Cultivation of Normal Human Epidermal Melanocytes in the Absence of Phorbol Esters

An important approach in studies of normal, diseased, and malignant cells is their growth in culture. The isolation and subsequent culture of human epidermal melanocytes has been attempted since 1957 (1 -5 ), but only since 1982 have pure normal human melanocyte cultures been reproducibly established to yield cells in sufficient quantity for biological, biochemical, and molecular analyses (6 ). Selective growth of melanocytes, which comprise only 3-7% of epidermal cells in normal human skin, was initially achieved by suppressing the growth of keratinocytes and fibroblasts in epidermal cell suspensions with the tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA) and the intracellular cyclic adenosine 3^’ , 5^’ monophosphate (cAMP) enhancer cholera toxin, respectively, which both also act as melanocyte growth promoters. However, phorbol ester is metabolically stable and has prolonged effects on multiple cellular responses (6 ). Recent progress in basic cell-culture technology, along with an improved understanding of culture requirements, has led to an effective and standardized isolation method, and special TPA-free culture media for selective growth and long-term maintenance of human melanocytes. The detailed description of this new method is aimed at encouraging its use in basic and applied biological research.