Research Article
Yukie Yoshida
Abstract
Melatonin is an amine derivative produced in the pineal body and retina, and is present in all vertebrates. Melatonin production and secretion are regulated by sunlight sensed by the eyes and control circadian rhythms. It mediates its effects through the melatonin receptors MT1 and MT2, expressed in the central nervous system and retina. Recent studies describing the expression of melatonin in mouse skin, binding to epidermal cells and epithelial hair follicles, and positive melatonin receptor antibody staining in human epidermis suggest the presence of melatonin receptors in the skin. However, the exact localization of melatonin receptor expression in the epidermal tissue and hair follicles is unclear. The aim of this study was to determine the precise location of MT1 in mouse skin, hair and whiskers, and to study the growth effects of melatonin on mouse whiskers in vitro. MT1 localization in mouse skin and whiskers was examined immunohistochemically. In addition, organ cultures of mouse whiskers were grown in media containing different concentrations of melatonin, and its effects on whisker growth were evaluated. MT1 was present in the granular layer of mouse epidermal keratinocytes and in the outer root sheath, and in vitro treatment of melatonin enhanced whisker growth. Thus, the effects of melatonin on keratinization suggest it may be useful as a drug for promoting hair growth.