Reconstituted 3-dimensional human skin of various ethnic origins as an in vitro model for studies of pigmentation

Reconstituted 3-dimensional human skin equivalents containing melanocytes and keratinocytes on an artificial dermal substitute are gaining popularity for studies of skin metabolism because they exhibit morphological and growth characteristics similar to human epidermis. In this study, we show that such a pigmented epidermis model can be used to assess the regulation of pigmentation by known melanogenic compounds. In monolayers or in melanocyte-keratinocyte co-cultures, melanocyte-keratinocyte interactions are missing or are spatially limited. The commercial skin equivalents used in this study were derived from epidermal cells obtained from donors of three different ethnic origins (African- American, Asian, and Caucasian), and they reflect those distinct skin phenotypes. We used these pigmented human epidermis models to test compounds for potential effects on pigmentation in a more physiologically relevant context, which allows further characterization and validation of interesting melanogenic factors. We used known melanogenic stimulators (alpha-melanocyte-stimulating hormone and 3,4-dihydroxyphenylalanine) and inhibitors (hydroquinone, arbutin, kojic acid, and niacinamide) and examined their effects on the production of melanin and its distribution in upper layers of the skin. Our studies indicate that commercial skin equivalents provide a convenient and cost-effective alternative to animal testing for evaluating the regulation of mammalian pigmentation by melanogenic factors and for elucidating their mechanisms of action.