Evolutionary and Developmental Biology Provide Insights Into the Regeneration of Organ of Corti Hair Cells.

Karen L Elliott,Bernd Fritzsch,Jeremy S Duncan

doi:10.3389/fncel.2018.00252

Karen L Elliott, Bernd Fritzsch + Show 1 more

Open Access

https://doi.org/10.3389/fncel.2018.00252

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Abstract

We review the evolution and development of organ of Corti hair cells with a focus on their molecular differences from vestibular hair cells. Such information is needed to therapeutically guide organ of Corti hair cell development in flat epithelia and generate the correct arrangement of different hair cell types, orientation of stereocilia, and the delayed loss of the kinocilium that are all essential for hearing, while avoiding driving hair cells toward a vestibular fate. Highlighting the differences from vestibular organs and defining what is known about the regulation of these differences will help focus future research directions toward successful restoration of an organ of Corti following long-term hair cell loss.

Highlights

All vertebrate hair cells (HCs) have stereocilia organized in a staircase pattern, displaying distinct apical polarities for stimuli to open mechanoelectrical transduction channels (METs) permitting endolymphatic potassium to enter the HCs and change their resting potential (Hudspeth, 2005; Reichenbach and Hudspeth, 2014)
In addition to HC morphology and distribution differences, there is a unique innervation by afferent (Rubel and Fritzsch, 2002; Dabdoub et al, 2016) and efferent neurons (Simmons et al, 2011; Sienknecht et al, 2014; Maison et al, 2016) and unique outer hair cells (OHC) contractility (Okoruwa et al, 2008; He et al, 2014)
This review provides an overview of our current understanding of specific aspects of OC-HC versus vestibular-like HCs (vHCs) morphological and molecular development

Summary

INTRODUCTION

All vertebrate hair cells (HCs) have stereocilia organized in a staircase pattern, displaying distinct apical polarities for stimuli to open mechanoelectrical transduction channels (METs) permitting endolymphatic potassium to enter the HCs and change their resting potential (Hudspeth, 2005; Reichenbach and Hudspeth, 2014). Only mammals possess specialized HCs within mammalian-specific organ of Corti (OC) that differ from vHCs (Fritzsch et al, 2013; Manley, 2017). In addition to HC morphology and distribution differences, there is a unique innervation by afferent (Rubel and Fritzsch, 2002; Dabdoub et al, 2016) and efferent neurons (Simmons et al, 2011; Sienknecht et al, 2014; Maison et al, 2016) and unique OHC contractility (Okoruwa et al, 2008; He et al, 2014) Both vHCs and OC-HCs die over time, leading to late onset vestibular and hearing dysfunction (Rauch et al, 2001; Fattal et al, 2018). We evaluate available developmental and evolutionary data to better molecularly understand the necessary steps that can transform vHCs into those of the OC (Figure 1) and transform a vestibular organ with unsymmetrically distributed HC types into a precisely organized OC with two distinctly distributed types of structurally and functional unique OC-HCs (Jahan et al, 2015a)

MOLECULAR DEVELOPMENTAL EVOLUTIONARY CONSIDERATIONS

PLANAR CELL POLARITY IN INNER EAR NEUROSENSORY DEVELOPMENT

AUTHOR CONTRIBUTIONS