Location and Phenotype of Human Adult Keratinocyte Stem Cells of the Skin

The study identified markers for distinguishing stem cell, transit amplifying, and differentiating compartments in adult human skin using flow cytometry. Epidermal cells with high α6 integrin and low CD71 (α6briCD71dim) were identified as stem cells, comprising 2%-5% of the K14bri fraction, characterized by quiescence, small size, and high clonogenic capacity. In contrast, cells with high levels of both α6 integrin and CD71 (α6briCD71bri) were identified as transit amplifying cells, actively cycling with intermediate clonogenic capacity. Differentiating cells were marked by low α6 integrin (α6dim) and poor clonogenic efficiency. The study concluded that stem and transient amplifying cells were located in the deep rete ridges, while differentiating cells were in the shallow rete ridges.