Pathogenesis of Axial Spondyloarthritis - Sources and Current State of Knowledge

Identification and bioinformatics analysis of lncRNAs in serum of patients with ankylosing spondylitis

OBJECTIVES

The aim of this study was to explore the long non-coding RNA (lncRNA) expression profiles in serum of patients with ankylosing spondylitis (AS). The role of these lncRNAs in this complex autoimmune situation needs to be evaluated.

METHODS

We used high-throughput whole-transcriptome sequencing to generate sequencing data from three patients with AS and three normal controls (NC). Then, we performed bioinformatics analyses to identify the functional and biological processes associated with differentially expressed lncRNAs (DElncRNAs). We confirmed the validity of our RNA-seq data by assessing the expression of eight lncRNAs via quantitative reverse transcription polymerase chain reaction (qRT-PCR) in 20 AS and 20 NC samples. We measured the correlation between the expression levels of lncRNAs and patient clinical index values using the Spearman correlation test.

RESULTS

We identified 72 significantly upregulated and 73 significantly downregulated lncRNAs in AS patients compared to NC. qRT-PCR was performed to validate the expression of selected DElncRNAs; the results demonstrated that the expression levels of MALAT1:24, NBR2:9, lnc-DLK1-35:13, lnc-LARP1-1:1, lnc-AIPL1-1:7, and lnc-SLC12A7-1:16 were consistent with the sequencing analysis results. Enrichment analysis showed that DElncRNAs mainly participated in the immune and inflammatory responses pathways, such as regulation of protein ubiquitination, major histocompatibility complex class I-mediated antigen processing and presentation, MAPkinase activation, and interleukin-17 signaling pathways. In addition, a competing endogenous RNA network was constructed to determine the interaction among the lncRNAs, microRNAs, and mRNAs based on the confirmed lncRNAs (MALAT1:24 and NBR2:9). We further found the expression of MALAT1:24 and NBR2:9 to be positively correlated with disease severity.

CONCLUSION

Taken together, our study presents a comprehensive overview of lncRNAs in the serum of AS patients, thereby contributing novel perspectives on the underlying pathogenic mechanisms of this condition. In addition, our study predicted MALAT1 has the potential to be deeply involved in the pathogenesis of AS.

Understanding Spondyloarthritis Pathogenesis: The Promise of Single-Cell Profiling

PURPOSE OF REVIEW

Single-cell profiling, either in suspension or within the tissue context, is a rapidly evolving field. The purpose of this review is to outline recent advancements and emerging trends with a specific focus on studies in spondyloarthritis.

RECENT FINDINGS

The introduction of sequencing-based approaches for the quantification of RNA, protein, or epigenetic modifications at single-cell resolution has provided a major boost to discovery-driven research. Fluorescent flow cytometry, mass cytometry, and image-based cytometry continue to evolve. Spatial transcriptomics and imaging mass cytometry have extended high-dimensional analysis to cells in tissues. Applications in spondyloarthritis include the indexing and functional characterization of cells, discovery of disease-associated cell states, and identification of signatures associated with therapeutic responses. Single-cell TCR-seq has provided evidence for clonal expansion of CD8+ T cells in spondyloarthritis. The use of single-cell profiling approaches in spondyloarthritis research is still in its early stages. Challenges include high cost and limited availability of diseased tissue samples. To harness the full potential of the rapidly expanding technical capabilities, large-scale collaborative efforts are imperative.

Biomechanics in the onset and severity of spondyloarthritis: a force to be reckoned with

Increasing evidence suggests that there is a pivotal role for physical force (mechanotransduction) in the initiation and/or the perpetuation of spondyloarthritis; the review contained herein examines that evidence. Furthermore, we know that damage and inflammation can limit spinal mobility, but is there a cycle created by altered spinal mobility leading to additional damage and inflammation?Over the past several years, mechanotransduction, the mechanism by which mechanical perturbation influences gene expression and cellular behaviour, has recently gained popularity because of emerging data from both animal models and human studies of the pathogenesis of ankylosing spondylitis (AS). In this review, we provide evidence towards an appreciation of the unsolved paradigm of how biomechanical forces may play a role in the initiation and propagation of AS.

RNA sequencing and bioinformatics analysis of differentially expressed genes in the peripheral serum of ankylosing spondylitis patients

BACKGROUND

Ankylosing spondylitis (AS) is a chronic progressive autoimmune disease characterized by spinal and sacroiliac arthritis, but its pathogenesis and genetic basis are largely unclear.

METHODS

We randomly selected three serum samples each from an AS and a normal control (NC) group for high-throughput sequencing followed by using edgeR to find differentially expressed genes (DEGs). Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes, Reactome pathway analyses, and Gene Set Enrichment Analysis were used to comprehensively analyze the possible functions and pathways involved with these DEGs. Protein-protein interaction (PPI) networks were constructed using the STRING database and Cytoscape. The modules and hub genes of these DEGs were identified using MCODE and CytoHubba plugins. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to validate the expression levels of candidate genes in serum samples from AS patients and healthy controls.

RESULTS

We successfully identified 100 significant DEGs in serum. When we compared them with the NC group, 49 of these genes were upregulated in AS patients and 51 were downregulated. GO function and pathway enrichment analysis indicated that these DEGs were mainly enriched in several signaling pathways associated with endoplasmic reticulum stress, including protein processing in the endoplasmic reticulum, unfolded protein response, and ubiquitin-mediated proteolysis. We also constructed a PPI network and identified the highly connected top 10 hub genes. The expression levels of the candidate hub genes PPARG, MDM2, DNA2, STUB1, UBTF, and SLC25A37 were then validated by RT-qPCR analysis. Finally, receiver operating characteristic curve analysis suggested that PPARG and MDM2 may be the potential biomarkers of AS.

CONCLUSIONS

These findings may help to further elucidate the pathogenesis of AS and provide valuable potential gene biomarkers or targets for the diagnosis and treatment of AS.

Imrecoxib and celecoxib affect sacroiliac joint inflammation in axSpA by regulating bone metabolism and angiogenesis

OBJECTIVE

To analyze the changes in the levels of bone metabolism markers related to sacroiliac joint (SIJ) inflammation in patients with axial spondyloarthritis (axSpA) after treatment with imrecoxib and celecoxib and evaluate their relationship with clinical efficacy.

METHODS

A total of 120 patients with axSpA with at least 2 magnetic resonance imaging (MRI) SIJ scans during a 12-week follow-up were enrolled. The levels of bone metabolism markers, including dickkopf-1(DKK-1), sclerostin, vascular endothelial growth factor (VEGF), bone morphogenetic protein-2 (BMP-2), osteoprotegerin (OPG), noggin, β-catenin, and RUNX2, were measured twice, and their association with disease activity and the Spondyloarthritis Research Consortium of Canada (SPARCC) score for SIJ were analyzed by univariate analysis of covariance.

RESULTS

A total of 116 patients completed the follow-up. The levels of sclerostin, OPG, noggin, DKK-1, and RUNX2 were increased, whereas those of VEGF and β-catenin were decreased. The levels of sclerostin and OPG were negatively correlated with disease duration. The levels of VEGF and β-catenin were significantly decreased (F = 7.866, P = 0.003; F = 4.106, P = 0.047) in patients with disease remission. A decrease in ESR was significantly correlated with decreased levels of Runx2 and SPARCC scores, with the levels of sclerostin being significantly elevated in the SPARCC-reduced group. There were no statistically significant differences between the imrecoxib and celecoxib groups (P> 0.05).

CONCLUSION

Imrecoxib and celecoxib affect SIJ inflammation, disease activity, and the course of disease by regulating bone metabolism and angiogenesis in axSpA. Key Points •After treatment with imrecoxib and celecoxib, the levels of sclerostin, OPG, noggin, DKK-1, and RUNX2 were increased, whereas those of VEGF and β-catenin were decreased, correlating with the course of disease, disease activity, and SIJ inflammation. • A decrease in ESR was significantly correlated with a decrease in the levels of RUNX2 and SIJ inflammation.. • The levels of sclerostin were more significantly elevated in SIJ inflammation remission group.. •Imrecoxib and celecoxib affect SIJ inflammation by regulating bone metabolism and angiogenesis in axSpA..

Inflammation, new bone formation and aorta

OBJECTIVES

This study describes the characteristics of vertebral osteophytes in different inflammatory and non-inflammatory diseases aiming to reflect the aortic-vertebrae interaction.

METHODS

We conducted a cross-sectional study including 4 group of patients, ankylosing spondylitis (AS, n = 52), Takayasu's arteritis (TKA, n = 31), diffuse idiopathic skeletal hyperostosis (DISH, n = 30), coronary artery disease (CAD, n = 10), 100 and also age-matched healthy controls (HC, n = 143). All subjects underwent a chest computed tomography scan and images of the upper and lower border of 7 adjacent thoracic vertebrae (T5 to T12) were captured. An "aorta ipsilateral ratio" (AIR) of the osteophyte was calculated as the area across the midline toward the aorta side divided by the total osteophyte area.

RESULTS

The frequency of subjects with osteophytes and osteophyte counts increased with age across the board. Frequencies of osteophytes in AS and TKA were much higher than age-matched HCs. The AIRs were significantly elevated in AS, TKA and CAD compared with DISH or age-matched HCs. In addition, the AIR of patients with higher C-reactive protein levels (>8 mg/L) were greater than those with lower levels, both among AS and CAD patients.

CONCLUSIONS

Our findings indicate that, in an inflammatory niche, regardless of the origin or the grade of the inflammation, ossification will be facilitated and screwed toward the aorta. There is a possible mechanistic connection between large vessel and new bone formation in the context of inflammation.

The impact of genetic background and sex on the phenotype of IL-23 induced murine spondyloarthritis

BACKGROUND

Overexpression of IL-23 in adult mice by means of hydrodynamic tail vein injection of IL-23 minicircles has been reported to result in spondyloarthritis-like disease. The impact of genetic background and sex on the disease phenotype in this model has not been investigated.

METHODS

We compared male B10.RIII mice with male C57BL/6 mice, and male with female B10.RIII mice after hydrodynamic injection of IL-23 enhanced episomal vector (EEV) at 8-12 weeks of age. We monitored clinical arthritis scores, paw swelling, and body weight. Animals were euthanized after two weeks and tissues were harvested for histology, flow cytometry and gene expression analysis. Serum cytokine levels were determined by ELISA.

FINDINGS

Male B10.RIII mice developed arthritis in the forepaws and feet within 6 days after IL-23 EEV injection; they also exhibited psoriasis-like skin disease, colitis, weight loss, and osteopenia. In contrast to previous reports, we did not observe spondylitis or uveitis. Male C57BL/6 mice injected with IL-23 EEV had serum IL-23 levels comparable with B10.RIII mice and developed skin inflammation, colitis, weight loss, and osteopenia but failed to develop arthritis. Female B10.RIII mice had more severe arthritis than male B10.RIII mice but did not lose weight.

CONCLUSIONS

The phenotype of IL-23 induced disease in mice is controlled by genetic background and sex of the animals. The development of extra-articular manifestations but absence of arthritis in C57BL/6 mice suggests that organ-specificity of IL-23 driven inflammation is genetically determined. The mechanisms behind the strain-specific differences and the sexual dimorphism observed in this study may be relevant for human spondyloarthritis and warrant further exploration.

Identification of lncRNAs associated with the pathogenesis of ankylosing spondylitis

Background

Ankylosing spondylitis (AS) is a chronic autoimmune disease affecting the sacroiliac joint. To date, few studies have examined the association between long non-coding RNAs (lncRNAs) and AS pathogenesis. As such, we herein sought to characterize patterns of AS-related lncRNA expression and to evaluate the potential role played by these lncRNAs in this complex autoimmune context.

Methods

We conducted a RNA-seq analysis of peripheral blood mononuclear cell (PBMC) samples isolated from five AS patients and corresponding controls. These data were then leveraged to characterize AS-related lncRNA expression patterns. We further conducted GO and KEGG enrichment analyses of the parental genes encoding these lncRNAs, and we confirmed the validity of our RNA-seq data by assessing the expression of six lncRNAs via qRT-PCR in 15 AS and control patient samples. Pearson correlation analyses were additionally employed to examine the associations between the expression levels of these six lncRNAs and patient clinical index values.

Results

We detected 56,575 total lncRNAs in AS and control patient samples during our initial RNA-seq analysis, of which 200 and 70 were found to be up- and down-regulated (FC > 2 or < 0.05; P < 0.05), respectively, in AS samples relative to controls. In qRT-PCR validation assays, we confirmed the significant upregulation of NONHSAT118801.2, ENST00000444046, and NONHSAT183847.1 and the significant downregulation of NONHSAT205110.1, NONHSAT105444.2, and NONHSAT051856.2 in AS patient samples. We further found the expression of NONHSAT118801.2 and NONHSAT183847.1 to be positively correlated with disease severity.

Conclusion

Overall, our findings highlight several lncRNAs that are specifically expressed in PBMCs of AS patients, indicating that they may play key functions in the pathogenesis of this autoimmune disease. Specifically, we determined that NONHSAT118801.2 and NONHSAT183847.1 may influence the occurrence and development of AS.