Bioengineered skin-substitutes incorporating rete-ridges using a bioprinting process

Bioprinting is a widely used technique for creating three-dimensional, complex, and heterogeneous artificial tissue constructs that are biologically and biophysically similar to natural tissues. The skin is composed of several layers including the epidermis, basement membrane (BM), and dermis. However, the unique undulating structure of basement membranes (i.e. rete ridges) and the function of BM have not been extensively studied in the fabrication of engineered skin substitutes. In this study, a novel engineered skin substitute incorporating an artificially designed rete ridge (i.e. mogul-shape) was developed using bioprinting and bioinks prepared using collagen and fibrinogen. To mimic the structure of the rete ridges of skin tissue, we developed a modified bioprinting technique, controlling rheological property of bioink to create a mogul-shaped layer. In vitro cellular activities, including the expression of specific genes (those encoding vimentin, laminin-5, collagen IV, and cytokeratins), demonstrated that the engineered skin substitute exhibited more potent cellular responses than the normally bioprinted control owing to the favorable biophysical BM structure and the bioink microenvironment. Additionally, the feasibility of utilizing the bioprinted skin-structure was evaluated in a mouse model, and in vivo results demonstrated that the bioprinted skin substitutes effectively promoted wound healing capabilities. Based on these results, we suggest that bioprinted skin tissues and the bioprinting technique for mimicking rete ridges can be used not only as potential lab-chip models for testing cosmetic materials and drugs, but also as complex physiological models for understanding human skin.