Hair follicle-inspired therapies for wound healing and scar remodelling

Human skin does not regenerate after severe injuries. Instead, the wound healing process repairs the skin as quickly as possible, which can lead to the formation of scar tissue. Scar tissue has reduced function compared to healthy skin; contractures limit movement, sensation is altered, the skin is itchy, and there are no functional appendages, such as sweat glands and hair follicles. As the cellular and molecular mechanisms of scarring are becoming better understood, most therapeutic strategies focus on preventing scar formation by targeting the wound healing process. One avenue of research takes inspiration from the hair follicle, as hairy skin heals with faster wound closure and reduced scar formation compared to non-hairy skin. It is thought that the hair follicle has a contributing role in this process and hair follicles transplanted into chronic (non-closing) wounds have been shown to kick-start wound closure. In the context of scarring, hair follicles transplanted into longstanding scar tissue also lead to scar remodelling. In this review, we discuss the role of hair follicles and cells or biomaterials derived from the hair follicle in both wound healing and scar remodelling.