Keratinocytes control the pheo/eumelanin ratio in cultured normal XXXX melanocytes.

@entity1 @entity43483 @entity18606
The pheo/eumelanin ratio of cultured normal @entity1 melanocytes is distinct from the ratio observed for the same cells in vivo where they are in close contact with keratinocytes. To study the possible involvement of keratinocytes in the control of melanogenesis, we compared quantitatively and qualitatively the melanin production in melanocyte mono-cultures, in melanocyte-keratinocyte co-cultures and in pigmented reconstructed epidermis. @entity18606 and eumelanin contents were assessed by high-performance liquid chromatography with electrochemical and fluorometric detection of their specific degradation products and revealed striking differences in the presence of keratinocytes. In the absence of keratinocytes (melanocyte mono-cultures), we observed a very limited eumelanin production and a very high @entity18606 synthesis. The pheo/eumelanin ratio in mono-cultures could be slightly influenced by changing the composition of the culture medium, however, the very strong imbalance in favor of @entity18606 remained unchanged. An induction of eumelanin synthesis accompanied by an important reduction of @entity18606 formation was only observed in the presence of keratinocytes. The pheo/eumelanin ratio in melanocyte mono-culture dropped from 1043 down to about 25 in the presence of keratinocytes (co-cultures). The same observations were made when the melanocytes were integrated into a reconstructed @entity1 epidermis. Interestingly, under co-culture conditions resulting in only a partial contact between melanocytes and keratinocytes, the reduction of the pheo/ @entity43483 ratio were less pronounced. From these results we conclude that keratinocytes play an important role in the melanin production, affecting the melanogenic pathways.
