Vitamin A-Mediated Regulation of Keratinocyte Differentiation

Abstract

The normal structure of the epidermis is the result of a highly regulated process of keratinocyte growth and differentiation. The first indication that retinoids may play a role in the control of epithelial differentiation came from observations of the effects of vitamin A deficiency in humans and experimental animals. Experiments involving the use of cultured cells to study vitamin A-mediated regulation of epithelial differentiation demonstrated that excess vitamin A inhibited keratinization in cultured chick ectoderm, transforming the tissue into a mucus-secreting epithelium. Conversely, removal of vitamin A from the medium of cultured human keratinocytes, by delipidization of the serum, resulted in the induction of terminal differentiation. In vitro culture systems have been used extensively to characterize the morphological and biochemical changes associated with vitamin A regulation of keratinization. This chapter presents the two major systems for culturing human epidermal cells and describes some of the analytical tools that have been used to study the biosynthetic changes that take place during induction or inhibition of keratinization. © 1990, Elsevier Inc. All rights reserved.