**1. Introduction**

In three-dimensional (3D) bioprinting, cells and biocompatible materials are used as a biological ink (bioink) that can be organized in the 3D space with the goal of generating constructs mimicking organs and tissues. Recent advancements in biofabrication techniques have opened the possibility to apply 3D bioprinting methodologies to human pluripotent stem cells (hPSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). The interest in using hPSCs as building blocks in 3D bioprinting comes from their ability to generate ideally any cell type of interest by in vitro differentiation. Laser-assisted [1] and extrusion-based [2] bioprinting are two layer-by-layer deposition methods recently applied to undifferentiated hPSCs [3–6]. Once embedded in a 3D construct, hPSCs maintain their plurilineage potential [3–5] and could be converted by directed differentiation into neural [4], cartilage [6] or cardiac cells [3]. An alternative approach relies on prior differentiation of hPSCs into cell types of interest, which are then printed to generate tissue-like 3D constructs. Examples of liver [7–9], cardiac [9,10], vascular [11], cornea [12] and spinal cord [13,14] cells, all derived from hPSCs by conventional differentiation and subsequently used for bioprinting, have been recently reported. Notably, to the best of our knowledge, cortical neurons and glial cells derived from hPSCs have never been successfully used for bioprinting. Obtaining cells that cannot be isolated from primary human tissues is one of the major purposes of hPSCs, which have been successfully used to generate a wide variety of derivatives of the nervous system, including neuron subtypes of interest for translational or basic science applications [15].

In this work we took advantage of a custom-made extrusion-based bioprinter, implemented with co-axial wet-spinning microfluidic devices [16], to build 3D constructs made of iPSC-derived cortical neurons and glial cells. Optimization of the printing process and bioink composition resulted in high survival of human neural cells. Bioprinting did not impair further differentiation of the cells within the 3D construct. We also report long term maintenance and acquisition of mature functional properties.
