Infiltration of the synovial membrane with macrophage subsets and polymorphonuclear cells reflects global disease activity in spondyloarthropathy

HIF-1α and MIF enhance neutrophil-driven type 3 immunity and chondrogenesis in a murine spondyloarthritis model

The hallmarks of spondyloarthritis (SpA) are type 3 immunity-driven inflammation and new bone formation (NBF). Macrophage migration inhibitory factor (MIF) was found to be a key driver of the pathogenesis of SpA by amplifying type 3 immunity, yet MIF-interacting molecules and networks remain elusive. Herein, we identified hypoxia-inducible factor-1 alpha (HIF1A) as an interacting partner molecule of MIF that drives SpA pathologies, including inflammation and NBF. HIF1A expression was increased in the joint tissues and synovial fluid of SpA patients and curdlan-injected SKG (curdlan-SKG) mice compared to the respective controls. Under hypoxic conditions in which HIF1A was stabilized, human and mouse neutrophils exhibited substantially increased expression of MIF and IL-23, an upstream type 3 immunity-related cytokine. Similar to MIF, systemic overexpression of IL-23 induced SpA pathology in SKG mice, while the injection of a HIF1A-selective inhibitor (PX-478) into curdlan-SKG mice prevented or attenuated SpA pathology, as indicated by a marked reduction in the expression of MIF and IL-23. Furthermore, genetic deletion of MIF or HIF1A inhibition with PX-478 in IL-23-overexpressing SKG mice did not induce evident arthritis or NBF, despite the presence of psoriasis-like dermatitis and blepharitis. We also found that MIF- and IL-23-expressing neutrophils infiltrated areas of the NBF in curdlan-SKG mice. These neutrophils potentially increased chondrogenesis and cell proliferation via the upregulation of STAT3 in periosteal cells and ligamental cells during endochondral ossification. Together, these results provide supporting evidence for an MIF/HIF1A regulatory network, and inhibition of HIF1A may be a novel therapeutic approach for SpA by suppressing type 3 immunity-mediated inflammation and NBF.

Identification of autoantibodies against PsoP27 in synovial fluid derived from psoriatic arthritis and rheumatoid arthritis patients

PsoP27 is an antigen expressed in psoriatic lesions. It plays an inflammatory role in psoriasis. This study objective was to characterize antibodies (Abs) against PsoP27 in patients with psoriatic arthritis (PsA) and rheumatoid arthritis (RA). Levels of Abs against native and citrullinated PsoP27 in PsA and RA patients' synovial fluid (SF) and sera were determined by ELISA. SF of osteoarthritis (OA) patients and sera of healthy donors were used as controls. Levels of Abs against PsoP27 were correlated with disease activity scores. Abs against native and citrullinated PsoP27 levels in SF of PsA (n = 48; 0.38 ± 0.03 and 0.44 ± 0.04, respectively) and RA (n = 22; 0.57 ± 0.1 and 0.62 ± 0.09, respectively) were significantly higher than in OA patients (n = 23; 0.14 ± 0.01 and 0.15 ± 0.01, respectively) (p < .0001). For both Abs, there were no significant differences between their level in PsA and RA patients. There was no difference in the level of Abs against citrullinated PsoP27 in SF of seronegative versus seropositive RA patients. Levels of Abs against both native and citrullinated PsoP27 in the SF and level of systemic C-reactive protein in PsA correlated positively, while in RA there were no significant correlations with disease activity scores. No differences in level of Abs against PsoP27 were found in the sera of all three study groups. Abs against native and citrullinated PsoP27 are present in PsA and RA SF but not in those of OA patients, suggesting a potential role of those Abs in inflammatory joint diseases.

Synovial biopsies for molecular definition of rheumatoid arthritis and treatment response phenotyping: where can we improve?

INTRODUCTION

The extensive knowledge gained in the cellular and molecular mechanisms underlying Rheumatoid Arthritis (RA) pathogenesis has led to therapeutic advances. However, up to 10-20% of patients fail to respond to multiple therapeutic agents being classified as multi-drugresistant. A key challenge moving forward will be the implementation of synovial biopsies in clinical practice to facilitate the shift from the current trial-and-error strategy toward new forms of clinical trials. Biomarker-driven trials have the potential to improve drug selection and patient stratification, reduce economic costs and unnecessary drug-related toxicity.

AREAS COVERED

This special report explores the clinical and research applications of synovial biopsy, the advancement in the molecular pathobiology of RA to better understand disease pathogenesis and treatment response, and the way forward for the paradigm shift needed.

EXPERT OPINION

In the current era of highly targeted biologic drugs which have dramatically transformed the outlook of RA patients, the use of synovial biopsy represents a valuable practical tool to dissect disease pathogenesis and, consequently, treatment response. In the near future, it is hoped that technological advances will allow for speeding up synovial molecular analysis and that the design of new biomarker-driven trials will enable the allocation of patients to more effective treatment.

Investigating the role of "Immature Myeloid Cells" as Drivers of Inflammation and Disease Persistence in Psoriatic Arthritis

Background

Despite the development of treatments targeting T cell co-stimulation and cytokines TNF, IL-12/23, and IL-17, less than half of patients within clinical trials achieve high levels of clinical response. This fact, as well as the absence of prognostic biomarkers represents major unmet clinical needs that necessitate further investigation of the disease pathophysiology. Myeloid cells are critical components of PsA inflammatory mechanisms, being a highly prevalent immune population in biopsies of PsA target tissues, such as the skin and the synovium. Through their antigen-presenting capacity and their pro-angiogenic and pro-inflammatory properties myeloid cells could contribute to persistent inflammation in PsA leading to treatment-resistant disease. To this end, we have recently shown the expansion of monocytes in the blood of PsA patients compared to healthy subjects. Importantly, we have also identified an immature myeloid cell population in patients with highly active, refractory disease, indicating the presence of an "emergency myelopoiesis" process in PsA.

Aim of the study

In this research protocol, we aim to decipher the pro-inflammatory "myeloid signature" in patients with active PsA and explore the role of immature myeloid cells in disease pathophysiology and their potential as prognostic biomarkers.

Methods

To address this, we will isolate and analyse monocytes and immature myeloid cells from PsA patients -before and after a 6-month treatment course- focusing on differences between responders and non-responders. In this context, we will perform a thorough phenotypic and functional analysis of these cells, identify their expression signature in an already established whole blood RNA-seq dataset and investigate their presence in target tissues, such as the skin and synovial fluid.

Anticipated benefits

This study will elucidate the role of myeloid cells in disease propagation by further defining the involvement of immature myeloid cells in PsA.

Synovial monocytes contribute to chronic inflammation in childhood-onset arthritis via IL-6/STAT signalling and cell-cell interactions

Introduction

Monocytes are key effector cells in inflammatory processes. We and others have previously shown that synovial monocytes in childhood-onset arthritis are activated. However, very little is known about how they contribute to disease and attain their pathological features. Therefore, we set out to investigate the functional alterations of synovial monocytes in childhood-onset arthritis, how they acquire this phenotype, and whether these mechanisms could be used to tailorize treatment.

Methods

The function of synovial monocytes was analysed by assays believed to reflect key pathological events, such as T-cell activation-, efferocytosis- and cytokine production assays using flow cytometry in untreated oligoarticular juvenile idiopathic arthritis (oJIA) patients (n=33). The effect of synovial fluid on healthy monocytes was investigated through mass spectrometry and functional assays. To characterize pathways induced by synovial fluid, we utilized broad-spectrum phosphorylation assays and flow cytometry, as well as inhibitors to block specific pathways. Additional effects on monocytes were studied through co-cultures with fibroblast-like synoviocytes or migration in transwell systems.

Results

Synovial monocytes display functional alterations with inflammatory and regulatory features, e.g., increased ability to induce T-cell activation, resistance to cytokine production following activation with LPS and increased efferocytosis. In vitro, synovial fluid from patients induced the regulatory features in healthy monocytes, such as resistance to cytokine production and increased efferocytosis. IL-6/JAK/STAT signalling was identified as the main pathway induced by synovial fluid, which also was responsible for a majority of the induced features. The magnitude of synovial IL-6 driven activation in monocytes was reflected in circulating cytokine levels, reflecting two groups of low vs. high local and systemic inflammation. Remaining features, such as an increased ability to induce T-cell activation and markers of antigen presentation, could be induced by cell-cell interactions, specifically via co-culture with fibroblast-like synoviocytes.

Conclusions

Synovial monocytes in childhood-onset arthritis are functionally affected and contribute to chronic inflammation, e.g., via promoting adaptive immune responses. These data support a role of monocytes in the pathogenesis of oJIA and highlight a group of patients more likely to benefit from targeting the IL-6/JAK/STAT axis to restore synovial homeostasis.

The Role of Neutrophils in Spondyloarthritis: A Journey across the Spectrum of Disease Manifestations

Spondyloarthritis (SpA) contemplates the inflammatory involvement of the musculoskeletal system, gut, skin, and eyes, delineating heterogeneous diseases with a common pathogenetic background. In the framework of innate and adaptive immune disruption in SpA, neutrophils are arising, across different clinical domains, as pivotal cells crucial in orchestrating the pro-inflammatory response, both at systemic and tissue levels. It has been suggested they act as key players along multiple stages of disease trajectory fueling type 3 immunity, with a significant impact in the initiation and amplification of inflammation as well as in structural damage occurrence, typical of long-standing disease. The aim of our review is to focus on neutrophils' role within the spectrum of SpA, dissecting their functions and abnormalities in each of the relevant disease domains to understand their rising appeal as potential biomarkers and therapeutic targets.

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.

How Has Molecular Biology Enhanced Our Undertaking of axSpA and Its Management

PURPOSE

This review aims at investigating pathophysiological mechanisms in spondyloarthritis (SpA). Analysis of genetic factors, immunological pathways, and abnormalities of bone metabolism lay the foundations for a better understanding of development of the axial clinical manifestations in patients, allowing physician to choose the most appropriate therapeutic strategy in a more targeted manner.

RECENT FINDINGS

In addition to the contribution of MHC system, findings emerged about the role of non-HLA genes (as ERAP1 and 2, whose inhibition could represent a new therapeutic approach) and of epigenetic mechanisms that regulate the expression of genes involved in SpA pathogenesis. Increasing evidence of bone metabolism abnormalities secondary to the activation of immunological pathways suggests the development of various bone anomalies that are present in axSpA patients. SpA are a group of inflammatory diseases with a multifactorial origin, whose pathogenesis is linked to the genetic predisposition, the action of environmental risk factors, and the activation of immune response. It is now well known how bone metabolism leads to long-term structural damage via increased bone turnover, bone loss and osteoporosis, osteitis, erosions, osteosclerosis, and osteoproliferation. These effects can exist in the same patient over time or even simultaneously. Evidence suggests a cross relationship among innate immunity, autoimmunity, and bone remodeling in SpA, making treatment approach a challenge for rheumatologists. Specifically, treatment targets are consistently increasing as new drugs are upcoming. Both biological and targeted synthetic drugs are promising in terms of their efficacy and safety profile in patients affected by SpA.

Joint together: The etiology and pathogenesis of ankylosing spondylitis

Spondyloarthritis (SpA) refers to a group of diseases with inflammation in joints and spines. In this family, ankylosing spondylitis (AS) is a rare but classic form that mainly involves the spine and sacroiliac joint, leading to the loss of flexibility and fusion of the spine. Compared to other diseases in SpA, AS has a very distinct hereditary disposition and pattern of involvement, and several hypotheses about its etiopathogenesis have been proposed. In spite of significant advances made in Th17 dynamics and AS treatment, the underlying mechanism remains concealed. To this end, we covered several topics, including the nature of the immune response, the microenvironment in the articulation that is behind the disease's progression, and the split between the hypotheses and the evidence on how the intestine affects arthritis. In this review, we describe the current findings of AS and SpA, with the aim of providing an integrated view of the initiation of inflammation and the development of the disease.

An in vivo toxicity assessment of piezoelectric sodium potassium niobate [NaxK1-xNbO3 (x = 0.2-0.8)] nanoparticulates towards bone tissue engineering approach

One of the recent challenges in the design/development of prosthetic orthopedic implants is to address the concern of local/systemic toxicity of debris particles, released due to wear or degradation. Such debris particles often lead to inflammation at the implanted site or aseptic loosening of the prosthesis which results in failure of the implant during long run. Several in vitro studies demonstrated the potentiality of piezoelectric sodium potassium niobate [Na_xK_1-xNbO₃ (x = 0.2, 0.5, 0.8), NKN] as an emerging next-generation polarizable orthopedic implant. In this perspective, we performed an in vivo study to examine the local and systemic toxicity of NKN nanoparticulates, as a first report. In the present study, male Wistar rats were intra-articularly injected to the knee joint with 100 μl of NKN nanoparticulates (25 mg/ml in normal saline). After 7 days of exposure, the histopathological analyses demonstrate the absence of any inflammation or dissemination of nanoparticulates in vital organs such as heart, liver, kidney and spleen. The anti-inflammatory cytokines (IL-4 and IL-10) profile analyses suggest the increased anti-inflammatory response in the treated rats as compared to non-injected (control) rats, preferably for the sodium and potassium rich NKN i.e., Na_0.8K_0.2NbO₃ and Na_0.2K_0.8NbO₃. The biochemical analyses revealed no pathological changes in the liver and kidney of particulate treated rats. The present study is the first proof to confirm the non-toxic nature of NKN nanoparticulates which provides a step forward towards the development of prosthetic orthopedic implants using biocompatible piezoelectric NKN ceramics.

Role of macrophage-associated chemokines in the assessment of initial axial spondyloarthritis

OBJECTIVES

To identify biomarkers that reflect disease activity scores and to investigate the role of macrophage-associated chemokines in initial axial spondyloarthritis (axSpA).

METHOD

Patients with axSpA were enrolled. The SpondyloArthritis Research Consortium of Canada (SPARCC) method was used to score bone marrow oedema (BMO) in the inflammatory lesions on magnetic resonance imaging (MRI). Radiographic assessment of the spine was performed using the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). Clinical variables, including inflammatory markers, serum CC chemokine ligand 2 (CCL2), CCL3, CCL7, CCL8 and C-X3-C motif ligand 1 (CX3CL1), were measured. Correlation analysis between serum levels of these macrophage-associated chemokines and clinical data was performed.

RESULTS

There were no significant differences between the axSpA group and the healthy control group in terms of serum levels of CCL2, CCL3 or CCL8. Compared to the healthy control group, the serum levels of CCL7 and CX3CL1 were significantly higher in ankylosing spondylitis (AS) (p = 0.045, p = 0.017, respectively). In the AS subgroup, the serum level of CX3CL1 had a positive correlation with SPARCC scores.

CONCLUSIONS

In AS, serum CCL7 and CX3CL1 levels are elevated. The serum level of CX3CL1 is associated with MRI-determined oedema in AS. CX3CL1 may be useful as a biomarker to predict active inflammation in the sacroiliac joint (SIJ) in AS. Key Points • Serum levels of CX3CL1 are associated with MRI-determined oedema in AS. • CX3CL1 may be a useful biomarker to predict active inflammation in the sacroiliac joint in AS.

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.

Ex vivo mass cytometry analysis reveals a profound myeloid proinflammatory signature in psoriatic arthritis synovial fluid

OBJECTIVES

A number of immune populations have been implicated in psoriatic arthritis (PsA) pathogenesis. This study used mass cytometry (CyTOF) combined with transcriptomic analysis to generate a high-dimensional dataset of matched PsA synovial fluid (SF) and blood leucocytes, with the aim of identifying cytokine production ex vivo in unstimulated lymphoid and myeloid cells.

METHODS

Fresh SF and paired blood were either fixed or incubated with protein transport inhibitors for 6 hours. Samples were stained with two CyTOF panels: a phenotyping panel and an intracellular panel, including antibodies to both T cell and myeloid cell secreted proteins. Transcriptomic analysis by gene array of key expanded cell populations, single-cell RNA-seq, ELISA and LEGENDplex analysis of PsA SF were also performed.

RESULTS

We observed marked changes in the myeloid compartment of PsA SF relative to blood, with expansion of intermediate monocytes, macrophages and dendritic cell populations. Classical monocytes, intermediate monocytes and macrophages spontaneously produced significant levels of the proinflammatory mediators osteopontin and CCL2 in the absence of any in vitro stimulation. By contrast minimal spontaneous cytokine production by T cells was detected. Gene expression analysis showed the genes for osteopontin and CCL2 to be among those most highly upregulated by PsA monocytes/macrophages in SF; and both proteins were elevated in PsA SF.

CONCLUSIONS

Using multiomic analyses, we have generated a comprehensive cellular map of PsA SF and blood to reveal key expanded myeloid proinflammatory modules in PsA of potential pathogenic and therapeutic importance.

Influence of IL10 (rs1800896) Polymorphism and TNF-α, IL-10, IL-17A, and IL-17F Serum Levels in Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a chronic autoimmune inflammatory disease that mainly affects the axial and sacroiliac joints. Single-nucleotide polymorphisms (SNPs) in genes encoding cytokines have been associated with AS, which can interfere with the production of these cytokines and contribute to the development of AS. In order to contribute to a better understanding of the pathology of AS, our objective was to investigate a possible association of the IL10 −1082 A>G SNP (rs1800896) with AS and to evaluate the serum levels of TNF-α, IL-10, IL-17A, and IL-17F in AS patients and controls comparing them with their respective genotypes (TNF rs1800629, IL10 rs1800896, IL17A rs2275913, and IL17F rs763780). Patients and controls were selected from the Maringá University Hospital and the Maringá Rheumatism Clinic, in Paraná State, Southern Brazil, and they were diagnosed by the ASAS Criteria. In total, 149 patients and 169 controls were genotyped for the IL10 −1082 A>G polymorphism using a polymerase chain reaction with sequence specific primers (PCR-SSP); the measurement of TNF-α serum levels was performed through the immunofluorimetric test and IL-10, IL-17A, and IL-17F using an ELISA test. There was a high frequency of the IL10 −1082 G allele in AS patients compared with controls with an odds ratio of 1.83 and 95% confidence interval of 1.32 to 2.54, and a significant difference in the genotype frequencies of the IL10 −1082 A/G+G/G between patients and healthy controls, with an odds ratio of 3.01 and 95% confidence interval of 1.75 to 5.17. In addition, increased serum levels of IL-10 were observed in AS patients: 2.38 (IQR, 0.91) pg/ml compared with controls 1.72 (IQR 0.93) pg/ml (P = 0.01). Our results also showed an association between IL17F rs763780 C/T+T/T genotypes and increased serum levels of IL-17F in patients with AS and also in controls. We can conclude that patients with the A/G and G/G genotypes for −1082 A>G (rs1800896) in the IL10 gene are three times more likely to develop AS, that the serum level of IL-10 was higher in AS patients and that the IL17F rs763780 polymorphism can affect the levels of IL-17F in the serum of patients and controls in the same way.

Transmembrane TNF drives osteoproliferative joint inflammation reminiscent of human spondyloarthritis

TNF plays a key role in immune-mediated inflammatory diseases including rheumatoid arthritis (RA) and spondyloarthritis (SpA). It remains incompletely understood how TNF can lead to different disease phenotypes such as destructive peripheral polysynovitis in RA versus axial and peripheral osteoproliferative inflammation in SpA. We observed a marked increase of transmembrane (tm) versus soluble (s) TNF in SpA versus RA together with a decrease in the enzymatic activity of ADAM17. In contrast with the destructive polysynovitis observed in classical TNF overexpression models, mice overexpressing tmTNF developed axial and peripheral joint disease with synovitis, enthesitis, and osteitis. Histological and radiological assessment evidenced marked endochondral new bone formation leading to joint ankylosis over time. SpA-like inflammation, but not osteoproliferation, was dependent on TNF-receptor I and mediated by stromal tmTNF overexpression. Collectively, these data indicate that TNF can drive distinct inflammatory pathologies. We propose that tmTNF is responsible for the key pathological features of SpA.

IL-12p40/IL-23p40 Blockade With Ustekinumab Decreases the Synovial Inflammatory Infiltrate Through Modulation of Multiple Signaling Pathways Including MAPK-ERK and Wnt

Background: Psoriatic arthritis (PsA) is a chronic inflammatory joint disease within the spondyloarthritis spectrum. IL-12p40/IL-23p40 blockade reduces PsA disease activity, but its impact on synovial inflammation remains unclear. Objectives: To investigate the cellular and molecular pathways affected by IL-12p40/IL-23p40 blockade with ustekinumab in the synovium of PsA patients. Methods: Eleven PsA patients with at least one inflamed knee or ankle joint were included in a 24-week single-center open-label study and received ustekinumab 45 mg/sc according to standard care at week 0, 4, and 16. Besides clinical outcomes, synovial tissue (ST) samples were obtained by needle arthroscopy from an inflamed knee or ankle joint at baseline, week 12 and 24 and analyzed by immunohistochemistry, RNA-sequencing and real-time quantitative polymerase chain reaction (qPCR). Results: We obtained paired baseline and week 12, and paired baseline, week 12 and 24 ST samples from nine and six patients, respectively. Eight patients completed 24 weeks of clinical follow-up. At 12 weeks 6/11 patients met ACR20, 2/11 met ACR50 and 1/11 met ACR70 improvement criteria, at 24 weeks this was 3/8, 2/8 and 1/8 patients, respectively. Clinical and serological markers improved significantly. No serious adverse events occurred. We observed numerical decreases of all infiltrating cell subtypes at week 12, reaching statistical significance for CD68+ sublining macrophages. For some cell types this was even more pronounced at week 24, but clearly synovial inflammation was incompletely resolved. IL-17A and F, TNF, IL-6, IL-8, and IL-12p40 were not significantly downregulated in qPCR analysis of W12 total biopsies, only MMP3 and IL-23p19 were significantly decreased. RNA-seq analysis revealed 178 significantly differentially expressed genes between baseline and 12 weeks (FDR 0.1). Gene Ontology and KEGG terms enrichment analyses identified overrepresentation of biological processes as response to reactive oxygen species, chemotaxis, migration and angiogenesis as well as MAPK-ERK and PI3K-Akt signaling pathways among the downregulated genes and of Wnt signaling pathway among the upregulated genes. Furthermore, ACR20 responders and non-responders differed strikingly in gene expression profiles in a post-hoc exploratory analysis. Conclusions: Ustekinumab suppresses PsA synovial inflammation through modulation of multiple signal transduction pathways, including MAPK-ERK, Wnt and potentially PI3K-Akt signaling rather than by directly impacting the IL-17 pathway.

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

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

GM-CSF Expression and Macrophage Polarization in Joints of Undifferentiated Arthritis Patients Evolving to Rheumatoid Arthritis or Psoriatic Arthritis

Background and Aims

GM-CSF-dependent macrophage polarization has been demonstrated in rheumatoid arthritis (RA). Our aim was to seek diagnostic/prognostic biomarkers for undifferentiated arthritis (UA) by analyzing GM-CSF expression and source, macrophage polarization and density in joints of patients with UA evolving to RA or PsA compared with established RA or PsA, respectively.

Methods

Synovial tissue (ST) from patients with UA evolving to RA (UA>RA, n=8), PsA (UA>PsA, n=9), persistent UA (UA, n=16), established RA (n=12) and PsA (n=10), and healthy controls (n=6), were analyzed. Cell source and quantitative expression of GM-CSF and proteins associated with pro-inflammatory (GM-CSF-driven) and anti-inflammatory (M-CSF-driven) macrophage polarization (activin A, TNFα, MMP12, and CD209, respectively) were assessed in ST CD163⁺ macrophages by multicolor immunofluorescence. GM-CSF and activin A levels were also quantified in paired synovial fluid samples. CD163⁺ macrophage density was determined in all groups by immunofluorescence.

Results

Synovial stromal cells (FAP⁺ CD90⁺ fibroblast, CD90⁺ endothelial cells) and CD163⁺ sublining macrophages were the sources of GM-CSF. ST CD163⁺ macrophages from all groups expressed pro-inflammatory polarization markers (activin A, TNFα, and MMP12). Expression of the M-CSF-dependent anti-inflammatory marker CD209 identified two macrophage subsets (CD163⁺ CD209^high and CD163⁺ CD209^low/-). CD209⁺ macrophages were more abundant in ST from healthy controls and PsA patients, although both macrophage subtypes showed similar levels of pro-inflammatory markers in all groups. In paired synovial fluid samples, activin A was detected in all patients, with higher levels in UA>RA and RA, while GM-CSF was infrequently detected. ST CD163⁺ macrophage density was comparable between UA>RA and UA>PsA patients, but significantly higher than in persistent UA.

Conclusions

GM-CSF is highly expressed by sublining CD90⁺ FAP⁺ synovial fibroblasts, CD90⁺ activated endothelium and CD163⁺ macrophages in different types of arthritis. The polarization state of ST macrophages was similar in all UA and established arthritis groups, with a predominance of pro-inflammatory GM-CSF-associated markers. CD163⁺ macrophage density was significantly higher in the UA phases of RA and PsA compared with persistent UA. Taken together, our findings support the idea that GM-CSF is a strong driver of macrophage polarization and a potential therapeutic target not only in RA but also in PsA and all types of UA.

Evaluation of contrast-enhanced ultrasound for activity of rheumatoid arthritis: A protocol for systematic review and meta-analysis

BACKGROUND

Contrast-enhanced ultrasound (CEUS) refers to a technique that uses contrast medium to strengthen the echo of backscatter, which can significantly improve the resolution, sensitivity and specificity of ultrasound diagnosis. As a quantitative imaging examination of blood flow signals, CEUS has allowed detection of synovial microvascularization in the joints of patients with rheumatoid arthritis (RA). However, the results of these studies have been contradictory. Therefore, the purpose of this study is to evaluate the value of CEUS in the activity of RA disease.

METHODS

We will search PubMed, Embase, Cochrane Library, and CNKI from their inception to the December 20, 2020, without restrictions of language and publication status. Two investigators will independently carry out searching literature records, scanning titles and abstracts, full texts, collecting data, and assessing risk of bias. This study will only include high quality clinical cohort or case control studies. Statistical analysis was performed by using the Review Manager version 5.3 and the STATA version 14.0 (Stata Corp, College Station, TX, USA) softwares.

RESULTS

This systematic review will determine the value of CEUS in RA activity scores.

CONCLUSION

The results of this study will provide a useful basis for high-quality CEUS to evaluate RA activity score.

SYSTEMATIC REVIEW REGISTRATION

INPLASY2020120125.

Targeting of CD163+ Macrophages in Inflammatory and Malignant Diseases

The macrophage is a key cell in the pro- and anti-inflammatory response including that of the inflammatory microenvironment of malignant tumors. Much current drug development in chronic inflammatory diseases and cancer therefore focuses on the macrophage as a target for immunotherapy. However, this strategy is complicated by the pleiotropic phenotype of the macrophage that is highly responsive to its microenvironment. The plasticity leads to numerous types of macrophages with rather different and, to some extent, opposing functionalities, as evident by the existence of macrophages with either stimulating or down-regulating effect on inflammation and tumor growth. The phenotypes are characterized by different surface markers and the present review describes recent progress in drug-targeting of the surface marker CD163 expressed in a subpopulation of macrophages. CD163 is an abundant endocytic receptor for multiple ligands, quantitatively important being the haptoglobin-hemoglobin complex. The microenvironment of inflammation and tumorigenesis is particular rich in CD163+ macrophages. The use of antibodies for directing anti-inflammatory (e.g., glucocorticoids) or tumoricidal (e.g., doxorubicin) drugs to CD163+ macrophages in animal models of inflammation and cancer has demonstrated a high efficacy of the conjugate drugs. This macrophage-targeting approach has a low toxicity profile that may highly improve the therapeutic window of many current drugs and drug candidates.

Hydrogen Sulfide as Potential Regulatory Gasotransmitter in Arthritic Diseases

The social and economic impact of chronic inflammatory diseases, such as arthritis, explains the growing interest of the research in this field. The antioxidant and anti-inflammatory properties of the endogenous gasotransmitter hydrogen sulfide (H₂S) were recently demonstrated in the context of different inflammatory diseases. In particular, H₂S is able to suppress the production of pro-inflammatory mediations by lymphocytes and innate immunity cells. Considering these biological effects of H₂S, a potential role in the treatment of inflammatory arthritis, such as rheumatoid arthritis (RA), can be postulated. However, despite the growing interest in H₂S, more evidence is needed to understand the pathophysiology and the potential of H₂S as a therapeutic agent. Within this review, we provide an overview on H₂S biological effects, on its role in immune-mediated inflammatory diseases, on H₂S releasing drugs, and on systems of tissue repair and regeneration that are currently under investigation for potential therapeutic applications in arthritic diseases.

Promotion of macrophage activation by Tie2 in the context of the inflamed synovia of rheumatoid arthritis and psoriatic arthritis patients

OBJECTIVE

To examine the role of Tie2 signalling in macrophage activation within the context of the inflammatory synovial microenvironment present in patients with RA and PsA.

METHODS

Clinical responses and macrophage function were examined in wild-type and Tie2-overexpressing (Tie2-TG) mice in the K/BxN serum transfer model of arthritis. Macrophages derived from peripheral blood monocytes from healthy donors, RA and PsA patients, and RA and PsA synovial tissue explants were stimulated with TNF (10 ng/ml), angiopoietin (Ang)-1 or Ang-2 (200 ng/ml), or incubated with an anti-Ang2 neutralizing antibody. mRNA and protein expression of inflammatory mediators was analysed by quantitative PCR, ELISA and Luminex.

RESULTS

Tie2-TG mice displayed more clinically severe arthritis than wild-type mice, accompanied by enhanced joint expression of IL6, IL12B, NOS2, CCL2 and CXCL10, and activation of bone marrow-derived macrophages in response to Ang-2 stimulation. Ang-1 and Ang-2 significantly enhanced TNF-induced expression of pro-inflammatory cytokines and chemokines in macrophages from healthy donors differentiated with RA and PsA SF and peripheral blood-derived macrophages from RA and PsA patients. Both Ang-1 and Ang-2 induced the production of IL-6, IL-12p40, IL-8 and CCL-3 in synovial tissue explants of RA and PsA patients, and Ang-2 neutralization suppressed the production of IL-6 and IL-8 in the synovial tissue of RA patients.

CONCLUSION

Tie2 signalling enhances TNF-dependent activation of macrophages within the context of ongoing synovial inflammation in RA and PsA, and neutralization of Tie2 ligands might be a promising therapeutic target in the treatment of these diseases.

Deregulation of microRNA expression in monocytes and CD4+ T lymphocytes from patients with axial spondyloarthritis

Background

MicroRNAs (MiRs) play an important role in the pathogenesis of chronic inflammatory diseases. This study is the first to investigate miR expression profiles in purified CD4⁺ T lymphocytes and CD14⁺ monocytes from patients with axial spondyloarthritis (axSpA) using a high-throughput qPCR approach.

Methods

A total of 81 axSpA patients fulfilling the 2009 ASAS classification criteria, and 55 controls were recruited from October 2014 to July 2017. CD14⁺ monocytes and CD4⁺ T lymphocytes were isolated from peripheral blood mononuclear cells. MiR expression was investigated by qPCR using the Exiqon Human MiRnome panel I analyzing 372 miRNAs. Differentially expressed miRNAs identified in the discovery cohort were validated in the replication cohort.

Results

We found a major difference in miR expression patterns between T lymphocytes and monocytes regardless of the patient or control status. Comparing disease-specific differentially expressed miRs, 13 miRs were found consistently deregulated in CD14⁺ cells in both cohorts with miR-361-3p, miR-223-3p, miR-484, and miR-16-5p being the most differentially expressed. In CD4⁺ T cells, 11 miRs were differentially expressed between patients and controls with miR-16-1-3p, miR-28-5p, miR-199a-5p, and miR-126-3p were the most strongly upregulated miRs among patients. These miRs are involved in disease relevant pathways such as inflammation, intestinal permeability or bone formation. Mir-146a-5p levels correlated inversely with the degree of inflammation in axSpA patients.

Conclusions

We demonstrate a consistent deregulation of miRs in both monocytes and CD4⁺ T cells from axSpA patients, which could contribute to the pathophysiology of the disease with potential interest from a therapeutic perspective.

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1829-7) contains supplementary material, which is available to authorized users.

Psoriatic Synovitis: Singularity and Potential Clinical Implications

Psoriatic arthritis (PsA) is an immuno-inflammatory disease with a heterogeneous clinical presentation as affects musculoskeletal tissues (arthritis, enthesitis, spondylitis), skin (psoriasis) and, less frequently, eye (uveitis) and bowel (inflammatory bowel disease). It has been suggested that distinct affected tissues could exhibit different immune-inflammatory pathways so complicating the understanding of the physiopathology of psoriatic disease as well as its treatment. Despite of the key pathogenic and clinical relevance that enthesitis has in PsA, peripheral arthritis is more easily perceived. At the macroscopic level, PsA synovitis has predominantly tortuous, bushy vessels, whereas rheumatoid arthritis (RA) is characterized by mainly straight, branching vessels so reflecting prominent neo-angiogenesis in PsA. Synovial biopsies have demonstrated a similar cellular and molecular picture in PsA and RA, although some differences have been reported at the group level, as higher density of vessels, CD163+ macrophages, neutrophils and mast cells in PsA. In fact, synovial IL-17+ mast cells are significantly increased in PsA and produce more IL-17A compared with RA, and a proof of concept study supports its relevant role in the synovitis of SpA, included PsA. As firstly reported in RA, synovial lymphoid neogenesis is found also in the same proportion of PsA as in RA patients, despite the lack of autoantibodies in PsA. These lymphoid structures are associated with activation of the IL-23/Th17 pathway in RA and seemly in PsA, which could be useful to stratify RA patients. Immunohistochemical and transcriptomic methodologies have still not found synovial biomarkers useful to distinguish psoriatic from rheumatoid synovitis at the patient level. However, modern methodologies, as MALDI-Mass Spectrometry Imaging, applied to the study of synovial tissue have revealed metabolic and lipid signatures which could support clinical decision-making in the diagnosis of PsA and RA and to go further toward the personalized medicine.

Brief Report: Interleukin-17 Blockade With Secukinumab in Peripheral Spondyloarthritis Impacts Synovial Immunopathology Without Compromising Systemic Immune Responses

OBJECTIVE

Secukinumab (anti-interleukin-17A [anti-IL-17A]) is an effective therapy for ankylosing spondylitis and psoriatic arthritis, the prototypical forms of spondyloarthritis (SpA). We undertook this study to determine whether secukinumab modulates the immunopathology of target lesions without blunting systemic immune responses, using peripheral SpA as a model.

METHODS

Twenty patients with active peripheral SpA were included in a 12-week open-label trial with secukinumab (300 mg once weekly from baseline to week 4 and then every 4 weeks thereafter). Outcomes included clinical response, cytokine production by peripheral blood cells using TruCulture technology, and histologic and real-time quantitative polymerase chain reaction analysis of synovial biopsy samples before and after treatment.

RESULTS

All patients completed the 12-week study without severe adverse events (AEs) or severe treatment-related AEs. The efficacy end point, the number of patients meeting the American College of Rheumatology 20% improvement criteria (achieving an ACR20 response) at 12 weeks, was achieved by 13 of the 20 patients, of whom 8 achieved an ACR50 response and 5 achieved an ACR70 response, with rapid and significant improvements in all clinical disease activity measures. Clinical improvement in joint counts was associated with a histologic decrease in synovial sublining macrophages (P = 0.028) and neutrophils (P = 0.004), both of which are sensitive synovial biomarkers of inflammatory response in peripheral SpA, as well as with decreased synovial expression of IL-17A messenger RNA (mRNA) (P = 0.010) but not of tumor necrosis factor mRNA. Systemically, secukinumab treatment decreased the C-reactive protein level and the erythrocyte sedimentation rate (both P < 0.01), and also decreased matrix metalloproteinase 3 production in the TruCulture system (P < 0.05). However, with the exception of IL-17A itself, the capacity of peripheral blood cells to produce a broad panel of cytokines and chemokines upon stimulation with microbial antigens was not affected.

CONCLUSION

This mechanism-of-action study in peripheral SpA indicates that clinical improvement with secukinumab treatment is paralleled by immunomodulation of inflamed target tissues without compromising systemic immune responses.

The pathogenesis of psoriatic arthritis

Psoriatic arthritis is a chronic, immune-mediated, inflammatory arthropathy that presents with inflammation of the joints and entheses, including those of the axial skeleton, and is associated with increased mortality from cardiovascular disease. Diagnosis is primarily based on clinical phenotype because of the diversity of the associated features, which can include skin and nail disease, dactylitis, uveitis, and osteitis. Improved understanding of the pathogenesis of psoriatic arthritis has led to the development of effective biologics and small-molecular drugs targeting specific cytokines and signalling pathways, which can prevent disease progression and improve quality of life. However, at least 40% of patients with psoriatic arthritis have only a partial response or fail to respond to such treatments. Cytokine inhibitors, mainly those specific for tumour necrosis factor and, more recently, the interleukin 23-T-helper-17 cell pathway, have been highly successful in the treatment of disease manifestations in several different tissues, although targeting the interleukin 23-T-helper-17 cell pathway might be more effective in psoriasis than in arthritis. However, the precise mechanisms underlying the pathogenesis of psoriatic arthritis-which include genetics, environmental factors, and immune-mediated inflammation-are complex, and the relationship between disease of the joint and that of other domains is poorly understood. Improving our understanding of psoriatic arthritis pathogenesis could help to establish validated biomarkers for diagnosis, predict therapeutic response and remission, develop precision medicines, and predict which patients will respond to which therapy. We discuss advances in pathogenetic translational research that could inform these issues.

Whether innate immune together with genetic factor are involved in leukemic arthritis?: A case report and review of the literature

We report a case of leukemic arthritis (LA) of monocytic differentiation, which presented with spondyloarthritis-like symptoms and a positive human leukocyte antigen-B27, and discuss its potential mechanisms.The patient was admitted because of pain in her right knee and lower back for 18 months. Magnetic resonance imaging showed diffuse hyperintense signal in the bilateral liac bones and bone marrow edema and synovitis in the right knee.The diagnosis of acute monocytic leukemia and LA were concluded by bone marrow aspiration and flow cytometry of the synovial fluid.The patient had poor response to nonsteroidal anti-inflammatory drugs. One week after she received chemotherapy, the symptoms were dramatically relieved.For 5-year follow-up, she got clinical remission without suffering pain of the right knee and the lower back.Leukemic arthritis is a rare manifestation of leukemia with unknown mechanism and may be the initial presentation of leukemia. The problem whether abnormal immune response of the neoplasitc monocytes together with hereditary factors contribute to the pathogenesis of LA in adult is raised from this case, which worth further research.

The Multifunctional Role of the Chemokine System in Arthritogenic Processes

PURPOSE OF REVIEW

The involvement of chemokines and their receptors in the genesis and perpetuation of rheumatoid arthritis, spondyloarthritis, and osteoarthritis has been clearly recognized for a long time. Nevertheless, the complexity of their contribution to these diseases is now becoming evident and this review focuses on published evidence on their mechanism of action.

RECENT FINDINGS

Studies performed on patients and in vivo models have identified a number of chemokine-mediated pathways involved in various aspects of arthritogenic processes. Chemokines promote leukocyte infiltration and activation, angiogenesis, osteoclast differentiation, and synoviocyte proliferation and activation and participate to the generation of pain by regulating the release of neurotransmitters. A number of chemokines are expressed in a timely controlled fashion in the joint during arthropathies, regulating all the aspects of inflammation as well as the equilibrium between damage and repair and between relief and pain. Thus, the targeting of specific chemokine/chemokine receptor interactions is considered a promising tool for therapeutic intervention.

A proof-of-concept study with the tyrosine kinase inhibitor nilotinib in spondyloarthritis

Background

To evaluate the immunomodulating and clinical effects of nilotinib, a tyrosine kinase inhibitor, in a proof-of-concept study in spondyloarthritis (SpA) assessing the mast cell as potential novel therapeutic target in this disease.

Methods

Twenty eight patients with active peripheral (pSpA) and/or axial SpA (axSpA) were included in a randomized, double-blind, placebo-controlled clinical trial (Trial registration: Trialregister.nl NTR2834). Patients were treated 1:1 with nilotinib or placebo for 12 weeks, followed by an open label extension for another 12 weeks. Paired synovial tissue biopsies, serum sampling and assessment of clinical symptoms were performed serially.

Results

In pSpA (n = 13) synovial inflammation appeared to diminish after 12 weeks of nilotinib treatment as evidenced by histopathology (decrease in number of infiltrating CD68+ and CD163+ macrophages and mast cells). Compared to placebo mRNA expression of c-Kit as mast cell marker (p = 0.037) and of pro-inflammatory cytokines such as IL-6 (p = 0.024) were reduced. The reduction of synovial inflammation was paralleled by a decrease in serum biomarkers of inflammation such as C-reactive protein (p = 0.024) and calprotectin (p = 0.055). Also clinical parameters such as patient’s global assessment of disease activity (p = 0.031) and ankylosing spondylitis disease activity score (p = 0.031) showed improvement upon 12 weeks of nilotinib but not placebo treatment. This improvement was further augmented at week 24. In contrast to pSpA, neither serum biomarkers of inflammation nor clinical parameters improved upon nilotinib treatment in axSpA. During the trial one serious adverse event occurred, which was considered unrelated to the study drug.

Conclusions

This small proof-of-concept study suggests that nilotinib treatment modulates inflammation and clinical symptoms in pSpA. A similar effect was not seen in axSpA.

Trial registration: trialregister.nl registration code NTR2834 registered 31 March 2011

Data showing non-conventional HLA-B27 expression in axial joints and gut tissue from B27 transgenic rats, and in frozen and paraffin-fixed synovial SpA tissue

Data is presented showing expression of non-conventional (NC) heavy chain forms of B27 in synovial tissues from SpA patients. Data is presented showing the expression patterns of NC-B27 in joint, gastrointestinal and lymphoid tissues from B27 transgenic (TG¹) rats with M. tuberculosis-induced SpA. Expression of NC-B27 was determined by immunohistochemistry and flow cytometry using HC10 and HD6 antibodies. These data are the extension of the data presented and discussed in “Non-conventional forms of HLA-B27 are expressed in Spondyloarthritis joints and gut tissue” (O. Rysnik, K. McHugh, L. M. van Duivenvoorde, M. N. van Tok, G. Guggino, J. D. Taurog, S. Kollnberger, F. Ciccia, D. L. Baeten, P. Bowness, 2016) [1].

Effect of Continuous-Wave Low-Intensity Ultrasound in Inflammatory Resolution of Arthritis-Associated Synovitis

BACKGROUND

Low-intensity ultrasound (LIUS) can reduce pain and improve function in arthritic joints. Neutrophils are first-line actors in host defense that recruit macrophages. Dead neutrophils are removed during resolution of inflammation. Delayed neutrophil clearance can lead to extended inflammation or even chronic autoimmune disease. Although neutrophil extracellular traps (NETs) in arthritic tissue are involved in the pathogenesis of arthritis, their functional role has not been clarified.

OBJECTIVES

This study aimed to investigate the effect of LIUS on synovial inflammation and its resolution via neutrophil clearance.

METHODS

Synovitis was induced by intra-articular injection of complete Freund's adjuvant (CFA) into the left knee joint of 58 adult male Sprague-Dawley rats. Low-intensity ultrasound (1 MHz, 200 mW/cm(2)) was applied for 10 minutes daily. Neutrophil clearance was assessed with the expression of myeloperoxidase (MPO). In addition, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and NET formation in the synovium were observed. In neutrophil and macrophage cultures from peripheral blood, the effect of NET clearance by LIUS was investigated.

RESULTS

In CFA-induced synovitis, MPO-positive neutrophils peaked after 2 to 3 days, filling the inflammatory core. Monocytes and macrophages in the periphery later infiltrated the core and were reduced thereafter. Low-intensity ultrasound reduced synovial hyperplasia and induced earlier MPO clearance. Neutrophils in the core of the inflamed synovium exhibited NET formation, which LIUS increased. Low-intensity also induced NETs in peripheral polymorphonuclear cells in an intensity-dependent manner and potentiated phorbol myristate acetate (PMA)-induced NETosis. The PMA-induced NETs were cleared by macrophages; clearance was enhanced by LIUS.

LIMITATIONS

The effect of LIUS on CFA-induced inflammation was observed only during the acute phase. Although the effect of LIUS on NETosis in the in vitro neutrophil culture system was clear, the in vivo NETosis cannot be quantified.

CONCLUSIONS

Neutrophil extracellular traps act in inflammatory synovitis, and LIUS enhanced the NETs and resulted in neutrophil clearance by enhancing the phagocytosis of macrophages, which might be a factor underlying the therapeutic effect of LIUS in arthritic synovium.

Non-conventional forms of HLA-B27 are expressed in spondyloarthritis joints and gut tissue

Objectives

Human leukocyte antigen (HLA)-B27 (B27) is the strongest genetic factor associated with development of Ankylosing Spondylitis and other spondyloarthropathies (SpA), yet the role it plays in disease pathogenesis remains unclear. We investigated the expression of potentially pathogenic non-conventional heavy chain forms (NC) of B27 in synovial and intestinal tissues obtained from SpA patients. We also determined the presence of NC-B27 in joints, lymphoid and gastrointestinal tissue from B27 transgenic (TG¹) rats with M.tuberculosis-induced SpA.

Methods

Expression of NC-B27 in human SpA joints and gut and in (21-3 × 283-2)F₁ HLA-B27/Huβ2m rat tissue was determined by immunohistochemistry, flow cytometry and confocal microscopy analysis using HC10 and HD6 antibodies.

Results

Both HC10- and HD6-reactive HLA molecules were present in synovial tissue from SpA patients. Both NC-B27 and KIR3DL2, a ligand for NC-B27, were expressed in inflamed terminal ileal tissues in patients with early SpA. Infiltrating cells in inflamed joint tissues isolated from B27 TG¹ rats expressed high levels of NC-B27. NC-B27 were also expressed in joint-resident cells from ankle and tail joints of B27 TG¹ rats prior to clinical arthritis. The expression of NC-B27 on B27 TG¹ rat CD11b/c⁺, CD8α⁺, cells from spleens and LNs increased with animal age and disease progression.

Conclusions

Non-conventional HLA class 1 molecules are expressed on resident and infiltrating cells in both synovial and GI tissues in human SpA. NC-B27 expression in joints and lymphoid tissues from B27 TG¹ rats prior to the onset of arthritis is consistent with the hypothesis that they play a pathogenic role in SpA.

•

HLA-B27 predisposes to Ankylosing Spondylitis and related Spondyloarthritis (SpA).

•

Non-conventional HLA-B27 free heavy chains (NC-B27) bind innate immune receptors.

•

NC HLA class I molecules are expressed in joint and gut tissues in human and rat SpA.

•

B27 transgenic rats express NC-B27 prior to arthritis onset.

•

These data support a pathogenic role for non-conventional B27 in SpA.

Optimal management of dactylitis in patients with psoriatic arthritis

Psoriatic arthritis (PsA) is an inflammatory arthropathy associated with cutaneous psoriasis, which is currently classified as a seronegative spondyloarthropathy. The presence of cutaneous psoriasis is important for correct and early diagnosis of PsA, because the onset of cutaneous lesions usually precedes the appearance of joint manifestation. Thus, dermatologists are able to detect the condition at its inception. PsA has several unique characteristics such as enthesopathy, dactylitis, and abnormal bone remodeling. In particular, dactylitis occurs on the easily observed sites such as digits, and is thus a significant indicator of PsA. It is important to observe not only the fingers but also the toes, because dactylitis involves both digits of the hands and feet. Recently, new ideas regarding the involvement of the interleukin (IL)-23/Th17 axis have emerged, and the dramatic effects of targeting therapies have highlighted the physiological roles of key cytokines such as tumor necrosis factor-α, IL-17A, and IL-23 in psoriasis. As recent insights are shedding light on the pathogenesis of PsA, understanding of the pathogenesis of dactylitis and enthesitis are also progressing. In this article, current views on the optimal management of dactylitis are discussed.

Occult spondyloarthritis in inflammatory bowel disease

Spondyloarthritis (SpA) is a frequent extra-intestinal manifestation in patients with inflammatory bowel disease (IBD), although its real diffusion is commonly considered underestimated. Abnormalities in the microbioma and genetic predisposition have been implicated in the link between bowel and joint inflammation. Otherwise, up to date, pathogenetic mechanisms are still largely unknown and the exact influence of the bowel activity on rheumatic manifestations is not clearly explained. Due to evidence-based results of clinical studies, the interest on clinically asymptomatic SpA in IBD patients increased in the last few years. Actually, occult enthesitis and sacroiliitis are discovered in high percentages of IBD patients by different imaging techniques, mainly enthesis ultrasound (US) and sacroiliac joint X-ray examinations. Several diagnostic approaches and biomarkers have been proposed in an attempt to correctly classify and diagnose clinically occult joint manifestations and to define clusters of risk for patient screening, although definitive results are still lacking. The correct recognition of occult SpA in IBD requires an integrated multidisciplinary approach in order to identify common diagnostic and therapeutic strategies. The use of inexpensive and rapid imaging techniques, such as US and X-ray, should be routinely included in daily clinical practice and trials to correctly evaluate occult SpA, thus preventing future disability and worsening of quality of life in IBD patients.

Immunopathology of synovitis: from histology to molecular pathways

Increased knowledge about pathological processes active in inflammatory joint diseases is needed to initiate personalized medicine based on targeted treatments in the future. The molecular and cellular pathways that are active during joint inflammation may differ between the various inflammatory joint diseases, between different patient subgroups within one disease, or even between different stages of the disease in a single patient. In this review, we evaluate synovial inflammation in terms of descriptive histopathology through to more functional studies on human synovial tissue inflammation in RA and SpA, in phenotypic subgroups of RA and SpA patients, and during the disease course of both diseases.

Axial spondyloarthritis

The term axial spondyloarthritis covers both non-radiographic disease and radiographic disease (also known as ankylosing spondylitis). Some studies have been performed to investigate the prevalence of axial spondyloarthritis, although most are limited to patients with radiographic disease. A strong genetic association has been shown between axial spondyloarthritis and human leukocyte antigen-B27 (HLA-B27), but the pathogenetic role of HLA-B27 has not yet been clarified. Tumour necrosis factor (TNF), IL-17, IL-23 and downstream pathways also seem to be important - based on the good results of therapies directed against these molecules - but their exact role in the inflammatory process is also not yet clear. Elucidating the interaction between osteoproliferation and inflammation will be crucial for the prevention of long-term structural damage of the bone. The development of new criteria for classification, diagnosis and screening of patients with axial spondyloarthritis will enable earlier intervention for this chronic inflammatory disease. MRI has become an important tool for the early detection of axial spondyloarthritis. NSAIDs and TNF blockers are effective therapies, including in the early non-radiographic stage. Therapeutic blockade of IL-17 or IL-23 seems to be a promising new treatment option. Tools for measuring quality of life in axial spondyloarthritis have become relevant to assess the impact that the disease has on patients. These diagnostic and therapeutic advances will continue to change the management of axial spondyloarthritis, and new insights into the disease pathogenesis will hopefully accelerate this process. For an illustrated summary of this Primer, visit: http://go.nature.com/51b1af.

Replacing heme with paclitaxel to prepare drug-loaded globin nanoassembles for CD163 targeting

Protein-based nanoparticles hold great promises in both preclinical and clinical practices, such as oncology diagnosis and treatment, because of their high biocompatibility and biodegradability. However, the complicated preparation and lack of targeting specific cells or tissues may limit their further uses. To overcome these limitations, we developed a novel replacing method for preparing dual-functional protein nanocarrier, such that one function is capable of encapsulating small molecule into protein, whereas the other function is cable of recognizing CD163 receptor [hemoglobin (Hb) scavenger receptor]. In this study, Hb was chosen as the targeting drug carrier. First, the heme group in the Hb was removed and replaced by paclitaxel (PTX) to form nanoparticles (Gb-NPs-PTX). The resulted Gb-NPs-PTX showed spherical shape and their diameter could be controlled in the range of 120-160 nm by altering the ratio of PTX to Hb. The binding activity of Gb-NPs-PTX to CD163 was confirmed by cell uptake in CD163(+) Chinese hamster ovary cells. Results in vivo also showed a CD163-dependent tissue accumulation of Gb-NPs-PTX in mice. In summary, by using the novel replacing method, PTX could be easily encapsulated into Hb nanoparticles and the targeting effects of Hb could also be kept.

Estradiol promotes M1-like macrophage activation through cadherin-11 to aggravate temporomandibular joint inflammation in rats

Macrophages play a major role in joint inflammation. Estrogen is involved in rheumatoid arthritis and temporomandibular disorders. However, the underlying mechanism is still unclear. This study was done to verify and test how estrogen affects M1/M2-like macrophage polarization and then contributes to joint inflammation. Female rats were ovariectomized and treated with increasing doses of 17β-estradiol for 10 d and then intra-articularly injected with CFA to induce temporomandibular joint (TMJ) inflammation. The polarization of macrophages and expression of cadherin-11 was evaluated at 24 h after the induction of TMJ inflammation and after blocking cadherin-11 or estrogen receptors. NR8383 macrophages were treated with estradiol and TNF-α, with or without blocking cadherin-11 or estrogen receptors, to evaluate the expression of the M1/M2-like macrophage-associated genes. We found that estradiol increased the infiltration of macrophages with a proinflammatory M1-like predominant profile in the synovium of inflamed TMJ. In addition, estradiol dose-dependently upregulated the expressions of the M1-associated proinflammatory factor inducible NO synthase (iNOS) but repressed the expressions of the M2-associated genes IL-10 and arginase in NR8383 macrophages. Furthermore, estradiol mainly promoted cadherin-11 expression in M1-like macrophages of inflamed TMJ. By contrast, blockage of cadherin-11 concurrently reversed estradiol-potentiated M1-like macrophage activation and TMJ inflammation, as well as reversed TNF-α-induced induction of inducible NO synthase and NO in NR8383 macrophages. The blocking of estrogen receptors reversed estradiol-potentiated M1-like macrophage activation and cadherin-11 expression. These results suggested that estradiol could promote M1-like macrophage activation through cadherin-11 to aggravate the acute inflammation of TMJs.

Calprotectin (S100A8/9) as serum biomarker for clinical response in proof-of-concept trials in axial and peripheral spondyloarthritis

Introduction

Biomarkers complementing clinical evaluations may help to reduce the length and size of proof-of-concept (PoC) trials aimed to obtain quick “go/no go” decisions in the clinical development of new treatments. We aimed to identify and validate serum biomarkers with a high sensitivity to change upon effective treatment in spondyloarthritis (SpA) PoC trials.

Methods

The candidate biomarkers high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), pentraxin-3 (PTX-3), alpha-2-macroglobulin (alpha-2-MG), matrix metalloproteinase-3 (MMP-3), calprotectin, and vascular endothelial growth factor (VEGF) were determined by enzyme-linked immunosorbent assay (ELISA) in healthy controls (n = 20) and SpA patients before and after 2 weeks of infliximab (n = 18) or placebo (n = 19) treatment in cohort 1. Clinical outcome was evaluated at week 12. Results were validated in ankylosing spondylitis (AS) with infliximab (cohort 2, n = 21) and peripheral SpA with etanercept (cohort 3, n = 20).

Results

Serum levels of calprotectin, hs-CRP, PTX-3, VEGF (all P < 0.001) and MMP-3 (P = 0.062), but not IL-6 and alpha-2-MG, were increased in SpA versus healthy controls. Treatment with infliximab, but not placebo, significantly decreased calprotectin (P < 0.001) and hs-CRP (P < 0.001) levels, with a similar trend for MMP-3 (P = 0.063). The standardized response mean (SRM), which reflects the ability to detect changes over time, was high for calprotectin (−1.26), good for hs-CRP (−0.96) and moderate for MMP-3 (−0.52). Calprotectin and hs-CRP, but not MMP-3, were good biomarkers for treatment response in axial and peripheral SpA as evaluated and confirmed in cohort 2 and 3 respectively.

Conclusions

Calprotectin and hs-CRP are good serum biomarkers with high sensitivity to change upon effective treatment at the group level in small-scale, short term PoC trials in SpA.

High expression levels of the B cell chemoattractant CXCL13 in rheumatoid synovium are a marker of severe disease

OBJECTIVE

The B cell chemoattractant chemokine ligand 13 (CXCL13) is emerging as a new biochemical marker in RA. This study was undertaken to dissect the relationship between CXCL13 expression levels in the synovium and clinico-pathological variables relevant to RA pathogenesis and outcome.

METHODS

Synovial tissues from 71 RA patients were evaluated by immunohistochemistry. Thirty paired samples were used for comparative gene expression analysis by quantitative real-time PCR. CXCL13 levels were analysed in relation to cellular, molecular and clinical features of inflammation, lymphocyte activation and joint damage.

RESULTS

In patients with early disease (<12 months duration), CXCL13 expression correlated significantly with synovial markers of local disease activity and systemic inflammation. Such correlation was less evident in established RA. Notably, the association with lymphocyte infiltration and with expression of B/T cell-related activation and proliferation genes, such as activation-induced cytidine deaminase, IFN-γ and IL-2, remained highly significant independent of disease duration and local disease activity. Patients featuring the highest levels of CXCL13 were more frequently ACPA positive and IgG ACPA titres were increased in the high CXCL13 expression group. Furthermore, the frequency of erosive disease on radiographs was significantly higher in the upper tertile of CXCL13 expression (P = 0.01 with adjustment for disease duration and ACPA). Accordingly, synovial CXCL13 and the local receptor activator of nuclear factor κB ligand (RANKL)/osteoprotegerin (OPG) ratio significantly co-varied (ρ = 0.52, P < 0.01), independent of the level of local inflammation.

CONCLUSION

Synovial CXCL13 appears to be a marker of a more severe pattern of RA disease, characterized by increased lymphocyte activation and bone remodelling beyond the level of conventional markers of inflammation.

Tie2 signaling cooperates with TNF to promote the pro-inflammatory activation of human macrophages independently of macrophage functional phenotype

Angiopoietin (Ang) -1 and -2 and their receptor Tie2 play critical roles in regulating angiogenic processes during development, homeostasis, tumorigenesis, inflammation and tissue repair. Tie2 signaling is best characterized in endothelial cells, but a subset of human and murine circulating monocytes/macrophages essential to solid tumor formation express Tie2 and display immunosuppressive properties consistent with M2 macrophage polarization. However, we have recently shown that Tie2 is strongly activated in pro-inflammatory macrophages present in rheumatoid arthritis patient synovial tissue. Here we examined the relationship between Tie2 expression and function during human macrophage polarization. Tie2 expression was observed under all polarization conditions, but was highest in IFN-γ and IL-10 –differentiated macrophages. While TNF enhanced expression of a common restricted set of genes involved in angiogenesis and inflammation in GM-CSF, IFN-γ and IL-10 –differentiated macrophages, expression of multiple chemokines and cytokines, including CXCL3, CXCL5, CXCL8, IL6, and IL12B was further augmented in the presence of Ang-1 and Ang-2, via Tie2 activation of JAK/STAT signaling. Conditioned medium from macrophages stimulated with Ang-1 or Ang-2 in combination with TNF, sustained monocyte recruitment. Our findings suggest a general role for Tie2 in cooperatively promoting the inflammatory activation of macrophages, independently of polarization conditions.

Caspase-1 level in synovial fluid is high in patients with spondyloarthropathy but not in patients with gout

Activation of caspase-1 by NALP3 inflammasomes has been shown to be important in initiating acute gouty arthritis. The objectives of this study were to measure the levels of caspase-1 in synovial fluid in gout and various arthritides, and to elucidate the clinical significance of caspase-1 levels in synovial fluid. Caspase-1, IL-1β, IL-18, and uric acid were measured in synovial fluid from 112 patients with gout and other arthritides, such as rheumatoid arthritis, osteoarthritis, and spondyloarthropathy. Caspase-1 in synovial fluid from patients with crystal-induced arthritis, inflammatory arthritis, osteoarthritis, and spondyloarthropathy was 35.9 ± 86.7, 49.7 ± 107.7, 2.1 ± 7.0, and 152.6 ± 155.7 pg/mL, respectively. The mean level and the frequency of high levels (≥125 pg/mL) of caspase-1 in spondyloarthropathy were significantly higher than those in the other arthritides including gout. Caspase-1 was detectible in the synovial fluid of patients with the various arthritides. Contrary to our hypothesis, the caspase-1 level in the synovial fluid of patients with gout was not higher than in that of other arthritides. High levels of caspase-1 may be helpful in differentiating spondyloarthropathy from other arthritides.