1658: Title: Inflammatory Arthritis Across the Age-Spectrum: Single-Cell Profiling of the Inflamed Synovium in Children with Juvenile Idiopathic Arthritis
Chrissy Bolton1, Christopher Mahony2, Charlotte Smith2, Vicky Alexiou3, Huong Nguyen3, Patricia Reis-Nisa2, Søren Lomholt4, Annie Hackland2, Sugrah Sultan5, Klaudia Kupiec3, Sunit Davda6, Charlene Foley6, Calliope Dendrou1, Elizabeth C Rosser7, Accelerating Medicines Partnership Program RA SLE Network8, Anna Helena Jonsson9, Fan Zhang10, Michael Brenner11, Soumya Raychaudhuri9, Christopher Buckley1, Manigandan Thyagarajan5, Zishan Shiekh5, Sandrine Compeyrot-Lacassagne6, Samantha Chippington6, Mark Coles1, Eslam Al-Abadi5, Andrew Filer2, Tissue Research in Childhood Onset Inflammatory Arthritis (TRICIA) Consortium12, Lucy R Wedderburn3 and Adam Croft2, 1University of Oxford, Oxford, United Kingdom, 2University of Birmingham, Birmingham, United Kingdom, 3UCL Great Ormond Street Institute of Child Health, London, United Kingdom, 4Aarhus University, Aarhus, Denmark, 5Birmingham Women’s and Children’s NHS Foundation Trust, Birmingham, United Kingdom, 6Great Ormond Street Hospital, London, United Kingdom, 7University College London, London, United Kingdom, 8Cedars-Sinai Medical Center, Los Angeles, CA, 9Brigham and Women's Hospital, Boston, MA, 10University of Colorado, Aurora, CO, 11Brigham and Women's Hospital and Harvard Medical School, Boston, MA, 12MRC, Birmingham, United Kingdom
Background/Purpose: Understanding the unique and shared pathogenic processes between childhood-onset and adult-onset inflammatory arthritides is needed to guide more effective drug development and their application to different age groups. Difficulties in accessing samples from the inflamed tissue site in children has limited our understanding of disease mechanisms that operate locally in the joint. As part of the Tissue Research in Childhood Onset Inflammatory Arthritis (TRICIA) Consortium, we have established the first single cell multi-omic atlas of the inflamed joint in Juvenile Idiopathic Arthritis (JIA).
Methods: Ultrasound-guided needle biopsies of synovial tissue, with matched synovial fluid and peripheral blood mononuclear cell samples were obtained from n=12 pediatric patients with JIA, who were naïve to disease-modifying anti-rheumatic drugs. Multimodal single-cell characterisation of cells (n = 250, 816 cells, with scRNA-seq, VDJ-sequencing and TotalSeq surface assays) and multiplexed imaging of synovial tissue fragments were performed.
Results: Transcriptomic profiles of hematopoietic cells at a global level of clustering revealed that synovial tissue and synovial fluid were proportionally enriched in the same cellular subtypes (dendritic cell subsets, myeloid and memory CD8+ T cells) compared to blood ( > 0.58 log2 fold difference, FDR < 0.01, Fig 1). Core tissue-enriched populations identified in adult rheumatoid arthritis (Zhang et al., 2022, the AMP RA/SLE network) were also prominent in pediatric synovial tissue samples, including GZMK+ memory CD8+ T cells, CXCL13+ CD4+ T peripheral helper cells and NR4A+ germinal centre-like B cells. Evidence for a distinct immune environment of the synovial fluid cavity relative to synovial tissue included upregulation of interferon-response genes, greater proportions of dendritic cells (Fig 1), less diversity of αβ T cell receptors on CD8+ T cells (P = 0.02) and more hyperexpanded CD8+ T cell clones: 13.6% of total T cells in synovial fluid had the same clonotype in ≥ 20 cells, compared to 3.8% in synovial tissue (n = 8091 and 7039 cells respectively).
Conclusion: Our work implicates the synovial fluid cavity in disease pathogenesis, with synovial fluid providing a reservoir of free-flowing activated cells as barrier integrity breaks down. Despite distinct disease features and physiology, our analysis identifies shared cellular phenotypes within inflamed synovium between children and adults. This suggests that certain pathogenic mechanisms extend across the age-spectrum in inflammatory arthritis, enabling a more informed approach to clinical trials in children in the future.
References: Zhang, F. et al. (2022) ‘Cellular deconstruction of inflamed synovium defines diverse inflammatory phenotypes in rheumatoid arthritis’. bioRxiv, p. 2022.02.25.481990. Available at: https://doi.org/10.1101/2022.02.25.481990.
Comparative analysis highlights conserved proportions of hematopoietic cells between synovial tissue and fluid in children with Juvenile Idiopathic Arthritis a) Integrated scRNA-seq global UMAP of major cellular clusters and their b) proportional difference between different specimen types, with bootstrap confidence intervals shown (10,000 permutations).
C. Bolton: None; C. Mahony: None; C. Smith: None; V. Alexiou: None; H. Nguyen: None; P. Reis-Nisa: None; S. Lomholt: None; A. Hackland: None; S. Sultan: None; K. Kupiec: None; S. Davda: None; C. Foley: None; C. Dendrou: None; E. Rosser: None; A. RA SLE Network: None; A. Jonsson: None; F. Zhang: None; M. Brenner: 4FO Ventures, 2, GlaxoSmithKlein(GSK), 2, Mestag Therapeutics, 2, 11, Third Rock Ventures, 2; S. Raychaudhuri: AbbVie, 6, Janssen, 1, Mestag, Inc, 2, 8, Pfizer, 1, Sanofi, 1, Sonoma, 1, 8; C. Buckley: Bristol-Myers Squibb(BMS), 5, Mestag, 11; M. Thyagarajan: None; Z. Shiekh: None; S. Compeyrot-Lacassagne: None; S. Chippington: None; M. Coles: None; E. Al-Abadi: None; A. Filer: Bristol-Myers Squibb(BMS), 5, GlaxoSmithKlein(GSK), 5, Janssen, 5, Nascient, 5, Sonoma Biotherapeutics, 2; T. Inflammatory Arthritis (TRICIA) Consortium: None; L. Wedderburn: AbbVie/Abbott, 5, GlaxoSmithKlein(GSK), 5, Pfizer, 1, SOBI, 5, UCB, 5; A. Croft: None.
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