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Sensory Cell Regeneration and Stem Cells: What We Have Already Achieved in the Management of Deafness

Vlastarakos, Petros V.*; Nikolopoulos, Thomas P.; Tavoulari, Evangelia*; Papacharalambous, George*; Tzagaroulakis, Antonios; Dazert, Stefan

doi: 10.1097/MAO.0b013e31817fdfad
Review Articles

Background/Objective: Genetic manipulation of the cell-cycle exit, induction of new hair cells (HCs) through gene modification therapy, and introduction of stem cells (SCs) into damaged cochleas potentially offer exciting new strategies in treating sensorineural hearing loss.

Materials and Methods: Literature review from Medline and database sources.

Study Selection: Ex vivo models, animal studies, in vitro studies, and review articles.

Data Synthesis: Embryonic SCs, neural SCs, or bone marrow SCs survive in the mammalian inner ear after transplantation. The scala media and the modiolus seem more functionally appropriate injection sites. The clear evidence that transplanted neural SCs can adopt the morphologic phenotypes of HCs was the most significant milestone achieved in the related research. The normal cytoarchitecture in the organ of Corti may also be restored through mouse atonal homologue 1 transgene expression and transduction of the nonsensory cells, producing clinically measured improvement in hearing thresholds. Embryonic SC-derived neurons have the potential for synapse formation with auditory HCs and reinnervation of the auditory epithelia. However, fluctuations in survival rates, functional recovery of the spiral-ganglion neurons, integration to the host tissue, and potential immune barriers are also areas of utmost importance.

Conclusion: There is an already exciting progress in the fields of sensory cell regeneration and SC research in an attempt to restore hearing or prevent deafness. However, further understanding of the underlying mechanisms of auditory genetics, continuing investigation of the human genome, refinement of the delivering techniques, and specification of the therapeutic strategies have to be developed before functional regeneration of the cochlea can be achieved in clinical practice.

*ENT Department, Hippokrateion General Hospital of Athens; †ENT Department, Atticon University Hospital, Athens, Greece; and ‡ENT Department, Ruhr University of Bochum, Bochum, Germany

Address correspondence and reprint requests to Petros V. Vlastarakos, M.D., M.Sc., ENT Department, Hippokrateion General Hospital of Athens, 114 Vas. Sofias Ave, Athens 11527, Greece; E-mail:;

© 2008 Otology & Neurotology, Inc.