A bioengineered spinal cord is fabricated via extrusion-based multimaterial 3D bioprinting, in which clusters of induced pluripotent stem cell (iPSC)derived spinal neuronal progenitor cells (sNPCs) and oligodendrocyte progenitor cells (OPCs) are placed in precise positions within 3D printed biocompatible scaffolds during assembly. The location of a cluster of cells, of a single type or multiple types, is controlled using a point-dispensing printing method with a 200 µm center-to-center spacing within 150 µm wide channels. The bioprinted sNPCs differentiate and extend axons throughout microscale scaffold channels, and the activity of these neuronal networks is confirmed by physiological spontaneous calcium flux studies. Successful bioprinting of OPCs in combination with sNPCs demonstrates a multicellular neural tissue engineering approach, where the ability to direct the patterning and combination of transplanted neuronal and glial cells can be beneficial in rebuilding functional axonal connections across areas of central nervous system (CNS) tissue damage. This platform can be used to prepare novel biomimetic, hydrogel-based scaffolds modeling complex CNS tissue architecture in vitro and harnessed to develop new clinical approaches to treat neurological diseases, including spinal cord injury.

A living platform to model complex spinal cord architecture was developed by Ann M. Parr, Michael C. McAlpine, and co‐workers and appears in article number https://doi.org/10.1002/adfm.201801850. The approach involves the 3D bioprinting of multicellular neural network structures in which stem‐cell derived neural progenitor cell types can be precisely positioned within a neuro‐compatible scaffold via a custom‐built, one‐pot printing process. The platform could ultimately be used to develop a clinical implant for treating neurological diseases, including spinal cord injury.

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