Expression of Epidermal Keratins and Filaggrin During Human Fetal Skin Development

The study analyzed keratins and filaggrin in over 50 samples of human embryonic and fetal skin, identifying four developmental periods: embryonic, stratification, follicular keratinization, and interfollicular keratinization. Keratins of 50 and 58 kD were consistently present, while 56.5 and 67 kD keratins increased during development. Filaggrin appeared around 15 weeks, initially in keratinizing cells near hair follicles, later in the granular and cornified layers. The findings indicated a relationship between protein expression and epidermal development, with keratin expression marking tissue commitment to stratification and keratinization. The study concluded that no unique "fetal" keratins were present, as only keratins found in adult tissues were expressed during fetal development.