0554: Loss of Synovial Tissue Macrophage Homeostasis Precedes Rheumatoid Arthritis Clinical Onset

Megan Hanlon¹, Mary Canavan², conor Smith³, Achilleas Floudas⁴, Nuno Neto⁵, Qingxuan Song⁶, Phil Gallagher⁷, Ronan Mullan⁸, Conor Hurson⁹, Barry Moran⁵, Michael Monaghan⁵, Sunil Nagpal¹⁰, Douglas Veale¹¹ and Ursula Fearon⁵, ¹Molecular Rheumatology, Dublin, Ireland, ²Trinity College, Dublin, Ireland, ³bTrinity College Dublin, Dublin, Ireland, ⁴Molecular Rheumatology Trinity Biomedical Sciences Institute, Dublin, Ireland, ⁵Trinity College Dublin, Dublin, Ireland, ⁶Janssen Research and Development, LLC, Spring House, PA, ⁷St Vincent's University Hospital, Dublin, Ireland, ⁸Tallaght University Hospital, Dublin, Ireland, ⁹St Vincents University Hospital, Dublin, Ireland, ¹⁰Janssen Research, Collegeville, PA, ¹¹St. Vincent's University Hospital, Blackrock, Dublin, Ireland

Background/Purpose: Synovial-tissue macrophages significantly contribute to Rheumatoid Arthritis, yet the precise nature/function of macrophage subsets within the inflamed joint remains unexplored. Here we explore the spectrum of distinct macrophage activation states residing within the synovium of RA, at risk and healthy individuals.

Methods: Single-cell synovial-tissue suspensions from RA(n=44), IAR(n=5), HC(n=11) were obtained, synovial macrophage subsets examined by advanced flow-cytometric analysis, single-cell/bulk RNA-sequencing, metabolic and functional assays.

Results: Multidimensional analysis identifies enrichment of CD206+CD163+ synovial-tissue macrophages co-expressing CD40 in RA compared to healthy synovial-tissue, with frequency of CD206+CD163+CD40+ macrophages associated with increased disease activity and treatment response. In contrast, CX3CR1-expressing macrophages enriched in healthy synovium are significantly depleted in RA. Importantly this signature of enriched CD40 expression coupled with depleted CX3CR1 expression is an early phenomenon, occurring prior to clinical manifestation of disease in individuals 'at-risk' of RA (IAR). In-depth RNAseq and metabolic profiling of sorted RA synovial-macrophages identified that this population is transcriptionally distinct, displaying unique inflammatory, phagocytic and tissue-resident gene signatures, paralleled by a bioenergetically stable profile as indicated by NAD(P)H emission. Functionally CD206+CD163+ RA macrophages are potent producers of pro-inflammatory mediators (reversed by CD40-signalling inhibition) and induce an invasive phenotype in healthy synovial-fibroblasts. These findings identify a distinct pathogenic population of synovial-tissue macrophage involved in shaping the immune response in RA.

Conclusion: We have identified a novel population of tissue-resident macrophages in the RA synovium which are transcriptionally/metabolically distinct and capable of contributing to disease pathology. Crucially, this signature is present pre-disease representing a unique opportunity for early diagnosis and therapeutic intervention.
Pathogenic synovial tissue macrophage signature predates clinical manifestations of disease

Disclosures: M. Hanlon, None; M. Canavan, None; c. Smith, None; A. Floudas, None; N. Neto, None; Q. Song, Janssen Research & Development, LLC, Johnson & Johnson; P. Gallagher, None; R. Mullan, None; C. Hurson, None; B. Moran, None; M. Monaghan, None; S. Nagpal, Janssen; D. Veale, AbbVie/Abbott, Pfizer, Eli Lilly, Novartis, Gilead; U. Fearon, AbbVie/Abbott, Pfizer, Janssen, Eli Lilly, GlaxoSmithKlein(GSK).