Monocyte transcriptomes from patients with axial spondyloarthritis reveal dysregulated monocytopoiesis and a distinct inflammatory imprint

Increased carotid intima-media thickness in patients with radiographic axial spondyloarthritis compared to controls and associations with markers of inflammation

OBJECTIVE

There is an increased risk for cardiovascular disease (CVD) in patients with radiographic axial spondyloarthritis (r-axSpA). In this cross-sectional study, we aimed to, overall and stratified by sex, (i) compare ultrasound derived carotid intima media thickness (cIMT), between patients and controls, and (ii) investigate associations between cIMT, clinical disease activity and inflammation-related laboratory markers in patients with r-axSpA.

METHOD

In total, 155 patients diagnosed with r-axSpA using the modified New York criteria and 400 controls were included. Bilateral carotid ultrasound, laboratory testing, and questionaries were acquired. Disease-specific assessments were carried out for patients. Linear regression analysis was used to assess associations.

RESULTS

Linear regression analyses showed that patients with r-axSpA had increased mean cIMT compared to controls (mean ± SD, 0.8 ± 0.1 mm vs 0.7± 0.1 mm, respectively, unstandardized β (95% CI) -0.076 (-0.10, -0.052), P < 0.001) adjusted for smoking status and age. Linear regression analyses for patients with r-axSpA showed that only males presented significant associations between cIMT and inflammation-related laboratory markers, white blood cell (WBC) count (mean ± SD, 6.8 ± 1.6 109/L) and monocytes (0.6 ± 0.2 109/L); WBC count (unstandardized β (95% CI) 0.019 (0.0065, 0.031), P = 0.003, R2 = 0.57) and monocytes (0.13 (0.0047, 0.26), P = 0.041, R2 = 0.55), adjusted for age, smoking status, body mass index, hypertension, dyslipidemia, diabetes mellitus, ASDAS-CRP, and treatment with DMARDs and glucocorticoids. No significant association was found between cIMT and clinical disease activity assessed by ASDAS-CRP.

CONCLUSION

Patients with r-axSpA had significantly increased cIMT compared to controls. In male patients, higher WBC and monocyte count were associated with an increase in cIMT suggesting the role of inflammation in the development of atherosclerosis. Key Points •Carotid intima-media thickness was increased in patients with radiographic axial spondyloarthritis compared to controls. •White blood cell and monocyte counts were associated with carotid intima-media thickness in male patients with radiographic axial spondyloarthritis.

The bone marrow side of axial spondyloarthritis

Spondyloarthritis (SpA) is characterized by the infiltration of innate and adaptive immune cells into entheses and bone marrow. Molecular, cellular and imaging evidence demonstrates the presence of bone marrow inflammation, a hallmark of SpA. In the spine and the peripheral joints, bone marrow is critically involved in the pathogenesis of SpA. Evidence suggests that bone marrow inflammation is associated with enthesitis and that there are roles for mechano-inflammation and intestinal inflammation in bone marrow involvement in SpA. Specific cell types (including mesenchymal stem cells, innate lymphoid cells and γδ T cells) and mediators (Toll-like receptors and cytokines such as TNF, IL-17A, IL-22, IL-23, GM-CSF and TGFβ) are involved in these processes. Using this evidence to demonstrate a bone marrow rather than an entheseal origin for SpA could change our understanding of the disease pathogenesis and the relevant therapeutic approach.

Evidence in support of the bone marrow as the primary lesion in axial spondyloarthritis

PURPOSE OF REVIEW

Over the past several decades, the concept that the primary lesion accounting for the development of axSpA is an enthesopathy has been widely accepted. However, the hallmark abnormality of axSpA occurs in the sacroiliac joint at the interface of cartilage and bone at a location remote from any anatomical enthesis. Both imaging and histopathological data from the sacroiliac joint point to immunopathogenetic events in the bone marrow as being of primary importance. Here, we discuss new developments in our understanding of immune events in the bone marrow relevant to axSpA that reinforce the need for a change in our conceptual paradigm for the pathogenesis of axSpA.

RECENT FINDINGS

Human spinal enthesis samples contain myeloperoxidase-expressing cells, a marker of neutrophils, and mucosal-associated invariant T cells in the perientheseal bone marrow, which may be activated by stromal cells and circulating microbial products to express IL-17A and IL-17F and tumor necrosis factor (TNF). Evaluation of transcriptomes of monocytes from patients with axSpA demonstrates a lipopolysaccharide/TNF signature characterized by the expression of genes associated with granulocytopoietic bone marrow cells. This neutrophil-like phenotype is more evident in established and more severe axSpA and may be activated by microbial products from the gut. A similar expansion of granulocyte-monocyte progenitor-driven hematopoiesis occurs in the SKG mouse driven by granulocyte-macrophage colony-stimulating factor. Mesenchymal stem cells (MSCs) from ankylosing spondylitis patients are more likely to exhibit osteogenic differentiation than MSCs from healthy donors, which may be mediated by the formation of specific clusters of transcriptional factors, super enhancers, regulated by axSpA-associated single nucleotide polymorphisms located mostly in noncoding regions. TNF-α may enhance directional migration of AS-MSC compared with MSC from healthy controls from the bone marrow to entheseal soft tissue, which is mediated by increased expression of engulfment and cell motility protein 1 (ELMO1). TNF and IL-17A display differential effects on adipogenesis and osteogenesis of MSC in perientheseal bone marrow and soft tissue.

SUMMARY

Bone marrow has the capacity to undergo rapid adaptation in terms of cell composition, differentiation, and immune function, resulting in inflammation and osteogenesis in axSpA.

Quantitative proteomic screening uncovers candidate diagnostic and monitoring serum biomarkers of ankylosing spondylitis

BACKGROUND

We sought to discover serum biomarkers of ankylosing spondylitis (AS) for diagnosis and monitoring disease activity.

METHODS

We studied biologic-treatment-naïve AS and healthy control (HC) patients' sera. Eighty samples matched by age, gender, and race (1:1:1 ratio) for AS patients with active disease, inactive disease, and HC were analyzed with SOMAscan™, an aptamer-based discovery platform. T-tests tests were performed for high/low-disease activity AS patients versus HCs (diagnosis) and high versus low disease activity (Monitoring) in a 2:1 and 1:1 ratio, respectively, to identify differentially expressed proteins (DEPs). We used the Cytoscape Molecular Complex Detection (MCODE) plugin to find clusters in protein-protein interaction networks and Ingenuity Pathway Analysis (IPA) for upstream regulators. Lasso regression analysis was performed for diagnosis.

RESULTS

Of the 1317 proteins detected in our diagnosis and monitoring analyses, 367 and 167 (317 and 59, FDR-corrected q < .05) DEPs, respectively, were detected. MCODE identified complement, IL-10 signaling, and immune/interleukin signaling as the top 3 diagnosis PPI clusters. Complement, extracellular matrix organization/proteoglycans, and MAPK/RAS signaling were the top 3 monitoring PPI clusters. IPA showed interleukin 23/17 (interleukin 22, interleukin 23A), TNF (TNF receptor-associated factor 3), cGAS-STING (cyclic GMP-AMP synthase, Stimulator of Interferon Gene 1), and Jak/Stat (Signal transducer and activator of transcription 1), signaling in predicted upstream regulators. Lasso regression identified a Diagnostic 13-protein model predictive of AS. This model had a sensitivity of 0.75, specificity of 0.90, a kappa of 0.59, and overall accuracy of 0.80 (95% CI: 0.61-0.92). The AS vs HC ROC curve was 0.79 (95% CI: 0.61-0.96).

CONCLUSION

We identified multiple candidate AS diagnostic and disease activity monitoring serum biomarkers using a comprehensive proteomic screen. Enrichment analysis identified key pathways in AS diagnosis and monitoring. Lasso regression identified a multi-protein panel with modest predictive ability.

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.

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.

Serum granulocyte-macrophage colony-stimulating factor (GM-CSF) is increased in patients with active radiographic axial spondyloarthritis and persists despite anti-TNF treatment

BACKGROUND

Accumulating evidence supports the role of monocytes and neutrophils in radiographic axSpA (r-axSpA). Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a growth factor for both leukocyte lineages and a pro-inflammatory cytokine activating myeloid cells and promoting osteoclastogenesis. It acts through the JAK-STAT pathway. We measured serum GM-CSF and markers of bone metabolism in patients with r-axSpA before and after anti-TNF treatment.

METHODS

Patients with active r-axSpA despite treatment with NSAIDs, all eligible for treatment with a biologic agent, were recruited. Healthy donors were sampled as controls. Serum was collected before (baseline) and after 4-6 months (follow-up) of anti-TNF treatment and the following molecules were measured with ELISA: GM-CSF, sclerostin (SOST), and dickkopf-1 (Dkk-1).

RESULTS

Twelve r-axSpA patients (7 males, 5 females, median age 37 years) with a median disease duration of 1 year and 16 age- and sex-matched controls were included. At baseline, patients had mean BASDAI 6.3±2 and ASDAS 3.2±0.7, which decreased to 4.1±1.7 and 2.2±0.6 at follow-up, respectively. At baseline, r-axSpA patients had significantly higher mean serum levels of GM-CSF (150 vs 62pg/ml, p=0.049), significantly lower Dkk-1 (1228 vs 3052pg/ml, p=0.001), but similar levels of SOST (369 vs 544pg/ml, p=0.144) compared to controls. Anti-TNF treatment did not affect GM-CSF, Dkk-1, or SOST levels. Spearman correlation analysis showed that GM-CSF correlated positively with ASDAS at baseline (r=0.61, p=0.039), while no correlations were identified between bone markers (Dkk-1, SOST) on one hand and GM-CSF or disease activity indices on the other.

CONCLUSIONS

GM-CSF is increased in patients with active AS and strongly correlates with disease activity. TNF inhibition does not affect GM-SCF levels, despite improving disease activity. GM-CSF may represent an important pathway responsible for residual inflammation during TNF blockade, but also a potential target of JAK inhibitors, explaining their efficacy in r-axSpA.