565 hiPSC-derived skin organoids as tools for disease modelling: characterization of the epidermal-dermal junction

Human induced pluripotent stem cell (hiPSC)-derived hair-bearing skin organoids offer exciting new possibilities for modelling diseases like epidermolysis bullosa. These inherited diseases affect 1 in 30,000 people worldwide and result from perturbed expression and/or structure of components of the epidermal-dermal junction, the interface between basal keratinocytes of the epidermis and stroma of the dermis. To establish whether hiPSC-derived skin organoids might be able to capture salient features of epidermolysis bullosa, it is thus important to understand the structure and developmental stage of their epidermal-dermal junction. To this end, we successfully generated hair-bearing skin organoids from three independent hiPSC lines following the multistep protocol recently developed by Koehler’s research group and thoroughly characterized their epidermal-dermal junction. Using immunofluorescence and electron microscopy, we showed that basal keratinocytes in organoids adhere to laminin-332 and type IV collagen-rich basement membrane via type I hemidesmosomes and integrin β1-based adhesion complexes. Importantly, we demonstrated that epidermal-dermal junctions in organoids are almost devoid of type VII collagen, a fibril that mediates anchorage of the epidermis to dermis. This indicates that further maturation is required to take full advantage of skin organoids as disease model for some forms of epidermolysis bullosa, in particular those caused by mutations in the COL7A1 gene.