In vivo and in vitro characterization of bone marrow-derived stem cells in the cochlea

OBJECTIVES/HYPOTHESIS: Stem cell replacement therapy has the potential to treat or cure an array of degenerative neurologic disorders, including sensorineural deafness. However, little is known about the potential for marrow-derived stem cells (MSCs) to take on properties of spiral ganglion neurons. The main purpose of this prospective animal study was to evaluate the survival of MSCs transplanted into the gerbil cochlea. METHODS: Eight 3- to 4-month-old Mongolian gerbils were used as recipients. The animals received an intraperilymphatic transplantation of 100,000 green fluorescent protein (GFP)-positive MSCs with scala tympani injection and modiolar injection. Seven days after transplantation, MSC survival was evaluated by microscopic examination of frozen sections cut through the cochleae of the recipient animals. RESULTS: MSCs isolated from the TgN (ACTbEGFP) mouse line used in this study exhibited bright green florescence after five to seven passages in vitro. Seven days after postoperatively, most transplanted MSCs were found in the scala tympani and scala vestibule and only a small number located in the scala media in animals that received both forms of injection. There were no GFP-positive MSCs in the modiolus in animals with scala tympani injection. In contrast, the mean profile count in animals with modiolar injection was 28, which was the highest in all regions. Although MSCs have the potential to migrate, the anatomic barrier between the perilymphatic space and the modiolus might account for the absence of GFP-positive MSCs in this region. CONCLUSION: These findings may have important clinical implications as a means of delivering MSCs in the cochlea for cell replacement therapy.