In vitro models to investigate pigmentation disorders inadequately capture the complex neuroectodermal-mesodermal signaling interplay controlling human epidermal melanogenesis. Here, we aimed at assessing the suitability of a standardized human ex vivo skin organ culture as a rapid detection-system to qualitatively and quantitatively assess the effects of topically or systemically applied candidate pigmentation modulators, under clinically relevant conditions. Full-thickness human skin samples were cultured in serum-free supplemented medium and exposed to selected test agents (hyperpigmentation controls: [Nle4, DPhe7]-α-melanocyte-stimulating hormone (α-MSH) or forskolin; hypopigmentation control: kojic acid or 4-butylresorcinol) for 3 days ex vivo, either through systemic or topical delivery routes, followed by assessing changes in tyrosinase activity in situ, gp100 protein expression (immunofluorescence microscopy) and melanin content (Warthin-Starry histochemistry) in the epidermis. We show that systemic administration (i.e. to the culturing medium) of α-MSH or forskolin significantly stimulates epidermal melanin production. Moreover, we demonstrate that topical application of DMSO or forskolin significantly enhances gp100 expression, tyrosinase activity and melanin production ex vivo. Addition of the tyrosinase inhibitors, kojic acid and 4-butylresorcinol, prevents melanogenesis as induced by systemic forskolin or topical DMSO treatment. Finally, we utilized this preclinical model to identify a novel, topically applicable, drug-free hyperpigmentation active as a candidate promoter of “UV-free tanning”. In conclusion, we introduce a pragmatic short-term human skin organ culture assay, which provides a simple, accessible, sensitive, quantifiable, and clinically relevant, pre-clinical ex vivo platform for identification of candidate modulators of human skin pigmentation to manage of hyper- and hypopigmentation disorders.

ESDR540 - A Novel Ex Vivo Assay Platform to Pre-Clinically Evaluate Candidate Hypo- or Hyperpigmentation-Inducing Agents in Human Epidermis

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.