RUNX2 regulates aberrant collagen gene expression in keloid fibroblasts

Keloids comprise an inflammatory fibroproliferative skin disorder characterized by excessive scarring. Fibroblasts play a pivotal role in skin fibrosis, exhibiting heightened collagen deposition. To investigate the molecular drivers of excessive collagen deposition in keloid, we compared the transcriptome of keloids and adjacent normal skin which demonstrated significant shifts towards bone and cartilage lineages in keloids, along with RUNX2, a key regulator of osteogenic and chondrogenic differentiation, notably upregulated. We then confirmed elevated levels of RUNX2 protein and phosphorylated RUNX2 in keloid tissue and fibroblasts compared to normal skin and normal dermal fibroblasts. To delve into how RUNX2 overexpression could contribute to keloids pathogenesis, we performed siRNA-mediated knockdown of RUNX2 in keloid fibroblasts followed by mRNA-sequencing. The results revealed significant downregulation of collagen genes COL11A1, COL5A3, COL15A1, and COL6A6, in knock-down vs. control groups along with GO enrichment analysis showing perturbation of genes involved in collagen and ECM organization. Further functional studies utilizing Runx2-knockout mice confirmed downregulation of these collagen genes along with reduced dermis thickness and reduced total dermal collagen in Runx2-knockout vs. Runx2- wild mice. These findings underscore the critical contribution of RUNX2 to collagen remodeling in keloid and provide potential therapeutic target.