Mapping the heterogeneity of pDCs and Monocytes of systemic sclerosis at single cell level [scRNA-seq]

Systemic sclerosis (SSc) is an uncommon disease characterized by elevated autoantibody production, vasculopathy and fibrosis of the skin and internal organs. pDCs are the core cell type to produce type I IFN and contributes to the ISG signature and SSc progression. Using single-cell RNA sequencing, we profiled 32529 pDCs enriched and T cell depleted peripheral blood mononuclear cells (PBMCs) from 4 patients with SSc and 4 matched controls. Increased CD16+ monocytes and decreased cDCs are the major changes in the cell composition between SSc and heathy controls. Increased expression of interferon-stimulated genes (ISGs) and apoptotic genes distinguished cells from patients with SSc from healthy control cells. The high ISG expression signature (ISGhi) derived from a small number of transcriptionally defined subpopulations within major cell types, including monocytes, natural killer cells, conventional and plasmacytoid dendritic cells, B cells. Profiling of 10976 pDCs revealed a newly identified PTGDS+ population and a clear increased ISG hi clusters in SSc pDCs. Profiling of 13317 Monocytes revealed increased CD16+ Monocytes and a clear increased ISG hi clusters in SSc monocytes. We then compared the TLRs-IFN response of the pDCs from SSc and Healthy control. RNASeq revealed SSc pDCs enables an unexpected TLR8-IFN signaling to increase the IFN signature. This study lays the groundwork for resolving the origin of the SSc transcriptional signatures and the disease heterogeneity towards precision medicine applications.