Correlation between expression of peroxisome proliferator-activated receptor β and squamous differentiation in epidermal and tracheobronchial epithelial cells

Previously, several members of the nuclear receptor superfamily have been implicated in the regulation of epidermal differentiation. In this study, we analyze the expression of members of the PPAR nuclear receptor subfamily in relation to the process of squamous differentiation in normal human epidermal keratinocytes (NHEK), human tracheobronchial epithelial (HBE) cells and the epidermis in vivo. Our results demonstrate that induction of differentiation in NHEK by either treatment with the phorbol ester phorbol 12-myristate-13-acetate (PMA), suspension culture or confluence greatly enhances the expression of PPAR beta mRNA. Likewise, topical treatment of mouse skin with PMA results in increased PPAR beta mRNA expression in the epidermis. In addition, the induction of squamous differentiation in HBE cells was also associated with an upregulation of PPAR beta mRNA expression. Finally, in situ hybridization analysis localized PPAR beta mRNA to the suprabasal layers of normal human skin. Our results demonstrate that the expression of PPAR beta is associated with squamous differentiation suggesting a regulatory role for this receptor in the control of specific genes during this differentiation process, (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.