Cochlea of the human fetus: A scanning electron microscope study.

Igarashi, Yoshiharu

doi:10.1679/aohc1950.43.195

Cited by 28 publications

(8 citation statements)

References 13 publications

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“…Morphologic data show that the maturation of cochlear structures in human fetuses is a rapid process. By 22 wk of gestation, OHC show both an elongated shape (14) and an adult-like pattern of stereocilia (15,16). In experimental animals, where functional correlations are available, these morphologic criteria just coincide with the onset of OHC electromotility (17,18).…”

Section: Discussionmentioning

confidence: 99%

Early Maturation of Evoked Otoacoustic Emissions and Medial Olivocochlear Reflex in Preterm Neonates

et al. 2006

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The present study was designed to investigate the early maturation of the brainstem regulation of the cochlear function in preterm neonates. Evoked otoacoustic emissions (EOAE) and their regulation via the medial olivocochlear efferent (MOC) reflex were investigated in a large population of preterm neonates and compared with full-term neonates and young babies from birth to 4 y and school-aged children. In 28-wk preterm neonates, EOAE were seen in the mid-frequency range. These responses extended both to the low (down to 1025 Hz) and high (up to 6152 Hz) frequency ranges at 38 wk of gestational age and remained stable up to 4 mo. At this stage, the amplitude of EOAE overlapped adult values. EOAE amplitudes then decreased to reach adult values at 3 y of age. Maturation of MOC efferents innervating the outer hair cells was investigated by studying the suppressive effect of contralateral sound on the EOAE amplitudes (MOC reflex T he cochlea, the auditory organ of the inner ear, contains two types of mechanosensory hair cells, inner hair cells, and OHC. OHC are precisely adapted for mechanoreception, i.e. transduction of cochlear partition vibration into a bioelectrical signal. OHC electromotile properties (1) led to the concept of a "cochlear amplifier" involving active biomechanical feedback from OHC to the basilar membrane. This assumption is further supported by the cochlea's ability to produce acoustic energy, which can be easily detected by a sensitive microphone placed in the ear canal (2). The emitted responses, named evoked otoacoustic emissions (EOAE), are vulnerable to the same forms of interference that reduce or destroy OHC function (3).The CNS controls the motor activity of the OHC via MOC neurons, originating in the medial nuclei of the superior olivary complex. Three populations of neurons projecting from the MOC efferents to each cochlea have been shown: 1) the largest group of efferent units, which are the most responsive to ipsilateral sound stimulation, originates in the contralateral medial olivary complex and constitutes the crossed projection; 2) a group consisting of efferent units, which respond best to a contralateral sound stimulation, originates in the ipsilateral medial olivary complex and constitutes the uncrossed projection; 3) a group of efferent neurons, which respond to both ipsi-and contralateral stimulation (4). Interrupting the MOC efferents at the floor of the fourth, which severed all the efferents crossing the middle line, but spared most of the uncrossed fibers, did not affect the suppression of auditory nerve responses induced by the contralateral sound stimulation (5). However, when cuts damaged both the crossed and uncrossed fibers at the vestibulocochlear anastomosis, the suppressive effect of the contralateral sound stimulation on auditory nerve responses was eliminated. Consequently, the suppressive effect of the contralateral sound stimulation is mediated by the uncrossed part of MOC efferents. Given that similar findings were also observed on distortion prod...

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Section: Discussionmentioning

confidence: 99%

Early Maturation of Evoked Otoacoustic Emissions and Medial Olivocochlear Reflex in Preterm Neonates

et al. 2006

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“…Several studies were performed on mammalian cochlea using SEM, but only a few on the human cochlea (Lim and Lane, 1969; Lim, 1972; Hunter‐Duvar, 1975; Hoshino, 1977; Nomura and Kawabata, 1979; Wright, 1980b, 1981a, b, 1982, 1983; Nadol, 1983; Nadol and Burgess 1994; Bagger‐Sjöbäck and Engström, 1985; Gleeson, 1985; Engström et al, 1987, 1990; Osborne et al, 1989; Comis et al, 1990; Hoshino, 1990; Reiss, 1990; Reiss and Vollrath, 1990; Pujol et al, 1991). Some were assessed in embryos (Tanaka et al, 1979; Igarashi, 1980; Fujimoto et al, 1981; Hoshino and Nakamura, 1985; Lavigne‐Rebillard et al, 1985a, b; Lavigne‐Rebillard and Pujol, 1986, 1987; Hoshino, 1990; Pujol et al, 1991). Here, we present results from ultrastructural analyses of human inner ear specimens obtained at surgery (Fig.…”

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confidence: 99%

Human Cochlea: Anatomical Characteristics and their Relevance for Cochlear Implantation

Rask‐Andersen

Liu

Erixon

et al. 2012

The Anatomical Record

144

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This is a review of the anatomical characteristics of human cochlea and the importance of variations in this anatomy to the process of cochlear implantation (CI). Studies of the human cochlea are essential to better comprehend the physiology and pathology of man's hearing. The human cochlea is difficult to explore due to its vulnerability and bordering capsule. Inner ear tissue undergoes quick autolytic changes making investigations of autopsy material difficult, even though excellent results have been presented over time. Important issues today are novel inner ear therapies including CI and new approaches for inner ear pharmacological treatments. Inner ear surgery is now a reality, and technical advancements in the design of electrode arrays and surgical approaches allow preservation of remaining structure/function in most cases. Surgeons should aim to conserve cochlear structures for future potential stem cell and gene therapies. Renewal interest of round window approaches necessitates further acquaintance of this complex anatomy and its variations. Rough cochleostomy drilling at the intricate ''hook'' region can generate intracochlear bone-dust-inducing fibrosis and new bone formation, which could negatively influence auditory nerve responses at a later time point. Here, we present macro-and microanatomic investigations of the human cochlea viewing the extensive anatomic variations that influence electrode insertion. In addition, electron microscopic (TEM and SEM) and immunohistochemical results, based on specimens removed at surgeries for lifethreatening petroclival meningioma and some well-preserved postmortal tissues, are displayed. These give us new information about structure as well as protein and molecular expression in man. Our aim was not to formulate a complete description of the complex human anatomy but to focus on aspects clinically relevant for electric stimulation, predominantly, the sensory targets, and how surgical atraumaticity best could be reached.

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“…The images clearly showed the presence of kinocilia, a unique feature of vestibular hair cells on the organoid surface that closely resembled the morphology of human fetal vestibular tissue at ~70 days gestation. It should be noted that during development, auditory hair cells also express a long stereocilia, resembling a kinocilium, however these are lost during development beginning at 24 weeks gestation (Igarashi, 1980; Lavigne-Rebillard and Pujol, 1986) and are not found in mature adult human cochlea. The maturation of hair cell-like cells was shown by functional MET channels and voltage-activated currents.…”

Section: Discussionmentioning

confidence: 99%

Generation of Vestibular Tissue-Like Organoids From Human Pluripotent Stem Cells Using the Rotary Cell Culture System

Mattei

Lim

Drury

et al. 2019

Front. Cell Dev. Biol.

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Hair cells are specialized mechanosensitive cells responsible for mediating balance and hearing within the inner ear. In mammals, hair cells are limited in number and do not regenerate. Human pluripotent stem cells (hPSCs) provide a valuable source for deriving human hair cells to study their development and design therapies to treat and/or prevent their degeneration. In this study we used a dynamic 3D Rotary Cell Culture System (RCCS) for deriving inner ear organoids from hPSCs. We show RCCS-derived organoids recapitulate stages of inner ear development and give rise to an enriched population of hair cells displaying vestibular-like morphological and physiological phenotypes, which resemble developing human fetal inner ear hair cells as well as the presence of accessory otoconia-like structures. These results show that hPSC-derived organoids can generate complex inner ear structural features and be a resource to study inner ear development.

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Cochlea of the human fetus: A scanning electron microscope study.

Cited by 28 publications

References 13 publications

Early Maturation of Evoked Otoacoustic Emissions and Medial Olivocochlear Reflex in Preterm Neonates

Early Maturation of Evoked Otoacoustic Emissions and Medial Olivocochlear Reflex in Preterm Neonates

Human Cochlea: Anatomical Characteristics and their Relevance for Cochlear Implantation

Generation of Vestibular Tissue-Like Organoids From Human Pluripotent Stem Cells Using the Rotary Cell Culture System

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