Generation of Cochlear Hair Cells from Sox2 Positive Supporting Cells via DNA Demethylation

Xin Deng,Zhengqing Hu

doi:10.3390/ijms21228649

Abstract

Regeneration of auditory hair cells in adult mammals is challenging. It is also difficult to track the sources of regenerated hair cells, especially in vivo. Previous paper found newly generated hair cells in deafened mouse by injecting a DNA methyltransferase inhibitor 5-azacytidine into the inner ear. This paper aims to investigate the cell sources of new hair cells. Transgenic mice with enhanced green fluorescent protein (EGFP) expression controlled by the Sox2 gene were used in the study. A combination of kanamycin and furosemide was applied to deafen adult mice, which received 4 mM 5-azacytidine injection into the inner ear three days later. Mice were followed for 3, 5, 7 and 14 days after surgery to track hair cell regeneration. Immunostaining of Myosin VIIa and EGFP signals were used to track the fate of Sox2-expressing supporting cells. The results show that (i) expression of EGFP in the transgenic mice colocalized the supporting cells in the organ of Corti, and (ii) the cell source of regenerated hair cells following 5-azacytidine treatment may be supporting cells during 5–7 days post 5-azacytidine injection. In conclusion, 5-azacytidine may promote the conversion of supporting cells to hair cells in chemically deafened adult mice.

Highlights

In the mammalian organ of Corti, inner hair cells are arranged in a single row and form synapses with afferent nerve terminals of spiral ganglion neurons [1]
Low magnification figures showed that Sox2, Myosin VIIa and enhanced green fluorescent protein (EGFP) mainly presented at the organ of Corti region (Figure 1)
The data of this study indicate that regeneration of hair cells by 5-aza may arise from Sox2 positive supporting cells during 5–7 days after 5-aza treatment

Summary

Introduction

In the mammalian organ of Corti, inner hair cells are arranged in a single row and form synapses with afferent nerve terminals of spiral ganglion neurons [1]. Supporting cells separate hair cells and provide support for the deflection of hair cells [2]. Hair cells and supporting cells are arranged in a mosaic pattern, in which each hair cell is separated from the by an interceding supporting cell [3]. The hair cells and supporting cells originate from common progenitors [4,5]. Development of hair cells is accompanied by downregulation of Sox2 [8]. Sox expression is restricted to supporting cells, while hair cells no longer express Sox2 [8]

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