RESUMO
Hair follicles undergo repeated cycles of growth and regression, throughout the entire life of the organism. These dynamic changes require closely co-ordinated regulation of gene expression. The CCAAT/enhancer-binding proteins are a family of basic region/leucine zipper transcription factors that regulate gene transcription in various tissues. They have been implicated in epidermal differentiation and may therefore play an important role in the hair follicle. We have investigated the localization of four members of this family--CCAAT/enhancer-binding protein-alpha, -beta, and -delta, and Gadd153--in both human and murine hair follicles by immunohistochemistry. Furthermore, we examined CCAAT/enhancer-binding protein-alpha, -beta, and -delta immunoreactivity at different stages of the depilation-induced murine hair growth cycle. Distinct immunoreactivity patterns for CCAAT/enhancer-binding protein-alpha, -beta, and -delta, and Gadd153 were observed in the outer root sheath, sebaceous gland, dermal papilla, and connective tissue sheath of human anagen hair follicles. In murine follicles, CCAAT/enhancer-binding protein-alpha was expressed in the outer root sheath, sebaceous gland, and dermal papilla, whereas CCAAT/enhancer-binding protein-beta expression was confined to the matrix, sebaceous gland, and inner and outer root sheaths. Both CCAAT/enhancer-binding protein-alpha and -beta were upregulated during anagen, then downregulated in catagen follicles. In contrast, CCAAT/enhancer-binding protein-delta showed no hair cycle-dependent variation in immunoreactivity. These data suggests that the expression of CCAAT/enhancer-binding protein-alpha and -beta may, in turn, play a part in regulating hair cycle-dependent gene expression. Moreover, as CCAAT/enhancer-binding protein-alpha, -beta, and -delta are crucial in the regulation of adipocyte differentiation and lipid metabolism, their expression in sebocytes suggests they may also play a similar role in differentiation and lipid metabolism of the sebaceous gland.
