Xiaoyan Sun1, Simon Joost2 and Maria Kasper1 1Department of Cell and Molecular Biology, Karolinska Institutet, 171 77 Stockholm, Sweden 2Cancer Biology and Genetics Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA Correspondence: xiaoyan.sunki.se; maria.kasperki.se

Epithelial tissues line the outer surfaces of the mammalian body and protect from external harm. In skin, the epithelium is maintained by distinct stem cell populations residing in the interfollicular epidermis and various niches of the hair follicle. These stem cells give rise to the stratified epidermal layers and the protective hair coat, while being confined to their respective niches. Upon injury, however, all stem cell progenies can leave their niche and collectively contribute to a central wound healing process, called reepithelialization, for restoring the skin's barrier function. This review explores how epithelial cells from distinct niches respond and adapt during acute wound repair. We discuss when and where cells sense and react to damage, how cellular identity is regulated at the molecular and behavioral level, and how cells memorize past experiences and their origin. This collective knowledge highlights cellular plasticity as a brilliant feature of epithelial tissues to heal.