Abstract Rationale Progressive pulmonary fibrosis is a frequent and often life-limiting feature of systemic sclerosis (SSc). Understanding the immunopathogenesis of SSc has the potential to identify novel biomarkers of ILD development and progression as well as targets for novel disease-modifying treatments for SSc patients. We hypothesized that peripheral blood single-cell transcriptomic profiling would reveal candidate biomarkers and mediators of ILD development and/or progression among SSc patients. Methods Single-cell RNA-sequencing was performed using cryopreserved peripheral blood mononuclear cells from 84 subjects with SSc (including 22 with paired longitudinal samples) and 10 age-matched control subjects enrolled in the MYSTIC cohort at Vanderbilt University Medical Center. Alignment, demultiplexing, quality control filtering and cell annotation were performed using a standard CellRanger/Scanpy workflow. Cell-type specific pseudobulk differential expression analysis was performed using a generalized linear model (limma-voom) and pathway enrichment was performed using MiSigDB. Results Among SSc subjects, median age was 59.65 IQR 49.2 to 66.3; 68 (81%) were female, and 14 were of non-European ancestry. Median disease duration at the time of enrollment was 8.7 years IQR 4.1 to 14.1. Compared to controls, SSc subjects had significantly fewer circulating B-cells (6.5% +/-4.5% vs. 19.2% +/- 8.0%) and plasmablasts (1.5% +/- 1.1% vs. 4.2% +/-2.1%), but increased monocytes (27.1% +/- 7.8% vs. 16.9% +/- 11.6%) and CD16+ Monocytes (5.7% +/- 2.7% vs. 2.4% +/- 2.1%). Pathway enrichment of differentially expressed genes demonstrated upregulated interferon and TNF pathways across multiple cell-types in SSc samples compared to controls. Comparing SSc subjects with (n = 64) vs. without (n = 20) ILD, there were no significant differences in PBMC proportions. In most cell-types, no genes were differentially expressed in SSc subjects with ILD compared to those without ILD. Conclusion Systemic sclerosis is associated with substantial differences in circulating immune cell profiles, including evidence of chronic immune activation (despite immunosuppressive therapies). These results suggest that systemic disease-related effects dominate circulating immune cell programs and suggest the presence of ILD is not itself associated with different PBMC profiles in SSc. This abstract is funded by: Boehringer-Ingelheim, NIH
Wilfong et al. (Fri,) studied this question.