Isolation and Characterization of Cutaneous Epithelial Stem Cells.

The outer layer of mammalian skin is a multilayered epithelium that perpetually renews multiple differentiated lineages. During homeostasis, the maintenance of skin epithelial turnover is ensured by regionalized populations of stem cells that largely remain dedicated to distinct epithelial lineages including squamous, follicular, sebaceous, Merkel, and sweat glands. Cutting edge developments in this field have focused on: (1) stem cell activation cues derived from a number of extrinsic sources including neurons, dermal fibroblasts and adipocyte, and immune cells; and (2) characterization of epithelial stem cell homeostasis via hierarchical versus stochastic paradigms. The techniques outlined in this chapter are designed to facilitate such studies and describe basic procedures for cutaneous stem cell isolation and purification, which are based on leveraging their unique expression of surface proteins for simultaneous targeting and purifying of multiple subpopulations in adult skin. In addition, protocols for assessment of in vitro and ex vivo progenitor capacity as well as techniques to visualize progenitor populations in whole skin are discussed.