Stellate Cells, Hepatocytes, and Endothelial Cells Imprint the Kupffer Cell Identity on Monocytes Colonizing the Liver Macrophage Niche.

Macrophages are strongly adapted to their tissue of residence. Yet, little is known about the cell-cell interactions that imprint the tissue-specific identities of macrophages in their respective niches. Using conditional depletion of liver Kupffer cells, we traced the developmental stages of monocytes differentiating into Kupffer cells and mapped the cellular interactions imprinting the Kupffer cell identity. Kupffer cell loss induced tumor necrosis factor (TNF)- and interleukin-1 (IL-1) receptor-dependent activation of stellate cells and endothelial cells, resulting in the transient production of chemokines and adhesion molecules orchestrating monocyte engraftment. Engrafted circulating monocytes transmigrated into the perisinusoidal space and acquired the liver-associated transcription factors inhibitor of DNA 3 (ID3) and liver X receptor-α (LXR-α). Coordinated interactions with hepatocytes induced ID3 expression, whereas endothelial cells and stellate cells induced LXR-α via a synergistic NOTCH-BMP pathway. This study shows that the Kupffer cell niche is composed of stellate cells, hepatocytes, and endothelial cells that together imprint the liver-specific macrophage identity.

Targeting SLC7A11 improves efferocytosis by dendritic cells and wound healing in diabetes.

Chronic non-healing wounds are a major complication of diabetes, which affects 1 in 10 people worldwide. Dying cells in the wound perpetuate the inflammation and contribute to dysregulated tissue repair1-3. Here we reveal that the membrane transporter SLC7A11 acts as a molecular brake on efferocytosis, the process by which dying cells are removed, and that inhibiting SLC7A11 function can accelerate wound healing. Transcriptomics of efferocytic dendritic cells in mouse identified upregulation of several SLC7 gene family members. In further analyses, pharmacological inhibition of SLC7A11, or deletion or knockdown of Slc7a11 using small interfering RNA enhanced efferocytosis in dendritic cells. Slc7a11 was highly expressed in dendritic cells in skin, and single-cell RNA sequencing of inflamed skin showed that Slc7a11 was upregulated in innate immune cells. In a mouse model of excisional skin wounding, inhibition or loss of SLC7A11 expression accelerated healing dynamics and reduced the apoptotic cell load in the wound. Mechanistic studies revealed a link between SLC7A11, glucose homeostasis and diabetes. SLC7A11-deficient dendritic cells were dependent on aerobic glycolysis using glucose derived from glycogen stores for increased efferocytosis; also, transcriptomics of efferocytic SLC7A11-deficient dendritic cells identified increased expression of genes linked to gluconeogenesis and diabetes. Further, Slc7a11 expression was higher in the wounds of diabetes-prone db/db mice, and targeting SLC7A11 accelerated their wound healing. The faster healing was also linked to the release of the TGFß family member GDF15 from efferocytic dendritic cells. In sum, SLC7A11 is a negative regulator of efferocytosis, and removing this brake improves wound healing, with important implications for wound management in diabetes.

Structural Activation of Pro-inflammatory Human Cytokine IL-23 by Cognate IL-23 Receptor Enables Recruitment of the Shared Receptor IL-12Rß1.

Interleukin-23 (IL-23), an IL-12 family cytokine, plays pivotal roles in pro-inflammatory T helper 17 cell responses linked to autoimmune and inflammatory diseases. Despite intense therapeutic targeting, structural and mechanistic insights into receptor complexes mediated by IL-23, and by IL-12 family members in general, have remained elusive. We determined a crystal structure of human IL-23 in complex with its cognate receptor, IL-23R, and revealed that IL-23R bound to IL-23 exclusively via its N-terminal immunoglobulin domain. The structural and functional hotspot of this interaction partially restructured the helical IL-23p19 subunit of IL-23 and restrained its IL-12p40 subunit to cooperatively bind the shared receptor IL-12Rß1 with high affinity. Together with structural insights from the interaction of IL-23 with the inhibitory antibody briakinumab and by leveraging additional IL-23:antibody complexes, we propose a mechanistic paradigm for IL-23 and IL-12 whereby cognate receptor binding to the helical cytokine subunits primes recruitment of the shared receptors via the IL-12p40 subunit.

Lipidomic scanning of self-lipids identifies headless antigens for natural killer T cells.

To broadly measure the spectrum of cellular self-antigens for natural killer T cells (NKT), we developed a sensitive lipidomics system to analyze lipids trapped between CD1d and NKT T cell receptors (TCRs). We captured diverse antigen complexes formed in cells from natural endogenous lipids, with or without inducing endoplasmic reticulum (ER) stress. After separating protein complexes with no, low, or high CD1d-TCR interaction, we eluted lipids to establish the spectrum of self-lipids that facilitate this interaction. Although this unbiased approach identified fifteen molecules, they clustered into only two related groups: previously known phospholipid antigens and unexpected neutral lipid antigens. Mass spectrometry studies identified the neutral lipids as ceramides, deoxyceramides, and diacylglycerols, which can be considered headless lipids because they lack polar headgroups that usually form the TCR epitope. The crystal structure of the TCR-ceramide-CD1d complex showed how the missing headgroup allowed the TCR to predominantly contact CD1d, supporting a model of CD1d autoreactivity. Ceramide and related headless antigens mediated physiological TCR binding affinity, weak NKT cell responses, and tetramer binding to polyclonal human and mouse NKT cells. Ceramide and sphingomyelin are oppositely regulated components of the "sphingomyelin cycle" that are altered during apoptosis, transformation, and ER stress. Thus, the unique molecular link of ceramide to NKT cell response, along with the recent identification of sphingomyelin blockers of NKT cell activation, provide two mutually reinforcing links for NKT cell response to sterile cellular stress conditions.

Tregs protect against invariant NKT cell-mediated autoimmune colitis and hepatitis.

Immunomodulatory T cells play a pivotal role in protection against (auto)immune-mediated diseases that open perspectives for therapeutic modulation. However, how immune regulatory networks operate in vivo is less understood. To this end, we focused on FOXP3+CD4+CD25+ regulatory T cells (Tregs) and invariant natural killer T (iNKT) cells, two lymphocyte populations that independently regulate adaptive and innate immune responses. In vitro, a functional interplay between Tregs and iNKT cells has been described, but whether Tregs modulate the function and phenotype of iNKT cell subsets in vivo and whether this controls iNKT-mediated autoimmunity is unclear. Taking advantage of the conditional depletion of Tregs, we examined the in vivo interplay between iNKT and Treg cells in steady state and in preclinical models of liver and gut autoimmunity. Under non-inflamed conditions, Treg depletion enhanced glycolipid-mediated iNKT cell responses, with a general impact on Type 1, 2 and 17 iNKT subsets. Moreover, in vivo iNKT activation in the absence of Tregs suppressed the induction of iNKT anergy, consistent with a reduction in programmed cell death receptor 1 (PD-1) expression. Importantly, we unveiled a clear role for an in vivo Treg-iNKT crosstalk both in concanavalin A-induced acute hepatitis and oxazolone-induced colitis. Here, the absence of Tregs led to a markedly enhanced liver and gut pathology, which was not observed in iNKT-deficient mice. Taken together, these results provide evidence for a functional interplay between regulatory T cell subsets critical in controlling the onset of autoimmune disease.

Specific descriptions of axial involvement are associated with radiographic damage development after 2 years in psoriatic arthritis patients.

OBJECTIVES: Investigating the association between different definitions of axial involvement and syndesmophytes development over 2 years in patients with psoriatic arthritis (PsA). METHODS: Patients from a prospective multicentre cohort (Belgian Epidemiological Psoriatic Arthritis Study) involving 17 Belgian rheumatology practices were recruited between December 2012 and July 2014 and included when fulfilling the Classification Criteria for Psoriatic Arthritis. Axial involvement included six clinical and two radiographic oriented definitions.Two calibrated central readers evaluated radiographic damage by assessing the modified Stoke Ankylosing Spondylitis Spinal Score and modified New York criteria. New syndesmophytes after 2 years were described conditional on axial involvement at baseline. Logistic regression analyses were used to investigate the association between syndesmophyte development and axial involvement. All definitions of axial involvement were evaluated separately. RESULTS: From 150 patients, a 2-year follow-up of spinal radiographs was obtained. There are 11 patients with new syndesmophytes after 2 years. For the clinical definitions of axial involvement 'global assessment', 'detailed assessment', 'back pain (BP)' and 'inflammatory BP (IBP)' the probabilities of developing syndesmophytes ranged between 0.06 and 0.08 and were similar for the presence or absence of the definition. When including elevated C reactive protein (CRP) to the definitions the probability of developing syndesmophytes over 2 years increased two times for CBP and seven times for IBP.With radiographic axial involvement a similar trend was seen; radiographic sacroiliitis as definition showed a probability three times higher. When combined with elevated CRP there would be a 14 times higher chance to develop syndesmophytes in 2 years. The ORs varied from 0.83 to 13.80, though none of them were statistically significant. CONCLUSIONS: The likelihood of syndesmophyte formation in PsA is low. The probability of developing syndesmophytes is much higher when axial involvement is determined radiographically rather than clinically, particularly in the context of high CRP.

Maximal Exercise Tolerance, Objective Trunk Strength, and Mobility Measurements in Axial Spondyloarthritis.

OBJECTIVE: Although exercise therapy is safe, effective, and recommended as a nonpharmacological treatment for axial spondyloarthritis (axSpA), there is a lack of guidelines regarding type and dosage. Insufficient knowledge about physical and physiological variables makes designing effective exercise programs challenging. Therefore, the goal of this study was to simultaneously assess trunk strength, spinal mobility, and the cardiorespiratory fitness of patients with axSpA. METHODS: In a cross-sectional study, 58 patients with axSpA (mean age 40.8 yrs, 50% male, mean symptom duration 10.3 yrs) performed maximal cervical and trunk mobility and isometric strength tests in all planes (using David Back Concept devices) and a maximal cardiopulmonary bicycle exercise test (n = 25). Mobility and strength data were compared to healthy reference data. Cut-off values for clinical cardiopulmonary exercise testing interpretation were used to judge normality. Patients were compared based on radiographic involvement and symptom duration. RESULTS: Both strength (P ≤ 0.02) and mobility (P ≤ 0.001) were significantly lower for the patients with axSpA compared to the reference. Strength deficits were comparable between the radiographic and nonradiographic groups (P > 0.05, except trunk extension [P = 0.03]), whereas mobility showed higher deficits in the radiographic group (cervical extension [P = 0.02] and rotation [P = 0.01], and trunk extension [P = 0.03] and rotation [P = 0.03]), regardless of symptom duration. Similarly, symptom duration positively affected oxygen pulse (P = 0.03), relative anaerobic threshold (P = 0.02), and aerobic capacity (P = 0.02). CONCLUSION: In patients with axSpA, strength is more affected than mobility when compared to healthy controls. Likewise, mainly the metabolic component of aerobic capacity is impaired, affecting cardiopulmonary fitness. These findings indicate that future personalized exercise programs in patients with axSpA should incorporate exercises for cardiopulmonary fitness next to strength and mobility training.

A20 controls RANK-dependent osteoclast formation and bone physiology.

The anti-inflammatory protein A20 serves as a critical brake on NF-κB signaling and NF-κB-dependent inflammation. In humans, polymorphisms in or near the TNFAIP3/A20 gene have been associated with several inflammatory disorders, including rheumatoid arthritis (RA), and experimental studies in mice have demonstrated that myeloid-specific A20 deficiency causes the development of a severe polyarthritis resembling human RA. Myeloid A20 deficiency also promotes osteoclastogenesis in mice, suggesting a role for A20 in the regulation of osteoclast differentiation and bone formation. We show here that osteoclast-specific A20 knockout mice develop severe osteoporosis, but not inflammatory arthritis. In vitro, osteoclast precursor cells from A20 deficient mice are hyper-responsive to RANKL-induced osteoclastogenesis. Mechanistically, we show that A20 is recruited to the RANK receptor complex within minutes of ligand binding, where it restrains NF-κB activation independently of its deubiquitinating activity but through its zinc finger (ZnF) 4 and 7 ubiquitin-binding functions. Together, these data demonstrate that A20 acts as a regulator of RANK-induced NF-κB signaling to control osteoclast differentiation, assuring proper bone development and turnover.

Association of anatomical variants of the sacroiliac joint with bone marrow edema in patients with axial spondyloarthritis.

OBJECTIVE: To determine the prevalence of sacroiliac joint variants in patients with axial spondyloarthritis (axSpA) using MRI-based synthetic CT images and to evaluate their relationships with the presence of bone marrow edema, as this may potentially complicate diagnosing active sacroiliitis on MRI in patients with suspected axSpA. METHODS: 172 patients were retrospectively included. All patients underwent MRI because of clinical suspicion of sacroiliitis. The diagnosis of axSpA was made by a tertiary hospital rheumatologist. Two readers independently determined the presence of bone marrow edema and the presence of one or more of the nine known sacroiliac joint (SIJ) variants. RESULTS: SIJ variants were common in axSpA patients (82.9%) and the non-SpA group (85.4%); there were no significant differences in prevalence. Bone marrow edema was frequently found in axSpA (86.8%) and non-SpA patients (34%). AxSpA patients with SIJ variants (except for accessory joint) demonstrated 4 to 10 times higher odds for bone marrow edema, however not statistically significant. The more variants were present in this group, the higher the chance of bone marrow edema. However, some multicollinearity cannot be excluded, since bone marrow edema is very frequent in the axSpA group by definition. CONCLUSION: SIJ variants are common in axSpA and non-SpA patients. SIJ variants were associated with higher prevalence of bone marrow edema in axSpA patients, potentially due to altered biomechanics, except for accessory joint which may act as a stabilizer.

Distinct immune modulatory roles of regulatory T cells in gut versus joint inflammation in TNF-driven spondyloarthritis.

OBJECTIVES: Gut and joint inflammation commonly co-occur in spondyloarthritis (SpA) which strongly restricts therapeutic modalities. The immunobiology underlying differences between gut and joint immune regulation, however, is poorly understood. We therefore assessed the immunoregulatory role of CD4+FOXP3+ regulatory T (Treg) cells in a model of Crohn's-like ileitis and concomitant arthritis. METHODS: RNA-sequencing and flow cytometry was performed on inflamed gut and joint samples and tissue-derived Tregs from tumour necrosis factor (TNF)∆ARE mice. In situ hybridisation of TNF and its receptors (TNFR) was applied to human SpA gut biopsies. Soluble TNFR (sTNFR) levels were measured in serum of mice and patients with SpA and controls. Treg function was explored by in vitro cocultures and in vivo by conditional Treg depletion. RESULTS: Chronic TNF exposure induced several TNF superfamily (TNFSF) members (4-1BBL, TWEAK and TRAIL) in synovium and ileum in a site-specific manner. Elevated TNFR2 messenger RNA levels were noted in TNF∆ARE/+ mice leading to increased sTNFR2 release. Likewise, sTNFR2 levels were higher in patients with SpA with gut inflammation and distinct from inflammatory and healthy controls. Tregs accumulated at both gut and joints of TNF∆ARE mice, yet their TNFR2 expression and suppressive function was significantly lower in synovium versus ileum. In line herewith, synovial and intestinal Tregs displayed a distinct transcriptional profile with tissue-restricted TNFSF receptor and p38MAPK gene expression. CONCLUSIONS: These data point to profound differences in immune-regulation between Crohn's ileitis and peripheral arthritis. Whereas Tregs control ileitis they fail to dampen joint inflammation. Synovial resident Tregs are particularly maladapted to chronic TNF exposure.

Efficacy and safety of bimekizumab in axial spondyloarthritis: results of two parallel phase 3 randomised controlled trials.

OBJECTIVES: Axial spondyloarthritis (axSpA) is a complex disease with diverse manifestations, for which new treatment options are warranted. BE MOBILE 1 (non-radiographic (nr)-axSpA) and BE MOBILE 2 (radiographic axSpA (r-axSpA)) are double-blind, phase 3 trials designed to evaluate efficacy and safety of bimekizumab, a novel dual interleukin (IL)-17A and IL-17F inhibitor, across the axSpA spectrum. METHODS: In parallel 52-week trials, patients with active disease were randomised 1:1 (nr-axSpA) or 2:1 (r-axSpA) to bimekizumab 160 mg every 4 weeks:placebo. From week 16, all patients received bimekizumab 160 mg every 4 weeks. Primary (Assessment of SpondyloArthritis international Society ≥40% improvement (ASAS40)) and secondary endpoints were assessed at week 16. Here, efficacy and treatment-emergent adverse events (TEAEs) are reported up to week 24. RESULTS: 254 patients with nr-axSpA and 332 with r-axSpA were randomised. At week 16, primary (ASAS40, nr-axSpA: 47.7% bimekizumab vs 21.4% placebo; r-axSpA: 44.8% vs 22.5%; p<0.001) and all ranked secondary endpoints were met in both trials. ASAS40 responses were similar across TNFi-naïve and TNFi-inadequate responder patients. Improvements were observed in Ankylosing Spondylitis Disease Activity Score (ASDAS) states and objective measures of inflammation, including high-sensitivity C-reactive protein (hs-CRP) and MRI of the sacroiliac joints and spine. Most frequent TEAEs with bimekizumab (>3%) included nasopharyngitis, upper respiratory tract infection, pharyngitis, diarrhoea, headache and oral candidiasis. More fungal infections (all localised) were observed with bimekizumab vs placebo; no major adverse cardiovascular events (MACE) or active tuberculosis were reported. Incidence of uveitis and adjudicated inflammatory bowel disease was low. CONCLUSIONS: Dual inhibition of IL-17A and IL-17F with bimekizumab resulted in significant and rapid improvements in efficacy outcomes vs placebo and was well tolerated in patients with nr-axSpA and r-axSpA.

Performance of an MRI scoring system for inflammation of joints and entheses in peripheral SpA: post-hoc analysis of the CRESPA trial.

OBJECTIVES: The aim of this study was to investigate the reliability, validity, and sensitivity to change of a novel MRI scoring system in early peripheral SpA (pSpA). METHODS: MRI of the pelvis and lower extremities was performed before initiation of the TNF inhibitor golimumab in 56 patients and repeated in 46 patients who achieved sustained clinical remission after 24, 36 or 48 weeks. Three readers applied a semi-quantitative MRI scoring system for lower-extremity joint and entheseal inflammation. Four lesion types were assessed: entheseal osteitis, entheseal soft-tissue inflammation, joint osteitis, and joint synovitis/effusion. MRI response was defined as a decrease in MRI lower-extremity inflammation index (sum of scores from 75 sites, each scored 0-3) above the smallest detectable change (SDC). RESULTS: At follow-up, the MRI index decreased in 34 of 46 patients (74%), and 15 (33%) patients achieved MRI response, i.e. a decrease above SDC of 2.8. When restricting the analysis to patients with clinical involvement of lower-extremity sites that were assessed by MRI, 13 of 28 (46%) achieved MRI response. Interreader reliability was very good, with an average-measure intraclass correlation coefficient of 0.92 (95% CI: 0.85-0.95) for status scores and 0.89 (0.80-0.94) for change in scores. The MRI index correlated with other measures of disease activity, including CRP [Spearman's rho 0.41 (0.23-0.56)], swollen joint count of 6 joints [0.47 (0.27-0.63)], tender enthesis count of 14 entheses [0.32 (0.12-0.50)] and pain score [0.28 (0.08-0.46)], all P < 0.05. CONCLUSION: The proposed MRI lower-extremity inflammation index demonstrated reliability, validity, and sensitivity to change in patients with early pSpA. TRIAL REGISTRATION: Clinicaltrials.gov, http://clinicaltrials.gov, NCT01426815.

Ultrasound-guided core needle biopsy and incisional biopsy of the parotid gland are comparable in diagnosis of primary Sjögren's syndrome.

OBJECTIVES: Salivary gland lymphocytic infiltrates are a hallmark of primary SS (pSS), but traditional biopsy techniques hold several disadvantages. Ultrasound-guided core needle (US-guided CN) parotid gland biopsy is minimally invasive and reliable for diagnosis of lymphoma in pSS. This proof-of-concept study aimed to explore this technique in the diagnostic work-up of pSS and is the first to address its value in a consecutive cohort independently of the presence of salivary gland swelling. METHODS: Combined incisional and US-guided CN parotid biopsy was performed in 20 patients with suspected or confirmed pSS from the Belgian Sjögren's Syndrome Transition Trial (BeSSTT). Surface area and presence of a focus score (FS) of at least one, germinal centres and lymphoepithelial lesions were recorded. RESULTS: Salivary gland tissue was interpretable in 19 patients. Fourteen patients had ≥4 mm2 salivary gland tissue by both techniques, in four US-guided CN biopsies salivary gland tissue was <4 mm2. Paired biopsies ≥4 mm2 displayed a concordance of 90% for FS ≥ 1. Presence of lymphoepithelial lesions and germinal centres showed absolute concordance. Of four US-guided CN biopsies <4 mm2, three interpretable incisional biopsies were available, 2/3 with perfect concordance. When including biopsies of <4 mm2 salivary gland tissue, presence of FS ≥ 1 or germinal centres gave a sensitivity of 70% in incisional and of 69% in US-guided CN biopsy. CONCLUSIONS: US-guided CN biopsy of the parotid gland is at least equivalent to incisional biopsy of the parotid gland in the diagnostic work-up of pSS.

Anti-CD74 IgA antibodies show diagnostic potential for axial spondyloarthritis but are not associated with microscopic gut inflammation.

OBJECTIVES: Gut inflammation commonly occurs in axial SpA (axSpA), and is linked to disease activity and outcome. Given the role of IgA in mucosal immunity, we explored the association between anti-CD74 IgA antibodies, gut inflammation and axSpA. METHODS: Anti-CD74 IgA was measured by ELISA in serum samples of axSpA patients, fulfilling the 2009 Assessment of SpondyloArthritis international Society classification criteria. A group of fibromyalgia (FM) and RA patients served as non-inflammatory and inflammatory controls. Newly diagnosed axSpA patients underwent ileocolonoscopy; mucosal biopsies were histopathologically assessed as normal, acute or chronically inflamed. Optimal anti-CD74 IgA cut-off values were determined with a receiver operating characteristics curve. RESULTS: axSpA patients (n = 281) showed higher anti-CD74 IgA levels [mean (s.d.) 18.8 (12.4) U/ml] compared with 100 FM patients [10.9 (5.0) U/ml, P < 0.001] and 34 RA patients [13.7 (9.6) U/ml, P = 0.02]. The area under the receiver operating characteristics curve for diagnosis (axSpA vs FM) was 0.70, providing a sensitivity of 60% and specificity of 87% (cut-off 15 U/ml). Antibody concentrations were not significantly different between axSpA patients with (n = 40) and without (n = 69) gut inflammation (P = 0.83), yielding an area under the receiver operating characteristics curve of 0.51. Anti-CD74 IgA levels were not associated with degree of bone marrow oedema on MRI of the sacroiliac joints, CRP or any other disease-specific feature such as the use of NSAIDs or biological treatment. CONCLUSION: Serum anti-CD74 IgA is a potentially useful diagnostic biomarker for axSpA. However, antibody levels do not correlate with any phenotypical feature, including microscopic gut inflammation, suggesting this to be a disease-specific rather than an inflammatory marker.

Work participation is unaffected in Belgian spondyloarthritis patients: data from the BelGian Inflammatory Arthritis and SpoNdylitis cohorT.

OBJECTIVES: This study aimed to (i) investigate actual work participation in Belgian spondyloarthritis (SpA) patients compared with the general population, and (ii) identify determinants of work-related outcomes. MATERIAL AND METHODS: Adult SpA patients from the Ghent University Hospital based Be-GIANT cohort (fulfilling ASAS classification criteria) were cross-sectionally questioned on their socio-economic status and completed a Work Productivity and Activity Impairment questionnaire (May 2018 to May 2019). Results were compared with national and regional data on the general population using indirect standardization. Associations between clinical and job characteristics and work-related outcomes were analysed with logistic regression (having a paid job) and negative binomial hurdle models (sick leave and presenteeism, i.e. restrictions while at work). RESULTS: A total of 215/262 (82%) patients of working age (<65 y/o) had a paid job, corresponding to an age- and sex-adjusted employment ratio of 1.00 (95% CI 0.88, 1.14). Patients worked 39.6h (10.5h)/week, and 49% (95% CI 42, 56%) reported sick leave in the previous year, similar to the general population (39.7h/week, 42%). In total, 56% reported presenteeism of median (IQR) 10% (0-20%). In multivariate analysis, functional impairment (BASFI) and health-related quality of life (HRQoL, EuroQoL-VAS) were associated with each work-related outcome, while contextual factors (education, physically demanding job) were positively associated with, respectively, having a paid job and presenteeism. Clinical characteristics showed no independent association with any of these outcomes. CONCLUSIONS: Evidence from this academic cohort study does not support a work participation gap between SpA patients and the general population, but confirms the role of physical function, overall HRQoL, and education or job type as risk factors for adverse work outcomes.

RORγt inhibition ameliorates IL-23 driven experimental psoriatic arthritis by predominantly modulating γδ-T cells.

OBJECTIVE: Divergent therapeutic outcomes on different disease domains have been noted with IL-23 and IL-17A-blockade in PsA. Therefore, elucidating the role of RORγt, the master regulator of type 17 immune responses, is of potential therapeutic interest. To this end, RORγt inhibition was assessed in combined skin, joint and gut inflammation in vivo, using a PsA model. METHODS: We tested the efficacy of a RORγt antagonist in B10.RIII mice challenged with systemic overexpression of IL-23 by hydrodynamic injection of IL-23 enhanced episomal vector (IL-23 EEV). Clinical outcomes were evaluated by histopathology. Bone density and surface erosions were examined using micro-computed tomography. Cytokine production was measured in serum and by intracellular flow cytometry. Gene expression in PsA-related tissues was analysed by qPCR. RESULTS: RORγt-blockade significantly ameliorated psoriasis, peripheral arthritis and colitis development in IL-23 EEV mice (improvement of clinical scores and weight loss respectively by 91.8%, 58.2% and 7.0%, P < 0.001), in line with profound suppression of an enhanced type IL-17 immune signature in PsA-affected tissues. Moreover, inflammation-induced bone loss and bone erosions were reduced (P < 0.05 in calcaneus, P < 0.01 in tibia). Sustained IL-23 overexpression resulted in only mild signs of sacroiliitis. Gamma-delta (γδ)-T cells, the dominant source of T cell-derived IL-17A and IL-22, were expanded during IL-23 overexpression, and together with Th17 cells, clearly countered by RORγt inhibition (P < 0.001). CONCLUSION: RORγt-blockade shows therapeutic efficacy in a preclinical PsA model with protection towards extra-musculoskeletal manifestations, reflected by a clear attenuation of type 17 cytokine responses by γδ-T cells and Th17 cells.

Neural network algorithm for detection of erosions and ankylosis on CT of the sacroiliac joints: multicentre development and validation of diagnostic accuracy.

OBJECTIVES: To evaluate the feasibility and diagnostic accuracy of a deep learning network for detection of structural lesions of sacroiliitis on multicentre pelvic CT scans. METHODS: Pelvic CT scans of 145 patients (81 female, 121 Ghent University/24 Alberta University, 18-87 years old, mean 40 ± 13 years, 2005-2021) with a clinical suspicion of sacroiliitis were retrospectively included. After manual sacroiliac joint (SIJ) segmentation and structural lesion annotation, a U-Net for SIJ segmentation and two separate convolutional neural networks (CNN) for erosion and ankylosis detection were trained. In-training validation and tenfold validation testing (U-Net-n = 10 × 58; CNN-n = 10 × 29) on a test dataset were performed to assess performance on a slice-by-slice and patient level (dice coefficient/accuracy/sensitivity/specificity/positive and negative predictive value/ROC AUC). Patient-level optimisation was applied to increase the performance regarding predefined statistical metrics. Gradient-weighted class activation mapping (Grad-CAM++) heatmap explainability analysis highlighted image parts with statistically important regions for algorithmic decisions. RESULTS: Regarding SIJ segmentation, a dice coefficient of 0.75 was obtained in the test dataset. For slice-by-slice structural lesion detection, a sensitivity/specificity/ROC AUC of 95%/89%/0.92 and 93%/91%/0.91 were obtained in the test dataset for erosion and ankylosis detection, respectively. For patient-level lesion detection after pipeline optimisation for predefined statistical metrics, a sensitivity/specificity of 95%/85% and 82%/97% were obtained for erosion and ankylosis detection, respectively. Grad-CAM++ explainability analysis highlighted cortical edges as focus for pipeline decisions. CONCLUSIONS: An optimised deep learning pipeline, including an explainability analysis, detects structural lesions of sacroiliitis on pelvic CT scans with excellent statistical performance on a slice-by-slice and patient level. CLINICAL RELEVANCE STATEMENT: An optimised deep learning pipeline, including a robust explainability analysis, detects structural lesions of sacroiliitis on pelvic CT scans with excellent statistical metrics on a slice-by-slice and patient level. KEY POINTS: • Structural lesions of sacroiliitis can be detected automatically in pelvic CT scans. • Both automatic segmentation and disease detection yield excellent statistical outcome metrics. • The algorithm takes decisions based on cortical edges, rendering an explainable solution.

Cluster analysis in early axial spondyloarthritis predicts poor outcome in the presence of peripheral articular manifestations.

OBJECTIVES: To assess whether two cluster analysis-based axial SpA (axSpA) endotypes (A for purely axial; B for both axial and peripheral) are stable over time and are associated with different long-term disease outcomes. METHODS: K-means cluster analysis was performed at each visit (until 5 years) on 584 patients from the DESIR cohort, who completed all planned visits, and validated in 232 consecutive axSpA patients from the BeGiant cohort. Cluster stability overtime was assessed by kappa statistics. A generalized linear mixed-effect analysis was applied to compare outcomes between clusters. Classification and regression tree (CART) analysis was performed to determine a decision rule able to assign a given patient to a definite cluster at onset. RESULTS: Both endotypes remained remarkably stable over time. In the DESIR cohort, patients in cluster B showed higher disease activity, worse functional outcome and higher need for anti-rheumatic drugs than patients in cluster A. CART analysis yielded three main clinical features (arthritis, enthesitis and dactylitis) that accurately determined cluster assignment. These results could be replicated in the Be-GIANT cohort. CONCLUSION: Cluster-based axSpA endotypes were reproducible in two different cohorts, stable over time and associated with different long-term outcome. The axSpA endotype with additional peripheral disease manifestations is associated with more severe disease and requires more intensive drug therapy. CLINICAL TRIAL REGISTRATION: clinicaltrials.gov, https://clinicaltrials.gov, NCT01648907.

Peripheral manifestations are major determinants of disease phenotype and outcome in new onset spondyloarthritis.

OBJECTIVES: To delineate the impact of peripheral musculoskeletal manifestations on stratification of disease phenotype and outcome in new-onset spondyloarthritis (SpA), using a prospective observational nationwide inception cohort, the BelGian Inflammatory Arthritis and spoNdylitis cohorT (Be-Giant). METHODS: Newly diagnosed adult SpA patients, fulfilling the Assessment of SpondyloArthritis International Society (ASAS) criteria for axial or peripheral SpA, were included in Be-Giant and prospectively followed every six months. Peripheral involvement (defined as arthritis, enthesitis and/or dactylitis) was determined in relation to clinically similar patient subsets at baseline and disease activity patterns during two-year follow-up, identified through K-means cluster analysis and latent class growth analysis. RESULTS: From November 2010 to March 2020, 367 patients were enrolled in Be-Giant, of whom 162 (44%) had peripheral manifestations. Two patient clusters [A, axial predominant (n = 248) and B, peripheral predominant (n = 119)] were identified at diagnosis. Longitudinal analysis (n = 115) revealed two trajectories of disease activity in each cluster: one with persistently high disease activity over time ('High'), the other rapidly evolving to low disease activity ('Low'). In cluster A patients, peripheral manifestations predisposed to the 'High' trajectory [odds ratio (OR) = 2.0, 95% CI: 1.3, 3.1, P = 0.001], despite more rapid initiation of biologics compared with patients without peripheral manifestations (hazard ratio (HR) = 2.1, 95% CI: 1.0, 4.4, P = 0.04 - Cox proportional-hazards model). CONCLUSION: Peripheral musculoskeletal manifestations are major determinants of phenotypical diversity in new-onset SpA. Intriguingly, stratification of axial SpA according to concomitant peripheral involvement identified an endotype with an unfavorable outcome despite more prompt therapeutic intensification with biologics. These observations justify an endotype-tailored approach beyond current ASAS/EULAR management recommendations.