Mechanism of action of factors involved in regulating the cellular interaction in melanocyte

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Mouse epidermal melanoblasts preferentially proliferated from disaggregated epidermal cell suspensions derived from newborn mouse skin in serum-free melanoblast-defined medium (MDM). After 14 days, almost all keratinocytes that existed predominantly in the early stage of primary culture died, and pure cultures of melanoblasts were obtained. Epidermal melanoblasts dramatically increased in number in MDMDF consisting of MDM supplemented with dibutyryl adenosine 3':5'-cyclic monophosphate (DBcAMP) and basic fibroblast growth factor (bFGF). Epidermal melanocytes increased in number in MDMD consisting of MDM supplemented with DBcAMP. On the other hand, epidermal melanocytes were induced to differentiate in MDMM consisting of MDM supplemented with □-melanocyte-stimulating hormone (MSH). Pure cultured primary melanoblasts or melanocytes in MDMDF or MDMD were further cultured with MDMDF or MDMD supplemented with endothelin (ET)-1 from 14 days. A dramatic increase in the number of melanoblasts … More or melanocytes was observed after 7 days. However, no increase in the number of melanoblasts or melanocytes was observed in the absence of ET-1. The increase in the number of melanoblasts or melanocytes was comparable with that of melanoblasts or melanocytes cocultured with secondary keratinocytes in MDMDF or MDMD. Also, pure cultured primary melanoblasts in MDM were further cultured with MDMM supplemented with ET-1 from 14 days. A dramatic increase in the percentage of melanocytes in the melanoblast-melanocyte population was observed after 7 days. However, no increase in the percentage of melanocytes was observed in the absence of ET-1. The increase was comparable with that of melanocytes cocultured with secondary keratinocytes in MDMM. Moreover, anti- ET-1 antibody inhibited both the proliferation of melanoblasts or melanocytes in MDMDF or MDMD and the differentiation of melanocytes in MDMM in primary culture. These results suggest that ET-1 is one member of the keratinocyte-derived factors that are involved in regulating the proliferation and differentiation of mouse epidermal melanocytes. By using the same method it was shown that ET-2, -3, leukemia inhibitory factor, hepatocyte growth factor, stem cell factor, granulocyte-macrophage colocy-stimulating factor are also one of the keratinocyte-derived factors. Less