ABSTRACT
It has been evident for some time that cell replacement in the epidermis of the skin is
a highly ordered process with a central role for keratinocyte stem and progenitor cells.
In recent years, many investigators have sought to distinguish keratinocyte stem
cells (KSCs) from their immediate progeny using molecular markers, both in situ and
ex vivo, and a number of molecular regulators that can perturb ordered cell renewal
in skin epithelium have also been identified. Although we are far from having a clear
understanding of the precise mechanisms that regulate ordered epidermal tissue morpho-
genesis and cell renewal, significant progress has been made that has begun to shed light
on these processes. Unequivocal identification and isolation of viable keratinocyte stem
and progenitors are now possible; this combined with the advent of molecular technol-
ogies, such as high-throughput genome-wide scanning and the ability to generate mice
with designer skin, and the development of assays for these cells, albeit at an early
stage, places us at an exciting time of experimental investigation and discovery,
poised to capitalize on the collective efforts expended by many laboratories across
the world.
