Skin Organoids As An In Vitro Skin Injury Model

Traditional 2D cell cultures or animal models do not represent well human skin physiology or reaction to skin injury and chemical irritation. A complex structure of 3D organoids can allow for physiological cell-cell/cell-matrix interactions and enable them to serve as a model for drug testing and disease. In this study, we created human skin organoids containing multiple skin cell types as a novel tool to recreate a skin microarchitecture and restore native cell interactions. Seeding a mix of skin cells in Low Attachment 96 Well Plates supported self-organization into spherical long-term viable organoids. The visual analysis showed maturation of the skin organoids by obtaining uniform pigmentation and decreasing their size significantly by day 21. Multi-parametric analysis including histology, SEM, and IHC revealed skin-specific layer organization within the organoids, with the surface layer formed by epidermal cells (keratinocytes, melanocytes) and the central core formed by dermal (fibroblasts and follicle dermal papillae cells) and hypodermal (pre-adipocytes) cells. In addition, the skin organoids capillary-like structures composed of endothelial cells were observed inside the organoids, as well as high production of extracellular matrix proteins (collagen III and laminin). To test the response of the skin organoids to external insults, they were exposed to UVB light and to skin-irritating chemicals. The organoids were able to metabolize retinol into retinoic acid and increase melanin synthesis in response to UVB and showed cell viability and anatomical changes in response to chemicals. Taken together, our novel approach for creating multicellular skin organoids is less technically demanding and is more reproducible compared to other skin organoid models. Ultimately, this technique could provide a reliable in vitro model of skin and be used as a platform for an investigation of different dermato-pathologies.