Immune-dominated cellular heterogeneity and stromal plasticity in keloid infiltrating and hypercellular zones revealed by single-cell RNA sequencing

Background: Keloids are aggressive fibroproliferative disorders characterized by a sclerotic core and an actively invading margin, yet the cellular and molecular basis of this spatial heterogeneity remains poorly understood. The roles of immune-stromal crosstalk in driving peripheral invasion have not been systematically dissected. Methods: Paired infiltrating and hypercellular zones were collected from anterior chest keloids of four patients. Single-cell RNA sequencing was performed on 128,678 cells after rigorous quality control. Unbiased clustering, differential gene expression analysis, pseudotime trajectory reconstruction, and cell-cell interaction profiling were applied to compare the landscapes of cell composition, function, and differentiation/development trajectories between the two zones. Results: The hypercellular zone was dominated by extracellular matrix-producing myofibroblasts, whereas the infiltrating zone was enriched in mononuclear phagocytes and endothelial cells, exhibiting a loose collagen architecture permissive for cellular invasion. Infiltrating zone fibroblasts adopted an immunomodulatory, inflammatory cancer-associated fibroblast-like phenotype, while macrophages displayed a type I interferon signature and immunoglobulin-mediated activation, indicating a chronic inflammatory state with features reminiscent of certain autoimmune conditions. Langerhans cells followed a three-stage developmental trajectory from a stress-responsive to a terminal NF-κB-driven effector state, orchestrating neutrophil and Th17 cell recruitment via chemokine and cytokine networks, with significant enrichment of the IL-17 signaling pathway. Endothelial cells at the margin underwent endothelial-to-mesenchymal transition, and Schwann cells exhibited phenotypic plasticity, mirroring aggressive tissue remodeling. Conclusions: In the context of this spatially resolved analysis, this study redefines the keloid margin as an immunology-dominated niche characterized by profound cellular and spatial heterogeneity that is associated with features that could drive peripheral invasion. These findings suggest a shift of the paradigm of keloid pathogenesis from a fibroblast-centric model to an immune-driven integrated landscape in this cohort and provide a theoretical foundation for keloid precision therapies and zone-specific biomarkers for treatment response and disease monitoring.