Transplantation of bone marrow-derived neurospheres into guinea pig cochlea

Objectives/Hypothesis. To investigate the potential of neurally induced bone marrow stromal cells (BMSCs) as transplants for replacement of spiral ganglion neurons. Methods. BMSCs were harvested from the femurs and tibias of adult guinea pigs. BMSCs were cultured with neural induction media and formed spheres. The capacity of BMSC-derived spheres for neural differentiation was examined by immunocytochemistry in vitro. BMSC-derived spheres were injected into the modiolus of the intact cochleae or those locally damaged by ouabain, followed by histological and functional analyses. Results. In vitro analysis revealed a high capacity of BMSC-derived spheres for neural differentiation. After transplantation into the cochlear modiolus, the survival and neural differentiation of BMSC-derived spheres was observed in both the intact and damaged cochleae. In intact cochleae, transplants settled in various portions of the cochlea, including the cochlear modiolus, whereas in damaged cochleae, transplants were predominantly observed in the internal auditory meatus. Transplantation of BMSC-derived spheres resulted in no functional recovery of the cochlea or protection of host spiral ganglion neurons. Conclusions. The present findings indicate that BMSC-derived spheres can be a source for replacement of spiral ganglion neurons, although further manipulations are required for functional recovery.