Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Stem Cells. Jun 26, 2020; 12(6): 422-437
Published online Jun 26, 2020. doi: 10.4252/wjsc.v12.i6.422
Stem cell-based approaches: Possible route to hearing restoration?
María Beatriz Durán-Alonso
María Beatriz Durán-Alonso, Institute of Biology and Molecular Genetics, University of Valladolid, Valladolid 47003, Spain
Author contributions: Durán-Alonso MB revised the published data and wrote the paper.
Conflict-of-interest statement: The author declares no conflict of interest for this article.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Corresponding author: María Beatriz Durán-Alonso, PhD, Postdoctoral Fellow, Postdoctoral scientist, Institute of Biology and Molecular Genetics, University of Valladolid, C/ Sanz y Forés 3, Valladolid 47003, Spain.
Received: February 29, 2020
Peer-review started: February 29, 2020
First decision: April 25, 2020
Revised: May 8, 2020
Accepted: May 21, 2020
Article in press: May 21, 2020
Published online: June 26, 2020

Disabling hearing loss is the most common sensorineural disability worldwide. It affects around 466 million people and its incidence is expected to rise to around 900 million people by 2050, according to World Health Organization estimates. Most cases of hearing impairment are due to the degeneration of hair cells (HCs) in the cochlea, mechano-receptors that transduce incoming sound information into electrical signals that are sent to the brain. Damage to these cells is mainly caused by exposure to aminoglycoside antibiotics and to some anti-cancer drugs such as cisplatin, loud sounds, age, infections and genetic mutations. Hearing deficits may also result from damage to the spiral ganglion neurons that innervate cochlear HCs. Differently from what is observed in avian and non-mammalian species, there is no regeneration of missing sensory cell types in the adult mammalian cochlea, what makes hearing loss an irreversible process. This review summarizes the research that has been conducted with the aim of developing cell-based strategies that lead to sensory cell replacement in the adult cochlea and, ultimately, to hearing restoration. Two main lines of research are discussed, one directed toward the transplantation of exogenous replacement cells into the damaged tissue, and another that aims at reactivating the regenerative potential of putative progenitor cells in the adult inner ear. Results from some of the studies that have been conducted are presented and the advantages and drawbacks of the various approaches discussed.

Keywords: Hearing loss, Cochlear hair cells, Spiral ganglion neurons, Cell regeneration, Adult stem cells, Cell transplantation

Core tip: This review summarizes the various approaches that are being explored to establish cell-based therapies that tackle the irreversible loss of sensory cells in the adult cochlea. Advantages and disadvantages of the various approaches are discussed, based on published results, and some considerations are made on future perspectives, taking into account the new developments in the field.