Distribution and Afferent Effects of Transplanted mESCs on Cochlea in Acute and Chronic Neural Hearing Loss Models

Hearing loss is a sensory deprivation that can affect the quality of life. Currently, only rehabilitation devices such as hearing aids and cochlear implants are used, without a definitive cure. However, in chronic hearing-deprived patients, in whom secondary auditory neural degeneration is expected, a relatively poor rehabilitation prognosis is projected. Stem cell therapy for cochlear neural structures would be an easier and feasible strategy compared with cochlear sensory cells. Considering the highly developed cochlear implantation technology, improving cochlear neural health has significant medical and social effects. Stem cell delivery to Rosenthal's canal in an acutely damaged mouse model has been performed and showed cell survival and the possibility of differentiation. The results of stem cell transplantation in chronic auditory neural hearing loss should be evaluated because neural stem cell replacement therapy for chronic (long-term) sensorineural hearing loss is a major target in clinics. In the present study, we established a mouse model that mimicked chronic auditory neural hearing loss (secondary degeneration of auditory neurons after loss of sensory input). Then, mouse embryonic stem cells (mESCs) were transplanted into the scala tympani and survival and distribution of transplanted cells were compared between the acute and chronic auditory neural hearing loss models induced by ouabain or kanamycin (KM), respectively. The mESC survival was similar to the acute model, and perilymphatic distribution of cell aggregates was more predominant in the chronic model. Lastly, the effects of mESC transplantation on neural signal transduction observed in the cochlear nucleus (CN) were compared and a statistical increase was observed in the chronic model compared with other models. These results indicated that after transplantation, mESCs survived in the cochlea and increased the neural signaling toward the central auditory pathway, even in the chronic (secondary) hearing loss mouse model.