Bioprinting with pre-cultured cellular constructs to-wards tissue engineering of hierarchical tissues

The fabrication of physiologically active tissue constructs from various tissue elements are vital for estab-lishing integrated bioprinting and transfer printing techniques as vital tools for biomedical research. Physiologically functional tissues are hierarchically constructed from a variety of tissue subunits with different feature sizes and topo-graphies. For example, skeletal muscles are composed of many muscle bundles, muscle fibers, and muscle cells respec-tively. The fundamental constituents of all types of muscle tissues include various sized blood vessels, and vascular re-lated cells. Nature has designed the direction of all the aforementioned components to have unidirectional alignment, so that muscle contractions can effectively generate the mechanical functions. In this study, we demonstrate a promising approach to fabricating such hierarchical tissues by applying bioprinting and a transfer patterning technique. Linear-patterned smooth muscle cells were obtained by culturing on the surface patterned discs, before being transferred onto the Matrigel substrate. The fiber-like tissues structures were successfully formed on the substrate after a few days of culturing; these are partially aligned smooth muscle cells. Additionally, stacked structures were also successfully fabricated using laminating printing technique. Our results indicate that bio-printing and transfer printing strategy of pre-cultured aligned muscular fiber-like tissues is very promising method to assemble tissue elements for biofabrication of hierarchical tissues.