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BACKGROUND: Transplantation of in vitro, cultured, neural stem cells or bone marrow stem cells into the cochlear wall or oval window has been used to observe survival, proliferation, and differentiation of cochlear stem cells, as well as migration of differentiated hair cells in scala tympani over a short period of time.OBJECTIVE: To investigate the relationship between survival, proliferation, differentiation, and migration of transplanted cochlear stem cells and hearing recovery from sensorineural hearing loss. DESIGN, TIME AND SETTING: A randomized, controlled, animal experiment was performed at the Laboratory of Neurobiology, Southeast University in 2009.MATERIALS: Stem cells were isolated from neonatal rats, followed by primary and passaged cultures.METHODS: A total of 30 adult, male rats with normal hearing were treated with gentamicin sulfate to establish models of sensorineural hearing loss. The model rats were randomly assigned to cochlear stem cell transplantation and control groups, which were respectively injected with a 10-μL cochlear stem cell suspension (1 × 105/μL) and phosphate-buffered saline into the scala tympani.MAIN OUTCOME MEASURES: Rat hearing recovery was detected by brainstem auditory-evoked potential at 1, 9, and 15 months following transplantation. The location of stem cells was detected using nestin immunofluorescence, proliferative capacity was detected using bromodeoxyuridine immunofluorescence, and hair cell differentiation was detected using Myosin VIIA immunofluorescence. RESULTS: Cochlear stem cells migrated from the needle track to the spiral organ along the scala tympani following transplantation, and the hair cell-like cells migrated to the basal membrane and organ of Corti. The threshold of brainstem auditory-evoked potential increased with increasing time (P < 0.05). CONCLUSION: Transplanted cochlear stem cells from the intal ear migrated to the basal membrane and reached the injury site. The cells differentiated into cells with intal ear functions to improve hearing in rat models of sensorineural hearing loss.