Neural connections between embryonic stem cell-derived neurons and vestibular hair cells in vitro

This study aimed to examine the potential of embryonic stem cell (ESC)-derived neural progenitors for restoration of the neural network in the peripheral vestibular system. Mouse ESC-derived neural progenitors were co-cultured with explants of vestibular sensory epithelia from neonatal mice. Histological analyses demonstrated that ESC-derived neurons substantially elongated their neurites towards vestibular hair cells, and attached to hair cells at the regions corresponding to the location of nerve endings in normal vestibular epithelia. Immunoreactivity for synaptophysin, a marker for synaptic vesicles, was present only in the cytoplasm of hair cells in sensory epithelia cultured alone, while the nerve endings of ESC-derived neurons attached to hair cells exhibited intense immunoreactivity for synaptophysin and some hair cells were moderately reactive in co-cultured specimens. The pattern of synaptophysin expression in co-cultured specimens was very similar to that observed in developing sensory epithelia, in which synaptic connections between hair cells and nerve endings are actively formed. These findings indicate that ESC-derived neurons have the potential to restore neural connections in the peripheral vestibular system.