Keratin 19 as a Biochemical Marker of Skin Stem Cells In Vivo and In Vitro: Localization and Variation with Age and Culture Stage

This study evaluated keratin 19 (K19) as a marker for skin stem cells, using a mouse model to identify these cells as [3H]thymidine-label-retaining cells. K19 was found to be a marker for skin stem cells in hair follicles, with expression varying by body site, donor age, and culture time. K19 was present in hair follicles but absent in interfollicular epidermis at hairy sites, while at glabrous sites, K19-positive cells were located in deep epidermal rete ridges. The study found a higher proportion of K19-positive cells in newborn foreskins compared to older ones, correlating with the variation in keratinocyte culture lifespan and potentially explaining why children heal faster than adults. The findings suggested that K19 expression could be a valuable tool for characterizing skin stem cells in various conditions.