Objectives A number of immune populations have been implicated in psoriatic arthritis (PsA) pathogenesis. This study used mass cytometry (CyTOF) combined with transcriptomic analysis to generate a high-dimensional dataset of matched PsA synovial fluid (SF) and blood leucocytes, with the aim of identifying cytokine production ex vivo in unstimulated lymphoid and myeloid cells.
Methods Fresh SF and paired blood were either fixed or incubated with protein transport inhibitors for 6 hours. Samples were stained with two CyTOF panels: a phenotyping panel and an intracellular panel, including antibodies to both T cell and myeloid cell secreted proteins. Transcriptomic analysis by gene array of key expanded cell populations, single-cell RNA-seq, ELISA and LEGENDplex analysis of PsA SF were also performed.
Results We observed marked changes in the myeloid compartment of PsA SF relative to blood, with expansion of intermediate monocytes, macrophages and dendritic cell populations. Classical monocytes, intermediate monocytes and macrophages spontaneously produced significant levels of the proinflammatory mediators osteopontin and CCL2 in the absence of any in vitro stimulation. By contrast minimal spontaneous cytokine production by T cells was detected. Gene expression analysis showed the genes for osteopontin and CCL2 to be among those most highly upregulated by PsA monocytes/macrophages in SF; and both proteins were elevated in PsA SF.
Conclusions Using multiomic analyses, we have generated a comprehensive cellular map of PsA SF and blood to reveal key expanded myeloid proinflammatory modules in PsA of potential pathogenic and therapeutic importance.
- synovial fluid
Data availability statement
Data relevant to the study are included in the article or uploaded as online supplemental information. Additional data that support the findings of this study are available on reasonable request.
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Handling editor Josef S Smolen
PB and HA-M contributed equally.
Contributors HA-M and PB conceived the project. NY and HA-M processed the blood and synovial fluid samples. HA-M, AM, NY and SC designed the CyTOF experiments; NY and SC performed the CyTOF assays; NY conducted the CyTOF analysis. NY, HA-M and PB analysed the data. SC performed the PCR array experiment; ALL and NY conducted the PCR array analysis. NY performed the ELISA. FP and HA-M performed the scRNAseq analysis. NY wrote the manuscript; PB and HA-M reviewed the manuscript. PB, JCK and HA-M supervised the study.
Funding NY and HA-M received funding from UCB and HA-M from National Institute for Health Research (NIHR) and the Academy of Medical Sciences. The study received support from the NIHR Oxford Biomedical Research Centre (BRC) (PB). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health.
Competing interests SC and AM are employees of UCB. HA-M received unrestricted research support from UCB. PB has received research support from Regeneron, Benevolent AI and GSK.
Provenance and peer review Not commissioned; externally peer reviewed.
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