Mechanism and Prevention of Spiral Ganglion Neuron Degeneration in the Cochlea

Li Zhang,Sen Chen,Yu Sun

doi:10.3389/fncel.2021.814891

Abstract

Sensorineural hearing loss (SNHL) is one of the most prevalent sensory deficits in humans, and approximately 360 million people worldwide are affected. The current treatment option for severe to profound hearing loss is cochlear implantation (CI), but its treatment efficacy is related to the survival of spiral ganglion neurons (SGNs). SGNs are the primary sensory neurons, transmitting complex acoustic information from hair cells to second-order sensory neurons in the cochlear nucleus. In mammals, SGNs have very limited regeneration ability, and SGN loss causes irreversible hearing loss. In most cases of SNHL, SGN damage is the dominant pathogenesis, and it could be caused by noise exposure, ototoxic drugs, hereditary defects, presbycusis, etc. Tremendous efforts have been made to identify novel treatments to prevent or reverse the damage to SGNs, including gene therapy and stem cell therapy. This review summarizes the major causes and the corresponding mechanisms of SGN loss and the current protection strategies, especially gene therapy and stem cell therapy, to promote the development of new therapeutic methods.

Highlights

Hearing loss is one of the major health problems worldwide, affecting over 5% of the population of the world or approximately 466 million people1
A unique case showed that the benefit of cochlear implantation (CI) was lost due to the use of cisplatin (Harris et al, 2011). These results indicate that spiral ganglion neurons (SGNs) are the primary injury sites after treatment with platinum-based antineoplastic agents, and they are not limited to hair cell loss
Budenz et al (2015) reported that brain-derived neurotrophic factor (BDNF) was more effective in preventing SGN degeneration after deafness, while NT3 had a greater effect in eliciting the regrowth of radial nerve fibers. These results suggest that combining the overexpression of BDNF and NT3 may have a better effect on SGN protection

Summary

Introduction

Hearing loss is one of the major health problems worldwide, affecting over 5% of the population of the world or approximately 466 million people1. Several studies in deaf animal models, including guinea pigs, mice (Fukui et al, 2012), rats (Wu et al, 2011) and cats, have reported improved SGN survival with virally mediated NT expression compared to controls after acoustic trauma (Table 1).

Results

Conclusion