Human iPSC-derived Melanocytes | Ref. PCi-MEL
 
Melanocytes are cells that synthesize melanin, a pigment responsible for skin pigmentation and UV protection. Depending on their location : skin, hair, or eye, we distinguish three kinds of melanocytes. We will focus on the one present inside the skin, more precisely in the epidermis bottom layer, or stratum basale. Melanocytes are the second biggest cell population in epidermis. They transfer melanosomes, the pigment containing units, to keratinocytes to effectively block excessive light. There are two kinds of melanin: eumelanin for brown colour and pheomelanin for yellow/red colour. The process of melanin production is called melanogenesis and differs in the last stages between eumelanin and pheomelanin. Everyone has a different ratio of these two melanins, which will determine six different phototypes (Types I to VI according to the Fitzpatrick classification). Each phototypes will react differently to sun’s UV depending on their melanin content.

Scientific data show that for each phototypes, while there is roughly the same number of melanocytes per skin surface, the differences observed come from melanosomes. For instance, the melanosome’s shape, size, organisation, or transfer is completely different for type I and type VI. This emphasizes the importance of working with melanocytes of the right phototype when developing new ingredients or formula, as pigmented cells from Caucasian, Asian or African skins will not display the same behaviour.