Pathobiology Of Early Arthritis Cohort Research Articles

Deconvolution of synovial myeloid cell subsets across pathotypes and role of COL3A1+ macrophages in rheumatoid arthritis remission.

Monocyte/macrophage (Mo/Mp) is a critical cell population involved in immune modulation of rheumatoid synovitis (RA) across different pathotypes. This study aims to investigate the contribution of Mo/Mp clusters to RA activity, and the biological function of particular subtypes in RA remission. We integrated single-cell RNA sequencing datasets from 4 published and 1 in-house studies using Liger selected by comparison. We estimated the abundance of Mo/Mp subtypes in bulk RNA-seq data from the 81 patients of the Pathobiology of Early Arthritis Cohort (PEAC) using deconvolution analysis. Correlations between Mo/Mp subtypes and RA clinical metrics were assessed. A particular cell type was identified using multicolor immunofluorescence and flow cytometry in vivo and successfully induced from a cell line in vitro. Potential immune modulation function of it was performed using immunohistochemical staining, adhesion assay, and RT-qPCR. We identified 8 Mo/Mp clusters. As a particular subtype among them, COL3A1+ Mp (CD68+, COL3A1+, ACTA2-) enriched in myeloid pathotype and negatively correlated with RA severity metrics in all pathotypes. Flow cytometry and multicolor immunofluorescence evidenced the enrichment and M2-like phenotype of COL3A1+ Mp in the myeloid pathotype. Further assays suggested that COL3A1+ Mp potentially attenuates RA severity via expressing anti-inflammatory cytokines, enhancing Mp adhesion, and forming a physical barrier at the synovial lining. This study reported unexplored associations between different pathologies and myeloid cell subtypes. We also identified a fibroblast-and-M2-like cluster named COL3A1+ Mp, which potentially contributes to synovial immune homeostasis. Targeting the development of COL3A1+ Mp may hold promise for inducing RA remission.

Predicting best treatment in rheumatoid arthritis

BackgroundAlthough targeted biological treatments have transformed the outlook for patients with rheumatoid arthritis (RA), 40% of patients show poor clinical response, and there is an imperative to unravel the molecular pathways and mechanisms underlying non-response and disease progression. 5–20% of RA individuals do not respond to all current medications including biologic and targeted therapies, which suggests that distinct pathogenic processes underlie multi-drug refractoriness. ObjectivesIn this brief review we discuss advances from recent studies in precision medicine in rheumatoid arthritis. MethodsBulk RNA-Sequencing of synovial biopsies from RA individuals combined with histology and deep clinical phenotyping has revealed substantial insights into divergent pathogenic pathways which lead to disease progression and illuminated mechanisms underlying failure to response to specific treatments. Biopsy-driven randomised controlled trials, such as R4RA and the forthcoming STRAP trial, have enabled the development of machine learning predictive models for predicting response to different therapies. ResultsIn the Pathobiology of Early Arthritis Cohort (PEAC), gene expression analysis showed that individuals could be classified into three gene expression subgroups which correlated with histopathotypes defined by histological markers: pauci-immune fibroid pathotype characterised by fibroblasts and an absence of immune inflammatory cells; diffuse-myeloid pathotype characterised by macrophage influx; and the lympho-myeloid pathotype delineated by the presence of B cells, but typically containing a complex inflammatory infiltrate with ectopic lymphoid structure formation. In the R4RA biopsy-driven randomised controlled trial, patients were randomised to either rituximab or tocilizumab. Comprehensive analysis of synovial biopsies pre/post-treatment identified gene signatures of response associated with pathogenic pathways which could be tracked over time. A group of true refractory patients were identified who had failed anti-TNF prior to the study (it was an entry criterion) and then subsequently failed both trial biologics during the trial. RNA-Seq analysis and digital spatial profiling identified specific cell types including DKK3+ fibroblasts as being associated with the refractory state. We identified machine learning predictive models based on specific gene signatures which were able to predict future response to therapy as well as the refractory state. ConclusionsRNA-sequencing of synovial biopsies has enabled substantial progress in understanding disease endotypes in RA and identifying synovial gene signatures which predict prognosis and future response to treatment.

Network analysis of synovial RNA sequencing identifies gene-gene interactions predictive of response in rheumatoid arthritis

BackgroundTo determine whether gene-gene interaction network analysis of RNA sequencing (RNA-Seq) of synovial biopsies in early rheumatoid arthritis (RA) can inform our understanding of RA pathogenesis and yield improved treatment response prediction models.MethodsWe utilized four well curated pathway repositories obtaining 10,537 experimentally evaluated gene-gene interactions. We extracted specific gene-gene interaction networks in synovial RNA-Seq to characterize histologically defined pathotypes in early RA and leverage these synovial specific gene-gene networks to predict response to methotrexate-based disease-modifying anti-rheumatic drug (DMARD) therapy in the Pathobiology of Early Arthritis Cohort (PEAC). Differential interactions identified within each network were statistically evaluated through robust linear regression models. Ability to predict response to DMARD treatment was evaluated by receiver operating characteristic (ROC) curve analysis.ResultsAnalysis comparing different histological pathotypes showed a coherent molecular signature matching the histological changes and highlighting novel pathotype-specific gene interactions and mechanisms. Analysis of responders vs non-responders revealed higher expression of apoptosis regulating gene-gene interactions in patients with good response to conventional synthetic DMARD. Detailed analysis of interactions between pairs of network-linked genes identified the SOCS2/STAT2 ratio as predictive of treatment success, improving ROC area under curve (AUC) from 0.62 to 0.78. We identified a key role for angiogenesis, observing significant statistical interactions between NOS3 (eNOS) and both CAMK1 and eNOS activator AKT3 when comparing responders and non-responders. The ratio of CAMKD2/NOS3 enhanced a prediction model of response improving ROC AUC from 0.63 to 0.73.ConclusionsWe demonstrate a novel, powerful method which harnesses gene interaction networks for leveraging biologically relevant gene-gene interactions leading to improved models for predicting treatment response.

Analysis of Complement Gene Expression, Clinical Associations, and Biodistribution of Complement Proteins in the Synovium of Early Rheumatoid Arthritis Patients Reveals Unique Pathophysiologic Features.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial hyperplasia and inflammation. The finding of autoantibodies in seropositive RA suggests that complement system activation might play a pathophysiologic role due to the local presence of immune complexes in the joints. Our first objective was to explore the Pathobiology of Early Arthritis Cohort (PEAC) mRNA sequencing data for correlations between clinical disease severity as measured by DAS28-ESR (disease activity score in 28 joints for erythrocyte sedimentation rate) and complement system gene expression, both in the synovium and in blood. Our second objective was to determine the biodistribution using multiplex immunohistochemical staining of specific complement activation proteins and inhibitors from subjects in the Accelerating Medicines Partnership (AMP) RA/SLE study. In the PEAC study, there were significant positive correlations between specific complement gene mRNA expression levels in the synovium and DAS28-ESR for the following complement genes: C2, FCN1, FCN3, CFB, CFP, C3AR1, C5AR1, and CR1 Additionally, there were significant negative correlations between DAS28-ESR and Colec12, C5, C6, MASP-1, CFH, and MCP In the synovium there were also significant positive correlations between DAS28-ESR and FcγR1A, FcγR1B, FcγR2A, and FcγR3A Notably, CFHR4 synovial expression was positively correlated following treatment with the DAS28-ESR at 6 mo, suggesting a role in worse therapeutic responses. The inverse correlation of C5 RNA expression in the synovium may underlie the failure of significant benefit from C5/C5aR inhibitors in clinical trials performed in patients with RA. Multiplex immunohistochemical analyses of early RA synovium reveal significant evidence of regional alterations of activation and inhibitory factors that likely promote local complement activation.

A Snap Shot of Complement Gene Expression and Presence of Complement Proteins in Synovial Biopsies from Early Rheumatoid Arthritis Patients

Abstract The etiology of rheumatoid arthritis (RA) is unknown. Previous studies of mouse models of RA have strongly implicated the alternative and lectin pathways of the complement system in disease pathogenesis. Here we explored the Pathobiology of Early Arthritis Cohort (PEAC) tissue RNA sequencing (RNA-seq) database and identify correlations among complement gene expression, Fc receptor expression and clinical severity, measured as disease activity score 28 - erythrocyte sendimentation rate (DAS28-ESR), in both blood and synovium. We also evaluated the biodistribution of complement activation pathway proteins and inhibitors using Multispectral ImmunoHistoChemical (MIHC) staining. Ultrasound guided synovial biopsies (n = 23), obtained from Accelerating Medicines Partnership (AMP) studies, were subjected to MIHC for various complement proteins. Our analyses revealed that in the synovium, but not in blood, significant positive correlations existed between complement gene expression and DAS28-ESR for C2, CFB, FCN1, C3AR1, C5AR1, and CR1. Surprisingly, levels of MASP1, Colec12, C5 and C6 RNA inversely correlated with baseline DAS28-ESR. After 6 months therapy, baseline CFHR4 positively correlated with delta DAS28-ESR. In the synovium, there were also significant positive correlations between DAS28-ESR and FcγR1A, FcγR1B, FcγR2A and FcγR3A. In early RA (ERA) synovium, a significantly (p < 0.05) higher levels of cells expressed CFH compared with CFB and CFHR4. We also found regional imbalance between C3 and CFH in ERA synovial biopsies. ERA synovial biopsies implicate the complement system in early disease and reveal intriguing differences among factors in clinical relevance, outcome and localized tissue dysregulation. Supported by R01AR51749-16

Role of synovial fibroblast subsets across synovial pathotypes in rheumatoid arthritis: a deconvolution analysis

ObjectivesTo integrate published single-cell RNA sequencing (scRNA-seq) data and assess the contribution of synovial fibroblast (SF) subsets to synovial pathotypes and respective clinical characteristics in treatment-naïve early arthritis.MethodsIn this in...

OP0011 INTEGRATION OF FLOW AND DIGITAL CYTOMETRY IN EARLY TREATMENT-NAÏVE RHEUMATOID ARTHRITIS IDENTIFIES DISTINCT IMMUNOPHENOTYPES IN PERIPHERAL BLOOD AND DISEASE TISSUE

Background:The study of synovial tissue in patients with Rheumatoid Arthritis (RA) has led to the identification of synovial patterns of immune cell infiltration and specific cellular subsets associated that have been disease activity and clinical outcomes(1–3). However, the relationship of circulating and synovial immune cell sub-sets with histopathological features and clinical outcomes remains to be defined.Objectives:To assess the relationship of peripheral blood and synovial immune cells with RA histopathology and clinical outcomes, by performing flow and digital cytometry in matched peripheral blood and synovial samples from patients with early RA.Methods:70 patients with early (<12 months) untreated RA (2010 criteria) recruited in the pathobiology of early Arthritis Cohort (PEAC) at the Barts Health NHS Trust were included(1). Peripheral blood mononuclear cells (n=70) were analysed by flow cytometry. Matched synovial tissues (n=70) obtained by minimally invasive ultrasound-guided synovial biopsy underwent semi-quantitative scoring (0-4) of immune cell infiltration and classification into lympho-myeloid (LM), diffuse-myeloid (DM) and pauci-immune (PI) pathotypes, as previously described(1). 49 synovial and 36 matched peripheral blood samples underwent RNA-sequencing and were analysed by digital cytometry (Xcell) (4) and Singular Value Decomposition (SVD).Results:Circulating B cells and their subsets showed significant inverse correlations with inflammatory markers (ESR, CRP), disease activity (swollen joints, four components and two components(5) DAS28) and ultrasound scores (Fig 1A). Among T cell subsets, CXCR5-PD1hiICOS+CD4+ T cells (T peripheral helper cells, Tph) had strong positive correlations with inflammatory markers (ESR and CRP), disease activity (DAS28) and ultrasound scores (Fig 1B). Tph in the peripheral blood also correlated with immune cell infiltration in synovia (Fig 1C) and were significantly higher in patients with a LM pathotype (Fig 1D). Accordingly, circulating Tph were associated with synovial LM pathotype independently of clinical features such as DAS28, ACPA positivity, Body Mass Index (BMI) and age (AUC 0.821). By applying digital cytometry in matched synovial and peripheral blood samples, synovial B and T cells were significantly higher in patients with a LM pathotype, in line with the histological definition of the LM pathotype – rich in B and T cells. On the contrary, circulating B cells and total CD4 and CD8 T cells were significantly lower in patients with a synovial LM pathotype (Fig 1E). The Tph signature in synovia derived by Singular Value Decomposition (SVD) correlated with baseline ESR (R 0.38, p<0.0001) and DAS28 (R 0.35, p <0.0001) and with delta-DAS28 after 6 months of treatment with conventional synthetic DMARDs (R 0.27, p 0.026). Finally, the baseline synovial Tph signature was significantly higher in patients who progressed to the use of biologics and was predictive of future biologic DMARDs use, independently of baseline DAS28, ACPA positivity, BMI and age (AUC 0.703).Conclusion:By combining conventional flow cytometry in the peripheral blood and digital cytometry on matched synovial and peripheral blood samples, we highlight diverging associations of circulating immune cell subsets with synovial inflammation and pathotypes. Tph cells, in particular, emerge as predictors of lympho-myeloid synovial inflammation and disease progression.

O20 Histological and molecular features of the diseased synovium in early untreated PsA in comparison with RA

Abstract Background Psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are clinically distinct autoimmune joint disorders both marked by the chronic infiltration of the synovial tissue (ST) by inflammatory cells. It has been proposed that a more prominent thickening of the lining layer and a higher number of T/B-cells within the sublining characterised RA-ST. However, in most studies, patients had established disease and were already exposed to treatments. Furthermore, a prevalent number of samples from large joints may have affected these conclusions. Here, we intended to portrait the histological and molecular characteristics of the PsA-ST before any therapeutic modulation and early in the disease in comparison with RA and correlate them with the clinical features. Methods 183 consecutive patients naïve to DMARDs/steroids with ongoing symptoms for less than 12 months and at least one inflamed joint entered the Pathobiology of Early Arthritis Cohort (PEAC) at the Barts Health NHS Trust and underwent a US-guided synovial biopsy. ST was immuno-stained for CD3-CD20-CD138-CD68 to quantify the cellular infiltrate by T-cells, B-cells, plasma cells and macrophages, respectively. Based on the semi-quantitative score (0-4) of the immune markers, patients were categorised in lympho-myeloid (CD20≥2 or CD138>2), diffuse-myeloid (CD68 sublining≥2, CD20 and CD138<2) and pauci-immune (CD68sublining<2 and/or CD3-CD20-CD138<1). Molecular analysis was performed using RNA-sequencing of 93 RA and 15 PsA-ST. RNA cellular content was quantified using Fantom5-gene-modules. Results Of 183 patients, 39 were diagnosed with PsA (32 polyarticular, 7 oligoarticular) and 144 with RA (2010 ACR/EULAR criteria). Age was significantly lower in PsA patients. Small joints were biopsied in 74.4% of PsA and 82% of RA patients. US-synovial thickening score of the biopsied joint was, on average, higher in PsA while the power-doppler signal was similar. The histological comparison proved fewer infiltrating T/B-cells, plasma cells and sublining macrophages in PsA than RA, yet a comparable macrophage composition of the lining. The pathotypes' distribution was different, with prevalent pauci-immune in PsA (43.2%) and lympho-myeloid in RA (43.2%). At baseline, the number of tender/swollen joints was significantly higher in RA, while there were no differences in other clinical parameters such as DAS28. In PsA, synovial pathotypes did not define clinical phenotypes, whereas RA pauci-immune patients had less severe disease activity than lympho-myeloid; this relation was confirmed in an age/gender-matched to PsA subset of 26 RA subjects. The molecular profiling revealed that PsA-ST composition had a greater content of fibroblasts, eosinophils and neutrophils. Moreover, PsA-ST had higher expression of neutrophil recruitment/enrichment, cell migration and cytoskeleton remodelling gene-modules clusters. Conclusion Discovering distinct synovial tissue signatures characterising early treatment-naive PsA will provide a better understanding of the disease pathogenesis and suggest innovative therapeutic targets. Disclosures A. Nerviani None. G. Lliso-Ribera None. M. Boutet None. K. Goldmann None. F. Rivellese None. S. Kelly None. M. Bombardieri None. M. Lewis None. F. Humby None. C. Pitzalis None.

P22 Micro-RNA enriched pathway impact analysis applied to synovial RNA-seq in early rheumatoid arthritis identifies response prediction pathways

Abstract Background We use a new pathway analysis tool MITHrIL (Mirna enriched paTHway Impact anaLysis) to analyse RNA-seq patterns in synovial biopsies from patients with rheumatoid arthritis from the Pathobiology of Early Arthritis Cohort (PEAC). MITHrIL augments pathways with missing regulatory elements, such as microRNAs, and their interactions with genes to enhance quantification of immunological pathway activation in bulk RNA-seq. MITHrIL pathways were compared with three major pathotypes (lympho-myeloid, diffuse myeloid and pauci-immune fibroid) in early treatment-naïve RA patients and responders vs non-responders to methotrexate-based DMARD regimens. Methods A differential gene expression analysis is performed on the PEAC observational cohort. The Log-Fold Changes retrieved from the pairwise comparisons between responders/non responders and across different pathotypes are used as input to the MITHrIL software. Using the KEGG biological pathways, MITHrIL proportionally spreads the known differential perturbation of a gene to the downstream nodes in the pathway. In so doing, a perturbation factor is assigned to each gene and, as a result, a list of differentially altered pathways is returned together with the corresponding statistical significance (p-values). Particular attention is given to immunological pathways. We show a list of differentially altered pathways for each comparison and provide specific insight to those more characterising pathways. Results The results show coherence with the previous findings providing greater granularity on how the gene level alterations can propagate through biological pathways. In particular, we found different gene expression levels in the pairwise comparisons across pathotypes highlighting different perturbations in the following pathways: chemokine signalling (adjusted P = 3.3E-13), Jak-STAT signalling (adjusted P = 6.5E-04), Leukocyte transendothelial migration (adjusted P = 3.7E-02), PI3K-Akt signalling (adjusted P = 4.6E-04), T cell receptor signalling (adjusted P = 3.7E-02), Antigen processing and presentation (adjusted P = 1.1E-08) and NF-kappa B signalling (adjusted P = 4.1E-02). We also found confirmation of changes in lymphoid and myeloid subtypes over time, while fibroid RA patients present no significant alteration in their expression levels after the methotrexate-based DMARD therapy. Finally, we found different levels of activation in MAPK and AMPK signalling pathways for patients that do not respond to the DMARD therapy in contrast to those who do. Conclusion A novel pathway analysis approach is used to show the most differentially active biological pathways between different RA pathotypes and responder-resistant patients to methotrexate-based DMARD therapy. The results identify responder-resistant gene expression pathway patterns in early RA which may help to stratify patients to biologic therapy at an earlier stage. Disclosures E. Sciacca None. S. Alaimo None. A. Pulvirenti None. V. Latora None. F. Humby None. A. Ferro None. M.J. Lewis None. C. Pitzalis None.

Synovial tissue signatures enhance clinical classification and prognostic/treatment response algorithms in early inflammatory arthritis and predict requirement for subsequent biological therapy: results from the pathobiology of early arthritis cohort (PEAC)

ObjectiveTo establish whether synovial pathobiology improves current clinical classification and prognostic algorithms in early inflammatory arthritis and identify predictors of subsequent biological therapy requirement.Methods200 treatment-naïve patients with early arthritis were...

Molecular Portraits of Early Rheumatoid Arthritis Identify Clinical and Treatment Response Phenotypes

SummaryThere is a current imperative to unravel the hierarchy of molecular pathways that drive the transition of early to established disease in rheumatoid arthritis (RA). Herein, we report a comprehensive RNA sequencing analysis of the molecular pathways that drive early RA progression in the disease tissue (synovium), comparing matched peripheral blood RNA-seq in a large cohort of early treatment-naive patients, namely, the Pathobiology of Early Arthritis Cohort (PEAC). We developed a data exploration website (https://peac.hpc.qmul.ac.uk/) to dissect gene signatures across synovial and blood compartments, integrated with deep phenotypic profiling. We identified transcriptional subgroups in synovium linked to three distinct pathotypes: fibroblastic pauci-immune pathotype, macrophage-rich diffuse-myeloid pathotype, and a lympho-myeloid pathotype characterized by infiltration of lymphocytes and myeloid cells. This is suggestive of divergent pathogenic pathways or activation disease states. Pro-myeloid inflammatory synovial gene signatures correlated with clinical response to initial drug therapy, whereas plasma cell genes identified a poor prognosis subgroup with progressive structural damage.

244 The clinical phenotype of inflammatory arthritis correlates with synovial immune cell infiltration: results from the pathobiology of early arthritis cohort

244 The clinical phenotype of inflammatory arthritis correlates with synovial immune cell infiltration: results from the pathobiology of early arthritis cohort

O09 A lymphoid pathotype at baseline, in early inflammatory arthritis, significantly associates with requirement for biologic therapy at 12 months follow up: results from the pathobiology of early arthritis cohort

O09 A lymphoid pathotype at baseline, in early inflammatory arthritis, significantly associates with requirement for biologic therapy at 12 months follow up: results from the pathobiology of early arthritis cohort

O49 Synovial Lymphocytic Aggregates Associate with Highly Active RA and Predict Erosive Disease Progression at 12 Months: Results from the Pathobiology of Early Arthritis Cohort

O49 Synovial Lymphocytic Aggregates Associate with Highly Active RA and Predict Erosive Disease Progression at 12 Months: Results from the Pathobiology of Early Arthritis Cohort

Ultrasound-guided synovial biopsy: a safe, well-tolerated and reliable technique for obtaining high-quality synovial tissue from both large and small joints in early arthritis patients

To determine the tolerability, safety and yield of synovial tissue in an early arthritis cohort using a minimally invasive, ultrasound (US)-guided, synovial biopsy technique in small, medium and large joints. 93 sequential biopsy procedures were assessed from a total of 57 patients (baseline and 36 repeat biopsies at 6 months) recruited as part of the 'Pathobiology of Early Arthritis Cohort' study. Patients completed a tolerability questionnaire prior to and following the synovial biopsy procedure. The synovial biopsy was performed under US guidance with US images of the joint recorded prior to each procedure. Synovial tissue was harvested for immunohistochemistry and RNA extraction. Five different joint sites were biopsied (knee, elbow, wrist, metacarpal phalangeal and proximal interphalangeal). No significant complications were reported following the procedure. No difference in pain, swelling and stiffness of the biopsied joint from before and after the procedure was demonstrated. A median of 14 biopsy samples was retrieved from each procedure with 93% of biopsy procedures yielding good quality tissue. RNA yield was good in all joints and in repeat biopsies. Multivariant analysis demonstrated a significantly greater yield of RNA and graded tissue in relation to a high prebiopsy, grey-scale synovitis score (0-3, semiquantitative). A minimally invasive approach to synovial tissue harvesting, using US guidance, is both safe and well-tolerated by patients. Tissue quality/RNA yield is preserved in subsequent biopsies following therapeutic intervention. A high US grey-scale synovitis score is a predictor of good quality/quantity of tissue and RNA.

SAT0014 Synovial Sublining Macrophages: A Sensitive Biomarker for Response to Treatment in Early RA Patients.

BackgroundThe synovial membrane is the primary site of inflammation in rheumatoid arthritis and as such the study of pathobiological synovial specimens has led to a greater understanding of disease pathogenesis....

THU0087 Synovial Ectopic Lymphoid-like Structures are Associated with Diagnosis of Rheumatoid Arthritis, Disease Activity and Antibody Status in Early Arthritis Patients

BackgroundThe presence of ectopic lymphoid-like structures (ELS) within the synovial tissue of a cohort of patients with inflammatory arthritis is well recognised. There is also data supporting the concept that...

Professor Samuel Pierpont Langley

<h3>Background</h3> RA is a systemic-autoimmune-disease characterized by chronic inflammation of the synovial-joints. Up to 30–40% of patients do not respond to treatment and current biomarkers are largely insensitive at predicting disease progression and response to treatment. It is well recognised that RA-synovitis is a heterogeneous pathology with different histological phenotypes i.e. lymphoid-(L), myeloid-(M) and fibroid-(F). As a result of inflammation the RA synovial microenvironment is hypoxic and acidic partly due to the accumulation of lactate, the end product of anaerobic glycolysis. Exposure of CD4⁺ T cells to lactate inhibits their migratory capabilities and induces their shift toward a Th17 phenotype^1,2. These effects are mediated via the interaction of lactate with its transporter SLC5A12, which is expressed on the CD4⁺ T cell surface^1,2. <h3>Objectives</h3> To characterize whether the newly identified lactate/SLC5A12-induced metabolic signalling pathway can be harnessed in the stratification of RA patients in the different histological phenotypes and to modulate inflammatory responses <i>in vitro</i> and <i>in vivo</i>. <h3>Methods</h3> RA peripheral blood cells, RA synovial tissues (ST, 21 lymphoid and 8 myeloid) and mononuclear cells from tonsil of patients undergoing tonsillectomy were included in the analysis. RNA sequencing of RA-ST was performed and data analysed for the expression of metabolic genes. SLC5A12 expression and IL17 production was performed by flow-cytometry. Cytokines and transcription factors mRNA relative expression was evaluated by RT-PCR. Seahorse and western blot analysis was performed for the evaluation of metabolic pathways. Transwell plates were used for migration assays. Human-glucose-6-phosphate-isomerase (hG6PI) induced arthritis model was used to evaluate the impact of anti-SLC5A12 on the clinical and histological score. <h3>Results</h3> We showed that: i) the expression of SLC5A12 is up-regulated by CD4⁺ T cells upon inflammation; ii) SLC5A12 is up-regulated in anti-CD3 stimulated RA CD4⁺ T cells cultured in autologous synovial fluid; iii) the lactate/SLC5A12 induced metabolic pathway is differentially activated in RA patients with distinctive synovial “pathotypes”; iv) SLC5A12 antibody reduces lactate-induced pro-inflammatory cytokines, limits Th17 and follicular helper T cell differentiation, reverses lactate impaired CD4⁺ T cell migration and restores lactate-mediated inhibition of glycolysis <i>in vitro</i>; v) antibody-mediated blockade of SLC5A12 ameliorates the clinical course in human-glucose-6-phosphate-isomerase (hG6PI)-induced arthritis. <h3>Conclusions</h3> Targeting lactate/SLC5A12-induced metabolic signalling pathway may provide a novel therapeutic strategy to reduce inflammation in RA patients. <h3>References</h3> Haas R. et al. PLoS Biology 2015. Pucino V. et al. Eur J Immunol 2017. <h3>Acknowledgements</h3> This work is supported by a fellowship from the Arthritis Research UK (ARUK) to V.P. by a fellowship from the British Heart Foundation, a project grant from the CARIPLO Foundation, a Proof of Concept award from Queen Mary Inno-vation, Ltd., to C.M. and MRC ARUK founded project “The Pathobiology of Early Arthritis Cohort (PEAC)” to C.P. <h3>Disclosure of Interest</h3> None declared