SUNGKYUNKWAN UNIVERSITY SCHOOL OF MEDICINE

Neuromuscular junction (NMJ)-on-chip is an efficient platform to study for understanding the functions and pathologies of NMJ and muscular disease. To conduct the platform more effectively, development of 3D muscle model that replicate native tissue, such as oriented muscle fibers, vessel formation, and innervation, is very essential. To address the issues, we fabricated a 3D muscle model consisting of uniaxially aligned muscle fibers and endothelial cell (EC) spheroids by development of a combinational bioprinting process supplemented of in situ electrical stimulation and microdroplet-based spheroid-forming techniques. In the advanced bioprinting process, E-field activated biological responses orientation of muscle cells, including ion-related channels, actin filament polymerization, and signaling molecule secretion, thereby promoting myogenesis. As for EC spheroids, they were self-assembled from the cells loaded in the printed microdroplets. The produced spheroids formed vessel structures, but also secreted abundant bioactive molecules facilitating synergistic cellular crosstalk and improving myogenesis and vessel formation. Moreover, when co-cultured with motor neuron spheroid using a simplified in vitro chip, those also encouraged NMJ formation in vitro. Our findings suggest that this hybrid muscle model has the potential to be applied to NMJ-on-chip studies by providing the in vivo muscle microenvironment and a more accurate representation of the NMJ. This study was published in Applied Physics Reviews (IF: 15) in August 2023 (https://doi.org/10.1063/5.0152924).