Kölliker’s organ-supporting cells and cochlear auditory development

Abstract

The Kölliker’s organ is a transient cellular cluster structure in the development of the mammalian cochlea. It gradually degenerates from embryonic columnar cells to cuboidal cells in the internal sulcus at postnatal day 12 (P12)–P14, with the cochlea maturing when the degeneration of supporting cells in the Kölliker’s organ is complete, which is distinct from humans because it disappears at birth already. The supporting cells in the Kölliker’s organ play a key role during this critical period of auditory development. Spontaneous release of ATP induces an increase in intracellular Ca2+ levels in inner hair cells in a paracrine form via intercellular gap junction protein hemichannels. The Ca2+ further induces the release of the neurotransmitter glutamate from the synaptic vesicles of the inner hair cells, which subsequently excite afferent nerve fibers. In this way, the supporting cells in the Kölliker’s organ transmit temporal and spatial information relevant to cochlear development to the hair cells, promoting fine-tuned connections at the synapses in the auditory pathway, thus facilitating cochlear maturation and auditory acquisition. The Kölliker’s organ plays a crucial role in such a scenario. In this article, we review the morphological changes, biological functions, degeneration, possible trans-differentiation of cochlear hair cells, and potential molecular mechanisms of supporting cells in the Kölliker’s organ during the auditory development in mammals, as well as future research perspectives.

Store-Operated Ca2+ Channels Contribute to the Generation of Ca2+ Waves in Interdental Cells in the Cochleae

“…In the auditory system of altricial mammals, intrinsically spontaneous calcium (Ca 2+ ) waves in the cochleae are prominently present before the ear canal opening at approximately postnatal day 12 (P12) ,, but diminish immediately after the onset of external sound-driven activity. ,, Two candidate mechanisms have been proposed to account for the spontaneous Ca 2+ waves in the developing cochlea. One theory is that the IHCs fire spontaneous Ca 2+ spikes. − The efferent neurotransmitter acetylcholine fine-tunes the IHC’s resting membrane potential by activating the acetylcholine receptors of IHCs.…”

“…22,23 In immature sensory systems before experience, such as visual and auditory stimuli, these activities are considered indispensable for instructing the early development of sense and sensibility within a critical period. 24−26 In the auditory system of altricial mammals, intrinsically spontaneous calcium (Ca 2+ ) waves in the cochleae are prominently present before the ear canal opening at approximately postnatal day 12 (P12) 21,27,28 but diminish immediately after the onset of external sound-driven activity. 4,12,25 Two candidate mechanisms have been proposed to account for the spontaneous Ca 2+ waves in the developing cochlea.…”

Ca2+ Dynamics of Gap Junction Coupled and Uncoupled Deiters’ Cells in the Organ of Corti in Hearing BALB/c Mice

“…In the middle region, P14-17 mice were sacrificed for the CBX experiments and P15-19 for the octanol experiments. The experiment protocol was based on previous studies [1,6,8].…”

“…In the organ of Corti, hair cells are the primary auditory receptor cells [ 5 ]. They are surrounded by supporting cells, including DCs [ 6 , 7 , 8 ] which provide physical and metabolic support to the outer hair cells (OHCs) [ 6 , 9 ]. In addition, they help maintain ion homeostasis in the endolymph via active K + uptake [ 6 , 10 ], and studies have demonstrated that they exhibit functions like glial cells [ 6 , 8 ].…”

“…They are surrounded by supporting cells, including DCs [ 6 , 7 , 8 ] which provide physical and metabolic support to the outer hair cells (OHCs) [ 6 , 9 ]. In addition, they help maintain ion homeostasis in the endolymph via active K + uptake [ 6 , 10 ], and studies have demonstrated that they exhibit functions like glial cells [ 6 , 8 ]. The function and properties of the mechanosensory hair cells are widely investigated with the aim of studying their connection to impaired hearing function and potentially developing therapeutic treatment [ 11 ].…”