Addressing Human Skin Ethnicity: Contribution of Tissue Engineering to the Development of Cosmetic Ingredients

Recent publications describe various skin disorders in relation to phototypes and aging. The highest phototypes (III to VI) are more sensitive to acne, with the appearance of dark spots due to the inflammation induced by Cutibacterium acnes (previously Propionibacterium acnes). Dryness with aging is due to a lower activity of specific enzymes involved in the maturation of lipids in the stratum corneum. To observe and understand these cutaneous issues, tissue engineering is a perfect tool. Since several years, pigmented epidermis with melanocytes derived from specific phototypes allow to develop in vitro models for biological investigations. In the present study, several models were developed to study various skin disorders associated with phototypes and aging. These models were also used to evaluate selected ingredients' ability to decrease the negative effects of acne, inflammation, and cutaneous dryness. Hyperpigmentation was observed on our reconstructed pigmented epidermis after the application of C. acnes, and pollutant (PM10) application induced increased inflammatory cytokine release. Tissue engineering and molecular biology offer the capability to modify genetically cells to decrease the expression of targeted proteins. In our case, GCase was silenced to decrease the maturation of lipids and in turn modify the epidermal barrier function. These in vitro models assisted in the development of ethnic skin-focused cosmetic ingredients.