Transplantation of Stem Cells to Modulate Spiral Ganglion Neuronal Density

Spiral ganglion neurons (SGNs) constitute the principal neural substrate for cochlear implantmediated auditory stimulation, and progressive SGN degeneration may limit the functional benefit of cochlear implantation. Stem-cell transplantation has therefore emerged as a potential strategy to preserve, replace, or increase the neuronal population within the spiral ganglion. Early studies demonstrated the survival and trophic effects of neural stem cells, followed by evidence of migration toward Rosenthal’s canal and modulation of SGN populations. Human mesenchymal stem cells and human embryonic stem-cell-derived otic progenitors subsequently provided the evidence of increased neuronal populations and functional auditory improvement. More recently, it has been shown that human dermal fibroblast-derived induced neural stem cells enhance cochlear neural structures, central auditory connectivity, and electrically evoke auditory responses. Collectively, these studies suggest that stem-cell therapy may improve the neural substrate for cochlear implantation not only through neuronal replacement but also through trophic preservation, targeted migration, and functional neural integration.