Analysis of synovitis patterns in early RA supports the importance of joint-specific factors.

BACKGROUND: Rheumatoid arthritis (RA) is classically considered a systemic disorder, but the role of local factors in driving synovial inflammation is increasingly being recognized. These joint-specific factors may consequently modulate disease phenotype. OBJECTIVES: Our goal was to study the spatial distribution of swelling, tenderness and erosions in a large cohort of early RA (ERA) patients, to assess for patterns of simultaneously-involved joint clusters. We also aimed to investigate the link between arthritis localization and phenotypic features such as bone erosions and response to methotrexate therapy. METHODS: DMARD-naive patients from the ERA UCLouvain Brussels cohort were included. Forty-four joints were clinically assessed for swelling and tenderness before treatment, and 6 months later for methotrexate-treated patients. Clusters of joints were identified using Principal component analysis and Cramer's correlation coefficients. Frequency of bone erosions and joint-specific response to methotrexate were compared across different clusters. RESULTS: 452 ERA patients were included. Analysis of the spatial distribution of swelling and tenderness allowed for the identification of 3 joint clusters that showed significant simultaneous involvement: (i) MTP1-5 joints, (ii) hand joints (MCPs and PIPs), and (iii) larger joints. These clusters were associated with different susceptibility to bone erosions and distinct clinical features, but similar local response (joint swelling resolution) to methotrexate. CONCLUSION: This is the first study investigating the spatial distribution of arthritis in a large cohort of early RA using an unbiased approach. We identify clusters of simultaneously involved joints, supporting the importance of local factors in driving synovitis in RA.

Inclusion of fibrinoid necrosis increases the accuracy of synovial tissue assessment in predicting response to methotrexate: analysis of the UCLouvain Brussels ERA Cohort.

OBJECTIVE: Rheumatoid Arthritis (RA) often exhibits suboptimal treatment response despite early diagnosis and treatment. This study aimed to analyze Early Rheumatoid Arthritis (ERA) synovial biopsies through histology and immunohistochemistry (IHC) to identify predictive factors for treatment response to Methotrexate (MTX). METHODS: 140 ERA patients from the UCLouvain Arthritis Cohort underwent synovial biopsy and were monitored after initiating Disease-Modifying Antirheumatic Drug (DMARD) therapy. Histological features [Synovial Hyperplasia, Fibrinoid Necrosis (FN), Hypervascularization and Inflammatory Infiltrate] and IHC (CD3, CD20, CD138, CD68) were each semi-quantitatively assessed on a 0-3 scale with 7 levels. RESULTS: A strong association was observed between synovial CD68 and Fibrinoid Necrosis scores [r = 0.44 (0.27 - 0.56); p < 0.0001]. CD68 correlated with C-Reactive Protein (CRP), DAS28, SDAI and CDAI. Fibrinoid Necrosis score correlated with CRP and DAS28. Patients were then categorized as CD68NecrosisHIGH (CD68 + Necrosis ≥ 3) and CD68NecrosisLOW (CD68 + Necrosis < 3). CD68NecrosisHIGH exhibited higher pre-treatment disease activity [5.48 (1.6) versus 4.8 (1.7); p = 0.03] and a greater fall in DAS28 [1.99 (2.06) versus 1.1 (2.27), p = 0.03], SDAI [21.45 (IQR 23.3) versus 11.65 (IQR 17.5); p = 0.003] and CDAI [16 [14.9] versus 10.5 (20.1), p = 0.04]. CD68NecrosisHIGH patients had a higher EULAR Moderate/Good Response rate. CD68Necrosis score was incorporated into a probability matrix model together with clinical features (SJC44 and DAS28) to predict achieving a Moderate/Good EULAR Response Criteria at 3 months with a good performance (AUC 0.724). CONCLUSION: FN and CD68 + in ERA synovial biopsies identify patients with higher disease activity and predict a better treatment response at three months. A model including synovial CD68 and fibrinoid necrosis with baseline clinical features predicts EULAR response at 3 months.

Hereditary C1q Deficiency is Associated with Type 1 Interferon-Pathway Activation and a High Risk of Central Nervous System Inflammation.

Hereditary C1q deficiency (C1QDef) is a rare monogenic disorder leading to defective complement pathway activation and systemic lupus erythematosus (SLE)-like manifestations. The link between impairment of the complement cascade and autoimmunity remains incompletely understood. Here, we assessed type 1 interferon pathway activation in patients with C1QDef. Twelve patients with genetically confirmed C1QDef were recruited through an international collaboration. Clinical, biological and radiological data were collected retrospectively. The expression of a standardized panel of interferon stimulated genes (ISGs) in peripheral blood was measured, and the level of interferon alpha (IFNα) protein in cerebrospinal fluid (CSF) determined using SIMOA technology. Central nervous system (encompassing basal ganglia calcification, encephalitis, vasculitis, chronic pachymeningitis), mucocutaneous and renal involvement were present, respectively, in 10, 11 and 2 of 12 patients, and severe infections recorded in 2/12 patients. Elevated ISG expression was observed in all patients tested (n = 10/10), and serum and CSF IFNα elevated in 2/2 patients. Three patients were treated with Janus-kinase inhibitors (JAKi), with variable outcome; one displaying an apparently favourable response in respect of cutaneous and neurological features, and two others experiencing persistent disease despite JAKi therapy. To our knowledge, we report the largest original series of genetically confirmed C1QDef yet described. Additionally, we present a review of all previously described genetically confirmed cases of C1QDef. Overall, individuals with C1QDef demonstrate many characteristics of recognized monogenic interferonopathies: particularly, cutaneous involvement (malar rash, acral vasculitic/papular rash, chilblains), SLE-like disease, basal ganglia calcification, increased expression of ISGs in peripheral blood, and elevated levels of CSF IFNα.

Two Broad Categories Overlapping With Rheumatoid Arthritis Observed in Synovial Biopsies from Patients With Juvenile Idiopathic Arthritis.

OBJECTIVE: The objective is to characterize transcriptomic profiles and immune cell composition and distribution in juvenile idiopathic arthritis (JIA) synovial biopsies, assess for associations of these features with clinical parameters, and compare JIA and rheumatoid arthritis (RA) synovial features. METHODS: RNA sequencing (RNASeq) was performed on 24 samples, with pathway analysis and inference of relative abundance of immune cell subsets based on gene expression data. Two multiplex fluorescence immunohistochemistry (IHC) panels were performed on 28 samples (including 13 on which RNASeq was performed), staining for CD206- classical and CD206+ nonclassical macrophages, and CD8+ and CD4+ T and B lymphocytes. Data were compared to a published series of early RA synovial biopsies. RESULTS: Pathway analysis of the most variably expressed genes (n = 339) identified a B and plasma cell signature as the main driver of heterogeneity in JIA synovia, with strong overlap between JIA and RA synovitis. Multiplex IHC confirmed heterogeneity of immune cell infiltration. M1-like macrophage-rich synovial lining was associated with greater lining hypertrophy and higher (CD45+) pan-immune cell and CD8+ T cell infiltration. CONCLUSION: Our study indicates significant similarities between JIA and RA synovitis. Similar to RA, JIA synovia may be broadly categorized into two groups: (1) those with an inflammatory/adaptive immune transcriptomic signature, M1-like macrophage and CD8+ T cell infiltration, and thicker, M1-like macrophage-rich synovial lining, and (2) those with an M2-like macrophage transcriptomic signature, greater M2/M1-like macrophage ratios, and thinner, M2-like macrophage-rich synovial lining. Synovial features were not significantly associated with clinical parameters, likely because of group size and heterogeneity.

Patterns and determinants of response to novel therapies in juvenile and adult-onset polyarthritis.

Biologic and targeted synthetic DMARDs (b/tsDMARDs) have revolutionized the management of multiple rheumatic inflammatory conditions. Among these, polyarticular JIA (pJIA) and RA display similarities in terms of disease pathophysiology and response pattern to b/tsDMARDs. Indeed, the therapeutic efficacy of novel targeted drugs is variable among individual patients, in both RA and pJIA. The mechanisms and determinants of this heterogeneous response are diverse and complex, such that the development of true 'precision'-medicine strategies has proven highly challenging. In this review, we will discuss pathophysiological, patient-specific, drug-specific and environmental factors contributing to individual therapeutic response in pJIA in comparison with what is known in RA. Although some biomarkers have been identified that stratify with respect to the likelihood of either therapeutic response or non-response, few have proved useful in clinical practice so far, likely due to the complexity of treatment-response mechanisms. Consequently, we propose a pragmatic, patient-centred and clinically based approach, i.e. personalized instead of biomarker-based precision medicine in JIA.

Disease activity drives transcriptomic heterogeneity in early untreated rheumatoid synovitis.

OBJECTIVES: Transcriptomic profiling of synovial tissue from patients with early, untreated rheumatoid arthritis (RA) was used to explore the ability of unbiased, data-driven approaches to define clinically relevant subgroups. METHODS: RNASeq was performed on 74 samples, with disease activity data collected at inclusion. Principal components analysis (PCA) and unsupervised clustering were used to define patient clusters based on expression of the most variable genes, followed by pathway analysis and inference of relative abundance of immune cell subsets. Histological assessment and multiplex immunofluorescence (for CD45, CD68, CD206) were performed on paraffin sections. RESULTS: PCA on expression of the (n=894) most variable genes across this series did not divide samples into distinct groups, instead yielding a continuum correlated with baseline disease activity. Two patient clusters (PtC1, n=52; PtC2, n=22) were defined based on expression of these genes. PtC1, with significantly higher disease activity and probability of response to methotrexate therapy, showed upregulation of immune system genes; PtC2 showed upregulation of lipid metabolism genes, described to characterise tissue resident or M2-like macrophages. In keeping with these data, M2-like:M1-like macrophage ratios were inversely correlated with disease activity scores and were associated with lower synovial immune infiltration and the presence of thinner, M2-like macrophage-rich synovial lining layers. CONCLUSION: In this large series of early, untreated RA, we show that the synovial transcriptome closely mirrors clinical disease activity and correlates with synovial inflammation. Intriguingly, lower inflammation and disease activity are associated with higher ratios of M2:M1 macrophages, particularly striking in the synovial lining layer. This may point to a protective role for tissue resident macrophages in RA.

Common Transcriptomic Effects of Abatacept and Other DMARDs on Rheumatoid Arthritis Synovial Tissue.

Objectives: Our goal was to assess for the histological and transcriptomic effects of abatacept on RA synovia, and to compare them with previously published data from four other DMARDs: tocilizumab, rituximab, methotrexate, and adalimumab. Methods: Synovial tissue was obtained using ultrasound-guided biopsy from affected joints of 14 patients, before and 16 weeks after treatment with subcutaneous abatacept 125 mg weekly. Paraffin-sections were stained and scored for CD3+, CD20+, and CD68+ cell infiltration. Transcriptional profiling was performed using GeneChip Human Genome U133 Plus 2.0 arrays (Affymetrix) and analyzed on Genespring GX (Agilent). Pathway analyses were performed on Genespring GX, Metascape, and EnrichR. Results: Gene expression analysis identified 304 transcripts modulated by abatacept in synovial tissue. Downregulated genes were significantly enriched for immune processes, strongly overlapping with our findings on other therapies. Data were pooled across these studies, revealing that genes downregulated by DMARDs are significantly enriched for both T-cell and myeloid leukocyte activation pathways. Interestingly, DMARDs seem to have coordinate effects on the two pathways, with a stronger impact in good responders to therapy as compared to moderate and non-responders. Conclusion: We provide evidence that the effects of five DMARDs on the RA synovium culminate in the same pathways. This confirms previous studies suggesting the existence of common mediators downstream of DMARDs, independent of their primary targets.

Paired Rheumatoid Arthritis Synovial Biopsies From Small and Large Joints Show Similar Global Transcriptomic Patterns With Enrichment of Private Specificity TCRB and TCR Signaling Pathways.

Objectives: We explored histological and transcriptomic profiles of paired synovial biopsies from rheumatoid arthritis (RA) patients, in order to assess homogeneity in synovial tissue at the individual level. Methods: Synovial biopsies were performed simultaneously in one small and one large joint per patient using needle-arthroscopy for the knee and ultrasound-guided biopsy for the hand or wrist. Synovium from individuals with osteoarthritis was used as controls. Paraffin-embedded samples were stained for CD3, CD20, and CD68. Total RNA was hybridized on high-density microarrays. TCRB variable sequences were obtained from synovial and blood RNA samples. Results: Twenty paired biopsies from 10 RA patients with active disease were analyzed. Semi-quantification of histological markers showed a positive correlation for synovial hyperplasia, inflammatory infiltrates and CD3-positive T cells between pairs. Pairwise comparison of transcriptomic profiles showed similar expression of RA-related molecular pathways (TCR signaling, T cell costimulation and response to TNFα). T cells clonotypes were enriched in all but one joints compared to blood, regardless of the magnitude of T cell infiltration. Enriched clonotypes were shared between pairs (23-100%), but this was less the case in pairs of joints displaying weaker T cell signatures and more pronounced germinal center-like transcriptomic profiles. Conclusion: Cellular and molecular alterations in RA synovitis are similar between small and large joints from the same patient. Interindividual differences in magnitude of T cell infiltrates and distribution of enriched T cell clonotypes support the concept of distinct synovial pathotypes in RA that are associated with systemic versus local antigen-driven activation of T cells.

Synovial Tissue: Turning the Page to Precision Medicine in Arthritis.

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease targeting the joints. Current treatment strategies are based on clinical, biological and radiological features, yet still fail to reach the goal of early low disease activity in a significant number of cases. Hence, there is a need for refining current treatment algorithms, using accurate markers of response to therapy. Because RA induces histological and molecular alterations in the synovium even before apparition of clinical symptoms, synovial biopsies are a promising tool in the search of such new biomarkers. Histological and molecular characteristics of RA synovitis are heterogeneous. Variations in synovial lining layer hyperplasia, in cellular infiltration of the sublining by immune cells of myeloid and lymphoid lineages, and in molecular triggers of these features are currently categorized using well-defined pathotypes: myeloid, lymphoid, fibroid and pauci-immune. Here, we first bring the plasticity of RA synovitis under scrutiny, i.e., how variations in synovial characteristics are associated with relevant clinical features (disease duration, disease activity, effects of therapies, disease severity). Primary response to a specific drug could be, at least theoretically, related to the representation of the molecular pathway targeted by the drug in the synovium. Alternatively, absence of primary response to a specific agent could be due to disease severity, i.e., overrepresentation of all synovial molecular pathways driving disease activity overwhelming the capacity of any drug to block them. Using this theoretical frame, we will highlight how the findings of previous studies trying to link response to therapy with synovial changes provide promising perspectives on bridging the gap to personalized medicine in RA.