39.9: Clinical Applications of Epidermal Stem Cells
Epidermal stem cells (EpiSCs) are mainly located at the basal layer of the epidermis. These cells repair minor injuries of the skin and replace dead skin cells. However, EpiSCs’ cannot heal severe wounds such as major burns or those from diabetes or hereditary disorders. In such cases, culturing the epidermal stem cells from the patient is possible and has yielded successful treatment options, such as laboratory-grown skin grafts. These grafts are synthesized using a patient’s own EpiSCs containing skin tissue which is taken out from an unaffected region. These grafts, called cultured epidermal autografts (CEA), have been used to treat severe burn wounds for more than three decades and have saved many lives.
The use of autografts or autologous skin grafts has some risks. For example, taking skin from an unaffected area itself creates a new wound. Proper healing of such secondary wounds along with the primary burn wound adds to the treatment challenge. For such patients, allografts, or healthy skin tissue from another person, are used as grafts for wound healing. Although allografts are immunologically rejected by the recipient patient within weeks, they can help wound healing by inducing endogenous regeneration of skin tissue.
As a wound heals, it may also form a scar—a mark that remains after wound closure. Scars are thicker than normal skin and lack sweat glands. Large scars, especially those around joints, may limit the movement of body parts. Hence, a scar is an undesirable event during wound healing. However, the risk of scar formation can be minimized using EpiSCs. This can be achieved through the use of EpiSC-derived exosomes. Exosomes are extracellular vesicles containing biomolecules such as proteins or RNAs. In rodents, the EpiSC-derived exosomes have been shown to transport microRNAs to the injured site, promote wound healing, and prevent scarring.