Inflammation-driven bone formation in a mouse model of ankylosing spondylitis: sequential not parallel processes

Single-cell transcriptome revealed dysregulated RNA-binding protein expression patterns and functions in human ankylosing spondylitis

Objective

To explore the expression characteristics and regulatory patterns of RBPs in different immune cell types of AS, and to clarify the potential key role of RBPs in the occurrence and development of AS disease.

Methods

PBMC sample data from scRNA-seq (HC*29, AS*10) and bulk RNA-seq (NC*3, AS*5) were selected for correlation analysis.

Results

(1) Compared with the HC group, the numbers of B, DC (dendritic cells), CD14+ Mono and CD8+ T cells were increased in AS group, while the numbers of platelet (platelets), CD8+ NKT, CD16+ Mono (non-classical monocytes), Native CD4+ T and NK were decreased. (2) Through the analysis of RBP genes in B cells, some RBPs were found to play an important role in B cell differentiation and function, such as DDX3X, SFPQ, SRRM1, UPF2. (3) It may be related to B-cell receptor, IgA immunity, NOD-like receptor and other signaling pathways; Through the analysis of RBP genes in CD8+ T cells, some RBPs that play an important role in the immune regulation of CD8+ T were found, such as EIF2S3, EIF4B, HSPA5, MSL3, PABPC1 and SRSF7; It may be related to T cell receptor, TNF, IL17 and other signaling pathways. (4) Based on bulk RNA-seq, it was found that compared with HC and AS patients, differentially expressed variable splicing genes (RASGs) may play an important role in the occurrence and development of AS by participating in transcriptional regulation, protein phosphorylation and ubiquitination, DNA replication, angiogenesis, intracellular signal transduction and other related pathways.

Conclusion

RBPs has specific expression characteristics in different immune cell types of AS patients, and has important regulatory functions. Its abnormal expression and regulation may be closely related to the occurrence and development of AS.

The complement factor H-related protein-5 (CFHR5) exacerbates pathological bone formation in ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease, characterized by excessive new bone formation. We previously reported that the complement factor H-related protein-5 (CFHR5), a member of the human factor H protein family, is significantly elevated in patients with AS compared to other rheumatic diseases. However, the pathophysiological mechanism underlying new bone formation by CFHR5 is not fully understood. In this study, we revealed that CFHR5 and proinflammatory cytokines (TNF, IL-6, IL-17A, and IL-23) were elevated in the AS group compared to the HC group. Correlation analysis revealed that CFHR5 levels were not significantly associated with proinflammatory cytokines, while CFHR5 levels in AS were only positively correlated with the high CRP group. Notably, treatment with soluble CFHR5 has no effect on clinical arthritis scores and thickness at hind paw in curdlan-injected SKG, but significantly increased the ectopic bone formation at the calcaneus and tibia bones of the ankle as revealed by micro-CT image and quantification. Basal CFHR5 expression was upregulated in AS-osteoprogenitors compared to control cells. Also, treatment with CFHR5 remarkedly induced bone mineralization status of AS-osteoprogenitors during osteogenic differentiation accompanied by MMP13 expression. We provide the first evidence demonstrating that CFHR5 can exacerbate the pathological bone formation of AS. Therapeutic modulation of CFHR5 could be promising for future treatment of AS. KEY MESSAGES: Serum level of CFHR5 is elevated and positively correlated with high CRP group of AS patients. Recombinant CFHR5 protein contributes to pathological bone formation in in vivo model of AS. CFHR5 is highly expressed in AS-osteoprogenitors compared to disease control. Recombinant CFHR5 protein increased bone mineralization accompanied by MMP13 in vitro model of AS.

An update of murine models and their methodologies in immune-mediated joint damage and pain research

Murine models have played an indispensable role in the understanding of rheumatic and musculoskeletal disorders (RMD), elucidating the genetic, endocrine and biomechanical pathways involved in joint pathology and associated pain. To date, the available models in RMD can be classified as induced or spontaneous, both incorporating transgenic alternatives that improve specific insights. It is worth noting that the selection of the most appropriate model together with the evaluation of their specific characteristics and technical capabilities are crucial when designing the experiments. Furthermore, it is also imperative to consistently adhere to the ethical standards concerning animal experimentation. Recognizing the inherent limitation that any model can entirely encapsulates the complexity of the pathophysiology of these conditions, the aim of this review is to provide an updated overview on the methodology of current murine models in major arthropathies and their immune-mediated pathways, addressing to basic, translational and pharmacological research in joint damage and pain.

The role of inflammation in autoimmune disease: a therapeutic target

Autoimmune diseases (AIDs) are immune disorders whose incidence and prevalence are increasing year by year. AIDs are produced by the immune system's misidentification of self-antigens, seemingly caused by excessive immune function, but in fact they are the result of reduced accuracy due to the decline in immune system function, which cannot clearly identify foreign invaders and self-antigens, thus issuing false attacks, and eventually leading to disease. The occurrence of AIDs is often accompanied by the emergence of inflammation, and inflammatory mediators (inflammatory factors, inflammasomes) play an important role in the pathogenesis of AIDs, which mediate the immune process by affecting innate cells (such as macrophages) and adaptive cells (such as T and B cells), and ultimately promote the occurrence of autoimmune responses, so targeting inflammatory mediators/pathways is one of emerging the treatment strategies of AIDs. This review will briefly describe the role of inflammation in the pathogenesis of different AIDs, and give a rough introduction to inhibitors targeting inflammatory factors, hoping to have reference significance for subsequent treatment options for AIDs.

Evaluation of preclinical efficacy of human umbilical cord mesenchymal stem cells in ankylosing spondylitis

Objective

Umbilical cord mesenchymal stem cells (UCMSCs) have significant regenerative, tissue repair, and immunomodulatory properties that can help reduce inflammatory responses in patients with ankylosing spondylitis (AS). In this study, we used a combination of bovine proteoglycan and dimethyldioctadecylammonium (DDA) to establish a mouse model of proteoglycan-induced spondylitis (PGISp). To evaluate the therapeutic effects of UCMSCs, we treated PGISp mice with different doses of hUCMSCs via tail vein injection.

Methods

At week 13, the PGISp mice exhibited thickened, erythematous paws, erythema in the extremities, and lameness. CT scans revealed necrotic lysis of chondrocytes, formation of fissures, visible hemorrhage, connective tissue hyperplasia, and focal infiltration of lymphocytes in the intervertebral discs. At week 14, the PGISp mice were randomly divided into three groups and administered different doses of hUCMSCs (0.25, 0.5, and 1.0×107 cells/kg, iv, QOW×2, n=10). To assess the therapeutic effects of hUCMSCs, we evaluated Th cell subsets in the spleen, spleen and thymus coefficients, peripheral blood inflammatory factors, and pathological and imaging observations of the spines and lumbar spines in the PGISp mice.

Results

The results demonstrated that injection of hUCMSCs shifted the balance axis between Th1 and Th2 cells in the spleen towards Th2 cells. Moreover, the spleen coefficient and levels of inflammatory cytokines (TNF-α and CCL-2) in the serum decreased after hUCMSC injection. CT imaging and pathological analysis indicated that hUCMSC treatment inhibited ectopic osteogenesis and maintained clear small joint gaps, which slowed down the progression of structural lesions in the disc, nucleus pulposus, fibrous ring, and cartilage in PGISp mice.

Conclusion

Administering hUCMSCs at the 14th week after modeling proved to be an effective treatment for PGISp mice. This experiment offers a valuable reference for the pre-clinical use of hUCMSCs in the treatment of AS.

Effects of ixekizumab treatment on structural changes in the sacroiliac joint: MRI assessments at 16 weeks in patients with non-radiographic axial spondyloarthritis

BACKGROUND

There is limited understanding regarding the inhibition of structural damage in the sacroiliac joint of patients with non-radiographic axial spondyloarthritis. This study evaluated the effect of the interleukin-17A inhibitor ixekizumab versus placebo on structural lesions in the sacroiliac joints as assessed by MRI at week 16 in patients with non-radiographic axial spondyloarthritis from the COAST-X study.

METHODS

COAST-X was a 52-week, randomised, double-blind, placebo-controlled, parallel-group study done at 107 sites in 15 countries in Europe, Asia, North America, and South America. Eligible participants were adults (aged ≥18 years) with active axial spondyloarthritis without definite radiographic sacroiliitis (non-radiographic axial spondyloarthritis), objective signs of inflammation (via MRI or C-reactive protein), and an inadequate response or intolerance to non-steroidal anti-inflammatory drugs. Patients were randomly allocated to placebo or double-blind ixekizumab 80 mg every 4 weeks (Q4W) or 2 weeks (Q2W), with an 80 mg or 160 mg starting dose. We report a post-hoc analysis of 266 patients with available MRI scans from baseline and week 16. MRI scans were scored using the Spondyloarthritis Research Consortium of Canada (SPARCC) sacroiliac joint structural score (SSS) method independently by two masked readers. Treatment comparisons used analysis of covariance based on observed cases. Correlations were evaluated among changes in SPARCC SSS for erosion, fat lesions, and backfill, and between changes in SPARCC SSS and sacroiliac joint inflammation scores and clinical measures. COAST-X was registered with ClinicalTrials.gov, NCT02757352.

FINDINGS

Between Aug 2, 2016, and Jan 29, 2018, 303 patients were enrolled to the COAST-X study. 290 (96%) of 303 participants completed the week 16 visit (95 in the ixekizumab Q4W group, 98 in the ixekizumab Q2W group, and 97 in the placebo group), and MRI scans were available for 266 patients at baseline and week 16 (85 in the ixekizumab Q4W group, 91 in the ixekizumab Q2W group, and 90 in the placebo group). Changes from baseline to week 16 in mean SPARCC SSS for erosion were -0·39 for ixekizumab Q4W (p=0·003 vs placebo), -0·40 for ixekizumab Q2W (p=0·002), and 0·16 for placebo; for fat lesions: 0·16 for ixekizumab Q4W (p=0·013), 0·10 for ixekizumab Q2W (p=0·067), and -0·04 for placebo; and for backfill: 0·21 for ixekizumab Q4W (p=0·011), 0·22 for ixekizumab Q2W (p=0·006), and -0·10 for placebo. Ankylosis did not change. Effects of ixekizumab versus placebo on structural changes were most pronounced in patients with baseline inflammation in the sacroiliac joints. Changes from baseline at week 16 in erosion, fat lesions, and backfill were correlated.

INTERPRETATION

Although the clinical relevance is not yet clear, patients with non-radiographic axial spondyloarthritis receiving ixekizumab had significant reductions in erosions and increases in fat lesions and backfill in the sacroiliac joints versus placebo at week 16, suggesting an early repair process with ixekizumab treatment.

FUNDING

Eli Lilly and Company.

Systemic Administration of Neutral Electrolyzed Saline as a Novel Treatment for Rheumatoid Arthritis Reduces Mechanical and Inflammatory Damage to the Joints: Preclinical Evaluation in Mice

Rheumatoid arthritis is globally present in about 1% of the population. This autoinflammatory disease modifies the connective tissue, causing pain and inflammation of the joints. Over time, it causes the loss of joint cartilage and bone mass, decreasing the patient's quality of life. Treatment options now available either give symptomatic alleviation or alter the disease process. Nonetheless, adherence to chronic treatment is typically limited due to adverse effects. As a result, new therapy approaches, such as systemic administration of neutral electrolyzed saline to improve patients' quality of life, are being investigated. The study is a randomized prospective preclinical trial with a single-blind and a 4-arm parallel group using a collagen-induced mice model to generate rheumatoid arthritis. It was carried out on 36 male BALB/c mice, with the primary outcome measure being a scoring system for histopathologic assessment. When all groups are compared, there are significant differences. In addition, the animal model was validated by the healthy group. The animals treated with neutral electrolyzed saline had much less cartilage degradation, bone erosion, pannus development, and inflammation than the placebo-treated mice. Serum IL-6 levels were evaluated in parallel with disease severity expressed as synovitis grading of the affected joints. Spearman's rank correlation coefficient (Rs) = 0.399 (P=0.016) between serum IL-6 levels and the synovitis grading suggests a direct correlation between IL-6 production and disease severity. An additional trial of 20 male BALB/c mice (10 treated with placebo and 10 with neutral electrolyzed saline for 30 days) showed no clinical nor histopathological evidence of adverse effects. According to histopathological and blood test results, we conclude that neutral electrolyzed saline minimizes mechanical and inflammatory damage to the joint and may be helpful as an alternative to rheumatoid arthritis therapy.

Efficacy of thunder-fire moxibustion in treating ankylosing spondylitis of kidney deficiency and governor meridian cold and its influence on TNF-α and RANKL: study protocol for a prospective, nonblinded, single-center, randomized controlled trial

Background

Ankylosing spondylitis (AS) is a common chronic inflammatory spondyloarthropathy. It is considered in traditional Chinese medicine (TCM) that the pathogenesis of AS is mainly due to Yang deficiency of kidney governor meridian and internal prosperity of cold evil. Thunder-fire moxibustion is a kind of moxibustion that is characterized in abundance in drug composition, high heat radiation, and strong penetration. Thunder-fire moxibustion on the spinal segment of the governor meridian in treating AS seems compatible with the main pathogenesis of kidney deficiency and governor meridian cold. The trial aims to explore the efficacy of thunder-fire moxibustion in patients with AS of kidney deficiency and governor meridian cold and its influence on bone metabolism, through a prospective randomized trial.

Methods

Sixty patients with AS of kidney deficiency and governor meridian cold will be recruited and randomly assigned to the treatment group (thunder-fire moxibustion three times a week plus basic treatment) and the control group (basic treatment) at the Center of TCM of Beijing Luhe Hospital Affiliated to Capital Medical University (Beijing, China). Each patient will be treated for 4 weeks. The primary outcome is the efficacy of TCM syndrome, and the secondary outcome indexes will include the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI), Short-Form-36 Questionnaire (SF-36), tumor necrosis factor-α (TNF-α), and receptor activator of nuclear factor-κB ligand (RANKL). TNF-α and RANKL with observation will be determined once respectively before and after treatment, while the other indexes will be observed once prior to the treatment, 2 weeks post-treatment, and at the end of the treatment. Side effects will be recorded and analyzed as well. Inter-group comparison and analysis will be performed based on the intention-to-treat set and per-protocol set.

Discussion

This prospective randomized trial will help verify the efficacy of thunder-fire moxibustion in treating AS of kidney deficiency and governor meridian cold, discuss preliminarily its mechanism in treating this disease, and provide high-quality evidences for scientific researches on clinical treatment with thunder-fire moxibustion against AS.

Trial registration

Chinese Clinical Trial Registry ChiCTR2100044227. Registered on 12 March 2021

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06227-7.

SOX9+ enthesis cells are associated with spinal ankylosis in ankylosing spondylitis

OBJECTIVE

Although cartilage degeneration and invasion of the subchondral bone plate in entheseal lesion has been considered to consequently lead bony ankylosis in ankylosing spondylitis (AS), no evident mechanisms are known.

DESIGN

To identify histopathological and physiological changes in enthesitis-related ankylosis in AS, we performed molecular characterization of transcription factors and surface markers, and transcriptome analysis with human tissues. Entheseal tissue containing subchondral bone was obtained from the facet joints of 9 patients with AS and 10 disease controls, and assessed by using differential staining techniques. Enthesis cells were isolated, characterized, stimulated with TNF and/or IL-17A, and analysed by cell-based experimental tools.

RESULTS

We found diffusely distributed granular tissue and cartilage in the subchondral bone in AS. Co-expression of SOX9, a specific transcription factor in cartilage, and matrix metalloproteinase 13 (MMP13) was found in the granular tissues within the subchondral bone from AS patients. Intriguingly, SOX9 expression was significantly higher in AS enthesis cells than controls and correlated with TNFR1 and IL-17RA expressions, which is important for high reactivity to TNF and IL-17A cytokines. Co-stimulation by TNF and IL-17A resulted in accelerated mineralization/calcification features, and increased OCN expression in AS enthesis cells. Furthermore, SOX9 overexpression in enthesis leads to promoting mineralization feature by TNF and IL-17A stimuli. Finally, OCN expression is elevated in the destructive enthesis of advanced AS.

CONCLUSION

These findings provide insight into the links between inflammation and the mineralization of entheseal tissue as the initiation of spinal ankylosis, emphasizing the importance of SOX9⁺ enthesis cells.

A Potential New Mouse Model of Axial Spondyloarthritis Involving the Complement System

Many mouse models of rheumatoid arthritis have been identified, but only a limited number are present for axial spondyloarthritis (AxSpA). Collagen Ab-induced arthritis (CAIA) is one of the most widely used mouse models of arthritis, and it is complement-dependent. We found that mice developing CAIA also developed spinal lesions similar to those found in AxSpA. To induce CAIA, mice were injected intraperitoneally at day 0 with anti-collagen Abs, followed by LPS injection at day 3. CAIA mice demonstrated a significant kyphosis through the spine, as well as hypertrophic cartilage and osseous damage of the intravertebral joints. Immunohistochemical staining of the kyphotic area revealed increased complement C3 deposition and macrophage infiltration, with localization to the intravertebral joint margins. Near Infrared (NIR) in vivo imaging showed that anti-collagen Abs conjugated with IRDye^® 800CW not only localized to cartilage surface in the joints but also to the spine in arthritic mice. We report here a novel preclinical mouse model in which, associated with the induction of CAIA, mice also exhibited salient features of AxSpA; this new experimental model of AxSpA may allow investigators to shed light on the local causal mechanisms of AxSpA bone and soft tissue changes as well as treatment.

Post-traumatic osteoarthritis progression is diminished by early mechanical unloading and anti-inflammatory treatment in mice

OBJECTIVE

Post-traumatic osteoarthritis (PTOA) is a degenerative joint disease initiated by injury. Early phase (0-7 days) treatments often include rest (unloading) and anti-inflammatory medications, but how those early interventions impact PTOA progression is unknown. We hypothesized that early unloading and anti-inflammatory treatment would diminish joint inflammation and slow PTOA progression.

DESIGN

Mice were injured with non-invasive ACL rupture followed by hindlimb unloading (HLU) or normal cage activity (ground control: GC) for 7 days, after which all mice were allowed normal cage activity. HLU and GC mice were treated with daily celecoxib (CXB; 10 mg/kg IP) or vehicle. Protease activity was evaluated using in vivo fluorescence imaging, osteophyte formation and epiphyseal trabecular bone were quantified using micro-computed tomography, and synovitis and articular cartilage were evaluated using whole-joint histology at 7, 14, 21, and 28 days post-injury.

RESULTS

HLU significantly reduced protease activity (-22-30% compared to GC) and synovitis (-24-50% relative to GC) at day 7 post-injury (during unloading), but these differences were not maintained at later timepoints. Similarly, trabecular bone volume was partially preserved in HLU mice at during unloading (-14-15% BV/TV for HLU mice, -21-22% for GC mice relative to uninjured), but these differences were not maintained during reloading. Osteophyte volume was reduced by both HLU and CXB, but there was not an additive effect of these treatments (HLU: -46%, CXB: -30%, HLU + CXB: -35% relative to vehicle GC at day 28).

CONCLUSIONS

These data suggest that early unloading following joint injury can reduce inflammation and potentially slow PTOA progression.

Biological DMARDs and disease modification in axial spondyloarthritis: a review through the lens of causal inference

Axial spondyloarthritis (axSpA) is a chronic rheumatic disease characterised by inflammation predominantly involving the spine and the sacroiliac joints. In some patients, axial inflammation leads to irreversible structural damage that in the spine is usually quantified by the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS). Available therapeutic options include biological disease-modifying antirheumatic drugs (bDMARDs), which have been proven effective in suppressing inflammation in several randomised controlled trials (RCT), the gold standard for evaluating causal treatment effects. RCTs are, however, unfeasible for testing structural effects in axSpA mainly due to the low sensitivity to change of the mSASSS. The available literature therefore mainly includes observational research, which poses serious challenges to the determination of causality. Here, we review the studies testing the effect of bDMARDs on spinal radiographic progression, making use of the principles of causal inference. By exploring the assumptions of causality under counterfactual reasoning (exchangeability, positivity and consistency), we distinguish between studies that likely have reported confounded treatment effects and studies that, on the basis of their design, have more likely reported causal treatment effects. We conclude that bDMARDs might, indirectly, interfere with spinal radiographic progression in axSpA by their effect on inflammation. Innovations in imaging are expected, so that placebo-controlled trials can in the future become a reality. In the meantime, causal inference analysis using observational data may contribute to a better understanding of whether disease modification is possible in axSpA.

Testing if Micro-CT Is Capable of Quantitating the Extent of Proteoglycan-Aggrecan Induced Axial Spondyloarthritis in Mice

Objective

Injections of proteoglycan aggrecan (PGA) have been reported to induce axial spondyloarthritis (ax-SpA) in BALB/c mice. It is considered to be a model for radiographic ax-SpA. However, evaluation of the extent of axial disease by histopathological assessment of every intervertebral space is labor-intensive. The objective of our paper is to test the feasibility of Micro Computed Tomography (Micro-CT) in rapidly enumerating the number of intervertebral spaces affected in each mouse.

Methods

Arthritis was induced in BALB/c mice by intraperitoneal injections of PGA. Involvement of several spinal segments, and selected sacroiliac and hip joints were evaluated by histopathology. The involvement of all intervertebral spaces, sacroiliac and hip joints was evaluated by Micro-CT.

Results

BALB/c mice injected with PGA developed histopathology of SpA-like axial lesions, including spondylitis, sacroiliac joint arthritis and hip joint arthritis. Micro-CT allowed us to clearly enumerate the number of lesions in each mouse.

Conclusion

Micro-CT allows quantitative assessment of the extent of axial involvement in PGA-induced mouse spondylitis. This can be a useful tool in assessing therapeutic interventions.

The emerging role of Interleukin 37 in bone homeostasis and inflammatory bone diseases

Interleukin 37 (IL-37) is a newly identified cytokine that belongs to the IL-1 family. Unlike other members of the IL-1 family, it has been demonstrated that IL-37 possesses anti-inflammatory characteristics in both innate and acquired immune responses. Recently, significant progress has been made in understanding the role of IL-37 in inflammatory signaling pathways. Meanwhile, IL-37 has also attracted more and more attention in bone homeostasis and inflammatory bone diseases. The latest studies have revealed that IL-37 palys an essential role in the regulation of osteoclastogenesis and osteoblastogenesis. The levels of IL-37 are abnormal in patients with inflammatory bone diseases such as rheumatoid arthritis (RA), osteoarthritis (OA), ankylosing spondylitis (AS), and periodontitis. In addition, in vivo studies have further confirmed that recombinant IL-37 treatment displayed therapeutic potential in these diseases. The present review article aims to provide an overview describing the biological functions of IL-37 in bone homeostasis and inflammatory bone diseases, thus shedding new light on a novel therapeutic strategy in the future.

Perspectives on the Genetic Associations of Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a common form of inflammatory spinal arthritis with a complex polygenic aetiology. Genome-wide association studies have identified more than 100 loci, including some involved in antigen presentation (HLA-B27, ERAP1, and ERAP2), some in Th17 responses (IL6R, IL23R, TYK2, and STAT3), and others in macrophages and T-cells (IL7R, CSF2, RUNX3, and GPR65). Such observations have already helped identify potential new therapies targeting IL-17 and GM-CSF. Most AS genetic associations are not in protein-coding sequences but lie in intergenic regions where their direct relationship to particular genes is difficult to assess. They most likely reflect functional polymorphisms concerned with cell type-specific regulation of gene expression. Clarifying the nature of these associations should help to understand the pathogenic pathways involved in AS better and suggest potential cellular and molecular targets for drug therapy. However, even identifying the precise mechanisms behind the extremely strong HLA-B27 association with AS has so far proved elusive. Polygenic risk scores (using all the known genetic associations with AS) can be effective for the diagnosis of AS, particularly where there is a relatively high pre-test probability of AS. Genetic prediction of disease outcomes and response to biologics is not currently practicable.

Associations of Platelet Count with Inflammation and Response to Anti-TNF-α Therapy in Patients with Ankylosing Spondylitis

Background: Increased platelet count has been reported in ankylosing spondylitis (AS) patients, but its clinical significance is still largely elusive. The objective of this study was to evaluate the clinical role of platelet count in AS patients, especially its impact on treatment outcomes.

Methods: A case-control study containing 35 AS patients receiving anti-tumor necrosis factor-α (anti-TNF-α) therapy and 45 healthy controls was performed, and AS patients were followed at least 6 months after anti-TNF-α therapy. A systematic review and meta-analysis of studies containing relevant data on outcomes of interest was also performed.

Results: AS patients had significantly higher platelet count than controls (p = 0.0001), and the significantly increased platelet count in AS patients was confirmed in a meta-analysis of 14 studies involving 1,223 AS patients and 913 controls (mean difference = 39.61, 95% CI 27.89–51.34, p < 0.001). Besides, platelet count was significantly correlated with ESR (p < 0.001) and was moderately correlated with ASDAS-CRP score (p = 0.002). Moreover, anti-TNF-α therapy could reduce platelet count in AS patients at the first month and the effect was maintained through the treatment duration. In the prospective follow-up study of those 35 AS patients, those responders to anti-TNF-α therapy had significantly lower platelet count than nonresponders (p = 0.015). Logistic regression analysis suggested that lower platelet count was associated with higher possibility of achieving good response to anti-TNF-α therapy in AS patients (odds ratio = 2.26; 95% CI = 1.06–4.82; p = 0.035).

Conclusion: This study suggested that platelet count was associated with inflammation severity and treatment outcomes in AS patients, and elevated platelet count was a promising biomarker of poorer response to anti-TNF-α therapy. The findings above need to be validated in more future studies.

Aberrant upregulation of CaSR promotes pathological new bone formation in ankylosing spondylitis

Pathological new bone formation is a typical pathological feature in ankylosing spondylitis (AS), and the underlying molecular mechanism remains elusive. Previous studies have shown that the calcium‐sensing receptor (CaSR) is critical for osteogenic differentiation while also being highly involved in many inflammatory diseases. However, whether it plays a role in pathological new bone formation of AS has not been reported. Here, we report the first piece of evidence that expression of CaSR is aberrantly upregulated in entheseal tissues collected from AS patients and animal models with different hypothetical types of pathogenesis. Systemic inhibition of CaSR reduced the incidence of pathological new bone formation and the severity of the ankylosing phenotype in animal models. Activation of PLCγ signalling by CaSR promoted bone formation both in vitro and in vivo. In addition, various inflammatory cytokines induced upregulation of CaSR through NF‐κB/p65 and JAK/Stat3 pathways in osteoblasts. These novel findings suggest that inflammation‐induced aberrant upregulation of CaSR and activation of CaSR‐PLCγ signalling in osteoblasts act as mediators of inflammation, affecting pathological new bone formation in AS.

Bone phenotypes in rheumatology - there is more to bone than just bone

Osteoarthritis, rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis, all have one clear common denominator; an altered turnover of bone. However, this may be more complex than a simple change in bone matrix and mineral turnover. While these diseases share a common tissue axis, their manifestations in the area of pathology are highly diverse, ranging from sclerosis to erosion of bone in different regions. The management of these diseases will benefit from a deeper understanding of the local versus systemic effects, the relation to the equilibrium of the bone balance (i.e., bone formation versus bone resorption), and the physiological and pathophysiological phenotypes of the cells involved (e.g., osteoblasts, osteoclasts, osteocytes and chondrocytes). For example, the process of endochondral bone formation in chondrocytes occurs exists during skeletal development and healthy conditions, but also in pathological conditions. This review focuses on the complex molecular and cellular taxonomy of bone in the context of rheumatological diseases that alter bone matrix composition and maintenance, giving rise to different bone turnover phenotypes, and how biomarkers (biochemical markers) can be applied to potentially describe specific bone phenotypic tissue profiles.

Short-Term Efficacy and Safety of Secukinumab for Ankylosing Spondylitis: A Systematic Review and Meta-Analysis of RCTs

Secukinumab is a novel IL-17A inhibitor that has been confirmed to be effective for treating PsA and RA. Several studies have demonstrated that secukinumab also provides benefits for AS patients. Thus, we performed a meta-analysis of RCTs to evaluate the short-term efficacy and safety of secukinumab for the management of AS. The PubMed, Medline, Embase, Web of Science, and Cochrane Library databases were searched for RCTs published prior to March 2020 on the treatment of AS with secukinumab. The primary outcome was the ASAS20 response, and the secondary outcomes included the ASAS40 response, ASAS5/6 response, SF-36 PCS score, ASQoL score, and AEs. Dichotomous data were expressed as pooled RRs with 95% CIs, while continuous data were expressed as pooled MDs with 95% CIs. Subgroup analysis was conducted based on whether the AS patients previously underwent treatment with TNFi. A total of 4 RCTs with 1166 patients were included in our meta-analysis. At week 16, secukinumab 150 mg yielded significant improvements in the clinical response and patient-reported outcomes for AS patients. There was no increased risk of AEs. Consistent results were detected in the meta-analysis of secukinumab 75 mg versus a placebo. Furthermore, no significant difference was detected between the secukinumab 75 mg group and secukinumab 150 mg group. We concluded that secukinumab is effective for treating AS and generally well tolerated by AS patients in the short term, regardless of whether they previously underwent TNFi treatment. The superiority of secukinumab 150 mg over secukinumab 75 mg seems to be limited, since no significant difference in any endpoint was detected between the two groups.

Positive transcriptional response on inflammation and joint remodelling influenced by physical exercise in proteoglycan-induced arthritis: An animal study

Aims

To assess the effect of physical exercise (PE) on the histological and transcriptional characteristics of proteoglycan-induced arthritis (PGIA) in BALB/c mice.

Methods

Following PGIA, mice were subjected to treadmill PE for ten weeks. The tarsal joints were used for histological and genetic analysis through microarray technology. The genes differentially expressed by PE in the arthritic mice were obtained from the microarray experiments. Bioinformatic analysis in the DAVID, STRING, and Cytoscape bioinformatic resources allowed the association of these genes in biological processes and signalling pathways.

Results

Arthritic mice improved their physical fitness by 42.5% after PE intervention; it induced the differential expression of 2,554 genes. The bioinformatic analysis showed that the downregulated genes (n = 1,371) were significantly associated with cellular processes that mediate the inflammation, including Janus kinase-signal transducer and activator of transcription proteins (JAK-STAT), Notch, and cytokine receptor interaction signalling pathways. Moreover, the protein interaction network showed that the downregulated inflammatory mediators interleukin (IL) 4, IL5, IL2 receptor alpha (IL2rα), IL2 receptor beta (IL2rβ), chemokine ligand (CXCL) 9, and CXCL12 were interacting in several pathways associated with the pathogenesis of arthritis. The upregulated genes (n = 1,183) were associated with processes involved in the remodelling of the extracellular matrix and bone mineralization, as well as with the processes of aerobic metabolism. At the histological level, PE attenuated joint inflammatory infiltrate and cartilage erosion.

Conclusion

Physical exercise influences parameters intimately linked to inflammatory arthropathies. Research on the effect of PE on the pathogenesis process of arthritis is still necessary for animal and human models.Cite this article: Bone Joint Res. 2020;9(1):36-48.

Serum miR-21 expression correlates with radiographic progression but also low bone mineral density in patients with ankylosing spondylitis: a cross-sectional study

Increased expressions of miR-21 have been detected in ankylosing spondylitis (AS) patients. The current study was performed to examine the serum miR-21 expression with radiographic severity in AS patients, which was determined based on the modified New York (NY) criteria for sacroiliac joints assessment and modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) system for spine involvement. Bone mineral density at lumbar 1–4 and femoral neck were examined by dual-energy absorptiometry (DXA). Serum miR-21 expressions were determined by quantitative real-time PCR, and receiver operating characteristic curve analysis was performed to identify the diagnostic value of miR-21 expression levels regarding the NY criteria. Elevated levels of serum miR-21 expressions were detected in AS patients compared with healthy controls. AS patients with modified NY grade 4 showed significantly higher miR-21 expression than grade 3 and grade 2. AS patients with spinal syndesmophytes had significantly higher serum miR-21 expressions than non-syndesmophyte patients. Increased miR-21 expressions were significantly related to the disease radiographic severity. In addition, serum miR-21 expressions were negatively associated with lumbar 1–4 and femoral neck bone mineral density. In summary, serum miR-21 expressions were related to structural damage and radiological progression in AS, indicating that miR-21 may act as a switch between inflammation and new bone information and regulate different signal ways between lesioned enthesis and trabecular bone.

The Effect of TNF Inhibition on Bone Density and Fracture Risk and of IL17 Inhibition on Radiographic Progression and Bone Density in Patients with Axial Spondyloarthritis: a Systematic Literature Review

PURPOSE OF REVIEW

Osteoporosis in axial spondyloarthritis may be modified by therapy. The purpose of this systematic review is to describe (i) the effect of TNFi on BMD, (ii) the effect of secukinumab on BMD, and (iii) the effect of secukinumab on radiographic disease progression in axSpA.

RECENT FINDINGS

We searched PubMed, Embase, and Cochrane using the following retrieval languages: spondyloarthritis, ankylosing spondylitis, TNF, IL-17, x-rays, and osteoporosis. Twenty-nine studies were included; 27 re: TNFi and BMD, and 2 re: IL-17 blockers and x-ray progression. TNFi over 2-4 years increased BMD of the lumbar spine (3.2-14.9%) and hip (2.26-4.7%) without reducing vertebral fractures. Secukinumab reduced radiographic progression; none (73%) and minimal (79%) at 4 years. No data on IL-17 blockade and bone were found. TNFi therapy improves bone density but not vertebral fracture rates. Secukinumab improves symptoms and may slow radiographic progression. Data is lacking regarding the effects of secukinumab on BMD and fractures. These are important questions which may impact the choice of therapy.

The role of ERAP1 in autoinflammation and autoimmunity

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

Regulatory role of capsaicin-sensitive peptidergic sensory nerves in the proteoglycan-induced autoimmune arthritis model of the mouse

Objective

The regulatory role of capsaicin-sensitive peptidergic sensory nerves has been shown in acute inflammation, but little is known about their involvement in T/B-cell driven autoimmune arthritis. This study integratively characterized the function of these nerve endings in the proteoglycan-induced chronic arthritis (PGIA), a translational model of rheumatoid arthritis.

Methods

Peptidergic afferents were defunctionalized by resiniferatoxin (RTX) pretreatment in BALB/c mice, PGIA was induced by repeated antigen challenges. Hind paw volume, arthritis severity, grasping ability and the mechanonociceptive threshold were monitored during the 17-week experiment. Myeloperoxidase activity, vascular leakage and bone turnover were evaluated by in vivo optical imaging. Bone morphology was assessed using micro-CT, the intertarsal small joints were processed for histopathological analysis.

Results

Following desensitization of the capsaicin-sensitive afferents, ankle edema, arthritis severity and mechanical hyperalgesia were markedly diminished. Myeloperoxidase activity was lower in the early, but increased in the late phase, whilst plasma leakage and bone turnover were not altered. Desensitized mice displayed similar bone spurs and erosions, but increased trabecular thickness of the tibia and bony ankylosis of the spine. Intertarsal cartilage thickness was not altered in the model, but desensitization increased this parameter in both the non-arthritic and arthritic groups.

Conclusion

This is the first integrative in vivo functional and morphological characterization of the PGIA mouse model, wherein peptidergic afferents have an important regulatory function. Their overall effect is proinflammatory by increasing acute inflammation, immune cell activity and pain. Meanwhile, their activation decreases spinal ankylosis, arthritis-induced altered trabecularity, and cartilage thickness in small joints.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1364-5) contains supplementary material, which is available to authorized users.

Regulation of osteoblasts by alkaline phosphatase in ankylosing spondylitis

AIM

Ankylosing spondylitis (AS) is characterized by excessive spinal ankylosis and bone formation. Alkaline phosphatase (ALP) activity is reported to be high in AS, but little is known about the molecular relationship between ALP and AS. The aims of this study were to investigate the relevance of ALP to AS and the role of ALP in the regulation of osteoblast differentiation in AS.

METHODS

High-throughput data with accession numbers GSE73754 and GSE41038 were downloaded from the Gene Expression Omnibus. We retrospectively collected and compared the ALP levels of male patients with AS to those of sex- and age-matched healthy controls (HC) and rheumatoid arthritis (RA) patients. Total serum ALP and ALP activity were measured in the AS and RA groups. ALP gene expression and intracellular ALP activity were analyzed in microarray data from primary diseases control (Ct) and AS-bone-derived cells (BdCs) and in vitro experiments. Furthermore, the effect of ALP inhibitor was examined in both primary Ct- and AS-BdCs under osteoblast differentiation. Regulation of runt-related transcription factor 2 (RUNX2) by ALP was also analyzed.

RESULTS

Alkaline phosphatase level was higher in AS compared with RA and HC and was associated with radiograph progression. ALP expression was also enriched in the bone tissue of AS patients. Furthermore, AS-BdCs exhibited increasing ALP activity, leading to accelerated osteoblastic activity and differentiation. Intriguingly, inhibition of ALP reduced RUNX2 expression, a master transcriptional factor in osteoblasts, and differentiation status of both primary Ct- and AS-BdCs. Treatment of ALP activator or inhibitor modulated RUNX2 protein level and RUNX2 regulated ALP promoter activity, indicating a reciprocal ALP-RUNX2 positive feedback to regulate osteoblast differentiation.

CONCLUSION

Alkaline phosphatase was highly expressed in AS patients, may be involved in the ankylosis of AS, and represents a possible therapeutic target for ankylosis.

Inflammation Intensity-Dependent Expression of Osteoinductive Wnt Proteins Is Critical for Ectopic New Bone Formation in Ankylosing Spondylitis

OBJECTIVE

To investigate the molecular mechanism underlying inflammation-related ectopic new bone formation in ankylosing spondylitis (AS).

METHODS

Spinal tissues and sera were collected from patients with AS and healthy volunteers and examined for the expression of Wnt proteins. An in vitro cell culture system mimicking the local inflammatory microenvironment of bone-forming sites was established to study the relationship between inflammation and Wnt expression, the regulatory mechanism of inflammation-induced Wnt expression, and the role of Wnt signaling in new bone formation. Modified collagen-induced arthritis (CIA) and proteoglycan-induced spondylitis (PGIS) animal models were used to confirm the key findings in vivo.

RESULTS

The levels of osteoinductive Wnt proteins were increased in sera and spinal ligament tissues from patients with AS. Constitutive low-intensity tumor necrosis factor (TNF) stimulation, but not short-term or high-intensity TNF stimulation, induced persistent expression of osteoinductive Wnt proteins and subsequent bone formation through NF-κB (p65) and JNK/activator protein 1 (c-Jun) signaling pathways. Furthermore, inhibition of either the Wnt/β-catenin or Wnt/protein kinase Cδ (PKCδ) pathway significantly suppressed new bone formation. The increased expression of Wnt proteins was confirmed in both the modified CIA and PGIS models. A kyphotic and ankylosing phenotype of the spine was seen during long-term observation in the modified CIA model. Inhibition of either the Wnt/β-catenin or Wnt/PKCδ signaling pathway significantly reduced the incidence and severity of this phenotype.

CONCLUSION

Inflammation intensity-dependent expression of osteoinductive Wnt proteins is a key link between inflammation and ectopic new bone formation in AS. Activation of both the canonical Wnt/β-catenin and noncanonical Wnt/PKCδ pathways is required for inflammation-induced new bone formation.

Cisplatin chemotherapy impairs the peri-implant bone repair around titanium implants: An in vivo study in rats

AIM

The purpose of this study in animals was to evaluate the peri-implant bone repair against systemic administration of the antineoplastic agent.

MATERIAL AND METHODS

We used 84 male rats (Rattus norvegicus, albinus, Wistar), divided into two groups: cisplatin (CIS) and saline solution (SS). The titanium implants were inserted into the right tibia at day 0 in all animals from both groups. Group SS received SS intraperitoneally at 15 and 17 days postoperatively. Group CIS received 5 and 2.5 mg/kg of CIS intraperitoneally at 15 and 17 days postoperatively, respectively. Euthanasia was performed at 22, 30 and 60 days postoperatively. Twenty-four undecalcified specimens were prepared for histometric analysis of bone/implant contact (BIC). Sixty specimens were selected to bone area (BA) measurement, histological analysis and immunohistochemical analysis of RUNX-2, osteocalcin (OCN) and tartrate-resistant acid phosphatase (TRAP). BIC and BA were considered to be the primary outcome parameters.

RESULTS

Group CIS showed lower BIC (11.87 ± 0.97 mm; 19.19 ± 0.8 mm; 17.69 ± 1.05 mm; p ≤ .05) and BA (3.68 ± 1.29 mm² ; 3.05 ± 0.88 mm² ; 3.23 ± 0.67 mm² ; p ≤ .05), as well as decreased number of RUNX-2 (102.8 ± 27.35 cells/mm² ; 100.04 ± 8.61 cells/mm² ; 118.82 ± 21.38 cells/mm² ; p ≤ .05)- and OCN-positive cells (120 ± 24.5 cells/mm² ; 102 ± 27.73 cells/mm² ; 100 ± 14.23 cells/mm² ; p ≤ .05) at 22, 30 and 60 days, respectively. The animals in group CIS also showed increased number of TRAP-positive cells (86.8 ± 6.37 cells/mm² ; 71.5 ± 4.72 cells/mm² ; 92.8 ± 9.52 cells/mm² ; p ≤ .05) and a persistent and exacerbated inflammatory response in all experimental periods.

CONCLUSION

Within the limits of this study, it was concluded that the chemotherapeutic CIS negatively affects the bone repair at peri-implant areas, jeopardizing the osseointegration of titanium implants.

[Ankylosing spondylitis and non-radiographic axial spondyloarthritis: Two stages of disease?]

AIM

To compare the clinical manifestations of ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nrAxSpA).

SUBJECTS AND METHODS

A Moscow early spondyloarthritis cohort has now included 132 patients with axial spondyloarthritis, of whom 69 patients who have been followed up at least 12 months are to be involved in a preliminary analysis. The mean age at the time of inclusion in the study was 28.1±5.5 years; the mean disease duration was 24.7±15.8 months; 63 (91.3%) patients were HLA-B27 positive; 41 and 28 included patients were diagnosed with AS and nrAxSpA, respectively.

RESULTS

Men were significantly more in the AS group than in the nrAxSpA group (58.5 and 32.1%, respectively; p=0.05). The patients of the two groups did not differ in main clinical parameters (the presence of arthritis and enthesitis), disease activity (BASDAI, ASDAS-CRP) and functional status (BASFI). All indicators of inflammatory activity decreased nearly 2-fold in both groups after 12 months of follow up. In 7 (25%) patients with nrAxSpA, radiologically detectable sacroiliitis (SI) developed over 12 months and the diagnosis of AS was verified. Among them, 2 (28.5%) patients had initially active SI detected by magnetic resonance imaging (MRI); 4 (57.1%) had chronic SI, and 1 (14.4%) had no pathological MRI changes.

CONCLUSION

Due to the fact that the clinical manifestations of AS and nrAxSpA are comparable, it can be assumed that the latter is an early stage of AS.

Targeting the interleukin-23/17 axis in axial spondyloarthritis

PURPOSE OF REVIEW

This article highlights and emphasizes how new knowledge of mechanisms linked to the interleukin-23 (IL-23)/IL-17 pathway is relevant to the pathophysiology of axial spondyloarthritis (axSpA) and demonstrates how molecules in IL-23/IL-17 pathway provide novel therapeutic targets for axSpA patients.

RECENT FINDINGS

Similarly to ankylosing spondylitis (AS), the increased frequency of Th17 cells in nr-axSpA patients underscores the concept that these disorders can be viewed on a spectrum. Recent findings suggest that the contribution of IL-23/IL-17 signaling pathways possibly differs in male and female AS patients. The finding that IL-17 and IL-22 secreting-type 3 innate lymphoid cells are increased in AS patients point to their potential role in the pathogenesis of axSpA. Reports of dysbiosis in the gut microbiome of AS patients support previous work indicating a possible causal relationship between altered gut flora, ileocolonic inflammation and axSpA. Of important clinical relevance are results from clinical trials supporting the efficacy and safety of agents that block IL-12/23 (ustekinumab) and IL-17 (secukinumab and ixekizumab) in AS patients.

SUMMARY

Recent studies further establish the central position of the IL-23/IL-17 pathway in the pathogenesis of axSpA. Targeting the IL-23/IL-17 pathway appears to be a safe and effective strategy for treatment of axSpA patients.

Early anti-inflammatory intervention ameliorates axial disease in the proteoglycan-induced spondylitis mouse model of ankylosing spondylitis

Background

Ankylosing spondylitis (AS) is characterised by immune-mediated arthritis and osteoproliferation, ultimately leading to joint ankylosis. Whether inflammation is necessary for osteoproliferation is controversial, fuelled by the unclear efficacy of anti-inflammatory treatments on radiographic progression. In proteoglycan-induced spondylitis (PGISp), a mouse model of AS, inflammation is the prerequisite for osteoproliferation as osteoproliferation was only observed following inflammation-driven intervertebral disc (IVD) destruction. We hypothesised that early intervention with a potent anti-inflammatory therapy would protect IVD integrity and consequently alter disease progression.

Methods

PGISp mice received vehicle or a combination of etanercept (ETN) plus prednisolone (PRD) therapy for 2 or 6 weeks initiated at an early disease stage. Peripheral arthritis was scored longitudinally. Spinal disease was assessed using a semi-quantitative histological scoring regimen including inflammation, joint destruction and excessive tissue formation.

Results

ETN + PRD therapy significantly delayed the onset of peripheral arthritis. IVD integrity was significantly protected when treatment was commenced in early disease. Six-weeks of treatment resulted in trends towards reductions in intervertebral joint damage and excessive tissue formation. IVD score distribution was dichotomized, likely reflecting the extent of axial disease at initiation of therapy. In the sub-group of mice with high IVD destruction scores, ETN + PRD treatment significantly reduced IVD destruction severity, inflammation and bone erosion and reduced cartilage damage and excessive tissue formation.

Conclusions

Early intervention with anti-inflammatory treatment not only improved inflammatory symptoms but also ameliorated structural damage of spine in PGISp mice. This preclinical observation suggests that early anti-inflammatory intervention may slow radiographic progression in AS patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1600-7) contains supplementary material, which is available to authorized users.