OP0013 SINGLE CELL PROFILE OF SKIN STROMAL AND IMMUNE CELLS AND PERIPHERAL BLOOD IMMUNE CELLS OF SCLERODERMA PATIENTS TOWARDS IDENTIFICATION OF DISEASE MECHANISM, PROGNOSTIC BIOMARKERS AND POTENTIAL THERAPEUTIC TARGETS
Authors: C. Gur, A. Balbir-Gurman, H. Peleg, S. Aamar, F. Kharouf, Y. Braun-Moscovici, S. Y. Wang, I. Amit
Journal: Annals of the Rheumatic Diseases (2020)

Background: Despite many years of research, our understanding of Systemic Sclerosis (SSc) pathogenic processes, patient-to-patient variability, and diversity of stromal and immune cells within the involved tissues microenvironment, their interaction, as well as the genes and pathways leading to the pathogenesis remains largely unclear. Current technologies for characterizing SSc have limited depth and resolution, which needed for molecular define the small skin stromal and immune cells sub-populations supposed to drive SSc pathogenesis. Single-cell sequencing technologies hold a great potential in genomic medicine since they offer high resolution and sensitivity for unbiased profiling of disease versus normal niches. Objectives: Comprehensive characterization of stromal and immune cells in the skin and blood of SSc patients, and healthy controls, their specific intra-skin cell states, pathways, cell-cell interactions, and unbiased characterization of cell types profile, biomarkers, drivers, and regulatory pathways associated with specific SSc patient subgroups. Methods: We applied the massively parallel single cell RNA-seq (MARS-seq) developed in our laboratory to conduct a comprehensive single-cell genomics analysis of skin stromal and immune cells obtained through punch biopsy and blood immune cells from 73 SSc patients (39 DcSSc, 34 LcSSc) and 30 healthy controls. We used the MetaCell analytical method to identify homogeneous and robust groups of cells from single cell RNA-seq data. The perturbed signaling pathways, pathogenic stromal or immune cell subsets are characterized using CyTOF, immunohistochemistry, P hysical I nteracting C ell sequencing ( PIC -seq), and in vitro functional assays. Results: We collected data from a total of 46,742 high-quality skin stromal cells, and 57,475 high-quality blood and skin immune cells. Analysis of stromal cell compartment led to a detailed map of 261 meta cells organized into 16 broad lineages including: Fibroblasts, Pericytes, Vascular cells, and other cells. In the immune cell compartment, we found 361 meta cells organized into 14 broad lineages (e.g unique skin T, B, NK and dendritic cells). We observed a unique population of stromal and immune cells in the skin and blood of SSc patients as compared to controls. The major and dramatic changes were observed in the stromal cell compartment of the patient’s skin compared to controls. In the fibroblast lineage we found a small cluster of cells that were significantly diminished in the SSc patients compared with control, expressed genes associated with fibrosis and vascular remodeling. Significantly higher number of specific subsets of pericytes and vascular cells was found in SSc patients compared to controls. Analysis of the immune cell compartment revealed only minor changes in the immune cell composition in patients compared with controls. Finally, we found known and novel pathways (e.g Wnt/Notch signaling, IFN type I/II, AP-1 pathway, complement cascade activation) and cell-cell interactions that play crucial roles in SSc pathogenicity. Conclusion: Our study provides a detailed and unprecedented high-resolution atlas of the immune and stromal cells that make up the skin and peripheral blood in a large cohort of SSc patients with diverse disease duration and clinical settings. Our findings of candidate stromal and immune cell subpopulation, genes and pathways constitute the basis for understanding of SSc pathogenesis and heterogeneity and holds great potential to provide clinicians with new and powerful molecular tools for understanding of the immune-stromal cell crosstalk, for finding new biomarkers for SSc activity and complications and for tailoring and identification of new therapeutic targets. Disclosure of Interests: Chamutal Gur: None declared, Alexandra Balbir-Gurman Consultant of: Novartis, Hagit Peleg: None declared, Suhail Aamar: None declared, Fadi Kharouf: None declared, Yolanda Braun-Moscovici: None declared, Shuang-Yin Wang: None declared, Ido Amit: None declared