Engrailed-1 inactivation leads to scarless skin wound healing through extracellular matrix remodeling

Abstract Hypertrophic scarring (HS) is a major source of morbidity after extensive cutaneous injury, and yet underlying mechanisms of hypertrophic scars and keloid lesions are not well understood. It has been shown that prevention of Engrailed-1 (EN-1) activation in fibroblasts was beneficial for wound healing without scarring. However, the role of EN-1 activation in wound healing and scarring needs to be further evaluated. In this study, we found EN-1 was upregulated in mouse wound dermis and in transforming growth factor-β1 (TGF-β1)-stimulated mouse dermal fibroblasts (mDFs). When mDFs were treated with Verteporfin or transduced with adenoviral vector expressing three siRNAs (Ad-simEn1), the expression of scar formation and hyaluronic acid (HA) catabolic related genes was down-regulated, the F-actin of cytoskeleton also decreased, the ultrastructure of the extracellular matrix (ECM) revealed a remarkable shift from dense to sparse with a marked reduction of component proteins fibronectin (FN-1) and fibrinogen (FIB), and a significant increase in HA content in ECM. Furthermore, we demonstrated that silencing EN-1 expression effectively suppressed keloid formation and promoted scarless healing in a rabbit model of ear skin injury, as further evidenced by the reduced ECM production and decreased expression of scar formation related gene products. These results demonstrated that inhibition of EN-1 function in dermal fibroblasts can effectively promote scarless healing of skin wounds through ECM remodeling.