High-Resolution Magnetic Resonance Imaging of the Regenerating Adult Zebrafish Heart

Jana Koth,Victoria L Thornton,Mahon L Maguire,Jürgen E Schneider,Darryl Mcclymont,Paul R Riley,Roger K Patient,John Beech,Leonie Diffley

doi:10.1038/s41598-017-03050-y

Abstract

The adult zebrafish is a well-established model for studying heart regeneration, but due to its tissue opaqueness, repair has been primarily assessed using destructive histology, precluding repeated investigations of the same animal. We present a high-resolution, non-invasive in vivo magnetic resonance imaging (MRI) method incorporating a miniature respiratory and anaesthetic perfusion set-up for live adult zebrafish, allowing for visualization of scar formation and heart regeneration in the same animal over time at an isotropic 31 µm voxel resolution. To test the method, we compared well and poorly healing cardiac ventricles using a transgenic fish model that exhibits heat-shock (HS) inducible impaired heart regeneration. HS-treated groups revealed persistent scar tissue for 10 weeks, while control groups were healed after 4 weeks. Application of the advanced MRI technique allowed clear discrimination of levels of repair following cryo- and resection injury for several months. It further provides a novel tool for in vivo time-lapse imaging of adult fish for non-cardiac studies, as the method can be readily applied to image wound healing in other injured or diseased tissues, or to monitor tissue changes over time, thus expanding the range of questions that can be addressed in adult zebrafish and other small aquatic species.

Highlights

Embryonic and larval zebrafish have been powerful models in basic science and biomedical research for several decades due to their external development and transparency, making them highly amenable for in vivo optical imaging
It is based on the assumption that the images are sparse in a domain that is incoherent with the magnetic resonance imaging (MRI) acquisition, which means that the acquisition can be under-sampled and the missing samples may later be recovered using non-linear reconstruction techniques
There is variability between fish, which has not been adequately addressed in zebrafish heart repair studies to date, and which is a confounding factor when discussing and comparing repair rates deduced from two-dimensional images from single post-injury time points and via sections of different hearts/animals subjected to varying injury settings/ drug treatments or interventions

Summary

Introduction

Embryonic and larval zebrafish have been powerful models in basic science and biomedical research for several decades due to their external development and transparency, making them highly amenable for in vivo optical imaging. The movement and high heart contraction rate (~130 beats per/min) is challenging for optical high-resolution imaging Tomographic techniques such as Magnetic Resonance Imaging (MRI), Computed Tomography (CT), or 2D/3D cardiac ultrasound (i.e. echocardiography) provide non-invasive deep tissue imaging without relying on optical transparency[3, 4] and can, be applied to the heart. MRI is routinely used clinically to assess cardiac anatomy and function, and to characterize the heart muscle at a tissue-level (for example the extent of injury after a myocardial infarction) in patients with heart disease. It can non-invasively provide structural and metabolic information. We have used cryo- and resection injury in our study as they are both distinctly localized to the apex of the ventricle

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