Novel neuromuscular junction model in 2D and 3D myotubes co-cultured with induced pluripotent stem cell-derived motor neurons

Motor neurons differentiated from induced pluripotent stem (iPS) cells have attracted attention for use in the construction of drug screening systems for neuronal diseases, such as amyotrophic lateral sclerosis. However, conventional drug screening systems using 2-dimensional (2D) cultures of iPS cell-derived motor neurons often evaluate the cell survival rate, morphological changes in the cells and/or gene expression analysis, and these parameters do not always reflect the actual functions of motor neurons, i.e., the induction of muscle contractions. In the present study, we developed a neuromuscular junction model comprising motor neurons and myotubes, which were differentiated from iPS cells and C2C12 myoblasts, respectively. Using this model, the contractile activity and force generation of the myotubes via the neuromuscular junction were successfully measured in both two- and three-dimensional (3D) cell culture systems. The results suggested that this neuromuscular junction model can be used to construct a drug candidate screening system for neuronal diseases.