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Poster Session B

Session: (0955–0977) Systemic Sclerosis & Related Disorders – Basic Science Poster I

0957: Multi-Omic Profiling Reveals a Monocyte-Vascular Signature Associated with the Regression of Skin Fibrosis in SSc

Monday, October 27, 2025

10:30 AM - 12:30 PM Central Time

Location: Hall F1

Abstract Poster Presenter(s)

AH

Astrid Hofman, MSc

Center of Experimental Rheumatology, Department of Rheumatology, University Hospital Zurich
Zurich, Switzerland

Disclosure(s): No financial relationships with ineligible companies to disclose

Background/Purpose: Regression of skin fibrosis is a feature of the natural history of dcSSc. The molecular mechanisms underlying this resolution remain unclear. This study aims to establish a molecular fingerprint characterizing regression of skin fibrosis in SSc patients.

Methods: All patients fulfilled the 2013 ACR/EULAR classification criteria for SSc. Regressors were defined by a 5-point decrease in the modified Rodnan’s Skin Score (mRSS), and progressors by a 5-point increase at annual follow-up. Serum proteomics using the Olink High Throughput Explore panel (5,400 proteins) was performed on 44 SSc patients (25 regressors, 19 stable/progressors=non-regressors). Differentially abundant proteins (DAPs) were identified using the limma package. For single-cell RNA sequencing (scRNA-seq), peripheral blood mononuclear cells (PBMCs) were isolated from 15 SSc patients (5 each: regressor, progressor, stable) and 5 healthy controls. Single-cell libraries were prepared, and raw reads were aligned to the human genome using Cellranger 7.0. Transcriptomic data were analyzed with Seurat (v5.1.0), and differential gene expression analysis (DGEA) was performed using the MAST package, followed by Gene Set Enrichment Analysis (GSEA).

Results: Olink proteomics analysis identified 124 DAPs between skin regressors and skin non-regressors. Pathway enrichment analysis (PEA) on the DAPs revealed that MDK, THY1, JAM3, XG and VEGFB relate to cellular extravasation processes and SMOC2, RAMP2, CD160, VEGFB, HSPG2, PGF, EPHA2 to angiogenesis as top processes (Fig. 1). Seventy-three percent of these proteins are linked to monocyte extravasation.

PBMC scRNA-seq revealed 5 distinct clusters of monocytes (Fig 2A). Compositional analysis revealed a significant increase of clusters 0, 1 and 3 in the regressors compared to progressors (Fig 2B). To find whether a specific subset is involved in monocyte-vascular interactions, the expression of extravasation markers ITGAM, SELL, ICAM1, and S100A8/9 was used. These markers localized to clusters 0, 1 and 3 (Fig 2C). Additionally, chemotaxis marker CCR1 had an increased expression in clusters 0, 1, and 3, whereas CCR5 was unique to cluster 1 (Fig 2D).

Further characterization of cluster 1 using GSEA revealed a suppression in the gene sets ‘vasculature development’ (including extravasation-related genes: ITGA5, MMP14, MMP2, MMP19, CCL2, SOCS3, HMOX1 and PPARG) and ‘cell adhesion’ (including extravasation-related genes: ITGA5, MMP14, MMP2, CCL2, SOCS3, SIGLEC1 and MERTK). The generated gene module scores reflect a consistent decrease in regressors compared to other patient groups (Fig 3A-C). Additionally, both PEA and GSEA on cluster 1 had a decreased expression of IFN-I genes in the regressors, which is linked to a decrease in vascular permeability (Fig 3D).

Conclusion: Our multi-omics approach identified a set of proteins linked to monocyte extravasation and a subcluster of monocytes characterized by extravasation markers. This subcluster also displayed a decreased IFN-I activity. Our data points to a reduction in monocyte extravasation to the tissue associated to the regression of skin fibrosis in SSc.