Keratinocyte
The predominant cell type in the epidermis, responsible for producing keratin and forming the skin's protective barrier. Keratinocytes undergo continuous turnover from the basal layer to the surface. Peptide-based skincare research investigates compounds that influence keratinocyte proliferation and differentiation.
Technical Context
Keratinocytes constitute approximately 90% of epidermal cells and are responsible for producing keratin (the structural protein of skin, hair, and nails) and maintaining the epidermal barrier. Keratinocyte lifecycle: stem cells in the basal layer divide → daughter cells progressively differentiate as they migrate upward through stratum basale → stratum spinosum → stratum granulosum → stratum corneum (where they are terminally differentiated, enucleated corneocytes). This transit takes approximately 28-40 days. During differentiation, keratinocytes produce keratins (K5/K14 in basal layer → K1/K10 in suprabasal layers), lipids (ceramides, cholesterol, fatty acids that form the stratum corneum lipid matrix), and involucrin/loricrin (forming the cornified envelope). Growth factors stimulating keratinocyte proliferation and migration: EGF, KGF (keratinocyte growth factor/FGF-7), TGF-α, and IGF-1. Understanding keratinocyte biology is fundamental to wound healing (re-epithelialisation) and skin barrier research.