183 Full Skin Equivalent Model for Burn Wound Healing Figure 1. Evaluation of skin development of cultured skin models. Images of ex vivo human skin (left) and full skin equivalents generated from de-epidermalized dermis, MatriDerm and Mucomaix (right) at T0 or T + 2 weeks. (A) Macroscopy and H&E staining; (B) Immunohistochemical pan-cytokeratin staining. Models were produced from 3 different skin donors in duplicate. For the full skin equivalent models, T0 was after the initial 3 weeks of culture. Black scale bar = 100 µm. Epidermal and dermal structures developed completely in full skin equivalents Epidermal and dermal development in the FSEs was examined by immunohistochemical analysis. Cytokeratin 15, present in progenitor keratinocytes [29], was consistently expressed in ex vivo human skin and DED-based FSEs from T0 onward (Figure 2A). In both MatriDerm- and Mucomaix-based models, cytokeratin-15-positive cells were present but did not display a well-organized basal layer. MatriDerm- and Mucomaix-based FSEs developed a basement membrane, as was shown by collagen IV and laminin α 5 expression at the dermal–epidermal junction (Figure 2B,C) [30]. Expression of collagen IV and laminin α 5 gradually increased over time, simultaneously with the improvement of the epidermal architecture. Although organization of the basal layer is not optimal, the FSE models produced an epidermis including a basement membrane, stratum spinosum, and stratum corneum that was similar to ex vivo human skin. Next, the differentiation status of keratinocytes in the FSEs was assessed by determining the presence of early differentiation marker cytokeratin 10 and late differentiation marker involucrin (Supplementary Figure 1A,B) [31,32]. In ex vivo human skin and DED-based 6
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