Skin Regeneration II: Epidermal Homeostasis and the Stem Cell System

Abstract

The establishment of human keratinocyte culture techniques and the successful transplantation of cultured epidermal autografts greatly advanced human epidermal keratinocyte stem cell research. Experimental evidence first demonstrated the presence of stem cells within the keratinocyte population, followed by the identification of diverse cell surface markers characteristic of keratinocyte stem cells. In addition, multiple models—driven by advances in research methodolo­gies—have been proposed to explain how keratinocyte stem cells located in the basal layer of the epidermis maintain epidermal homeostasis, a subject that continues to be actively debated. Furthermore, this research field has been applied to gene therapy for congenital epidermal disorders by combining cultured epidermal autografts with genetic modification of keratinocyte stem cells. This review outlines how studies on human keratinocyte stem cells have contributed to the conceptual development of the stem cell system and to elucidating the mechanisms by which stem cells maintain tissue homeostasis.