All Keratinocytes are available in 1 human phototypes: Caucasian.
Keratinocytes, a key component of the epidermis. They represent 80 % of epidermis cell and have three main functions:
- Epidermis cohesion, by junction between keratinocytes, or with the dermis.
- Protective barrier between the environment and the body, thanks to cornified cells at the surface of the epidermis.
- Protection against damaging UV light, by accumulation of pigmented granules within the cells.
The epidermis is organized in several layers, with different roles. The basal layer is made of keratinocyte stem cells, which can self-renew, as well as produce transit-amplifying cells. As their name suggest it, these cells proliferate to produce new stock of keratinocytes for the epidermis. Newly produced keratinocytes will then progress through the different epidermis layers and finally reach the stratum corneum, in direct contact with the environment. At this point, they will lose their nuclei, and form an impermeable, or hydrophilic layer.
It is actually the stratum corneum that protects from UV thanks to pigmented granules they received from another cell population of the epidermis, the melanocytes. After a sunburn, it is the stratum corneum layer that desquamate intensively, and lead to skin peeling. Keratinocytes acts like the shield of our body, playing a crucial role for the hydration of skin and UV protection. Because they are a key barrier between us and our environment, it is crucial to understand their biology and provide adapted cosmetic formulation.