Understanding brain regeneration in a zebrafish larval model of intracerebral haemorrhage

Why did we fund this Fellowship?

This award aims to replace the use of mice in intracerebral haemorrhage brain regeneration studies by using a transgenic larval zebrafish model.  

Intracerebral haemorrhages are the most severe type of stroke and have high mortality and morbidity rates, often resulting in death or disability. Research is currently ongoing into how the brain regenerates after a haemorrhage and how to increase this regenerative capacity. Mice are often used to model a haemorrhage through an invasive procedure where collagenase is injected into the brain to induce bleeding and the following brain regeneration is analysed. In her NC3Rs funded PhD, Dr Siobhan Crilly developed a larval zebrafish model that spontaneously develops a haemorrhage as an alternative model system. The larval zebrafish used are less than five days of age (before they begin independently feeding) and are therefore not protected under the UK legislation on the protection of animals used in research. Based on current thinking, at this early stage the embryos are not considered capable of suffering and they therefore provide a partial replacement for the use of other animals.

Siobhan undertook an extensive characterisation of the larval zebrafish model during her PhD studies, demonstrating evidence of brain damage and subsequent regeneration. During her Fellowship, Siobhan will apply the model to investigate the immune and neuronal cellular response during regeneration. The aim of this is to demonstrate the utility of the model and increase buy-in from the mammalian model stroke community. Siobhan will develop skills in cell culture, fluorescence microscopy, and transcriptomic and proteomic analysis.

Brain haemorrhages are the most severe type of stroke, and patients are often left with disabilities due to brain damage. We currently do not know much about how the brain tissue adapts after the bleed. Presently, the research into brain regeneration following haemorrhage mostly uses invasive, surgically-induced rodent models that do not accurately recreate the spontaneous nature of the human condition. Experimentally, stem cells and synthetic scaffolds are injected into the brain to encourage regrowth, however once delivered into the body, the response is very difficult to measure accurately. Zebrafish can regenerate from injuries, including damage to the central nervous system. We have previously shown that zebrafish larvae, a small, transparent, immature organism can exhibit spontaneous brain bleeds like humans and then quickly recover from injury, growing into healthy adults. I think that we can learn more from the zebrafish brain recovery after a haemorrhage, and utilise their unique transparency, to non-invasively visualise the live recovery response, something that is impossible in rodent models. This work would lead to a reduction in the number of protected animals required for such experiments, as a single pair of breeding zebrafish can produce ~200 embryos.

The first step of my project will be to image the cells inside the brain responding to the bleed, to answer the following questions: How quickly do immune cells clear the blood? What fills the space left by the haematoma? Do new brain cells form in the space, or do existing ones spread across the gap? The second part of my project will require extracting these brain stem cells from the zebrafish and investigating the genetic and proteomic factors that influence their behaviour. In the final stage of my project I will apply what I have learnt to human brain stem cell cultures in a dish and determine if turning on the same genes, or exposing them to the same proteins, encourages the same regenerative behaviours we observe in the zebrafish. The ultimate aim of this work is to enable scientists to develop better models of brain regeneration in which to investigate regenerative therapies for patients that could potentially prevent long-term disability after a brain haemorrhage, and reduce the need for animal models in the long term.

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University of Manchester

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Award date

Apr 2021 - Apr 2023

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