Emerging synovial cell states in rheumatoid arthritis as potential therapeutic targets.

Purpose of review: To summarize recently discovered novel cell states in rheumatoid arthritis (RA) synovium that could have important implications for disease treatment.

Recent findings: The use of multiomic technologies, including single-cell and spatial transcriptomics and mass cytometry, has led to the discovery of several novel cell states, which could have important implications for the treatment of RA. These cells can be found in patient blood, synovial fluid, or synovial tissue and span several immune cell subsets as well as stromal cell types. These diverse cell states may represent the targets of current or future therapeutics, while their fluctuations may inform the ideal timing for therapy. Future efforts are needed to implicate how each cell state functions in the pathophysiologic network within affected joints and how medications perturb each cell state and ultimately the tissue.

Summary: Multiomic molecular technologies have afforded the discovery of numerous novel cellular states in RA synovium; the next challenge will be to link these states to pathophysiology and treatment response.