Arthritis & Rheumatology

Objective: To determine whether autoantibodies are present in giant cell arteritis (GCA) using a high-dimensional autoantibody array. Methods: Serum was collected from patients with GCA (n=20), other related vascular inflammatory diseases (Takayasu arteritis n=12, IgG4-RD n=5, Behcet's disease n=6), SLE (n=5) and healthy controls (n=12). Autoantibodies to 15,312 protein targets were measured using the GeneCopeia OmicsArray proteomic antigen microarray panel. Results: Differential abundance analysis revealed no autoantibodies significantly elevated in GCA or other related vascular inflammatory diseases. In contrast, the SLE group showed a strong and promiscuous autoantibody response, with 175 significantly associated autoantibodies (Benjamini-Hochberg-adjusted P <0.05). Conclusions: No autoantibodies were significantly elevated in GCA. We identified known and novel autoantibodies in SLE.

Thrombotic primary antiphospholipid syndrome (thrPAPS) outcomes are associated with thrombosis type (arterial versus venous), recurrence, and antiphospholipid antibody (aPL) profile (single versus triple-aPL). We investigated molecular signatures underlying disease status and high-risk phenotypes. We performed whole-blood transcriptomics and mass spectrometry-based plasma proteomics in patients with thrPAPS and age/sex-matched healthy controls. Analyses included differential expression, pathway enrichment, weighted gene co-expression network analysis (WGCNA) and machine learning. Multi-Omics Factor Analysis (MOFA2) and network propagation were applied to identify latent molecular programmes associated with high-risk phenotypes. Transcriptomic and WGCNA analyses revealed an interferon-associated module associated with high-risk phenotypes. Plasma proteomics distinguished thrPAPS from healthy controls through a coordinated thromboinflammatory signature encompassing complement, acute-phase, platelet, and coagulation-associated pathways. Complement factor D, a rate-limiting enzyme of the alternative complement pathway, discriminated recurrent from single-event thrPAPS (AUC = 0.79) and correlated with thrombotic event count (Spearman's correlation = 0.62, p < 0.001). Mixed arterial/venous phenotype showed the greatest degree of subgroup-specific dysregulation, including complement and coagulation/fibrinolysis-related proteins. MOFA2 identified a proteome-dominant latent factor that increased with aPL burden (Spearman's correlation = 0.33, p = 0.017) and was enriched for complement cascade proteins. Network propagation embedded this signature within immune-cell signalling (STAT-1, PI3K-AKT, MAPK8, SRC), N-linked glycosylation, and mitochondrial oxidative phosphorylation. Longitudinal profiling identified reactive oxygen species-associated proteins during active disease. ThrPAPS is characterised by a complement-, interferon- and platelet-driven thromboinflammatory programme that scales with aPL and thrombosis burden, converging on innate immune activation as a central feature of high-risk disease.

Background: Interstitial lung disease (ILD) is one of the most common and potentially most devastating extra-articular complication of rheumatoid arthritis (RA) and is associated with substantial morbidity and mortality. However, reliable tools for the early identification of ILD in patients with RA remain limited. This study aimed to identify plasma protein biomarkers of RA-ILD and develop an interpretable machine learning model for risk prediction using data from the UK Biobank. Methods: We first evaluated the association between baseline RA and the risk of incident ILD in the UK Biobank using Cox proportional hazards models. Mendelian randomization analysis was then performed to investigate the potential causal relationship between RA and ILD. Finally, we analyzed 2,920 plasma proteins measured using the Olink platform in 781 eligible RA patients. Proteins associated with ILD risk were identified using Cox proportional hazards models and subsequently used to construct eight machine learning models. Model performance was assessed using the receiver operating characteristic curve (ROC) and decision curve analysis. The best-performing model was further interpreted using Shapley additive explanations (SHAP) to evaluate feature importance. Results: Compared with participants without RA, Patients with baseline RA had a significantly higher risk of developing ILD (Hazard ratio: 4.425, 95% CI: 3.549,5.518). The MR supported a potential causal association between RA and ILD (Odds ratio: 1.227, 95% CI: 1.121,1.343). Among the eight machine learning models, the CatBoost model showed the best performance, achieving an area under the curve (AUC) of 0.884 (95% CI: 0.773,0.996). The SHAP analysis identified LAG3, NPC2, and LAMP3 are the three most important plasma protein predictors of ILD development in patients with RA. Conclusion: Plasma proteomics combined with machine learning may provide a promising approach for identifying biomarkers and predicting ILD risk in patients with RA. LAG3, NPC2, and LAMP3 may serve as candidate biomarkers for RA-ILD and warrant further validation. Keywords: Rheumatoid arthritis, Interstitial lung disease, Mendelian randomization, Machine learning, Plasma proteins.

Background Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease which can lead to progressive disability and damage to multiple organs. Obesity is associated with higher disease activity in RA and inadequate long-term outcomes, so better understanding of mechanisms linking adiposity to immune dysregulation might help to refine optimal treatments. Monocytes are important contributors to immune activation in RA through antigen presentation and costimulatory signaling. We hypothesized that adiposity enhances monocyte costimulatory programming in RA, thereby promoting adaptive immune activation. Methods Single-cell RNA sequencing was performed using the 10x Genomics Flex platform on purified circulating monocytes from 31 donors (16 RA participants fulfilling 2010 ACR/EULAR classification criteria and 15 non-RA controls) generating transcriptomic profiles for approximately 135,599 monocytes. Donor-level pathway enrichment scores were calculated for predefined immune activation pathways including antigen processing and presentation, interferon signaling, and regulation of T-cell costimulation. Analyses were performed at the donor level to avoid cell-level pseudoreplication. Associations with disease status and body mass index were evaluated using factorial linear models and Spearman correlation analyses. Results Single-cell transcriptomic profiling identified classical, intermediate-like, non-classical, and interferon-responsive monocyte populations. RA was associated with enrichment of antigen processing and presentation programs in circulating monocytes (p=0.0106), indicating a primed antigen-presenting state. In contrast, regulation of T-cell costimulation pathway enrichment did not differ by RA status alone. However, within RA participants, higher BMI was associated with increased enrichment of monocyte T-cell costimulatory pathways (Spearman {rho}=0.56, p=0.0248), unlike in non-RA controls. Gene-level analyses demonstrated strong baseline expression of CD86, while ICOSLG and TNFSF4 transcripts were expressed at low levels overall, consistent with inducible costimulatory signaling programs. Conclusions These findings support a model in which metabolic dysregulation amplifies monocyte-mediated immune activation and may contribute to worsened disease outcomes in RA.

Objective: Tissue-specific biomarkers that are reliable and associated with clinical manifestations of idiopathic inflammatory myopathy (IIM) are lacking. The blood circulation in individuals serves as a central conduit, allowing communication between tissues and facilitating clearance and recycling of tissue-derived proteins. Thus we applied a dual antibody-based proximity extension assay to profile the plasma proteome in subtypes of patients with IIM. Methods: Plasma samples from 201 patients diagnosed with IIM at Karolinska University Hospital were analyzed using Olink. Clinical manifestations, disease activity measurements, and laboratory results were collected. First, we evaluated differential protein abundance across IIM subtypes. Then we calculated tissue scores for each disease subtype using tissue gene expression databases. Finally, interferon (IFN) and complement pathway scores were calculated. Results: Plasma from patients with dermatomyositis was enriched for IFN signaling and skin associated proteins, anti-synthetase syndrome (ASyS) for lung associated proteins, immune-mediated necrotizing myopathy (IMNM) for muscle associated proteins, and inclusion body myositis for T cell response proteins. Patients with IMNM showed the highest tissue score for skeletal muscles, and ASyS for lung tissue score. Skeletal muscle scores correlated strongly with muscle disease activity visual analog scale scores, creatinine kinase levels, and muscle weakness score. Patients with interstitial lung disease along with and those with anti-Jo1 autoantibodies showed differential enrichment of surfactant proteins and IFN pathway activation. Conclusions: Circulatory proteome is a promising tool to capture distinct tissue-specific responses that correlate with disease activity and tissue injury in patients with IIM.

BackgroundADP-ribosylation factor-like protein 15 (ARL15) is a rheumatoid arthritis (RA) susceptibility gene identified through GWAS. Previous studies suggested a role for ARL15 in synovial fibroblast (SF) pathogenicity, but its contribution to inflammatory arthritis remains unclear. We investigated the inflammatory role of ARL15 and its therapeutic potential in RA. MethodsARL15 was overexpressed in MH7A cells followed by bulk RNA sequencing and pathway enrichment analyses. Therapeutic relevance was evaluated in collagen-induced arthritis (CIA) mouse model using anti-ARL15 monoclonal antibodies, ARL15-targeting siRNA, or isoquinoline. Arthritis scores, histopathology, micro-CT and serum cytokines were assessed. Publicly available single-cell RNA sequencing (scRNA-seq) datasets were analyzed to determine ARL15 expression in RASF subsets. ResultsARL15 overexpression induced a pro-inflammatory transcriptional program characterized by upregulation of IL1A, IL1B, IL6, IL8, CXCL1, CXCL10, and CCL20. Gene set enrichment analysis revealed activation of IL6-JAK-STAT, TNF, interferon-response, and KRAS signaling pathways, with suppression of oxidative phosphorylation, lipid metabolism, and mTORC1 signaling. In CIA mice, ARL15 inhibition significantly reduced arthritis severity, inflammatory infiltrates, and joint destruction while preserving cartilage and bone integrity. Serum TNF-, IL-6, and IL-1{beta} levels were markedly decreased following ARL15 blockade. Combination monoclonal antibody treatment demonstrated the greatest therapeutic benefit. scRNA-seq analysis showed broad ARL15 expression across RA fibroblast populations, with enrichment in inflammatory lining and SF subsets. ConclusionsARL15 is a pro-inflammatory regulator of SF activation and arthritis progression. Integrated transcriptomic, single-cell, and in vivo analyses identify ARL15 as a therapeutic target for RA and support further translational development of ARL15 based therapies.

Background: Psoriatic arthritis (PsA) is an inflammatory condition involving joints, tendon-bone entheses and synovium that can develop in individuals with psoriasis. Early, accurate clinical diagnosis remains difficult. Extracellular vesicles (EVs) carry proteins and miRNAs that Methods: PubMed and Embase were searched from inception through May 21st, 2026, and human studies examining EV-associated protein or miRNA biomarkers in PsA and related psoriatic or inflammatory diseases were included, with risk of bias assessed using a modified Newcastle-Ottawa Scale and diagnostic accuracy summarized using HSROC/BRMA models when data were sufficient. Results: Seven studies met the inclusion criteria, including 119 individuals with PsA (weighted mean age: 49.8 years; 43.7% female), 205 individuals with non-PsA psoriasis (weighted mean age: 46.4 years; female %: NA), 55 controls (weighted mean age: 44.5 years; 38.2% female), and 50 individuals with other inflammatory joint disorders (weighted mean age: 58.0 years; 58.0% female). EV-associated protein markers demonstrated heterogeneous findings related to immune, vascular, inflammatory, and osteoimmunological signaling. Only 4.2% (4/95) of miRNAs were consistently identified across studies comparing PsA with non-PsA psoriasis, with lower overlap (1.5%, 1/67) in studies comparing PsA with controls. ROC meta-analysis suggested preliminary diagnostic potential, particularly for distinguishing PsA from non-PsA psoriasis, although evidence was constrained by small study numbers. Conclusions: EV-associated proteins and miRNAs are potential biomarker candidates for PsA, reflecting inflammatory, vascular, and osteoimmunological processes underlying disease pathophysiology. However, current evidence remains preliminary and limited by small cohorts, methodological heterogeneity, and inconsistent reporting across studies.

Background Pain frequently persists in rheumatoid arthritis (RA), despite effective control of inflammation. The mechanisms driving this residual pain remain poorly characterised in individual patients. Methods In 172 patients with established RA and clinically relevant pain (mean NRS 6.5/10) and 80 pain free controls, we combined indicators of inflammatory disease (CRP, joint counts, power Doppler ultrasound), centrally mediated pain (Widespread Pain Index, painDETECT), psychological distress (PHQ ADS) and quantitative sensory testing (QST). Latent profile analysis was applied without predefined thresholds. Results Four phenotypes were identified: a peripheral, low-inflammation/low-central phenotype (38%); a predominantly inflammatory phenotype (7%); and moderate (43%) and severe (12%) centrally mediated phenotypes. Centrally mediated phenotypes reported the highest pain (NRS 8.2), worst disease impact and lowest employment. DAS28 CRP was similar in both the inflammatory and severe centrally mediated phenotypes but for different reasons, swollen joints and CRP versus tender joints , and did not distinguish them. Conditioned pain modulation was impaired relative to controls (p<0.001) and most reduced in the severe centrally mediated phenotype. Psychological distress was the strongest independent predictor of pain severity (model R squared=0.33), whereas inflammatory markers were not. Principal components analysis identified swollen joint count (loading 0.63) and the tender swollen joint difference (loading 0.60) as accessible clinical markers of the inflammatory and centrally mediated phenotypes respectively. Conclusions A data driven approach identified four mechanism-based pain phenotypes in RA. This framework moves pain assessment beyond inflammation alone and provides a basis for testing analgesic strategies to target the predominant pain mechanism in individual patients.

Objective: Clonal hyperexpansion of CD4 T cells is a characteristic feature of rheumatoid arthritis (RA). Equally large T cell clones also arise in physiological ageing or latent viral infection and adopt a replicative senescence programme - a tolerance mechanism that limits immune activation by innate-like reprogramming and proliferative arrest. We aimed to characterise the senescence programme of hyperexpanded CD4 T cell clones in RA and to define their clinical associations. Methods: Hyperexpanded T cell clones were characterised by single-cell RNA and T cell receptor profiling of peripheral T cells from RA patients and healthy donors. Flow cytometric validation was performed in two cross-sectional cohorts (n=15, n=45), paired blood and synovial fluid (n=20) or synovial tissue (n=18) sampling, and a non-interventional study of co-stimulatory blockade with abatacept (n=6). Results: Hyperexpanded CD4 T cell clones exhibited a CCR7-CD27- phenotype and accumulated in RA joints. Their frequency correlated with disease activity and their surface profile was modulated by abatacept, suggesting susceptibility to therapeutic intervention. At the molecular level, hyperexpanded clones converged on a phenotype consistent with replicative senescence, characterised by natural killer (NK) cell-reminiscent cytotoxic reprogramming, loss of co-stimulatory molecules, and reduced translational activity. However, compared with healthy donor counterparts, hyperexpanded RA CD4 T cell clones showed reduced senescence-associated cytotoxic and NK cell markers, and increased IL-7 receptor signalling, indicating attenuated senescence and preserved capacity for homeostatic proliferation. Conclusion: We propose that replicative senescence insufficiently constrains hyperexpanded clones in RA, resulting in sustained antigen reactivity in autoreactive clones and perpetuation of chronic inflammation.

Plasma proteins are promising biomarkers and potential drug targets in psoriasis. We conducted a two-sample Mendelian randomisation analysis integrating protein quantitative trait loci from UK Biobank and deCODE genetics with a psoriasis GWAS meta-analysis of 36,466 cases. To strengthen causal inference, we performed colocalisation analyses to evaluate shared genetic signals and applied summary data-based MR (SMR) with HEIDI testing using expression quantitative trait loci to exclude linkage-driven associations. After correction for multiple testing, 78 circulating proteins showed genetically predicted associations with psoriasis, with 27 demonstrating strong colocalisation (PPH4>80%). Triangulation prioritised 12 Tier 1 proteins, STX4, FLT3, NFKB1, IL18, PRSS53, SPAG1, SGSH, PLAT, RALB, TNFSF11, SPHK2, and STAT3, supported by consistent effects and no heterogeneity. Network profiling and Genome for REPositioning analyses assessed biological connectivity and druggability, revealing enrichment in anatomical therapeutic chemical groups L and B. Single-cell RNA sequencing confirmed cell-type-specific expression and modulation following IL-23 blockade.

Joint involvement is a major driver of disability in systemic sclerosis (SSc), yet its pathophysiology remains poorly understood. In the absence of specific evidence, SSc synovitis is treated by analogy with rheumatoid arthritis (RA). Here, we present the first comprehensive molecular characterization of SSc synovitis, integrating histology, single-cell RNA sequencing, and spatial multi-omics of synovial biopsies from SSc patients, RA patients, and non-inflammatory controls with in vitro validation. We show that SSc synovitis is characterized by distinct pathomechanisms from RA. Histologically, most SSc biopsies displayed a pauci-immune pathotype with sparse immune infiltrates and predominant stromal cells. At molecular level, synovial fibroblasts in SSc were characterized by a disease-specific type I interferon (IFN) response program, in contrast to the TNF-dominant profile of RA, accompanied by dysregulation of the complement cascade. This IFN program extended across multiple synovial cell types, including monocyte-derived macrophages and endothelial cells, and was spatially organized into focal myeloid niches and a diffuse stromal program. Systemically, elevated serum IFN-2a levels were associated with the presence of clinical synovitis in an independent cohort of SSc patients. We furthermore show that similar IFN-driven programs are shared between skin and synovium in SSc. Genes downregulated by IFNAR1 blockade in SSc skin were enriched in SSc synovium, supporting IFN receptor blockade as a multi-organ target therapeutic strategy. These findings reframe SSc synovitis as a less destructive, IFN-driven stromal condition distinct from RA and provide a mechanistic basis for dedicated clinical trials for joint inflammation in SSc.

Inhibition of tumor necrosis factor receptor 1 (TNFR1) represents a major therapeutic strategy for chronic autoimmune and inflammatory diseases such as rheumatoid arthritis (RA). As current anti-TNF therapies can cause adverse side effects due to global blockade of the ligand, receptor-specific inhibition of TNFR1 signaling has emerged as a highly sought-after strategy. We have recently identified a novel peptide-based allosteric inhibitor, FKC (FKCRRWQWRMKK), that targets TNFR1 conformationally active region to alter receptor conformational states and disable receptor-ligand signaling complex. Here, we evaluated the therapeutic efficacy of FKC in a human TNF (hTNF) transgenic mouse model of RA. FKC treatment improves clinical RA scores in hTNF mice, accompanied by enhanced grip strength and increased walking distance. Importantly, FKC treatment inhibits TNF/TNFR1-mediated inflammation and attenuates RA pathology in hTNF mice. Together, our findings establish FKC as a promising new class of peptide-based therapeutics for chronic inflammatory diseases through selective inhibition of TNFR1 signaling.

ObjectivesThe long non-coding RNA HOTAIR has previously been shown to drive pro-fibrotic gene expression in SSc dermal fibroblasts through its ability to interact with EZH2. Targeting EZH2 enzymatic activity can reverse HOTAIR mediated pro-fibrotic gene expression but its many functions make it an undesirable therapeutic target for SSc. Recently inhibitors selectively targeting the HOTAIR/EZH2 interaction have been developed. The aim of this study was to characterise the ability of one of these inhibitors to modulate SSc tissue remodelling. MethodsExplanted healthy and SSc dermal fibroblasts were treated with the HOTAIR/EZH2 inhibitor AC1Q3QWB (AQB) (20{micro}M) for 48 hours. In addition, healthy dermal fibroblasts were transduced with a lentivirus encoding HOTAIR or a scrambled control. Conditioned media from healthy, SSc and HOTAIR-expressing dermal fibroblasts was used to stimulate human keratinocytes (HaCaTs). Scramble control and HOTAIR expressing fibroblasts were grown in 3D skin equivalents containing primary keratinocytes and keratin 9 (K9) immunohistochemistry performed. ResultsAQB inhibits pro-fibrotic gene expression in HOTAIR expressing dermal fibroblasts, validating the specificity of the inhibitor. In SSc patient dermal fibroblasts, AQB blocked pro-fibrotic gene expression but did not affect gene expression in healthy dermal fibroblasts. SSc patient skin was shown to express high levels of the palmoplantar specific K9 and Epithelial to Mesenchymal transition (EMT) markers. Through co-culture experiments we showed these effects were mediated by SSc dermal fibroblasts. This tissue remodelling was disrupted when HOTAIR/EZH2 interaction was inhibited in the fibroblasts with AQB. ConclusionsWe have shown for the first time that directly inhibiting HOTAIR/EZH2 interaction blocks pro-fibrotic gene expression in SSc fibroblasts and tissue re-modelling found in SSc patient skin. This may represent a novel therapeutic intervention.

Background and Aims: Residual pulmonary vascular obstruction (RPVO) defined as the persistence of thrombotic material within the pulmonary arteries several months after an acute pulmonary embolism (PE) is associated with an increased risk of severe complications, including recurrent events and chronic pulmonary hypertension. However, the genomic architecture underlying RPVO in unprovoked PE remains poorly understood, and this study aims to address this gap. Method: By leveraging genetic and imaging RPVO data from three independent cohorts totaling 586 unprovoked PE patients, we conducted a meta-analysis of genome wide association study (GWAS) of RPVO using a dedicated statistical method to handle the semi-continuous distribution of RPVO. The meta-GWAS was complemented by haplotype association analyses and transcriptome wide association studies as well as Mendelian Randomization (MR) approaches based on plasma metabolites and proteins. Results: Through meta-GWAS, we identified one locus, OSTN, associated with RPVO (lead variant rs59109356 associated with a ~2-fold increase of RPVO, p=3.92x10-8). A second locus, CCN4, previously reported to associate with pulmonary fibrosis, was also identified, with evidence of association approaching genome-wide significance (p=6.7x10-8). We also identified a common haplotype spanning over AHSG/HRG/KNG1 associated with a ~3-fold increase of RPVO (p=2.96x10-8). Using plasma protein-based MR, we demonstrated that one unit increase in genetically determined plasma levels of IL-1 R AcP encoding IL1RAP was associated with a 28% (p=1.32x10-6) reduction in RPVO. We also observed statistical evidence that the CCN4 (p=0.06) and IL1RAP (p=0.02) loci associate with the risk of PE recurrence in a sample of 1,617 unprovoked PE patients. Conclusions: By identifying novel molecular determinants of RPVO that map to loci involved in inflammatory pathways and vascular remodeling, our study provides evidence that inflammation is the predominant, and likely the key mechanism underlying RPVO, whereas impaired fibrinolysis appears to play a more limited role.

Numbers of ARID3a (AT-Rich Interaction Domain 3a) -expressing B lymphocytes from patients with systemic lupus erythematosus (SLE) are associated with increased disease activity. Normally, ARID3a-expressing circulating naive B cells are rare, but in SLE naive B cells dramatically increase ARID3a expression. We found that in vitro stimulation of B lymphocytes from healthy individuals with a cocktail of cytokines and agonists induced ARID3a in a subset of activated naive B cells and in IgD-CD27- double negative B cells previously associated with autoimmunity. Single cell RNA-seq of isolated naive B cells from ten SLE patients, with varying frequencies of ARID3a-expressing cells, revealed that ARID3a-associated genes included activation markers. Moreover, our data revealed the unexpected co-expression of the scavenger receptor CD68 with ARID3a, at both the transcript and protein level, in activated subsets of naive B cells. Inhibition of ARID3a in stimulated B cell cultures blocked naive B cell activation and CD68 expression. Together, these data identify ARID3a and CD68 as markers of naive B cell precursors associated with autoimmunity in SLE.

Rheumatoid arthritis (RA) remains incompletely understood, limiting targeted prevention. In this work, genome-wide association study meta-analyses were performed for RA and seropositive RA, comprising approximately one million participants of European ancestry. Eight and six novel genomic risk loci were defined for RA and seropositive RA, and candidate causal genes were identified, highlighting relevant biological pathways, including established immune pathways and estrogen metabolism. Novel disease-specific polygenic risk scores (PRSs) were constructed, enhancing predictive performance over clinical risk factors (incremental C-statistics of 2.7 and 5.1 for RA and seropositive RA, respectively). In parallel, integrating metabolomic data into high-dimensional models enhanced risk stratification over models based on clinical risk factors and genomics, particularly for seropositive RA, where the hazard ratio of the highest decile increased from 4.869 to 5.697. These findings expand the understanding of genetic factors underlying RA and support the value of including PRSs in risk assessment, while suggesting metabolomic integration may further enhance risk stratification, particularly for seropositive RA.

Objective We developed a patient- and joint-specific explant co-culture system to model active psoriatic arthritis (PsA) and capture donor-specific tissue responses to therapeutic interventions. Methods Based on convergent joint pathology between end-stage osteoarthritis (OA) and PsA, OA cartilage-bone and synovium tissues from arthroplasty patients were exposed to synovial fluid (SF) obtained from PsA and OA patients. Histological outcomes (synovitis, proteoglycan distribution), curated gene expression, soluble mediators, and proteinase activity were assessed over 7-21-days. Model responses to dexamethasone (DEX) and the anti-tumor necrosis factor antibody adalimumab (ADA) were evaluated. Results PsA SF induced distinct inflammatory and tissue remodeling responses compared to OA SF and control conditions, including altered cartilage proteoglycan distribution, increased synovitis, and tissue-specific transcriptional changes. Multivariate analyses identified distinct osteochondral and synovial transcriptional responses to PsA SF, characterized by reduced osteochondral COL2A1 expression and increased synovial expression of inflammatory and matrix-remodeling genes, including MMP1 and CXCL8. DEX and ADA elicited donor-specific responses across histological, transcriptional, and protein readouts. Among multivariable model outputs, histologic synovitis scores emerged as the most clinically aligned parameter, demonstrating associations with baseline PsA donor disease activity, active joint counts, pain, high-sensitivity C-reactive protein (hsCRP), and radiographic scores. Synovitis score changes to DEX and ADA treatments also aligned with corresponding PsA SF donor clinical improvements to corticosteroid and TNF-modifying therapies. Conclusion This osteochondral-synovial explant co-culture model captured donor-specific inflammatory and treatment-responsive features of PsA SF-induced pathology, thereby providing a clinically relevant ex vivo platform for studying patient-specific therapeutic responses in PsA.

Fc{gamma}RIIa, encoded by FCGR2A, is a widely expressed Fc receptor implicated in autoimmunity and infectious disease susceptibility. To fine-map the rheumatoid arthritis (RA) association at the complex FCGR locus, we combined gene-specific resequencing, genetic association studies in UK and Spanish European cohorts, functional genomics, structural biology, biophysical analyses, and cellular assays. We identified a common European FCGR2A haplotype (2A.3), defined by Q27W, H131H, and the RA-associated SNP rs12746613, which showed the strongest association with RA. Multi-omics analyses demonstrated that 2A.3 is associated with reduced expression of the soluble FCGR2A splice variant and lower circulating soluble Fc{gamma}RIIa levels. Functional studies revealed altered IgG interactions and delayed Fc{gamma}RIIa signal transduction associated with Q27W, while structural analyses found no evidence for stable ectodomain dimerisation. Together, these findings identify 2A.3 as an important functional contributor to RA susceptibility and provide mechanistic insight into how FCGR2A variation may influence immune regulation and disease risk in Europeans.

Psoriatic disease (PsD) is associated with metabolic dysfunction-associated steatotic liver disease (MASLD), but the hepatic effects of biologic therapies are unclear. We evaluated paired liver MRI and multi-modal immunoprofiling in PsD patients initiating new systemic therapy. COLIPSO is a prospective cohort of adults with moderate-to-severe psoriasis or psoriatic arthritis (PsA) starting a new conventional synthetic or biologic disease-modifying antirheumatic drug (DMARD). Liver MRI was performed at baseline and ~6 months. A subset of participants with PsA underwent peripheral blood flow cytometry and single-cell RNA sequencing (scRNAseq). Primary outcomes were within-subject change in quantitative MRI measures of liver disease activity and fat content (iron-corrected T1 [cT1] and proton density fat fraction [PDFF]). Bayesian models were used. Thirty-five participants (mean age 50 +/- 13 years; 61% male) were followed for ~29 weeks. Baseline disease activity was moderate (mean DAPSA 29) and 40% had MASLD. IL 17 inhibitors (IL-17i) improved PDFF (-1.58 +/- 1.61%) and cT1(-43.6 +/- 52.7ms), whereas TNFi showed little change. Compared with csDMARD, IL 17i improved PDFF (probability of direction [pd] 89%) and cT1 (pd 93%), which was not seen with TNFi. Flow cytometry (n=17) linked baseline gamma delta T-cell and ThGM-CSF T-cell abundance with cT1 and PDFF. scRNAseq highlighted baseline transcriptomic signatures in MAIT cells associated with cT1 and PDFF. Naive T-cell RNA signatures at baseline were associated with MRI improvements. In PsD, only IL-17i were associated with improved liver disease in addition to improving clinical PsD outcomes. T-cell subtypes bridging innate and adaptive immunity were associated with liver disease features.

Background: Smartphone enabled remote patient monitoring has the potential to complement conventional follow-up in inflammatory arthritis. We previously presented the finger fold index (FFI) derived from hand photographs as ratio of automated detected proximal interphalangeal (PIP) joint diameter and surface of dorsal finger folds as a digital biomarker for clinical joint swelling and disease activity in rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Objective: To evaluate the feasibility, image quality, patient engagement, and clinical utility of both HCP- and patient-collected hand photographs integrated into a national rheumatology registry, and to assess the performance of the FFI as an image-derived digital biomarker for clinical joint swelling of the proximal interphalangeal joints in a real-world arthritis cohort. Methods: In this longitudinal multicenter study, a photo function with written instructions were integrated into the Swiss Clinical Quality Management in Rheumatic Diseases (SCQM) registry and their mySCQM mobile application, respectively. Patients with RA or PsA contributed longitudinal smartphone photographs together with patient-reported outcomes (PROs) via the mySCQM mobile application while health care professionals (HCPs) acquired images during routine visits. After manual quality assessment, images were processed using an automated computer vision pipeline to derive the FFI, a digital biomarker based on dorsal finger-fold morphology. Image quality was evaluated for both HCP- and participant-collected photographs, and patient engagement was assessed. Associations between FFI, clinical proximal interphalangeal (PIP) joint swelling, RADAI-5, DAS28-CRP and longitudinal changes were assessed. A generalized linear mixed model was used to estimate the association between FFI and joint swelling while accounting for repeated measures and within-subject correlations. Results: Between 2023 and 2025, 374 RA and PsA patients were included. HCPs captured 977 hand images while 174 patients collected 1228 hand images via the mySCQM app. Patients demonstrated sustained engagement after instruction, contributing a mean of seven images during data collection. Following quality control, 1729 hand images comprising 4048 PIP joints were included for analysis. Image quality was comparable between patient-acquired and HCP-acquired photographs; 78.3% of the patient-acquired vs. 73.5% of the HCP-acquired hand images were suitable to run the ML-model. 23.1% of the cropped joints had to be removed after the running of the FFI algorithm due to false diameter or finger fold detection e.g. due to wrong hand positioning. In images taken by HCPs, mean FFI and DAS28-CRP were weakly but significantly correlated (Spearmans {rho} = 0.164; 95% CI [0.004 to 0.317]; p = 0.039). Conversely, RADAI-5 scores did not correlate with the mean FFI in RA patients (r = 0.007, p = 0.932, 95% CI [-0.169-0.183]). At follow-up visits, clinical swelling resolved in 40 joints, of which in 68.0% the direction of the delta FFI was concordant with the clinical change. In contrast, 13 joints developed incident clinical swelling, of which 87.5% had a direction of the delta FFI that was concordant with the clinical change. However, the GLMM showed no significant associations between swelling and joint location or time-varying FFI, and no evidence of interaction between FFI and PIP joint. Conclusion: Integration of patient self-imaging into a remote monitoring application for inflammatory arthritis is feasible and achieves image quality comparable to clinician acquired photographs. The FFI derived from collected images shows association with clinical joint swelling and disease activity scores, but not PROs. In a substantial proportion of images, the FFI algorithm could not be applied because of insufficient image quality. More standardized image acquisition and further refinement of the FFI algorithm are warranted.