Flow cytometry-based characterization of label-retaining stem cells following transplacental BrdU labelling

A method to characterize and culture stem cells from neonate mouse epidermis after transplacental BrdU (bromo-deoxyuridine) administration is described. We have characterized stem cells by their properties viz. to retain BrdU label, adhere rapidly onto collagen-fibronectin substratum and express a specific biomarker beta-1-integrin. BrdU-labelled cells (detected using monoclonal antibody) constituted a sum of 18% of the total number of cells. The ability of freshly isolated keratinocytes [LRCs (label-retaining cells)] to bind to primary BrdU antibody or to pick up PI (propidium iodide) stain was distinguishable. Viable LRCs did not retain PI. Such cells, termed EpSC (epidermis stem cell), were PI negative and BrdU positive. EpSC constituted 6% of the total cell yield. Culture in low Ca2+ medium and susceptibility to differentiation in the presence of high Ca2+ levels further characterized the stem cells. This protocol is useful for studying transplacental carcinogenesis.