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Title: Inducing Mild Traumatic Brain Injury in C. elegans via Cavitation-Free Surface Acoustic Wave-Driven Ultrasonic Irradiation
Abstract

Mild traumatic brain injury is an all-too-common outcome from modern warfare and sport, and lacks a reproducible model for assessment of potential treatments and protection against it. Here we consider the use of surface acoustic wave (SAW) irradiation ofC.elegansworms—without cavitation—as a potential, ethically reasonable animal-on-a-chip model for inducing traumatic brain injury in an animal, producing significant effects on memory and learning that could prove useful in a model that progress from youth to old age in but a few weeks. We show a significant effect by SAW on the ability of worms to learn post-exposure through associative learning chemotaxis. At higher SAW intensity, we find immediate, thorough, but temporary paralysis of the worms. We further explore the importance of homogeneous exposure of the worms to the SAW-driven ultrasound, an aspect poorly controlled in past efforts, if at all, and demonstrate the absence of cavitation through a change in fluids from a standard media for the worms to the exceedingly viscous polyvinyl alcohol. Likewise, we demonstrate that acoustic streaming, when present, is not directly responsible for paralysis nor learning disabilities induced in the worm, but is beneficial at low amplitudes to ensuring homogeneous ultrasound exposure.

 
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NSF-PAR ID:
10153529
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
Nature Publishing Group
Date Published:
Journal Name:
Scientific Reports
Volume:
9
Issue:
1
ISSN:
2045-2322
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Background

    Brain tissue hypoxia is a common consequence of traumatic brain injury (TBI) due to the rupture of blood vessels during impact and it correlates with poor outcome. The current magnetic resonance imaging (MRI) techniques are unable to provide a direct map of tissue hypoxia.

    Purpose

    To investigate whether GdDO3NI, a nitroimidazole‐based T1MRI contrast agent allows imaging hypoxia in the injured brain after experimental TBI.

    Study Type

    Prospective.

    Animal Model

    TBI‐induced mice (controlled cortical impact model) were intravenously injected with either conventional T1agent (gadoteridol) or GdDO3NI at 0.3 mmol/kg dose (n = 5 for each cohort) along with pimonidazole (60 mg/kg) at 1 hour postinjury and imaged for 3 hours following which they were euthanized.

    Field Strength/Sequence

    7 T/T2‐weighted spin echo and T1‐weighted gradient echo.

    Assessment

    Injured animals were imaged with T2‐weighted spin‐echo sequence to estimate the extent of the injury. The mice were then imaged precontrast and postcontrast using a T1‐weighted gradient‐echo sequence for 3 hours postcontrast. Regions of interests were drawn on the brain injury region, the contralateral brain as well as on the cheek muscle region for comparison of contrast kinetics. Brains were harvested immediately post‐imaging for immunohistochemical analysis.

    Statistical Tests

    One‐way analysis of variance and two‐samplet‐tests were performed with aP < 0.05 was considered statistically significant.

    Results

    GdDO3NI retention in the injury region at 2.5–3 hours post‐injection was significantly higher compared to gadoteridol (mean retention fraction 63.95% ± 27.43% vs. 20.68% ± 7.43% for gadoteridol at 3 hours) while it rapidly cleared out of the muscle region. Pimonidazole staining confirmed the presence of hypoxia in both gadoteridol and GdDO3NI cohorts, and the later cohort showed good agreement with MRI contrast enhancement.

    Data Conclusion

    GdDO3NI was successfully shown to visualize hypoxia in the brain post‐TBI using T1‐weighted MRI at 2.5–3 hours postcontrast.

    Evidence Level

    1

    Technical Efficacy

    Stage 1

     
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    This article was corrected on 19 July 2022. See the end of the full text for details.

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