“…This method, although not specific for stem cells, has been previously been demonstrated to reproducibly isolate a keratinocyte population with high clonogenic potential, extensive long term growth capacity (exceeding 100 cell doublings) and the ability to generate a pluristratified epidermis. Transcriptomic profiling studies have additionally shown a strong similarity of this population with the cell population selected for high surface expression of integrin α6, a marker often associated with epithelial stem cells 14. The cells were then resuspended in a DMEM Hams F12 medium (3:1 mixture) containing 2 mM L-glutamine and 1 mM sodium pyruvate (all from Gibco-Life Technologies SAS) and supplemented with 10 fetal calf serum (HyClone-Fisher Scientific SAS, Illkirch, France), nonessential amino acids (Gibco-Life Technologies SAS, Saint Aubin, France), 5 mg/ml insulin, 0.18 mM adenine, 0.4 mg/mL hydrocortisone, 2 nm tri-iodothyronine (all from Sigma-Aldrich Chimie S.a.r.l, Lyon, France), 10 ng/mL epidermal growth factor (Chemicon, Temecula, CA), 1 mM isoproterenol (Sigma-Aldrich Chimie S.a.r.l), 5 mg/mL transferin (Sigma-Aldrich Chimie S.a.r.l), 4 mM glutamine (Gibco-Life Technologies SAS), and 50 U/mL penicillin/streptomycin (Gibco-Life Technologies SAS) and seeded at very low densities (1000 cells per Petri dish) on a feeder-layer of irradiated 3T3 fibroblasts.…”