Regeneration of Lateral Line and Inner Ear Vestibular Cells

2007 ◽  
pp. 151-170 ◽  
Author(s):  
Jørgen Mørup Jørgensen
Keyword(s):  
Inner Ear ◽  
Lateral Line

scholarly journals Evolution of Endolymph Secretion and Endolymphatic Potential Generation in the Vertebrate Inner Ear

2018 ◽  
Vol 92 (1-2) ◽  
pp. 1-31 ◽  
Author(s):  
Christine Köppl ◽  
Viviane Wilms ◽  
Ian John Russell ◽  
Hans Gerd Nothwang
Keyword(s):  
Inner Ear ◽  
Lateral Line ◽  
Vestibular System ◽  
Molecular Mechanisms ◽  
Receptor Potential ◽  
Cell Types ◽  
Cell Receptor ◽  
Striking Difference ◽  
High K ◽  
Endolymphatic Potential

The ear of extant vertebrates reflects multiple independent evolutionary trajectories. Examples include the middle ear or the unique specializations of the mammalian cochlea. Another striking difference between vertebrate inner ears concerns the differences in the magnitude of the endolymphatic potential. This differs both between the vestibular and auditory part of the inner ear as well as between the auditory periphery in different vertebrates. Here we provide a comparison of the cellular and molecular mechanisms in different endorgans across vertebrates. We begin with the lateral line and vestibular systems, as they likely represent plesiomorphic conditions, then review the situation in different vertebrate auditory endorgans. All three systems harbor hair cells bathed in a high (K+) environment. Superficial lateral line neuromasts are bathed in an electrogenically maintained high (K+) microenvironment provided by the complex gelatinous cupula. This is associated with a positive endocupular potential. Whether this is a special or a universal feature of lateral line and possibly vestibular cupulae remains to be discovered. The vestibular system represents a closed system with an endolymph that is characterized by an enhanced (K+) relative to the perilymph. Yet only in land vertebrates does (K+) exceed (Na+). The endolymphatic potential ranges from +1 to +11 mV, albeit we note intriguing reports of substantially higher potentials of up to +70 mV in the cupula of ampullae of the semicircular canals. Similarly, in the auditory system, a high (K+) is observed. However, in contrast to the vestibular system, the positive endolymphatic potential varies more substantially between vertebrates, ranging from near zero mV to approximately +100 mV. The tissues generating endolymph in the inner ear show considerable differences in cell types and location. So-called dark cells and the possibly homologous ionocytes in fish appear to be the common elements, but there is always at least one additional cell type present. To inspire research in this field, we propose a classification for these cell types and discuss potential evolutionary relationships. Their molecular repertoire is largely unknown and provides further fertile ground for future investigation. Finally, we propose that the ultimate selective pressure for an increased endolymphatic potential, as observed in mammals and to a lesser extent in birds, is specifically to maintain the AC component of the hair-cell receptor potential at high frequencies. In summary, we identify intriguing questions for future directions of research into the molecular and cellular basis of the endolymph in the different compartments of the inner ear. The answers will provide important insights into evolutionary and developmental processes in a sensory organ essential to many species, including humans.

scholarly journals Inner ear and lateral line expression of a zebrafish Nkx5-1 gene and its downregulation in the ears of FGF8 mutant, ace

2000 ◽  
Vol 97 (1-2) ◽  
pp. 161-165 ◽  
Author(s):  
Maja Adamska ◽  
Sophie Léger ◽  
Michael Brand ◽  
Thorsten Hadrys ◽  
Thomas Braun ◽  
...  
Keyword(s):  
Inner Ear ◽  
Lateral Line

Mutations affecting development of the zebrafish inner ear and lateral line

Development ◽  
1996 ◽  
Vol 123 (1) ◽  
pp. 241-254 ◽  
Author(s):  
T.T. Whitfield ◽  
M. Granato ◽  
F.J. van Eeden ◽  
U. Schach ◽  
M. Brand ◽  
...  
Keyword(s):  
Inner Ear ◽  
Lateral Line ◽  
Large Scale ◽  
Sensory System ◽  
Semicircular Canals ◽  
Abnormal Development ◽  
Pigment Cells ◽  
Otic Vesicle ◽  
In The Wild ◽  
Complementation Groups

Mutations giving rise to anatomical defects in the inner ear have been isolated in a large scale screen for mutations causing visible abnormalities in the zebrafish embryo (Haffter, P., Granato, M., Brand, M. et al. (1996) Development 123, 1–36). 58 mutants have been classified as having a primary ear phenotype; these fall into several phenotypic classes, affecting presence or size of the otoliths, size and shape of the otic vesicle and formation of the semicircular canals, and define at least 20 complementation groups. Mutations in seven genes cause loss of one or both otoliths, but do not appear to affect development of other structures within the ear. Mutations in seven genes affect morphology and patterning of the inner ear epithelium, including formation of the semicircular canals and, in some, development of sensory patches (maculae and cristae). Within this class, dog-eared mutants show abnormal development of semicircular canals and lack cristae within the ear, while in van gogh, semicircular canals fail to form altogether, resulting in a tiny otic vesicle containing a single sensory patch. Both these mutants show defects in the expression of homeobox genes within the otic vesicle. In a further class of mutants, ear size is affected while patterning appears to be relatively normal; mutations in three genes cause expansion of the otic vesicle, while in little ears and microtic, the ear is abnormally small, but still contains all five sensory patches, as in the wild type. Many of the ear and otolith mutants show an expected behavioural phenotype: embryos fail to balance correctly, and may swim on their sides, upside down, or in circles. Several mutants with similar balance defects have also been isolated that have no obvious structural ear defect, but that may include mutants with vestibular dysfunction of the inner ear (Granato, M., van Eeden, F. J. M., Schach, U. et al. (1996) Development, 123, 399–413,). Mutations in 19 genes causing primary defects in other structures also show an ear defect. In particular, ear phenotypes are often found in conjunction with defects of neural crest derivatives (pigment cells and/or cartilaginous elements of the jaw). At least one mutant, dog-eared, shows defects in both the ear and another placodally derived sensory system, the lateral line, while hypersensitive mutants have additional trunk lateral line organs.

scholarly journals The overlapping roles of the inner ear and lateral line: the active space of dipole source detection

2000 ◽  
Vol 355 (1401) ◽  
pp. 1115-1119 ◽  
Author(s):  
Christopher B. Braun ◽  
Sheryl Coombs
Keyword(s):  
Inner Ear ◽  
Lateral Line ◽  
Near Field ◽  
Dipole Source ◽  
Source Detection ◽  
Sound Sources ◽  
Distance Range ◽  
Spatial Gradients ◽  
Theoretical Predictions ◽  
Benthic Fishes

The problems associated with the detection of sounds and other mechanical disturbances in the aquatic environment differ greatly from those associated with airborne sounds. The differences are primarily due to the incompressibility of water and the corresponding increase in importance of the acoustic near field. The near field, or hydrodynamic field, is characterized by steep spatial gradients in pressure, and detection of the accelerations associated with these gradients is performed by both the inner ear and the lateral line systems of fishes. Acceleration–sensitive otolithic organs are present in all fishes and provide these animals with a form of inertial audition. The detection of pressure gradients, by both the lateral line and inner ear, is the taxonomically most widespread mechanism of sound–source detection amongst vertebrates, and is thus the most likely primitive mode of detecting sound sources. Surprisingly, little is known about the capabilities of either the lateral line or the otolithic endorgan in the detection of vibratory dipole sources. Theoretical considerations for the overlapping roles of the inner ear and lateral line systems in midwater predict that the lateral line will operate over a shorter distance range than the inner ear, although with a much greater spatial resolution. Our empirical results of dipole detection by mottled sculpin, a benthic fish, do not agree with theoretical predictions based on midwater fishes, in that the distance ranges of the two systems appear to be approximately equal. This is almost certainly as a result of physical coupling between the fishes and the substrate. Thus, rather than having a greater active range, the inner ear appears to have a reduced distance range in benthic fishes, and the lateral line distance range may be concomitantly extended.

scholarly journals Selective and Reversible Blocking of the Lateral Line in Freshwater Fish

1987 ◽  
Vol 133 (1) ◽  
pp. 249-262 ◽  
Author(s):  
HANS ERIK KARLSEN ◽  
OLAV SAND
Keyword(s):  
Inner Ear ◽  
Lateral Line ◽  
Near Field ◽  
Low Frequency ◽  
Rutilus Rutilus ◽  
Directional Hearing ◽  
Roach Rutilus Rutilus ◽  
Cobalt Ions ◽  
Lateral Line Nerve ◽  
Pharmacological Method

Fish possess two separate systems for detection of low-level sound and water motions in the low-frequency range: the inner ear and the lateral line. The relative roles of these systems in normal fish behaviour is still not clear. There is, for instance, a lack of experimental evidence showing the involvement of the lateral line and the inner ear in detection of infrasound, in directional hearing in the near field, and in detection and attack of swimming prey below the surface. To provide a useful tool for such studies, we have developed a pharmacological method for selective and reversible blocking of the lateral line in the roach (Rutilus rutilus). By recording multi-unit activity from the lateral line nerve and microphonic potentials from the inner ear, we have shown that cobalt ions in the external water may completely block the mechanosensitivity of the lateral line without affecting the utricular microphonic activity. This inhibiting effect of Co2+ is antagonized by Ca2+, making the ratio between these ions the important blocking factor. For practical work, we recommend 12–24h exposure to 0.1 mmol 1−1 Co2+ at a Ca2+ concentration of less than 0.1 mmol 1−1. The fish showed no sign of general behavioural disorders even after 1 week in this solution, and the microphonic sensitivity of the inner ear was not reduced. The blocking effect of Co2+ was clearly reversible, and the recovery was dependent upon both the duration of the Co2+ exposure and the Ca2+ concentration of the recovery solution.

scholarly journals Macrophages Respond Rapidly to Ototoxic Injury of Lateral Line Hair Cells but Are Not Required for Hair Cell Regeneration

2021 ◽  
Vol 14 ◽  
Author(s):  
Mark E. Warchol ◽  
Angela Schrader ◽  
Lavinia Sheets
Keyword(s):  
Hair Cell ◽  
Inner Ear ◽  
Lateral Line ◽  
Hair Cells ◽  
Control Fish ◽  
Cell Regeneration ◽  
Cellular Interactions ◽  
Hair Cell Regeneration ◽  
Genetic Ablation ◽  
Larval Zebrafish

The sensory organs of the inner ear contain resident populations of macrophages, which are recruited to sites of cellular injury. Such macrophages are known to phagocytose the debris of dying cells but the full role of macrophages in otic pathology is not understood. Lateral line neuromasts of zebrafish contain hair cells that are nearly identical to those in the inner ear, and the optical clarity of larval zebrafish permits direct imaging of cellular interactions. In this study, we used larval zebrafish to characterize the response of macrophages to ototoxic injury of lateral line hair cells. Macrophages migrated into neuromasts within 20 min of exposure to the ototoxic antibiotic neomycin. The number of macrophages in the near vicinity of injured neuromasts was similar to that observed near uninjured neuromasts, suggesting that this early inflammatory response was mediated by “local” macrophages. Upon entering injured neuromasts, macrophages actively phagocytosed hair cell debris. The injury-evoked migration of macrophages was significantly reduced by inhibition of Src-family kinases. Using chemical-genetic ablation of macrophages before the ototoxic injury, we also examined whether macrophages were essential for the initiation of hair cell regeneration. Results revealed only minor differences in hair cell recovery in macrophage-depleted vs. control fish, suggesting that macrophages are not essential for the regeneration of lateral line hair cells.

scholarly journals Vestibular and Auditory Hair Cell Regeneration Following Targeted Ablation of Hair Cells With Diphtheria Toxin in Zebrafish

2021 ◽  
Vol 15 ◽  
Author(s):  
Erin Jimenez ◽  
Claire C. Slevin ◽  
Luis Colón-Cruz ◽  
Shawn M. Burgess
Keyword(s):  
Hair Cell ◽  
Inner Ear ◽  
Lateral Line ◽  
Hair Cells ◽  
Diphtheria Toxin ◽  
Adult Zebrafish ◽  
Hair Cell Regeneration ◽  
Cell Ablation ◽  
Aquatic Vertebrates

Millions of Americans experience hearing or balance disorders due to loss of hair cells in the inner ear. The hair cells are mechanosensory receptors used in the auditory and vestibular organs of all vertebrates as well as the lateral line systems of aquatic vertebrates. In zebrafish and other non-mammalian vertebrates, hair cells turnover during homeostasis and regenerate completely after being destroyed or damaged by acoustic or chemical exposure. However, in mammals, destroying or damaging hair cells results in permanent impairments to hearing or balance. We sought an improved method for studying hair cell damage and regeneration in adult aquatic vertebrates by generating a transgenic zebrafish with the capacity for targeted and inducible hair cell ablation in vivo. This model expresses the human diphtheria toxin receptor (hDTR) gene under the control of the myo6b promoter, resulting in hDTR expressed only in hair cells. Cell ablation is achieved by an intraperitoneal injection of diphtheria toxin (DT) in adult zebrafish or DT dissolved in the water for larvae. In the lateral line of 5 days post fertilization (dpf) zebrafish, ablation of hair cells by DT treatment occurred within 2 days in a dose-dependent manner. Similarly, in adult utricles and saccules, a single intraperitoneal injection of 0.05 ng DT caused complete loss of hair cells in the utricle and saccule by 5 days post-injection. Full hair cell regeneration was observed for the lateral line and the inner ear tissues. This study introduces a new method for efficient conditional hair cell ablation in adult zebrafish inner ear sensory epithelia (utricles and saccules) and demonstrates that zebrafish hair cells will regenerate in vivo after this treatment.

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