Microfluidic devices for the generation of centimetre‐long motor nerve organoids derived from iPSCs

Although a microfluidic neuronal culture technique that utilised a microchannel structure to generate a motor nerve organoid consisted of neurospheres and fascicles of motor neuronal axons derived from human induced pluripotent stem cells (iPSCs) was reported recently, the lengths of the axonal fascicles were limited to less than 1 cm, which corresponded to the microchannel length. In this study, the authors fabricated microfluidic devices composed of a polydimethylsiloxane chip with a glass substrate and 20-mm-long and 150-μm-wide microchannels to obtain centimetre-long axonal fascicles. They investigated the effects of microchannel height on fascicle length by using three different microchannel heights (120, 150, and 220 μm), neurospheres containing 80,000 motor neuronal cells derived from a human iPSCs cell line (409B2), and N2B27 medium. Maximum and average fascicle lengths of 2 and 1.25 cm, respectively, were successfully achieved with 150-μm-high microchannels. The fascicles grew in length, with an increase in the number of days spent in the culture (ranging from 0.44 to 0.60 mm per day), growing to over 1 cm around the 23rd day of culture. The difference in fascicle length obtained with 120-μm and 150-μm-high microchannels suggests that height significantly affects the length of the axonal fascicle of the nerve organoid.