Evaluating the Death and Recovery of Lateral Line Hair Cells Following Repeated Neomycin Treatments.

Alexandra Venuto,Timothy Erickson

doi:10.3390/life11111180

Abstract

Acute chemical ablation of lateral line hair cells is an important tool to understand lateral line-mediated behaviors in free-swimming fish larvae and adults. However, lateral line-mediated behaviors have not been described in fish larvae prior to swim bladder inflation, possibly because single doses of ototoxin do not effectively silence lateral line function at early developmental stages. To determine whether ototoxins can disrupt lateral line hair cells during early development, we repeatedly exposed zebrafish larvae to the ototoxin neomycin during a 36 h period from 3 to 4 days post-fertilization (dpf). We use simultaneous transgenic and vital dye labeling of hair cells to compare 6-h and 12-h repeated treatment timelines and neomycin concentrations between 0 and 400 µM in terms of larval survival, hair cell death, regeneration, and functional recovery. Following exposure to neomycin, we find that the emergence of newly functional hair cells outpaces cellular regeneration, likely due to the maturation of ototoxin-resistant hair cells that survive treatment. Furthermore, hair cells of 4 dpf larvae exhibit faster recovery compared to 3 dpf larvae. Our data suggest that the rapid functional maturation of ototoxin-resistant hair cells limits the effectiveness of chemical-based methods to disrupt lateral line function. Furthermore, we show that repeated neomycin treatments can continually ablate functional lateral line hair cells between 3 and 4 dpf in larval zebrafish.

Highlights

Fish and some amphibians possess a unique sensory system called the mechanosensory lateral line, which comprises clusters of mechanically sensitive hair cells distributed all over the body in organs called neuromasts
To complement our studies with this mutant, here, we aim to identify a timeline of repeated neomycin treatments in larval zebrafish aged 3–4 dpf that will mimic the congenital loss of lateral line function, while minimizing off-target toxicity
We find find that the proportions of functional hair cells that remain after neomycin treatment that the proportions of functional hair cells that remain after neomycin treatment are staare statistically

Summary

Introduction

Fish and some amphibians possess a unique sensory system called the mechanosensory lateral line, which comprises clusters of mechanically sensitive hair cells distributed all over the body in organs called neuromasts. Aquatic organisms can identify locations of predators and prey by combining the direction and force of the water interacting with the neuromast pattern along the body [6,7]. To investigate these lateral line-mediated behaviors, researchers use a variety of physical and chemical strategies to functionally disrupt the lateral line [8,9]. Common ototoxins include aminoglycoside antibiotics (e.g., neomycin), certain heavy metals (e.g., copper), and various platinum derivatives (e.g., cisplatin) [10,11,12,13] These compounds disrupt the lateral line by entering hair cells through functional mechanotransduction channels, causing oxidative stress, and triggering apoptotic cell death [14,15,16,17,18]. Understanding how zebrafish hair cells respond to ototoxic assaults may lead to preventative or therapeutic strategies to combat human hearing loss [20]

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