Single-cell RNA-seq reveals increased TNFRSF9⁺ senescent fibroblasts and enhanced crosstalk between TNFRSF9⁺ fibroblasts and neural cells in keloids.

Abstract

Keloids are the result of abnormal wound healing, characterized by excessive and uncontrolled scar tissue growth that extends beyond the boundaries of the original injury. Understanding the underlying mechanisms of keloid formation is essential for improving clinical treatments. Fibroblasts, which play a central role in scar tissue formation, have been shown to be heterogeneous in keloids, but the mechanisms driving this heterogeneity remain unclear. We investigate fibroblast heterogeneity in keloids using single-cell RNA sequencing (scRNA-seq). This technique allowed us to explore the different subpopulations of fibroblasts present in keloid tissues and examine their roles in the pathological process. Our analysis identified four distinct subpopulations of fibroblasts in keloid tissues: mesenchymal, secretory-reticular, secretory-papillary, and pro-inflammatory fibroblasts. Notably, mesenchymal fibroblasts were predominantly increased in keloids. A subset of these mesenchymal fibroblasts exhibited a senescent phenotype, marked by TNFRSF9 expression, and were designated as TNFRSF9+ senescent fibroblasts. Furthermore, pseudo-chronological analysis revealed that TNFRSF9+ fibroblasts represent a mature stage of fibroblast differentiation, supporting their critical role in keloid formation. Cell-cell interaction analysis using CellChat demonstrated that TNFRSF9+ senescent fibroblasts strongly interact with neural cells, which are also implicated in keloid development. These findings enhance our understanding of the fibroblast heterogeneity and the mechanisms underlying keloid formation. The identification of TNFRSF9+ senescent fibroblasts and their interactions with neural cells opens potential therapeutic avenues for targeting fibroblast senescence and neural dysregulation in keloid treatment.