Investigating human keratinocyte stem cell identity

Studies of the regulatory networks controlling intrinsic properties and fate of adult stem cells are in a large part performed in animal models. Epidermis is one of the most accessible human tissues for researchers, which is a critical parameter for conducting programs dedicated to this knowledge in human stem cell systems. Keratinocyte stem cells constitute a particularly valuable model, because of this practical aspect, but more importantly because their existence is for decades validated by the clinical demonstration of their impressive capacity for epidermis regeneration. For the fundamentalist, human keratinocyte stem cells represent a unique system to dissect the genetic and epigenetic controls of "stemness" and self-renewal. For this purpose, a highly limiting point is our current inability of obtaining a cellular material corresponding to keratinocyte stem cells with homogeneous phenotypic and functional characteristics. The search for tools suitable for the prospective selection of keratinocyte stem cells will benefit from studies conducted at the broad level of the global stem cell field, as well as from more specifically targeted approaches. Advances in that direction are tightly linked to the development of functional assays allowing reliable assessment and modeling of the different stem cell-associated functional characteristics.