Early identification of inner pillar cells during rat cochlear development

Abstract

Although the structure of the auditory organ in mature mammals, the organ of Corti, is clearly established, its development is far from being elucidated. Here, we examine its spatio-temporal development in rats from embryonic day 16 (E16) to E19 by using cytochemical and immunocytochemical methods at the light- and electron-microscope levels. We demonstrate that the organ of Corti develops from a non-proliferating cell zone that is located in the junctional region between two edges of the dorsal epithelium of the cochlear duct. We also reveal that the first cells to develop in this zone are the inner pillar cells, a particular type of non-sensory supporting cell, which arise in the base of the cochlear duct at the boundary between the two ridges at E16. Cell differentiation in this prosensory region continues according to a base-to-apex gradient; the inner hair cells appear in the greater epithelial ridge at E17 and the outer hair cells in the lesser epithelial ridge at E18. At E19, the various cell types of the organ of Corti are in place. Finally, we show that unlike the development of all the supporting cell types of the organ of Corti, the development of inner pillar cells within the prosensory domain seems not to involve Notch1 activation. These results highlight the central role that the inner pillar cells probably play in the development of the organ of Corti.

Genetic rescue of Muenke syndrome model hearing loss reveals prolonged FGF-dependent plasticity in cochlear supporting cell fates

“…The present study examined the development and molecular identity of support cells in the Muenke syndrome model. Inner pillar cells are the first support cells to differentiate (Thelen et al 2009), and this occurs at E16 in rats (approximately E14.5 in mice). By E17 (approximately E15.5 in mice), these cells express p75 NTR (von Bartheld et al 1991), although the timing of specificity for inner pillar cells in mice may be somewhat later (Mueller et al 2002;Woods et al 2004).…”

Cochlear Development; New Tools and Approaches

“…While IHCs are thought to be the first cells to differentiate, it is important to consider that inner pillar cells may actually be specified, at some level, prior to the onset of IHC development ( Thelen et al, 2009 ). Early histological studies of cross-sections through the embryonic cochlear duct often noted a physical notch located in the general region of the future OC which creates two clusters of epithelial cells referred to as the greater (medial) and lesser (lateral) epithelial ridges ( Figure 2B ).…”

Spatio-temporal dynamics of β-tubulin isotypes during the development of the sensory auditory organ in rat

“…The cochleae were prepared as previously described (Thelen et al 2009). They were fixed for 2 h at room temperature in 2.5 % glutaraldehyde in 0.1 M Sörensen's buffer pH 7.4.…”