Carnosic acid in topical rosemary extract promotes TRPA1-mediated scarless wound healing

Mammalian skin wounds typically heal with a scar, characterized by fibrotic tissue that disrupts original tissue architecture and function. Therapies to reduce fibrosis and scar formation remain a large unmet clinical need. Rosemary extract, particularly in the form of topical oils and creams, has gained massive popularity within the general public as a potential treatment to reduce scar formation. However, its efficacy and potential mechanism of action remain unknown. We show in adult wound healing mouse models that an ethanol-based rosemary extract reduces fibrosis and promotes scarless wound healing. More specifically, carnosic acid within rosemary leaves acts as an active ingredient and stimulates the TRPA1 nociceptor on cutaneous sensory neurons to promote scarless wound healing. Mice lacking TRPA1 on sensory neurons do not exhibit rosemary-induced tissue regeneration. Taken together, topical rosemary extract may be an effective and cost-efficient therapeutic to reduce scar formation in skin wounds. Overall design: Inured ears of WT mice treated with control cream or rosemary cream collected at day 7 post injury