Identification and analysis of epidermal stem cells from primary mouse keratinocytes.

The skin, one of the largest organs of the body, is a dynamic tissue in which terminally differentiated keratinocytes are replaced by the proliferation and differentiation of epidermal stem cells. Epidermal stem cells are relatively undifferentiated, retain a high capacity for self-renewal throughout their lifetime, and normally have a slow cell division cycle in vivo. Furthermore, they have a high proliferation potential in vitro, and it is often desirable to isolate and culture them from adult mice to use in conjunction with in vivo studies. However, the isolation of these cells has been problematic. Here, we describe reliable methods for identifying a population of isolated bulge stem cells by flow cytometry and for measuring the growth and differentiation potential of primary mouse keratinocytes by clonal analysis.