title: Reinnervation of hair cells by neural stem cell-derived neurons.
abstract: BACKGROUND
  Replacement of spiral ganglion neurons would be one prioritized step in an attempt to restore sensory neuronal hearing loss. However, the possibility that transplanted neurons could regenerate new synaptic connections to hair cells has not been explored. The objective of this study was to test whether neural stem cell (NSC)-derived neurons can form synaptic connections with hair cells in vitro.
  
  
  METHODS
  NSCs were mechanically separated from the hippocampus in SD rat embryos (E12-E14) and cultured in a serum-free medium containing basic fibroblast growth factor and epidermal growth factor. Rat NSCs were co-cultured with explants of cochlea sensory epithelia obtained from postnatal Day 3 rats under transway filter membrane.
  
  
  RESULTS
  At Day 3, the NSCs began to show chemotactic differentiation and grew toward cochlea sensory epithelia. After 9-day co-culture, neurites of NSC-derived neurons predominantly elongated toward hair cells. Immunohistochemical analyses revealed the fibers overlapped with synapsin and hair cells, indicating the formation of new synaptic connections. After 14-day culture, triple staining revealed the fibers overlapped with PSD95 (postsynaptic density) which is juxtaposed with CtBP2 (presynaptic vesicle), indicating the formation of new ribbon synapse.
  
  
  CONCLUSIONS
  NSC-derived neurons can make synaptic connections with hair cells and provide a model for studying synaptic plasticity and regeneration. Whether the newly forming synapse is functional merits further electrophysiological study.
authors.affiliation: Department of ENT-Head & Neck Surgery, Eye, Ear, Nose and Throat Hospital, Shanghai 200031, China; Shanghai Medical School, FuDan University, Shanghai 210029, China.
authors.forename: Yasheng
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: Department of Anatomy, Shanghai Medical School, FuDan University, Shanghai 210029, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of ENT-Head & Neck Surgery, Eye, Ear, Nose and Throat Hospital, Shanghai 200031, China; Shanghai Medical School, FuDan University, Shanghai 210029, China.
authors.forename: Fanglu
authors.initials: F
authors.lastname: Chi
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D004815:Epidermal Growth Factor / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006198:Hair Cells, Auditory / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D058953:Neural Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000187:drug effects / Q000378:metabolism
chemical_list: D016222:Fibroblast Growth Factor 2; D004815:Epidermal Growth Factor