The epidermis functions as a barrier against the environment by means of several layers of terminally differentiated, dead keratinocytes - the cornified layer, which forms the endpoint of epidermal differentiation and death. The cornified envelope replaces the plasma membrane of differentiating keratinocytes and consists of keratins that are enclosed within an insoluble amalgam of proteins, which are crosslinked by transglutaminases and surrounded by a lipid envelope. New insights into the molecular mechanisms and the physiological endpoints of cornification are increasing our understanding of the pathological defects of this unique form of programmed cell death, which is associated with barrier malfunctions and ichthyosis.

The cornified envelope: a model of cell death in the skin

https://www.jidonline.org/article/S0022-202X(15)43890-4/pdf

Epidermal lipids, barrier function, and desquamation.

Publisher Summary This chapter discusses the structural and lipid biochemical correlates of the epidermal permeability barrier. A pivotal point in terrestrial adaptation is prevention of desiccation and maintenance of internal water homeostasis. The outermost integumentary tissue, the epidermis, maintains a reserve of germinal cell layers whose proliferation, stratification, and differentiation result in the production of the outermost layer, the anucleate stratum corneum. The stratum corneum has heterogeneous tissue structure possessing a selected array of enzymatic activity. The sequestration of lipids to intercellular domains and their organization into a unique multilamellar system have broad implications for permeability barrier function, water retention, desquamation, and percutaneous drug delivery. Yet, the functions and organization of specific lipid species in this membrane system are still unknown. Further, elucidation of the molecular architecture and interactions of lipid and nonlipid components of the stratum corneum intercellular domains will be a prerequisite for a comprehensive understanding of stratum corneum function.

Structural and Lipid Biochemical Correlates of the Epidermal Permeability Barrier

https://www.jidonline.org/article/S0022-202X(15)32393-9/pdf

Jon. Goerke

Papers

Mammalian Epidermal Barrier Layer Lipids: Composition and Influence on Structure