O16 Activated glia cell population promotes fibrotic progression of fibroblasts in skin fibrosis

Abstract Introduction and aims Skin fibrosis is caused by the persistent activation of skin fibroblasts after tissue injury that results in excessive scarring and can seriously affect morbidity. Using a ­single-cell transcriptomic approach, we uncovered the key fibroblast subsets and skin cell signalling crosstalks that are integral to the onset of fibrosis and explore their therapeutic potential. Methods Using a bleomycin-induced skin fibrosis mouse model, we can mimic early and advanced skin fibrosis. We performed single-cell RNA sequencing (scRNAseq) time course analysis of early and advanced fibrotic tissue and identified key changes in fibroblast composition and signalling crosstalk using advanced bioinformatic analysis. Selected interactions were targeted through therapeutic intervention in vivo. Results Our scRNAseq data showed a loss of fibroblast heterogeneity through fibrotic disease progression and the emergence of one profibrotic subcluster residing predominantly in the lower dermis with distinct gene signatures from wound bed myofibroblasts. RNA velocity analysis indicated that neighbouring fibroblast subclusters converge towards this profibrotic population, pointing to its key role in driving skin fibrosis. Prior to fibroblast changes there is a doubling of other skin cell types at the early fibrotic timepoint including Schwann, immune and endothelial cells in early fibrotic skin. Exploring ligand-receptor crosstalk with CellChat and immunohistochemistry revealed a wound-activated glia population that is interacting with the emerging fibrotic fibroblast subcluster through Angptl4 and Sulf2 signalling in early fibrotic skin, potentially driving their profibrotic conversion. Inhibition of Sulf2 signalling with OKN-007 efficiently halts the progression of fibrosis in vivo. Conclusions Through our skin fibrosis time course, we have mapped the fibroblast subpopulation profibrotic evolution and identified a key signalling crosstalk with glia cells crucial for skin fibrosis initiation and progression that can be modulated through therapeutic intervention.