BIOPRINTING FOR SKIN - 3D Bioprinting and Nanotechnology in Tissue Engineering and Regenerative Medicine - page 287

FIGURE 13.5 Sections of the printed skin constructs, cultured in vitro at the air-liquid interface.
Printed skin constructs were cultured at the air-liquid interface with differentiation medium for 11 days. Sections (A)
to (C) show the printed cells, which directly exhibit fluorescence due to transduction (keratinocytes - red, fibroblasts
- green), Masson's trichrome staining shows connective tissue in green and the cells in red. The fibroblasts start to
migrate into the Matriderm™ already on day one (A, D, G) and continue to do so later on. The keratinocytes are
rounded and not connected on day 1, but already form a dense tissue on day 5. The epidermis even increases in
height until day 11. Scale bars represent 200 m m (A-F) and 100 m m (G-I). Reprint from Michael et al. (2013b) .
A color version of this figure can be viewed online.
whose wounds heal by granulation tissue and re-epithelialization, wounds in rodents are mainly closed
by contraction. In the chambers, the skin is fixed and no contraction of the wound area is possible.
Furthermore, due to the cover slip, a continuous observation of the wound is possible and no change of
dressings is needed. This considerably reduces the stress for the animals.
Skin constructs were printed analogously to the previously described ones and inserted into the
chamber the day after printing (day 0). The in vitro culture overnight gave the printed cells the op-
portunity to adhere to their surroundings. The animals were sacrificed after 11 days and analyzed by
histology and immunohistochemistry.
At the end of the experiments, the skin constructs were tightly connected to the surrounding host
tissue ( Figure 13.6 ). This macroscopic observation could be confirmed on the histological level. The
printed cells were alive and could directly be tracked via fluorescence microscopy.