From Gene to Scar: Proteome-Wide Causal Insights into Keloid Pathogenesis and Prevention

Objective: Keloids (KLs) and hypertrophic scars are common fibroproliferative disorders that cause significant functional and psychosocial distress. The lack of effective prevention and treatment strategies underscores the urgent clinical need to identify novel therapeutic targets and modifiable risk factors to improve patient outcomes. Approach: We conducted a comprehensive large-scale Mendelian randomization study to systematically assess the causal effects of 4,907 plasma proteins and 8,155 lifestyle and disease-related traits on KL risk. To validate our findings and explore the underlying cellular mechanisms, we analyzed the largest to-date single-cell RNA sequencing dataset for KLs, comprising 194,366 cells from 30 patients. Mediation analysis was used to dissect the pathways through which the identified proteins exert their effects. Results: Our proteome-wide analysis revealed R-spondin 3 (RSPO3) as a potent causal risk factor for KL development. These findings were corroborated at the tissue level, where RSPO3 expression was significantly upregulated specifically in KL-derived fibroblasts. Furthermore, our phenome-wide association screen revealed that several lifestyle and psychological factors, including alcohol intake, depression, and sleep disorders, are causally associated with an increased risk of KLs, whereas higher adult education status was identified as a protective factor. Innovation: This study establishes a pioneering multilayered causal inference framework by systematically integrating large-scale proteomics, phenomics, and single-cell transcriptomics. It moves beyond traditional association studies to first perform an unbiased, proteome-wide search for causal drivers of KL pathogenesis and then validate the top candidates at single-cell resolution. This "gene-cell-phenotype" strategy is the first to robustly link a genetically validated protein target (RSPO3) to its specific cellular origin (fibroblasts) in KLs. Conclusions: This study identifies RSPO3 as a promising, fibroblast-derived therapeutic target for KLs. In addition, we established a causal link between modifiable lifestyle factors and KL risk. These findings integrate genetic, proteomic, and single-cell data to significantly advance our understanding of KL pathogenesis.