STAT3 Signaling Pathway in Keloid Pathogenesis Implicated by Preliminary Transcriptome and ATAC Analyses

Keloids are wounding-induced fibroproliferative human tumor–like skin scars of complex genetic makeup and poorly defined pathogenesis. Fibroblasts are the principal mediator of fibroproliferative disorders. To reveal dynamic epigenetic and transcriptome changes of keloid fibroblasts, a vertical study from RNA-seq and ATAC-seq analyses followed by in vivo confirmation of candidate molecule expression and subsequent functional testing was carried out using an early passage, freshly isolated keloid fibroblast cell strain and its paired normal control. These keloid fibroblasts produce keloid-like scars in a plasma clot-based skin equivalent humanized keloid animal model. RNA-seq analysis reveals that Hepatic fibrosis is the most significant pathway followed by Wnt–b-catenin signaling, TGF-b signaling, regulation of the EMT pathway, the STAT3 pathway, and adherens junction signaling. ATAC-seq analysis shows that STAT3 signaling is the most active pathway in keloid fibroblasts, followed by Wnt signaling (Wnt5) and regulation of the EMT pathway. Immunohistochemistry confirms that activated STAT3, (Tyr705 phospho-STAT3) and/or b-catenin are upregulated in dermal fibroblasts of keloid clinical specimens and mature keloid skin equivalent implants from the humanized mouse model compared to the normal control. The effect of STAT3 signaling on keloid fibroblast collagen expression was further tested in plasma clot-based skin equivalents using Cucurbitacin I, a selective JAK2/STAT3 inhibitor. A non-linear dose response of Cucurbitacin I was observed in collagen type I expression indicating a likely role of STAT3 signaling pathway in keloid pathogenesis. This work also demonstrates the utility of the recently established humanized keloid mouse model in exploring the mechanism of keloid formation.