. With the continuous improvement of clinical medical research in recent years, the development process of rheumatic diseases has been gradually elucidated; with the intensely study of epigenetics, it is realized that environmental changes can affect genetics, among which histone acetylation is one of the essential mechanisms in epigenetics. Histone deacetylases (HDACs) play an important role in regulating gene expression in various biological processes, including differentiation, development, stress response, and injury. HDACs are involved in a variety of physiological processes and are promising drug targets in various pathological conditions, such as cancer, cardiac and neurodegenerative diseases, inflammation, metabolic and immune disorders, and viral and parasitic infections. In this paper, we reviewed the roles of HDACs in rheumatic diseases in terms of their classification and function.

Role of MicroRNAs in Inflammatory Joint Diseases: A Review

Inflammatory arthritis commonly initiates in the soft tissues lining the joint. This lining swells, as do the cells in it and inside the joint fluid, producing chemicals that induce inflammation signs such as heat, redness, and swelling. MicroRNA (miRNA), a subset of non-coding small RNA molecules, post-transcriptionally controls gene expression by targeting their messenger RNA. MiRNAs modulate approximately 1/3 of the human genome with their multiple targets. Recently, they have been extensively studied as key modulators of the innate and adaptive immune systems in diseases such as allergic disorders, types of cancer, and cardiovascular diseases. However, research on the different inflammatory joint diseases, such as rheumatoid arthritis, gout, Lyme disease, ankylosing spondylitis, and psoriatic arthritis, remains in its infancy. This review presents a deeper understanding of miRNA biogenesis and the functions of miRNAs in modulating the immune and inflammatory responses in the above-mentioned inflammatory joint diseases. According to the literature, it has been demonstrated that the development of inflammatory joint disorders is closely related to different miRNAs and their specific regulatory mechanisms. Furthermore, they may present as possible prognostic and diagnostic biomarkers for all diseases and may help in developing a therapeutic response. However, further studies are needed to determine whether manipulating miRNAs can influence the development and progression of inflammatory joint disorders.

Cross-population applications of genomics to understand the risk of multifactorial traits involving inflammation and immunity

The interplay between genetic and environmental factors plays a significant role in interindividual variation in immune and inflammatory responses. The availability of high-throughput low-cost genotyping and next-generation sequencing has revolutionized our ability to identify human genetic variation and understand how this varies within and between populations, and the relationship with disease. In this review, we explore the potential of genomics for patient benefit, specifically in the diagnosis, prognosis and treatment of inflammatory and immune-related diseases. We summarize the knowledge arising from genetic and functional genomic approaches, and the opportunity for personalized medicine. The review covers applications in infectious diseases, rare immunodeficiencies and autoimmune diseases, illustrating advances in diagnosis and understanding risk including use of polygenic risk scores. We further explore the application for patient stratification and drug target prioritization. The review highlights a key challenge to the field arising from the lack of sufficient representation of genetically diverse populations in genomic studies. This currently limits the clinical utility of genetic-based diagnostic and risk-based applications in non-Caucasian populations. We highlight current genome projects, initiatives and biobanks from diverse populations and how this is being used to improve healthcare globally by improving our understanding of genetic susceptibility to diseases and regional pathogens such as malaria and tuberculosis. Future directions and opportunities for personalized medicine and wider application of genomics in health care are described, for the benefit of individual patients and populations worldwide.

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.

Proteomic and genomic profiling of plasma exosomes from patients with ankylosing spondylitis

INTRODUCTION

Recent advances in understanding the biology of ankylosing spondylitis (AS) using innovative genomic and proteomic approaches offer the opportunity to address current challenges in AS diagnosis and management. Altered expression of genes, microRNAs (miRNAs) or proteins may contribute to immune dysregulation and may play a significant role in the onset and persistence of inflammation in AS. The ability of exosomes to transport miRNAs across cells and alter the phenotype of recipient cells has implicated exosomes in perpetuating inflammation in AS. This study reports the first proteomic and miRNA profiling of plasma-derived exosomes in AS using comprehensive computational biology analysis.

METHODS

Plasma samples from patients with AS and healthy controls (HC) were isolated via ultracentrifugation and subjected to extracellular vesicle flow cytometry analysis to characterise exosome surface markers by a multiplex immunocapture assay. Cytokine profiling of plasma-derived exosomes and cell culture supernatants was performed. Next-generation sequencing was used to identify miRNA populations in exosomes enriched from plasma fractions. CD4+ T cells were sorted, and the frequency and proliferation of CD4+ T-cell subsets were analysed after treatment with AS-exosomes using flow cytometry.

RESULTS

The expression of exosome marker proteins CD63 and CD81 was elevated in the patients with AS compared with HC (q<0.05). Cytokine profiling in plasma-derived AS-exosomes demonstrated downregulation of interleukin (IL)-8 and IL-10 (q<0.05). AS-exosomes cocultured with HC CD4+ T cells induced significant upregulation of IFNα2 and IL-33 (q<0.05). Exosomes from patients with AS inhibited the proliferation of regulatory T cells (Treg), suggesting a mechanism for chronically activated T cells in this disease. Culture of CD4+ T cells from healthy individuals in the presence of AS-exosomes reduced the proliferation of FOXP3+ Treg cells and decreased the frequency of FOXP3+IRF4+ Treg cells. miRNA sequencing identified 24 differentially expressed miRNAs found in circulating exosomes of patients with AS compared with HC; 22 of which were upregulated and 2 were downregulated.

CONCLUSIONS

Individuals with AS have different immunological and genetic profiles, as determined by evaluating the exosomes of these patients. The inhibitory effect of exosomes on Treg in AS suggests a mechanism contributing to chronically activated T cells in this disease.

Impact of immune regulation and differentiation dysfunction of mesenchymal stem cells on the disease process in ankylosing spondylitis and prospective analysis of stem cell transplantation therapy

Ankylosing spondylitis (AS) is a rheumatic bone and joint disease caused by inflammation, erosion, and pathological bone formation. The pathological features of chronic inflammation, bone destruction, and pathological ossification occur due to the disruption of the body's immune regulation and altered bone remodeling balance. Mesenchymal stem cells (MSCs) have multidirectional differentiation potential and immunomodulatory functions and play an important role in immune regulation and bone formation. The immune regulation and osteogenic capacity of MSCs in AS are altered by factors such as genetic background, internal environment, infection, and mechanical forces that drive disease development. This review further evaluates the role of MSCs dysfunction in inflammation and pathological bone formation by analyzing the effects of the above-mentioned factors on MSCs function and also looks forward to the prospects of MSCs in treating AS, providing some ideas for an in-depth study of inflammation and ectopic ossification.

KEY MESSAGES

Diagnostic serum biomarkers associated with ankylosing spondylitis

Ankylosing spondylitis (AS) is an autoimmune rheumatic disease that mostly affects the axial skeleton. This study aimed to investigate reliable diagnostic serum biomarkers for AS. Serum samples were collected from 20 AS patients and 20 healthy controls (HCs) and analyzed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The differential metabolites between the AS patients and HCs were profiled using univariate and multivariate statistical analyses. Pathway analysis and a heat map were also conducted. Random forest (RF) analysis and the least absolute shrinkage and selection operator (LASSO) were used to establish predictive and diagnostic models. After controlling the variable importance in the projection (VIP) value > 1 and false discovery rate (FDR) < 0.05, a total of 61 differential metabolites were identified from 995 metabolites, which exhibited significant differences in the pathway analysis and heat map between the AS patients and HCs. RF as a predictive model also identified differential metabolites with 95% predictive accuracy and a high area under the curve (AUC) of 1. A diagnostic model comprising nine metabolites (cysteinylglycine disulfide, choline, N6, N6, N6-trimethyllysine, histidine, sphingosine, fibrinopeptide A, glycerol 3-phosphate, 1-linoleoyl-GPA (18:2), and fibrinopeptide A (3-16)) was generated using LASSO regression, capable of distinguishing HCs from AS with a high AUC of 1. Our results indicated that the UPLC-MS/MS analysis method is a powerful tool for identifying AS metabolite profiles. We developed a nine-metabolites-based model serving as a diagnostic tool to separate AS patients from HCs, and the identified diagnostic biomarkers appeared to have a diagnostic value for AS.

Pathophysiology and immunolgical basis of axial spondyloarthritis

Over the recent years the wider availability and application of state-of-the-art immunological technologies greatly advanced the insight into the mechanisms that play an important role in axial spondyloarthritis (axSpA) pathophysiology. This increased understanding has facilitated the development of novel treatments that target disease relevant pathways, hereby improving outcome for axSpA patients. In axSpA pathophysiology genetic and environmental factors as well as immune activation by mechanical or bacterial stress resulting in a chronic inflammatory response have a central role. The TNF and IL-23/IL-17 immune pathways play a pivotal role in these disease mechanisms. This review provides an outline of the immunological basis of axSpA with a focus on key genetic risk factors and their link to activation of the pathological immune response, as well as on the role of the gut and entheses in the initiation of inflammation with subsequent new bone formation in axSpA.

Identification of potential biomarkers for ankylosing spondylitis based on bioinformatics analysis

OBJECTIVE

The aim of this study was to search for key genes in ankylosing spondylitis (AS) through comprehensive bioinformatics analysis, thus providing some theoretical support for future diagnosis and treatment of AS and further research.

METHODS

Gene expression profiles were collected from Gene Expression Omnibus (GEO, http://www.ncbi.nlm.nih.gov/geo/ ) by searching for the term "ankylosing spondylitis". Ultimately, two microarray datasets (GSE73754 and GSE11886) were downloaded from the GEO database. A bioinformatic approach was used to screen differentially expressed genes and perform functional enrichment analysis to obtain biological functions and signalling pathways associated with the disease. Weighted correlation network analysis (WGCNA) was used to further obtain key genes. Immune infiltration analysis was performed using the CIBERSORT algorithm to conduct a correlation analysis of key genes with immune cells. The GWAS data of AS were analysed to identify the pathogenic regions of key genes in AS. Finally, potential therapeutic agents for AS were predicted using these key genes.

RESULTS

A total of 7 potential biomarkers were identified: DYSF, BASP1, PYGL, SPI1, C5AR1, ANPEP and SORL1. ROC curves showed good prediction for each gene. T cell, CD4 naïve cell, and neutrophil levels were significantly higher in the disease group than in the paired normal group, and key gene expression was strongly correlated with immune cells. CMap results showed that the expression profiles of ibuprofen, forskolin, bongkrek-acid, and cimaterol showed the most significant negative correlation with the expression profiles of disease perturbations, suggesting that these drugs may play a role in AS treatment.

CONCLUSION

The potential biomarkers of AS screened in this study are closely related to the level of immune cell infiltration and play an important role in the immune microenvironment. This may provide help in the clinical diagnosis and treatment of AS and provide new ideas for further research.

Integrated Proteomics and Single-Cell Mass Cytometry Analysis Dissects the Immune Landscape of Ankylosing Spondylitis

Mass cytometry is a powerful single-cell technology widely adopted to depict immune cell heterogeneity in different contexts. However, this method is only capable of examining several dozens of proteins simultaneously and requires a prior knowledge of the markers to be analyzed. Here we propose that the integration of mass cytometry with shot-gun proteomics may serve as a valuable tool to achieve an in-depth understanding of the immune system. By implementing such a strategy, we investigated the immune landscape of ankylosing spondylitis (AS), a chronic inflammatory arthritis with unclear etiology. The proteome alteration in peripheral blood mononuclear cells (PBMCs) was investigated by quantitative proteomics, and then mass cytometry analysis was conducted to decipher the immunome by considering the signaling molecules identified with differential expression by proteomics. As a result, we identified a wide spectrum of proteins dysregulated in AS, e.g., upregulation of glycolytic enzymes, downregulation of lipid transporters, and dysregulation of chemokine signaling molecules involved in proinflammatory cytokine production and leucocyte migration. Moreover, the single-cell analysis showed the upregulation of chemokine signaling regulators in subclusters of both innate and adaptive immune cells in AS. In addition, correlation analysis unveiled the interplay among Phenograph-identified subclusters of monocytes, CD4+ T cells, and CD8+ T cells. Taken together, our findings demonstrated that the integration of mass spectrometry-based proteomics and single-cell mass cytometry may serve as a useful tool to reveal clinically relevant information regarding useful targets and cellular phenotypes that could be further exploited to develop novel therapeutic strategies.

Alterations in the gut virome in patients with ankylosing spondylitis

Introduction

Ankylosing spondylitis (AS), a chronic autoimmune disease, has been linked to the gut bacteriome.

Methods

To investigate the characteristics of the gut virome in AS, we profiled the gut viral community of 193 AS patients and 59 healthy subjects based on a metagenome-wide analysis of fecal metagenomes from two publicly available datasets.

Results

AS patients revealed a significant decrease in gut viral richness and a considerable alteration of the overall viral structure. At the family level, AS patients had an increased abundance of Gratiaviridae and Quimbyviridae and a decreased abundance of Drexlerviridae and Schitoviridae. We identified 1,004 differentially abundant viral operational taxonomic units (vOTUs) between patients and controls, including a higher proportion of AS-enriched Myoviridae viruses and control-enriched Siphoviridae viruses. Moreover, the AS-enriched vOTUs were more likely to infect bacteria such as Flavonifractor, Achromobacter, and Eggerthellaceae, whereas the control-enriched vOTUs were more likely to be Blautia, Ruminococcus, Collinsella, Prevotella, and Faecalibacterium bacteriophages. Additionally, some viral functional orthologs differed significantly in frequency between the AS-enriched and control-enriched vOTUs, suggesting the functional role of these AS-associated viruses. Moreover, we trained classification models based on gut viral signatures to discriminate AS patients from healthy controls, with an optimal area under the receiver operator characteristic curve (AUC) up to 0.936, suggesting the clinical potential of the gut virome for diagnosing AS.

Discussion

This work provides novel insight into the AS gut virome, and the findings may guide future mechanistic and therapeutic studies for other autoimmune diseases.

MIF Variant rs755622 Is Associated with Severe Crohn's Disease and Better Response to Anti-TNF Adalimumab Therapy

Crohn's disease (CD), rheumatoid arthritis, psoriatic arthritis and other inflammatory diseases comprise a group of chronic diseases with immune-mediated pathogenesis which share common pathological pathways, as well as treatment strategies including anti-TNF biologic therapy. However, the response rate to anti-TNF therapy among those diseases varies, and approximately one third of patients do not respond. Since pharmacogenetic studies for anti-TNF therapy have been more frequent for other related diseases and are rare in CD, the aim of our study was to further explore markers associated with anti-TNF response in other inflammatory diseases in Slovenian CD patients treated with the anti-TNF drug adalimumab (ADA). We enrolled 102 CD patients on ADA, for which the response was defined after 4, 12, 20 and 30 weeks of treatment, using an IBDQ questionnaire and blood CRP value. We genotyped 41 SNPs significantly associated with response to anti-TNF treatment in other diseases. We found novel pharmacogenetic association between SNP rs755622 in the gene MIF (macrophage migration inhibitory factor) and SNP rs3740691 in the gene ARFGAP2 in CD patients treated with ADA. The strongest and most consistent association with treatment response was found for the variant rs2275913 in gene IL17A (p = 9.73 × 10-3).

Innate and adaptive immune abnormalities underlying autoimmune diseases: the genetic connections

With the exception of an extremely small number of cases caused by single gene mutations, most autoimmune diseases result from the complex interplay between environmental and genetic factors. In a nutshell, etiology of the common autoimmune disorders is unknown in spite of progress elucidating certain effector cells and molecules responsible for pathologies associated with inflammatory and tissue damage. In recent years, population genetics approaches have greatly enriched our knowledge regarding genetic susceptibility of autoimmunity, providing us with a window of opportunities to comprehensively re-examine autoimmunity-associated genes and possible pathways. In this review, we aim to discuss etiology and pathogenesis of common autoimmune disorders from the perspective of human genetics. An overview of the genetic basis of autoimmunity is followed by 3 chapters detailing susceptibility genes involved in innate immunity, adaptive immunity and inflammatory cell death processes respectively. With such attempts, we hope to expand the scope of thinking and bring attention to lesser appreciated molecules and pathways as important contributors of autoimmunity beyond the 'usual suspects' of a limited subset of validated therapeutic targets.

Temporomandibular joint involvement in individuals with ankylosing spondylitis: A scoping review

OBJECTIVE

This scoping review aimed to identify the signs and symptoms of temporomandibular joint (TMJ) involvement in individuals with ankylosing spondylitis (AS).

DESIGN

Systematic literature searches were performed on PubMed, Embase, and Web of Science databases (up to April 2022). Studies with signs and symptoms of temporomandibular joint disorder (TMD) in adults with AS were included. TMJ outcomes were extracted and analyzed qualitatively.

RESULTS

From 527 potentially eligible studies, 22 were included. A total of 4309 individuals with AS were evaluated, aged between 18 and 80 years, being males approximately 65% of the sample. Signs and symptoms of pain, tenderness to palpation on TMJ and masticatory muscles, joint noises (i.e., clicking or crepitus), limited mouth opening, disc displacement, and radiographic changes were often observed.

CONCLUSION

The available evidence shows that different signs and symptoms of TMD co-occur with AS disease, with a higher prevalence of TMD observed in individuals with AS than in individuals without AS. Indeed, it seems that individuals suffering from AS disease have an increased risk of developing TMD.

MicroRNA Let-7i Regulates Innate TLR4 Pathways in Peripheral Blood Mononuclear Cells of Patients with Ankylosing Spondylitis

Purpose

This study aimed to compare the changes in the expression of microRNA Let-7i in peripheral blood mononuclear cells (PBMCs) of patients with ankylosing spondylitis (AS) and the correlation between Let-7i and innate pro-inflammatory factors. It is necessary to search for a new biomarker to guide the prognosis of AS.

Methods

A total of 10 patients with AS and 10 healthy volunteers were selected as AS and control groups, respectively. The expression levels of Let-7i, Toll-like receptor 4 (TLR4), nuclear factor-κB (NF-κB), and interferon-gamma (IFN-γ) in PBMCs were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting (WB) to explore the relationship between Let-7i and pro-inflammatory factors. Furthermore, the relationship between Let-7i and TLR4 was determined by the luciferase reporter technology.

Results

The expression level of Let-7i in PBMCs of patients with AS was significantly lower than that of healthy control. The expression levels of TLR4, NF-κB, and IFN-γ in PBMCs derived from patients with AS were significantly higher than those of healthy control. The results show that Let-7i manipulation can regulate lipopolysaccharide (LPS)-induced TLR4 and IFN-γ expression in CD4+ T cells of patients with AS. The overexpression of Let-7i in T cells of patients with AS can suppress TLR4 and IFN-γ LPS-induced expression levels of cellular mRNA and protein. Let-7i can directly interfere TLR4-3'untranslated region (UTR) sequence and regulate the expression of the TLR4 gene in Jurkat T cells.

Conclusion

Let-7i may be involved in the pathogenesis of AS, and Let-7i expression in PBMCs may be helpful for the diagnosis and treatment of AS in the future.

Role of neutrophil interleukin-23 in spondyloarthropathy spectrum disorders

Neutrophilic inflammation is a pervasive characteristic common to spondyloarthropathies and related disorders. This inflammation manifests as Munro's microabscesses of the skin and osteoarticular neutrophilic inflammation in patients with psoriatic arthritis, intestinal crypt abscesses in patients with inflammatory bowel disease, ocular hypopyon in anterior uveitis, and neutrophilic macroscopic and microscopic inflammation in patients with Behçet's disease. Strong MHC class I associations are seen in these diseases, which represent so-called MHC-I-opathies, and these associations indicate an involvement of CD8 T-cell immunopathology that is not yet well understood. In this Personal View, we highlight emerging data suggesting that the T-cell-neutrophil axis involves both a T-cell-mediated and interleukin (IL)-17-mediated (type 17) recruitment and activation of neutrophils, and also a sequestration of activated neutrophils at disease sites that might directly amplify type 17 T-cell responses. This amplification likely involves neutrophilic production of IL-23 and proteases as well as other feedback mechanisms that could be regulated by local microbiota, pathogens, or tissue damage. This crosstalk between innate and adaptive immunity offers a novel explanation for how bacterial and fungal microbes at barrier sites could innately control type 17 T-cell development, with the aim of restoring tissue homoeostasis, and could potentially explain features of clinical disease and treatment response, such as the fast-onset action of the IL-23 pathway blockade in certain patients. This axis could be crucial to understanding non-response to IL-23 inhibitors among patients with ankylosing spondylitis, as the axial skeleton is a site rich in neutrophils and a site of haematopoiesis with myelopoiesis in adults.

Novel regulatory role of non-coding RNAs in ankylosing spondylitis

Ankylosing spondylitis (AS) is a type of arthritis that primarily affects the spine and involves disorders of the immune and skeletal systems. However, the exact pathogenesis of AS is not fully understood. Non-coding RNAs (ncRNAs), particularly, long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and micro RNAs (miRNAs) and their interactions have been shown to influence many biological processes such as inflammatory responses, osteogenic differentiation and apoptosis, pyroptosis, and proliferation. In addition, ncRNAs reflect the disease activity of AS. In this review, we discuss the regulatory roles of ncRNAs in AS cell functions (inflammatory responses, cellular osteogenic differentiation and apoptosis, pyroptosis, and proliferation) and their potential applications in AS diagnosis and treatment. Understanding the role of ncRNAs in the pathogenesis of AS will lay the foundation for exploring potential new therapeutic approaches for AS.

Two phenotypes of chronic recurrent multifocal osteomyelitis with different patterns of bone involvement

INTRODUCTION

Chronic Recurrent Multifocal Osteomyelitis (CRMO) is an autoinflammatory bone disorder with predominantly paediatric onset. Children present with multifocal osteolytic lesions accompanied by bone pain and soft tissue swelling. Patients often exhibit extraosseous co-morbidities such as psoriasis, inflammatory bowel disease, and arthritis.

OBJECTIVES

Comparison of children with two different phenotypes of CRMO defined by presence or absence of extraosseous co-morbidities.

METHODS

Children diagnosed with CRMO at the Motol University Hospital between 2010 and 2020 were retrospectively reviewed, and according to the absence or presence of extraosseous manifestations divided into two cohorts - bone limited CRMO and complex CRMO. The two groups were compared in terms of demographic data, age at disease onset, number and site of bone lesions, laboratory biomarker values, and need of escalation to a second-line therapy.

RESULTS

Thirty-seven children (30 female, 7 male) with confirmed CRMO were included in the analysis. The mean age at disease onset was 10 years. All but 3 patients presented with multifocal disease. Twenty-three children (62%) had at least one extraosseous manifestation (13 sacroiliitis, 8 inflammatory bowel disease, 6 skin disease [acne, pustulosis, or psoriasis], 7 arthritis). Complex CRMO was associated with a significantly higher ESR rate (p = 0.0064) and CRP level (p = 0.018). The groups did not differ in number of foci or in age at disease onset. Bone lesion distribution differed between the two groups with significantly more frequent involvement of clavicle (p = 0.011) and pelvis (p = 0.038) in patients with complex CRMO. Children with complex CRMO more often needed escalation of therapy to DMARDs and biologic agents.

CONCLUSION

Our data suggest that CRMO affecting solely the skeleton has milder course compared to complex CRMO with extraskeletal features. Further studies are needed to explore the clinical as well as the patient reported outcomes and promote individually tailored therapeutic strategies in both CRMO phenotypes.

Circ_0018168 inhibits the proliferation and osteogenic differentiation of fibroblasts in ankylosing spondylitis via regulating miR-330-3p/DKK1 axis

Background

Circular RNAs (circRNAs) play a crucial regulatory role in human diseases. However, the roles of circRNAs in ankylosing spondylitis (AS) are barely known. In this study, the functions of circ_0018168 in AS were investigated.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot assay were used for circ_0018168, microRNA-330-3p (miR-330-3p), dickkopf-1 (DKK1), alkaline phosphatase (ALP), osteocalcin (OCN), Runt-related transcription factor 2 (Runx2) levels. Cell Counting Kit-8 (CCK-8) assay and 5′-ethynyl-2′-deoxyuridine (EdU) assay were conducted to analyze cell proliferation ability. Flow cytometry analysis was manipulated for cell cycle process. ALP activity was examined with a commercial kit. RNA immunoprecipitation (RIP) assay, RNA pull-down assay and dual-luciferase reporter assay were used to analyze the relationships of circ_0018168, miR-330-3p and DKK1.

Results

Circ_0018168 and DKK1 levels were lowly expressed in AS hip capsule specimens. Circ_0018168 overexpression repressed cell proliferation, cell cycle process as well as reduced ALP activity and ALP, OCN and Runx2 protein levels in AS fibroblasts. DKK1 silencing ameliorated the impact of circ_0018168 on AS progression. In addition, circ_0018168 served as the sponge for miR-330-3p, which could target DKK1. MiR-330-3p inhibition suppressed the proliferation, cell cycle and osteogenic differentiation in AS fibroblasts, but DKK1 silencing reversed the impacts. Besides, the effect of circ_0018168 on AS development was abolished by miR-330-3p upregulation.

Conclusion

Circ_0018168 overexpression restrained fibroblast proliferation and osteogenic differentiation in AS by elevating DKK1 through adsorbing miR-330-3p.

T cell Repertoire Profiling and the Mechanism by which HLA-B27 Causes Ankylosing Spondylitis

Purpose of Review

Ankylosing spondylitis (AS) is strongly associated with the HLA-B27 gene. The canonical function of HLA-B27 is to present antigenic peptides to CD8 lymphocytes, leading to adaptive immune responses. The ‘arthritogenic peptide’ theory as to the mechanism by which HLA-B27 induces ankylosing spondylitis proposes that HLA-B27 presents peptides derived from exogenous sources such as bacteria to CD8 lymphocytes, which subsequently cross-react with antigens at the site of inflammation of the disease, causing inflammation. This review describes findings of studies in AS involving profiling of T cell expansions and discusses future research opportunities based on these findings.

Recent Findings

Consistent with this theory, there is an expanding body of data showing that expansion of a restricted pool of CD8 lymphocytes is found in most AS patients yet only in a small proportion of healthy HLA-B27 carriers.

Summary

These exciting findings strongly support the theory that AS is driven by presentation of antigenic peptides to the adaptive immune system by HLA-B27. They point to new potential approaches to identify the exogenous and endogenous antigens involved and to potential therapies for the disease.

Inhibiting IL-17A and IL-17F in Rheumatic Disease: Therapeutics Help to Elucidate Disease Mechanisms

PURPOSE OF REVIEW

Psoriatic arthritis and ankylosing spondylitis belong to a family of rheumatological diseases that lead to painful joint inflammation that impacts on patient function and quality of life. Recent studies have shown that the pro-inflammatory cytokine IL-17 is involved in the inflammatory joint changes in spondyloarthritides. We will review the pathophysiology of IL-17 and review the biological therapies targeting IL-17.

RECENT FINDINGS

IL-17 is produced and released from T cells and is dependent on multiple upstream cytokines, which include IL-23. There are six members of the IL-17 family that are secreted from multiple populations of T cells. The initial biologic medications have been developed against IL-17A, which is the best-studied member of this family. These medications appear to be effective in controlling joint inflammation, improving patient quality of life, and are generally well tolerated. More recently, medications have been developed that target both IL-17A and IL-17F. In addition, brodalumab, an antibody targeting the IL-17 receptor, has had a resurgence after initial concerns for an increased risk of suicide. IL-17 is an inflammatory cytokine that is critical in the pathobiology of axial spondyloarthritides. Recent biological therapies targeting IL-17A are effective and well tolerated in patients with axial spondyloarthritis. Specific targeting of the Il-17A/F heterodimer is also effective and provides another viable option in the clinician's armamentarium.

The emerging multifunctional roles of ERAP1, ERAP2 and IRAP between antigen processing and renin-angiotensin system modulation

The Endoplasmic Reticulum Aminopeptidase 1 and 2 (ERAP1 and ERAP2) and Insulin Regulated Aminopeptidase (IRAP) are three M1 zinc metalloproteases whose role in antigen processing is the refining of peptidome either in the Endoplasmic reticulum (ERAP1 and ERAP2), or in the endosomes (IRAP). However, other novel and distinct functions are emerging. Here, we focus specifically on ERAP2. This gene has a peculiar evolutionary history, being absent in rodents and undergoing in humans to a balanced selection of two haplotypes, one of which not expressing the full length ERAP2. These observations suggest that its role in antigen presentation is not essential. An additional, less investigated role is in the regulation of the Renin Angiotensin System (RAS). ERAP1 and ERAP2 cleave Angiotensin II (Ang II) into Ang III and IV, which counteract the action of Ang II whereas IRAP is itself the receptor for Ang IV. We have recently reported that macrophages, independently from the haplotype, express and release a N-terminus ERAP2 “short” form which directly binds IRAP and the two molecules are co-expressed in the endosomes and on the cell membrane. This new evidence suggests that the maintenance of the ERAP2 gene in humans could be due to its activity in the regulation of the RAS system, possibly as an Ang IV agonist. Its role in the immune-mediated diseases as well as in disorders more specifically related to an imbalance of the RAS system, including hypertension, pre-eclampsia but also viral infections such as COVID-19, is discussed here.

Association of anti-TNF-α treatment with gut microbiota of patients with ankylosing spondylitis

OBJECTIVE

Gut dysbiosis contributes to multiple autoimmune diseases, including ankylosing spondylitis, which is commonly treated with tumor necrosis factor (TNF)-α inhibitors (TNFis). Because host TNF-α levels are considered to interact with gut microbiota, we aimed to systematically investigate the microbiota profile of ankylosing spondylitis patients with anti-TNF-α-based treatment and identify potential key bacteria.

METHODS

Fecal samples were collected from 11 healthy controls and 24 ankylosing spondylitis patients before/after anti-TNF-α treatment, the microbiota profiles of which were evaluated by 16S ribosomal DNA amplicon sequencing and subsequent bioinformatic analysis.

RESULTS

Significantly different microbial compositions were observed in samples from ankylosing spondylitis patients compared with healthy controls, characterized by a lower abundance of short-chain fatty acid (SCFA)-producing bacteria. All patients exhibited a positive response after anti-TNF-α treatment, accompanied by a trend of restoration in the microbiota compositions and functional profile of ankylosing spondylitis patients to healthy controls. In particular, the abundance of SCFA-producing bacteria (e.g. Megamonsa and Lachnoclostridium ) was not only significantly lower in ankylosing spondylitis patients than in healthy controls and restored after anti-TNF-α treatment but also negatively correlated with disease severity (e.g. cor  = -0.52, P  = 8 × 10 -5 for Megamonsa ). In contrast, Bacilli and Haemophilus may contribute to ankylosing spondylitis onset and severity.

CONCLUSIONS

Microbiota dysbiosis in ankylosing spondylitis patients can be restored after anti-TNF-α treatment, possibly by impacting SCFA-producing bacteria.

Functional ERAP1 Variants Distinctively Associate with Ankylosing Spondylitis Susceptibility under the Influence of HLA-B27 in Taiwanese

Epistasis of ERAP1 single nucleotide variations (SNVs) and HLA-B27 has been linked to ankylosing spondylitis susceptibility (AS). The current study examined how prevalent ERAP1 allelic variants (SNV haplotypes) in Taiwan affect ERAP1 functions and AS susceptibility in the presence or absence of HLA-B27. Sanger sequencing was used to discover all ERAP1 coding SNVs and common allelic variants in Taiwanese full-length cDNAs from 45 human patients. For the genetic association investigation, TaqMan genotyping assays were utilized to establish the genotypes of ERAP1 SNVs in 863 AS patients and 1438 healthy controls. Ex vivo biological analysis of peripheral blood mononuclear cells from homozygous donors of two common-risk ERAP1 allelic variants was performed. Two common-risk ERAP1 allelic variants were also cloned and functionally studied. In Taiwanese, eleven frequent ERAP1 SNVs and six major ERAP1 allelic variants were discovered. We discovered that in Taiwanese, the most prevalent ERAP1-001 variant with 56E, 127R, 276I, 349M, 528K, 575D, 725R, and 730Q interacting with HLA-B27 significantly contributed to the development of AS. In HLA-B27 negative group, however, the second most prevalent ERAP1-002 variant with 56E, 127P, 276M, 349M, 528R, 575D, 725R, and 730E was substantially related with an increased risk of AS. Ex vivo and in vitro research demonstrated that ERAP1 allelic variants have a significant impact on ERAP1 functions, suggesting that ERAP1 plays a role in the development of AS. In an HLA-B27-dependent manner, common ERAP1 allelic variants are related with AS susceptibility.

Upregulated lncRNA-NEF predicts recurrence and poor treatment outcomes of ankylosing spondylitis

INTRODUCTION

Osteoporosis is related to lncRNA-neighboring enhancer of FOXA2 (NEF) and inversely correlated to ankylosing spondylitis (AS), implying that lncRNA-NEF might also relate to AS. Thus, the study was carried out to investigate the involvement of lncRNA-NEF in AS.

METHODS

The study included 60 AS patients and 60 healthy controls. LncRNA-NEF expression in synovial fluid samples was analyzed by reverse transcription quantitative real-time polymerase chain reaction. Disease activity of the 60 AS patients was determined using the Ankylosing Spondylitis Disease Activity Score (ASDAS) 1-4 and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). Western blot was carried out to investigate the effects of lncRNA-NEF on inflammatory factors in human fibroblast-like synovial (HFLS) cells. A 3-year follow-up was performed to analyze the role of lncRNA-NEF in the prediction of the recurrence of AS.

RESULTS

Our study observed that lncRNA-NEF expression was upregulated in synovial fluid of AS patients and significantly correlated with the ASDAS 1-4, BASDAI, erythrocyte sedimentation rate (ESR), and C-reactive protein level (p < .05). Treatment with nonsteroidal anti-inflammatory drugs significantly downregulated lncRNA-NEF expression (p < .01). A 3-year follow-up showed that patients with high lncRNA-NEF levels had a high recurrence rate (hazard ratio = 2.266). In addition, lncRNA-NEF was found to regulate the expression of inflammatory factors in HFLS cells.

CONCLUSIONS

Therefore, lncRNA-NEF upregulation can predict recurrence and poor treatment outcomes of AS and has a great potential to serve as a predictive biomarker factor for the recurrent AS.

New Insights into the Regulatory Role of Ferroptosis in Ankylosing Spondylitis via Consensus Clustering of Ferroptosis-Related Genes and Weighted Gene Co-Expression Network Analysis

Background: The pathogenesis of ankylosing spondylitis (AS) remains undetermined. Ferroptosis is a newly discovered form of regulated cell death involved in multiple autoimmune diseases. Currently, there are no reports on the connection between ferroptosis and AS. Methods: AS samples from the Gene Expression Omnibus were divided into two subgroups using consensus clustering of ferroptosis-related genes (FRGs). Weighted gene co-expression network analysis (WGCNA) of the intergroup differentially expressed genes (DEGs) and protein–protein interaction (PPI) analysis of the key module were used to screen out hub genes. A multifactor regulatory network was then constructed based on hub genes. Results: The 52 AS patients in dataset GSE73754 were divided into cluster 1 (n = 24) and cluster 2 (n = 28). DEGs were mainly enriched in pathways related to mitochondria, ubiquitin, and neurodegeneration. Candidate hub genes, screened by PPI and WGCNA, were intersected. Subsequently, 12 overlapping genes were identified as definitive hub genes. A multifactor interaction network with 45 nodes and 150 edges was generated, comprising the 12 hub genes and 32 non-coding RNAs. Conclusions: AS can be divided into two subtypes according to FRG expression. Ferroptosis might play a regulatory role in AS. Tailoring treatment according to the ferroptosis status of AS patients can be a promising direction.

Glycolysis in Innate Immune Cells Contributes to Autoimmunity

Autoimmune diseases (AIDs) refer to connective tissue inflammation caused by aberrant autoantibodies resulting from dysfunctional immune surveillance. Most of the current treatments for AIDs use non-selective immunosuppressive agents. Although these therapies successfully control the disease process, patients experience significant side effects, particularly an increased risk of infection. There is a great need to study the pathogenesis of AIDs to facilitate the development of selective inhibitors for inflammatory signaling to overcome the limitations of traditional therapies. Immune cells alter their predominant metabolic profile from mitochondrial respiration to glycolysis in AIDs. This metabolic reprogramming, known to occur in adaptive immune cells, i.e., B and T lymphocytes, is critical to the pathogenesis of connective tissue inflammation. At the cellular level, this metabolic switch involves multiple signaling molecules, including serine-threonine protein kinase, mammalian target of rapamycin, and phosphoinositide 3-kinase. Although glycolysis is less efficient than mitochondrial respiration in terms of ATP production, immune cells can promote disease progression by enhancing glycolysis to satisfy cellular functions. Recent studies have shown that active glycolytic metabolism may also account for the cellular physiology of innate immune cells in AIDs. However, the mechanism by which glycolysis affects innate immunity and participates in the pathogenesis of AIDs remains to be elucidated. Therefore, we reviewed the molecular mechanisms, including key enzymes, signaling pathways, and inflammatory factors, that could explain the relationship between glycolysis and the pro-inflammatory phenotype of innate immune cells such as neutrophils, macrophages, and dendritic cells. Additionally, we summarize the impact of glycolysis on the pathophysiological processes of AIDs, including systemic lupus erythematosus, rheumatoid arthritis, vasculitis, and ankylosing spondylitis, and discuss potential therapeutic targets. The discovery that immune cell metabolism characterized by glycolysis may regulate inflammation broadens the avenues for treating AIDs by modulating immune cell metabolism.

Increased proportions of inflammatory T cells and their correlations with cytokines and clinical parameters in patients with ankylosing spondylitis from northern Sweden

Ankylosing spondylitis (AS) is an autoimmune disease affecting parts of the skeletal structure in particular. Previously increased levels of the inflammatory cell types Th17, Th22, Tc17 and Tc22 cells have been shown to be associated with AS. Here, we analysed the levels of inflammatory T cell subsets, related cytokines and clinical characteristics of AS patients vs controls from northern Sweden. Peripheral blood mononuclear cells (PBMCs) obtained from 50 AS patients and 50 matched controls were short term stimulated with PMA/Ionomycin, stained and analysed by flow cytometry. Plasma levels of Interleukin (IL)‐17, IL‐22, IL‐10 as well as clinically relevant markers were determined. Compared to male controls, male AS patients showed 1.5‐ to 2‐fold increases of Th17 (P = .013), Th22 (P = .003) and Tc22 (P = .024) among CD45⁺CD3⁺ lymphocytes. Plasma IL‐22 levels correlated with the Tc17 proportion in male patients (R_s = 0.499, P = .003) and plasma IL‐10 levels were inversely correlated with Tc17 among all patients (R_s = −0.276, P = .05). Male patients with syndesmophytes showed significantly higher Th17 proportions (P = .038). In female AS patients, Tc22 was negatively correlated with C‐reactive protein (high sensitivity) (hsCRP) (R_s = −0.573, P = .016). We confirmed increased proportions of inflammatory T cells and correlations with relevant cytokines from male AS patients. The correlation between Th17 and syndesmophytes supports a role of Th17 in the pathogenic process.

Mortality rates in patients with ankylosing spondylitis with and without extra-articular manifestations and co-morbidities: A retrospective cohort study

Objective

To examine the mortality rates in hospitalised patients with ankylosing spondylitis (AS), and the association of extra-articular manifestations (EAM) and co-morbidities with mortality rates.

Methods

The study was a retrospective population-based cohort study using linked administrative data of hospitalised AS patients (n=1,791) and a matched comparison group (n=8,955). Mortality data for patients were obtained from the Western Australian Death Register. The presence of EAM and co-morbidities were identified from hospital records. Mortality rates were compared between the two groups using Cox proportional hazard models, overall and stratified by a history of EAM, comorbidities and smoking status.

Results

Crude mortality rates were significantly higher in AS patients than the comparison group (HR:1.85, 95%CI:1.62-2.12) with excess mortality in the AS group associated with cardiovascular disease (HR:5.32, 95%:3.84-7.35), cancer (HR:1.68, 95%CI:1.27-2.23), external causes (HR:3.92, 95%CI:2.28-6.77) and infections (HR:25.92, 95%CI:7.50-89.56). When patients were stratified by a history of EAM, cardiovascular disease, and smoking the risk of mortality was elevated in both patients with and without each risk factor. Within patients with AS, a history of cardiovascular disease (HR:6.33, 95%CI:4.79-8.38), diabetes (HR:2.81, 95%CI:1.99-3.95), smoking (HR:1.49, 95%CI:1.18-1.89) and EAM (HR:1.62, 95%CI: 1.24–2.11) were associated with an increased risk of mortality.

Conclusion

The presence of co-morbidities, EAMs, and smoking contribute to an increased risk of all-cause mortality in hospitalised AS patients compared to the comparison group. These results support the need to prevent or reduce the occurrence of co-morbidity and smoking in AS patients.

Hsa_circ_0000652 Aggravates Inflammation by Activation of Macrophages and Enhancement of OX40/OX40L Interaction in Ankylosing Spondylitis

Circular RNAs (circRNAs) have emerged as important roles in various inflammatory processes of rheumatic diseases. However, their expression profiles and influences in the pathogenesis of ankylosing spondylitis (AS) remain unclear. In this study, we revealed the differential expression profiles of circRNAs in peripheral blood mononuclear cells (PBMCs) in AS by circRNA sequencing. We screened the differentially expressed circRNAs in AS and verified that hsa_circ_0000652 was upregulated and had potential to be a biomarker of progression. Functionally, hsa_circ_0000652 promoted proliferation and cytokine production in macrophages and inhibited apoptosis. Through dual-luciferase assays and RNA pull-down assays, we demonstrated that hsa_circ_0000652 acted as a competing endogenous RNA (ceRNA) by binding with hsa-miR-1179 and regulated OX40L, which is characterized as a co-stimulatory molecule and found to be upregulated in AS patients. As a result, hsa_circ_0000652 aggravated the inflammation in the coculture system containing CD4⁺ T cells and macrophages via OX40/OX40L interaction. Our findings suggest that hsa_circ_0000652 was upregulated in AS patients and may serve as a pro-inflammatory factor in macrophages and a positive regulator of OX40/OX40L by sponging hsa-miR-1179.

Interleukin-17 family members in health and disease

The interleukin-17 (IL-17) family consists of six family members (IL-17A-IL-17F) and all the corresponding receptors have been identified recently. This family is mainly involved in the host defense mechanisms against bacteria, fungi and helminth infection by inducing cytokines and chemokines, recruiting neutrophils, inducing anti-microbial proteins and modifying T-helper cell differentiation. IL-17A and some other family cytokines are also involved in the development of psoriasis, psoriatic arthritis and ankylosing spondylitis by inducing inflammatory cytokines and chemokines, and antibodies against IL-17A as well as the receptor IL-17RA are being successfully used for the treatment of these diseases. Involvement in the development of inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis and tumors has also been suggested in animal disease models. In this review, we will briefly review the mechanisms by which IL-17 cytokines are involved in the development of these diseases and discuss possible treatment of inflammatory diseases by targeting IL-17 family members.

Significance of structural changes in the sacroiliac joints of patients with axial spondyloarthritis detected by MRI related to patients symptoms and functioning

Axial spondyloarthritis (axSpA) is a chronic inflammatory rheumatic disease that manifests primarily in the axial skeleton, initially mostly in the sacroiliac joints (SIJ), usually later spreading to the spine. The disease is characterised by inflammation and new bone formation which are mainly assessed by conventional radiography (CR) and magnetic resonance imaging (MRI). Tumour necrosis factor inhibitors (TNFi) and interleukin-17 antagonists have been shown to be efficacious and efficient in patients with axSpA. This treatment seems to also inhibit structural damage, for example, retard radiographic progression. Indeed, a reduction of new bone formation in the spine, as assessed by CR, has been reported to occur after at least 2 years of therapy with TNFi. Recently, a reduction of erosions and ankylosis in the SIJ has also been observed in axSpA patients treated with etanercept and filgotinib. In this narrative review, we discuss the limited significance of such findings.

Recent Updates in Juvenile Spondyloarthritis

Spondyloarthritis represents a group of disorders characterized by enthesitis and axial skeletal involvement. Juvenile spondyloarthritis begins before age 16. Joint involvement is usually asymmetric. Bone marrow edema on noncontrast MRI of the sacroiliac joints can facilitate diagnosis. The most significant risk factor for axial disease is HLA-B27. Most patients have active disease into adulthood. Enthesitis and sacroiliitis correlate with greater pain intensity and poor quality-of-life measures. Tumor necrosis factor inhibitors are the mainstay of biologic therapy. Although other biologics such as IL-17 blockers have shown benefit in adult spondyloarthritis, none are approved by the US Food and Drug Administration.

Association analysis of B7-H3 and B7-H4 gene single nucleotide polymorphisms in susceptibility to ankylosing spondylitis in eastern Chinese Han population

This study was conducted to describe the association between the genetic variation of the recently identified immune checkpoint molecules B7-H3 and B7-H4, and the susceptibility to ankylosing spondylitis (AS). Two single nucleotide polymorphisms (SNPs) of B7-H3 gene and three SNPs of B7-H4 gene were genotyped in 649 AS patients and 646 age- and sex-matched healthy controls. Allele, genotype frequencies and different inheritance models were performed to calculate odds ratios (ORs) and 95% confidence intervals (CIs), and the demographic and clinical parameters of patients were recorded. Our data indicated that B7-H4 rs10801935 and rs3738414 polymorphisms were correlated with AS susceptibility. In the stratification analyses, the minor A allele and GA genotype of B7-H4 rs3738414 increased the risk of AS in male patients (OR = 1.244, 95%CI = 1.026-1.508; OR = 1.453, 95%CI = 1.120-1.886, respectively). However, the association did not reach statistical significance after Bonferroni correction. Furthermore, haplotype analysis revealed that B7-H4 haplotype block TAG was a risk factor for the onset of AS (OR = 1.190, 95%CI = 1.020-1.389). These findings suggested that B7-H4 gene polymorphism may contribute to AS susceptibility in eastern Chinese Han population.

Axial spondyloarthritis: emerging drug targets

INTRODUCTION

Axial spondyloarthritis (AxSpA) is an inflammatory disorder that affects the joints, entheses, and bone tissues and is sometimes associated with psoriasis, anterior uveitis, and gut inflammation. Its pathogenesis is not wholly understood and treatment strategies require optimization. Data concerning AxSpA pathogenesis support a critical role of abnormal CD4⁺ T cell differentiation and exacerbated type 3 immune response. This knowledge boosted the development of interleukin (IL)-17 and Janus kinase inhibitors for AxSpA treatment beyond tumor necrosis factor-α inhibition.

AREAS COVERED

Emerging drug targets in animal and cellular models and with phase-II clinical trials have been evaluated. We also reflect on key issues for preclinical and clinical research going forward.

EXPERT OPINION

Some of the most promising approaches include: (i) modulation of transforming growth factor-β family that could exert a specific role on bone formation; (ii) blockade of granulocyte-macrophage colony-stimulating factor that could reduce type 3 immune responses, and (iii) rebalancing of biased immune response by cytokines such as IL-2 or IL-27 that could favor anti-inflammatory response and sustained drug-free remission. Multiomics tools and artificial intelligence could contribute to identification of optimal targets and help stratify patients for the most appropriate treatment options.

Imbalance of Peripheral Lymphocyte Subsets in Patients With Ankylosing Spondylitis: A Meta-Analysis

Ankylosing spondylitis is a complicated consequence of genetic predisposition and environmental factors. Enthesitis is believed to be the hallmark of ankylosing spondylitis, and the chronic inflammatory state of this disease is perpetuated by the disturbances of both the innate immune system and the acquired immune system. To clarify the alteration of immune system in patients with AS, we conducted a meta-analysis concerning the proportions of major lymphocyte subsets in the peripheral blood of AS patients. We systematically searched PubMed and China National Knowledge Infrastructure (CNKI) for articles related to this subject. A total of 95 articles involving 4,020 AS patients and 3,065 healthy controls were included in the analysis. This meta-analysis is performed on R platform using R package "meta", and Egger's tests were used to determine the presence of publication bias. Results showed that the percentages of T cells, NK cells and NKT cells were not significantly different between AS patients and healthy controls, but B cells were significantly increased. Among the subsets of T cells, the proportions of CD4+ T cells, Th17 cells, Tfh cells as well as Th1/Th2 ratio were significantly increased, while Tregs were significantly decreased. Subgroup analysis showed that the proportions of Th17 among both PBMCs, T cells and CD4+ T cells were significantly elevated, while Tregs were only significantly lower in PBMCs. Subgroup analysis also demonstrated that Tregs defined by "CD4+CD25+FoxP3+", "CD4+CD25+CD127low"or "CD4+CD25+CD127-"were significantly downregulated, indicating that the selection of markers could be critical. Further study is warranted in order to elucidate the complicated interactions between different lymphocyte subsets in AS patients. This study implied that the disequilibrium between Th17 and Tregs, as well as between Th1 and Th2 could contribute to the pathogenesis of ankylosing spondylitis, further cementing the understanding that ankylosing spondylitis is a consequence of disrupted balance of innate immune system and acquired immune system.