Mechanical overstimulation causes acute injury and synapse loss followed by fast recovery in lateral-line neuromasts of larval zebrafish

Excess noise damages sensory hair cells, resulting in loss of synaptic connections with auditory nerves and, in some cases, hair-cell death. The cellular mechanisms underlying mechanically induced hair-cell damage and subsequent repair are not completely understood. Hair cells in neuromasts of larval zebrafish are structurally and functionally comparable to mammalian hair cells but undergo robust regeneration following ototoxic damage. We therefore developed a model for mechanically induced hair-cell damage in this highly tractable system. Free swimming larvae exposed to strong water wave stimulus for 2 hours displayed mechanical injury to neuromasts, including afferent neurite retraction, damaged hair bundles, and reduced mechanotransduction. Synapse loss was observed in apparently intact exposed neuromasts, and this loss was exacerbated by inhibiting glutamate uptake. Mechanical damage also elicited an inflammatory response and macrophage recruitment. Remarkably, neuromast hair-cell morphology and mechanotransduction recovered within hours following exposure, suggesting severely damaged neuromasts undergo repair. Our results indicate functional changes and synapse loss in mechanically damaged lateral-line neuromasts that share key features of damage observed in noise-exposed mammalian ear. Yet, unlike the mammalian ear, mechanical damage to neuromasts is rapidly reversible.

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Mechanical overstimulation causes acute injury followed by fast recovery in lateral-line neuromasts of larval zebrafish

10.1101/2020.07.15.205492 ◽

2020 ◽

Cited By ~ 1

Author(s):

Melanie Holmgren ◽

Michael E. Ravicz ◽

Kenneth E. Hancock ◽

Olga Strelkova ◽

Artur A. Indzhykulian ◽

...

Keyword(s):

Hair Cell ◽

Lateral Line ◽

Hair Cells ◽

Cell Damage ◽

Acute Injury ◽

Water Current ◽

Functional Changes ◽

Larval Zebrafish ◽

Auditory Nerves ◽

Hair Cell Damage

AbstractNoise exposure damages sensory hair cells, resulting in loss of synaptic connections with auditory nerves and hair-cell death. The cellular mechanisms underlying noise-induced hair-cell damage and subsequent repair are not completely understood. Hair cells in neuromasts (NMs) of larval zebrafish are structurally and functionally comparable to mammalian hair cells but undergo robust regeneration following damage. We therefore developed a model for noise-induced hair-cell damage in this highly tractable system. Free swimming larvae exposed to strong water current for 2 hours displayed damage to NMs, including synapse loss, afferent neurite retraction, damaged hair bundles, and reduced mechanotransduction. Overstimulation also elicited an inflammatory response and macrophage recruitment. Remarkably, NM morphology and function appeared to fully recover within 2 days following exposure. Our results reveal morphological and functional changes in mechanically overstimulated lateral-line NMs that are analogous to changes observed in noise-exposed mammalian ear yet are rapidly and completely repaired.

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Distinct progenitor populations mediate regeneration in the zebrafish lateral line

eLife ◽

10.7554/elife.43736 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 6

Author(s):

Eric D Thomas ◽

David W Raible

Keyword(s):

Hair Cell ◽

Lateral Line ◽

Hair Cells ◽

Cell Damage ◽

Cell Populations ◽

Support Cell ◽

Cell Ablation ◽

Hair Cell Damage ◽

Transgenic Lines ◽

Mechanosensory Hair Cells

Mechanosensory hair cells of the zebrafish lateral line regenerate rapidly following damage. These renewed hair cells arise from the proliferation of surrounding support cells, which undergo symmetric division to produce two hair cell daughters. Given the continued regenerative capacity of the lateral line, support cells presumably have the ability to replenish themselves. Utilizing novel transgenic lines, we identified support cell populations with distinct progenitor identities. These populations show differences in their ability to generate new hair cells during homeostasis and regeneration. Targeted ablation of support cells reduced the number of regenerated hair cells. Furthermore, progenitors regenerated after targeted support cell ablation in the absence of hair cell damage. We also determined that distinct support cell populations are independently regulated by Notch signaling. The existence of independent progenitor populations could provide flexibility for the continued generation of new hair cells under a variety of conditions throughout the life of the animal.

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Distinct progenitor populations mediate regeneration in the zebrafish lateral line

10.1101/482737 ◽

2018 ◽

Author(s):

Eric D. Thomas ◽

David W. Raible

Keyword(s):

Hair Cell ◽

Lateral Line ◽

Hair Cells ◽

Cell Damage ◽

Cell Populations ◽

Support Cell ◽

Cell Ablation ◽

Hair Cell Damage ◽

Transgenic Lines ◽

Mechanosensory Hair Cells

ABSTRACTMechanosensory hair cells of the zebrafish lateral line regenerate rapidly following damage. These renewed hair cells arise from the proliferation of surrounding support cells, which undergo symmetric division to produce two hair cell daughters. Given the continued regenerative capacity of the lateral line, support cells presumably have the ability to replenish themselves. Utilizing novel transgenic lines, we identified support cell populations with distinct progenitor identities. These populations show differences in their ability to generate new hair cells during homeostasis and regeneration. Targeted ablation of support cells reduced the number of regenerated hair cells. Furthermore, progenitors regenerated after targeted support cell ablation in the absence of hair cell damage. We also determined that distinct support cell populations are independently regulated by Notch signaling. The existence of independent progenitor populations could provide flexibility for the continued generation of new hair cells under a variety of conditions throughout the life of the animal.

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Ultrastructural Changes in the Cochlea of the Guinea Pig after Fast Neutron Irradiation

Otolaryngology ◽

10.1177/019459989411000412 ◽

1994 ◽

Vol 110 (4) ◽

pp. 419-427 ◽

Cited By ~ 21

Author(s):

Ilsa Schwartz ◽

Chong-Sun Kim ◽

See-Ok Shin

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Hair Cell ◽

Neutron Irradiation ◽

Hair Cells ◽

Cell Damage ◽

Outer Hair Cells ◽

Transmission Electron ◽

Fast Neutron Irradiation ◽

Hair Cell Damage

Guinea pigs were irradiated with fast neutrons. After a single dose of 2, 6, 10, or 15 Gy was applied, scanning and transmission electron microscopy of the temporal bone was performed to assess the effect of fast neutron irradiation on the cochlea. Outer hair cell damage appeared with neutron irradiation of more than 10 Gy, and Inner hair cell damage with neutron Irradiation of more than 15 Gy. Outer hair cells were more severely damaged than Inner hair cells. No statistically significant differences were found in damage of basal, middle, and apical turns. The second and third rows of outer hair cells were more severely damaged than the first row of outer hair cells. The most significant findings in transmission electron microscopy were clumping of chromatin and extension of the heterochromatin in the nuclei of hair cells. The cytoplasmic changes were sequestration of cytoplasm, various changes of mitochondria, formation of vacuoles, and irregularly arranged stereocilia. The morphologic change in stria vascularis was intercellular and perivascular fluid accumulation. It appeared to be a reversible process.

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

Frontiers in Cellular Neuroscience ◽

10.3389/fncel.2020.613246 ◽

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.

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In vivo assessment of the toxicity of electronic cigarettes to zebrafish (Danio rerio) embryos, following gestational exposure, in terms of mortality, developmental toxicity, and hair cell damage: Toxicity of E-cigs to zebrafish embryos

Human & Experimental Toxicology ◽

10.1177/0960327120947785 ◽

2020 ◽

Vol 40 (1) ◽

pp. 148-157

Author(s):

YS Chang ◽

SM Park ◽

YC Rah ◽

EJ Han ◽

SI Koun ◽

...

Keyword(s):

Heart Rate ◽

Hair Cell ◽

Hair Cells ◽

Cell Damage ◽

Developmental Toxicity ◽

Zebrafish Embryos ◽

Dorsal Fin ◽

Gestational Exposure ◽

Hair Cell Damage ◽

High Concentrations

With the ban of conventional cigarettes from public spaces, electronic cigarette (E-cig) liquids have emerged as a nicotine replacement treatment for smoking cessation. However, consumers possess little knowledge of the ingredients and health effects of E-cig liquids following exposure. This study evaluated hair cell damage and developmental toxicities following gestational exposure to E-cig liquids. Zebrafish embryos were exposed to E-cig liquids at different concentrations (0.1%, 0.2%, and 0.4%). Embryonic developmental toxicity and hair cell damage was evaluated at 6 and 7 d, respectively, after fertilization. The average number of hair cells in the anterior lateral line (ALL) and posterior lateral line (PLL) following E-cig exposure was compared to that of the control. Morphological abnormalities and heart rate were evaluated. E-cig liquids significantly damaged the hair cells in the ALL, compared to the control (control; 52.85 ± 5.29 cells, 0.1% E-cig; 49.43 ± 7.70 cells, 0.2% E-cig; 40.68 ± 12.00 cells, 0.4% E-cig; 32.14 ± 20.75%; n = 29–40; p < 0.01). At high concentrations, E-cig liquids significantly damaged the hair cells in the PLL (control; 36.88 ± 5.43 cells, 0.1% E-cig; 33.06 ± 5.21 cells, 0.2% E-cig; 30.95 ± 8.03 cells, 0.4% E-cig; 23.72 ± 15.53%, n = 29–40; p < 0.01). No morphological abnormalities in body shape, somites, notochord, tail, and pectoral fin were observed; however, abnormalities were observed in the dorsal fin and heart rate at high concentrations. Thus, gestational exposure to E-cigs significantly damaged hair cells in a concentration-dependent manner and induced developmental toxicities to the dorsal fin and heart rate at high concentrations.

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Unmyelinated type II afferent neurons report cochlear damage

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1515228112 ◽

2015 ◽

Vol 112 (47) ◽

pp. 14723-14727 ◽

Cited By ~ 54

Author(s):

Chang Liu ◽

Elisabeth Glowatzki ◽

Paul Albert Fuchs

Keyword(s):

Hair Cell ◽

Hair Cells ◽

Outer Hair Cell ◽

Cell Damage ◽

Large Diameter ◽

Outer Hair Cells ◽

Type I ◽

Type Ii ◽

Inner Hair Cell ◽

Hair Cell Damage

In the mammalian cochlea, acoustic information is carried to the brain by the predominant (95%) large-diameter, myelinated type I afferents, each of which is postsynaptic to a single inner hair cell. The remaining thin, unmyelinated type II afferents extend hundreds of microns along the cochlear duct to contact many outer hair cells. Despite this extensive arbor, type II afferents are weakly activated by outer hair cell transmitter release and are insensitive to sound. Intriguingly, type II afferents remain intact in damaged regions of the cochlea. Here, we show that type II afferents are activated when outer hair cells are damaged. This response depends on both ionotropic (P2X) and metabotropic (P2Y) purinergic receptors, binding ATP released from nearby supporting cells in response to hair cell damage. Selective activation of P2Y receptors increased type II afferent excitability by the closure of KCNQ-type potassium channels, a potential mechanism for the painful hypersensitivity (that we term “noxacusis” to distinguish from hyperacusis without pain) that can accompany hearing loss. Exposure to the KCNQ channel activator retigabine suppressed the type II fiber’s response to hair cell damage. Type II afferents may be the cochlea’s nociceptors, prompting avoidance of further damage to the irreparable inner ear.

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Macrophages respond rapidly to ototoxic injury of lateral line hair cells but are not required for hair cell regeneration

10.1101/2020.09.28.314922 ◽

2020 ◽

Cited By ~ 1

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

AbstractThe 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 similar 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 close proximity 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. Such phagocytosis was significantly reduced by inhibiting Src-family kinases. Using chemical-genetic ablation of macrophages prior to ototoxic injury, we also examined whether macrophages were essential for the initiation of hair cell regeneration after neomycin exposure. 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.

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Influence of Mpv17 on Hair-Cell Mitochondrial Homeostasis, Synapse Integrity, and Vulnerability to Damage in the Zebrafish Lateral Line

Frontiers in Cellular Neuroscience ◽

10.3389/fncel.2021.693375 ◽

2021 ◽

Vol 15 ◽

Author(s):

Melanie Holmgren ◽

Lavinia Sheets

Keyword(s):

Hair Cell ◽

Lateral Line ◽

Hair Cells ◽

Noise Exposure ◽

Water Current ◽

Mitochondrial Activity ◽

Mitochondrial Homeostasis ◽

Synapse Loss ◽

Intracellular Ca ◽

Inner Membrane Protein

Noise exposure is particularly stressful to hair-cell mitochondria, which must produce enough energy to meet high metabolic demands as well as regulate local intracellular Ca2+ concentrations. Mitochondrial Inner Membrane Protein 17 (Mpv17) functions as a non-selective cation channel and plays a role in maintaining mitochondrial homeostasis. In zebrafish, hair cells in mpv17a9/a9 mutants displayed elevated levels of reactive oxygen species (ROS), elevated mitochondrial calcium, hyperpolarized transmembrane potential, and greater vulnerability to neomycin, indicating impaired mitochondrial function. Using a strong water current to overstimulate hair cells in the zebrafish lateral line, we observed mpv17a9/a9 mutant hair cells were more vulnerable to morphological disruption than wild type (WT) siblings simultaneously exposed to the same stimulus. To determine the role of mitochondrial homeostasis on hair-cell synapse integrity, we surveyed synapse number in mpv17a9/a9 mutants and WT siblings as well as the sizes of presynaptic dense bodies (ribbons) and postsynaptic densities immediately following stimulus exposure. We observed mechanically injured mpv17a9/a9 neuromasts were not more vulnerable to synapse loss; they lost a similar number of synapses per hair cell relative to WT. Additionally, we quantified the size of hair cell pre- and postsynaptic structures following stimulation and observed significantly enlarged WT postsynaptic densities, yet relatively little change in the size of mpv17a9/a9 postsynaptic densities following stimulation. These results suggest chronically impaired hair-cell mitochondrial activity influences postsynaptic size under homeostatic conditions but does not exacerbate synapse loss following mechanical injury.

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Protective role of quercetin against cisplatin-induced hair cell damage in zebrafish embryos

Human & Experimental Toxicology ◽

10.1177/0960327114567766 ◽

2015 ◽

Vol 34 (11) ◽

pp. 1043-1052 ◽

Cited By ~ 14

Author(s):

SK Lee ◽

KH Oh ◽

AY Chung ◽

HC Park ◽

SH Lee ◽

...

Keyword(s):

Hair Cell ◽

Hair Cells ◽

Cell Damage ◽

Protective Role ◽

Ultrastructural Changes ◽

Control Group ◽

Zebrafish Embryos ◽

Protective Effects ◽

Hair Cell Damage

Background and objectives: The aim of this study was to evaluate the protective effects of quercetin on cisplatin-induced hair cell damage in transgenic zebrafish embryos. Materials and methods: Five days postfertilization zebrafish embryos were exposed to 1 mM cisplatin and quercetin at 10, 50, 100, or 200 μM for 4 h. Hair cells within neuromasts of the supraorbital, otic, and occipital lateral lines were analyzed by fluorescent microscopy ( n = 10). Survival of hair cells was calculated as the average number of hair cells in the control group that were not exposed to cisplatin. Ultrastructural changes were evaluated using scanning electron microscopy. Results: Hair cell damage in neuromasts was decreased by co-treatment of quercetin and cisplatin (quercetin 100 μM: 8.6 ± 1.1 cells; 1 mM cisplatin only: 5.0 ± 0.5 cells; n = 10, p < 0.05); apoptosis of hair cells examined by special stain was also decreased by quercetin. The ultrastructure of hair cells within neuromasts was preserved in zebrafish by the combination of quercetin (100 μM) and cisplatin (1 mM). Conclusion: In conclusion, quercetin showed protective effects against cisplatin-induced toxicity in a zebrafish model. The results of this study suggest the possibility of a protective role of quercetin against cisplatin-induced apoptotic cell death in zebrafish.

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