Initiation of Supporting Cell Activation for Hair Cell Regeneration in the Avian Auditory Epithelium: An Explant Culture Model

Mami Matsunaga,Koichi Omori,Takayuki Nakagawa,Ryosuke Yamamoto,Norio Yamamoto,Takayuki Okano,Tomoko Kita,Satoko Sakamoto

doi:10.3389/fncel.2020.583994

Mami Matsunaga, Koichi Omori + Show 6 more

Open Access

https://doi.org/10.3389/fncel.2020.583994

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Abstract

Sensorineural hearing loss is a common disability often caused by the loss of sensory hair cells in the cochlea. Hair cell (HCs) regeneration has long been the main target for the development of novel therapeutics for sensorineural hearing loss. In the mammalian cochlea, hair cell regeneration is limited, but the auditory epithelia of non-mammalian organisms retain the capacity for hair cell regeneration. In the avian basilar papilla (BP), supporting cells (SCs), which give rise to regenerated hair cells, are usually quiescent. Hair cell loss induces both direct transdifferentiation and mitotic division of supporting cells. Here, we established an explant culture model for hair cell regeneration in chick basilar papillae and validated it for investigating the initial phase of hair cell regeneration. The histological assessment demonstrated hair cell regeneration via direct transdifferentiation of supporting cells. Labeling with 5-ethynyl-2′-deoxyuridine (EdU) revealed the occurrence of mitotic division in the supporting cells at specific locations in the basilar papillae, while no EdU labeling was observed in newly generated hair cells. RNA sequencing indicated alterations in known signaling pathways associated with hair cell regeneration, consistent with previous findings. Also, unbiased analyses of RNA sequencing data revealed novel genes and signaling pathways that may be related to the induction of supporting cell activation in the chick basilar papillae. These results indicate the advantages of our explant culture model of the chick basilar papillae for exploring the molecular mechanisms of hair cell regeneration.

Highlights

The mammalian cochlea cannot regenerate hair cells (HCs) after birth (Bohne et al, 1976; Hawkins et al, 1976; Oesterle et al, 2008)
These findings demonstrate that HC regeneration occurred in explant cultures of post-hatched 1-day old chick basilar papilla (BP) and that newly generated HCs already appeared 48 h after SM exposure
To explore the molecular events associated with the responses in supporting cell (SC) during initiation of HC regeneration, we focused on Clusters 3 and 7 that included differentially expressed gene (DEG) upregulated from SM24

Summary

Introduction

The mammalian cochlea cannot regenerate hair cells (HCs) after birth (Bohne et al, 1976; Hawkins et al, 1976; Oesterle et al, 2008). There is limited information regarding the molecular pathways and their interactions during HC regeneration in chick BPs compared to that in the zebrafish (Kniss et al, 2016; Denans et al, 2019). A road map of molecular events during the development of mouse cochlear sensory epithelia has been reported using single-cell ribonucleic acid (RNA) sequencing (RNA-seq; Kolla et al, 2020). These findings provide valuable information for the development of novel strategies for the promotion of HC regeneration in adult mammalian cochleae

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