3D printing human induced pluripotent stem cells with novel hydroxypropyl chitin bioink: scalable expansion and...

Human induced pluripotent stem cells (hiPSCs) are more likely to successfully avoid the immunological rejection and ethical problems that are often encountered by human embryonic stem cells in various stem cell studies and applications. To transfer hiPSCs from the laboratory to clinical applications, researchers must obtain sufficient cell numbers. In this study, 3D cell printing was used as a novel method for iPSC scalable expansion. Hydroxypropyl chitin (HPCH), utilized as a new type of bioink, and a set of optimized printing parameters were shown to achieve high cell survival (>90%) after the printing process and high proliferation efficiency (∼32.3 folds) during subsequent 10 d culture. After the culture, high levels of pluripotency maintenance were recognized by both qualitative and quantitative detections. Compared with static suspension culture, hiPSC aggregates formed in 3D-printed constructs showed a higher uniformity in size. Using a novel dual-fluorescent labeling method, hiPSC aggregates in the constructs were found more inclined to form by in situ proliferation rather than multicellular aggregation. This study revealed unique advantages of non-ionic crosslinking bioink material HPCH, including high gel strength and rapid temperature response in hiPSC printing, and achieved primed state hiPSC printing for the first time. Features achieved in this study, such as high cell yield, high pluripotency maintenance and uniform aggregation provide good foundations for further hiPSC studies on 3D micro-tissue differentiation and drug screening.