Epidermal label-retaining cells: background and recent applications.

Epidermal label-retaining cells (LRC) can be identified by giving neonatal mice repeated injections of 3H-thymidine or 5-bromo-2'-deoxyuridine and then finding the cells that are still labelled in adulthood. Although label retention is simply a marker of the proliferative history of a cell, there is, nevertheless, evidence that it is a characteristic of epidermal stem cells. Here we review the early literature on LRC and then highlight two recent applications. We describe how LRC can be visualized by whole-mount labelling of the epidermis and how purified LRC can be used to screen for markers of the epidermal stem cell compartment.