Asian J Beauty Cosmetol. 2015; 13(6): 713-720.

Epidermal Differentiation and Skin Barrier

Jung Sook Oh, and Hyun Hee Jang

The skin is a organ that represents an immune response while performing an essential barrier function that prevent water loss from the body inside and external factors from breaking inside. Stratum corneum generated by normal differentiation on healthy skin perform a skin barrier function, which is the most important role of epidermis. The principal cell of epidermal cell is keratinocyte, which is divided into 4 layers according to the level of differentiation, and various structural proteins are expressed. Corneodesmosome is expressed on the upper part of stratum spinosum and granular layer, which is stored in lamellar body and secreted outside the cells in stratum corneum, connecting one keratinocyte to another. Lipids that were contained in lamellar body of epidermal keratinocytes on the boundary of strata cornea and granular layer are secreted between keratinocytes, forming lipid cell envelope among keratinocytes. If epidermal keratinocytes reach the granular layer, they synthesize keratohyalin granule, which contains profilaggrin and loricrin. The skin barrier is formed by epidermal differentiation, acting as an epidermal permeability barrier as a “brick and mortar" structure of corneocyte and surrounding intercellular lipid layer. The typical ingredients that form stratum corneum are corneodesmosome that is a protein structure connecting keratinocytes, cornified protein envelope that surrounds keratinocytes, and cornified lipid envelope. Cornified envelope, which is a protein envelope on the outside of keratinocytes, and cornified lipid envelope, which exists on the outside of the cornified envelope, are connected in a covalent bond. Thus, it forms a combination necessary to the barrier function of stratum corneum, thereby performing the role of a support for precise array of lipids among keratinocytes. If differentiation of epidermal keratinocytes is abnormal, it will cause defects to the skin barrier function and dehydrate the skin, consequently resulting in chronic skin diseases such as atopy.

Keywords : Skin barrier, Keratinocytes, Cornified cell envelope, Epidermal differentiation, Stratum corneum