Expression of Keratin K14 in the Epidermis and Hair Follicle: Insights Into Complex Programs of Differentiation

The study explored the expression of keratin K14 in human skin, particularly comparing its presence in the epidermis and hair follicle. It was found that keratin K14 and its mRNA are expressed differently in these tissues, with outer root sheath (ORS) cells in hair follicles showing lower levels of K14 compared to basal epidermal cells. As ORS cells differentiate, they increase K14 expression and form denser keratin bundles, similar to epidermal cells. In contrast, matrix cells in hair follicles, which can differentiate into various hair structures, do not express K14 or form keratin filaments. These findings suggested that the expression patterns of K14 correlate with the pluripotency of epithelial cells and highlight the distinct differentiation programs of hair follicles compared to other stratified squamous epithelia.