The effects of essential fatty acid deficiency on the fine structure of mouse skin

Mice raised from weaning on a diet free of essential fatty acids (EFA) develop a greatly thickened epidermis and stratum corneum with a concomitant increase in transepidermal water loss. The hyperplastic epidermis of EFA deficient mice is characterized by widely separated columnar cells in the stratum basale, an abundance of keratinosomes at the periphery of the cells in the stratum spinosum, and an unusually well‐developed stratum granulosum in which many keratinosomes are fused with the plasma membranes. Many vacuoles, lacking a membrane, are observed in the stratum granulosum and stratum corneum; these presumably correspond to histochemically demonstrable droplets of phospholipid. The horny cells in the stratum corneum of deficient mice also contain many membrane bound vesicles many of which can be identified as mitochondria. The most striking change in the horny cells, however, is the wide separation of epidermal filaments which may allow free diffusion of bulk water through the stratum corneum. The low rate of transepidermal water loss in normal skin may result in part from the ability of the stratum corneum to bind water in the small intersticies between the keratin filaments. The EFA, i.e., arachidonic acid, may serve to bind phospholipids to the structural protein of filaments and membranes thus binding water at these protein‐lipid interfaces.