Histological sections of the tissue engineered skin constructs <i>in vitro.</i>

<p>Skin constructs were cultivated at the air-liquid-interface with differentiation medium for 11 days. Sections show cells using fluorescent microscopy and Masson’s trichrome staining, respectively. The time points indicated in A–C are valid for the whole respective columns. The skin constructs were cultivated at the air-liquid-interface. The keratinocytes (HaCaT-mCherry) exhibit red fluorescence while the fibroblasts (NIH3T3-eGFP) appear in green (A–C). Masson’s trichrome staining reveals the connective tissue containing collagen (green) and the cells (reddish) (D–I). The fibroblasts already start to grow into the Matriderm® underneath one day after printing (A, D, G). The keratinocytes, which still are rounded and are not connected to each other on day 0 (A, D, G), already form a dense tissue on day 5 (B, E, H). The thereby formed epidermis increases in height until day 11 (C, F, I). Scale bars depict 200 µm (A–F) and 100 µm (G–I).