Single-Cell Transcriptome Analysis Identifies Subclusters with Inflammatory Fibroblast Responses in Localized Scleroderma

Abstract

Localized scleroderma (LS) is an autoimmune disease with both inflammatory and fibrotic components causing an abnormal deposition of collagen in the skin and underlying tissue, often leading to disfigurement and disability. Much of its pathophysiology is extrapolated from systemic sclerosis (SSc) since the histopathology findings in the skin are nearly identical. However, LS is critically understudied. Single-cell RNA sequencing (scRNA seq) technology provides a novel way to obtain detailed information at the individual cellular level, overcoming this barrier. Here, we analyzed the affected skin of 14 patients with LS (pediatric and adult) and 14 healthy controls. Fibroblast populations were the focus, since they are the main drivers of fibrosis in SSc. We identified 12 fibroblast subclusters in LS, which overall had an inflammatory gene expression (IFN and HLA-associated genes). A myofibroblast-like cluster (SFRP4/PRSS23) was more prevalent in LS subjects and shared many upregulated genes expressed in SSc-associated myofibroblasts, though it also had strong expression of CXCL9/10/11, known CXCR3 ligands. A CXCL2/IRF1 cluster identified was unique to LS, with a robust inflammatory gene signature, including IL-6, and according to cell communication analysis are influenced by macrophages. In summary, potential disease-propagating fibroblasts and associated gene signatures were identified in LS skin via scRNA seq.

Clinical, Histologic, and Transcriptomic Evaluation of Sequential Fat Grafting for Morphea

“…The reduced expression of PAI-1 , EDN1 , and NFKBIA was confirmed by IHC, while changes in skin tissue expression of MYC were not significant (eFigure 9 in Supplement 1). We also found several sclerosis-mediating genes among the downregulated hub genes, such as CTGF (eFigure 9A in Supplement 1), CXCR4 (eFigure 9F in Supplement 1), IGFBP3 , and THBS1 . To further understand how the cellular immunology of morphea is modulated by sequential fat grafting, we performed an immune cell infiltrate analysis and cell types enrichment analysis.…”

“…We also found several sclerosis-mediating genes among the downregulated hub genes, such as CTGF (eFigure 9A in Supplement 1), CXCR4 (eFigure 9F in Supplement 1), IGFBP3, and THBS1. [22][23][24][25][26][27][28] To further understand how the cellular immunology of morphea is modulated by sequential fat grafting, we performed an immune cell infiltrate analysis and cell types enrichment analysis. Both results suggested reduced CD4 + memory T cells after treatment (eFigure 10 in Supplement 1).…”

Type-2 immunity associated with type-1 related skin inflammatory diseases: friend or foe?

“…The same study also demonstrated the crosstalk between fibroblasts and infiltrated immune cells (e.g. macrophages and T cells) to perpetuate inflammatory signals in lesions ( 47 ). Indeed, inflammatory fibrosis was shown to be dependent on CXCL9 and its receptor CXCR3 in a mouse model of skin fibrosis, thereby confirming the involvement of a type-1 immune response in the early phase of skin fibrosis ( 48 ).…”

Single-Cell RNA-Sequencing Analyses Identify APLNR, INS-IGF2, RGCC Genes May Be Involved in the Pathogenesis of Systemic Sclerosis Skin

“… 25 Another study examining potential disease-associated fibroblasts and related genetic signatures in SSc skin revealed a prevalent myofibroblast-like cluster (SFRP4/PRSS23) that shared numerous upregulated genes expressed in SSc-associated myofibroblasts. 26 Gaydosik et al identified a distinct cluster of recirculating CXCL13 + T cells in SSc skin, expressing a T helper follicular-like gene expression signature, that poised to promote B-cell responses within inflamed tissue. 27 Here, this study sheds light on the potential involvement of APLNR, INS-IGF2 , and RGCC in the pathogenesis of SSc skin through the process of EndMT ( Figure Supplementary 3 ).…”