Stepwise Induction of Inner Ear Hair Cells From Mouse Embryonic Fibroblasts via Mesenchymal- to-Epithelial Transition and Formation of Otic Epithelial Cells.

Qiong Yang,Wei-Qiang Gao,Qianqian Chen,Hai-Bo Shi,Yonghui Wang,Zhongzhong Ji,Haosong Shi,Wang Li,Li Wang,Shan-Kai Yin,Yizhou Quan,Huiming Xu

doi:10.3389/fcell.2021.672406

Abstract

Although embryonic stem cells or induced pluripotent stem cells are able to differentiate into inner ear hair cells (HCs), they have drawbacks limiting their clinical application, including a potential risk of tumourigenicity. Direct reprogramming of fibroblasts to inner ear HCs could offer an alternative solution to this problem. Here, we present a stepwise guidance protocol to induce mouse embryonic fibroblasts to differentiate into inner ear HC-like cells (HCLs) via mesenchymal-to-epithelial transition and then acquisition of otic sensory epithelial cell traits by overexpression of three key transcription factors. These induced HCLs express multiple HC-specific proteins, display protrusions reminiscent of ciliary bundle structures, respond to voltage stimulation, form functional mechanotransduction channels, and exhibit a transcriptional profile of HC signature. Together, our work provides a new method to produce functional HCLs in vitro, which may have important implications for studies of HC development, drug discovery, and cell replacement therapy for hearing loss.

Highlights

Inner ear hair cells (HCs), the mechanoreceptors for perception of sound and balance, can convert the sound or motion into electrochemical signals (Carey and Amin, 2006; Costa et al, 2015)
To investigate whether mouse embryonic fibroblasts (MEFs) can be used to convert into inner ear HCs, first, we prepared the primary MEFs from embryonic day 13.5 (E13.5) C57BL/6J mice (Vierbuchen et al, 2010)
To study if the MEFs that we isolated were pure fibroblasts without contamination of any HCs, supporting cells (SCs), or otic epithelial cells (OECs), we characterized them in the cultures by immunofluorescence staining with Vimentin, E-cadherin, Myo7a, P27kip, Pax2, Pax8, Sox2, Jag1, and Sox10 antibodies

Summary

Introduction

Inner ear hair cells (HCs), the mechanoreceptors for perception of sound and balance, can convert the sound or motion into electrochemical signals (Carey and Amin, 2006; Costa et al, 2015). They are terminally differentiated cells and are positioned in the sensory epithelium of the inner ear. The latter grows from the otic placode during embryogenesis (Zhai et al, 2005; Kelley, 2006). Development of a novel method of producing new HCs in vitro may provide a cell replacement therapy method and serve as a helpful system for our studies of HC biology, disease, and regeneration

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Conclusion