Open-Chamber Co-Culture Microdevices for Single-Cell Analysis of Skeletal Muscle Myotubes and Motor Neurons with Neuromuscular Junctions

Degeneration of motor neurons and skeletal muscles or the collapse of neuromuscular junctions (NMJs) causes progressive motility disturbances in many neuromuscular diseases. Although various microdevices for the co-culture of skeletal muscle myotubes and motor neurons have been developed to investigate neuromuscular diseases in vitro, it remains difficult to isolate single myotubes and motor neurons from the device for single-cell analyses, such as gene expression analysis. Here, we developed open chamber-coculture microdevices that contain cell culture chambers with narrow widths. Given the small chamber width (0.2 mm), the device significantly prevented the overlap among myotubes within the chamber. The percentage of non-overlapping was 95.6 +/- 7.7% for the 0.2-mmwidth chamber and 11.8 +/- 6.4% for the 7-mm-width chamber as a control. In addition, the device with the 0.2-mm chamber promoted myotube maturation, as indicated by the longer widths and lengths of the myotubes relative to those in the control chamber. Single C2C12 myotubes and human induced pluripotent stem cell (hiPSC)-derived motor neurons were successfully collected from the device with the 0.2-mm chamber using a micromanipulator equipped with a glass capillary. Furthermore, myotubes and hiPSC-derived motor neurons were co-cultured in the device with the 0.2- mm chamber, and the formation of NMJs were observed. Thus, the developed device is a useful tool for performing single-cell analysis for studying neuromuscular diseases in vitro.