Hair Follicles in Wound Healing and Skin Remodelling

Abstract

Introduction: Besides the primary role of hair follicles in producing hair shafts, these mini-organs have been shown to contribute to the healing and remodelling of the skin in the response to injury. There is an increasing number of clinical and experimental studies exploring the mechanisms by which hair follicles contribute to skin recovery. Mouse tracing experiments demonstrated that after skin injury, epithelial stem cells migrate out of the follicle to support wound re-epithelialization, while the mesenchymal cells from the hair follicle are mobilised to migrate into the wound bed and contribute to the repair of the dermis. Accordingly, there is a significant delay in wound healing in the absence of hair follicles, observed both in experimental studies in mice and in humans during clinical practice. In the healthy state, hair follicles induce changes to the surrounding skin, which occur in synchrony with the hair follicle cycle. Besides supporting wound healing and healthy skin remodelling, it remains to be investigated whether hair follicles could also remodel the fibrotic tissue formed after skin injuries. Methods: For the selection of literature covered in this chapter, we used Pubmed database with the keywords hair follicles in wound healing and skin remodelling, and hair follicles transplantation and wound healing. Publications related to the clinical use of hair follicle grafts for healing chronic cutaneous wounds are also discussed. Results: A large body of evidence supports the role of hair follicles in wound healing and skin remodelling. As demonstrated in several clinical studies, transplantation of autologous hair follicle grafts into chronic ulcers and difficult to heal wounds accelerate the healing of wounds. Conclusions: There is a great potential in exploring the role of hair follicles in wound healing and skin regeneration. Once we understand the exact mechanism by which hair follicles contribute to skin recovery, we can try to mimic this effect with therapeutic solutions. A potential approach involves deciphering the populations of hair follicle cells that contribute to the observed effect and injecting them directly into wounds or scar tissue to improve the clinical outcomes. Alternatively, elucidating the paracrine effect of transplanted follicles would open up new avenues for therapeutic discovery, to replicate the combination of required factors that facilitate healing or scar remodelling.KeywordsHair folliclesWound healingSkin remodellingHair follicle cycleAutologous hair transplantation