Keratin 15 Expression in Stratified Epithelia: Downregulation in Activated Keratinocytes

The study investigated the expression of Keratin 15 (K15) in stratified epithelia, finding that K15 was primarily expressed in basal keratinocytes and absent in hair bulbs, but present in the outer root sheath of hair follicles. K15 expression increased when Keratin 14 (K14) was absent, suggesting a compensatory role. However, K15 was downregulated in activated keratinocytes, such as those in psoriasis and hypertrophic scars, indicating that K15 expression was not compatible with keratinocyte activation. The study concluded that K15 might play a crucial role in maintaining tissue integrity and could be involved in keratinocyte growth and differentiation, particularly in basal keratinocytes, which may include stem cell populations.