Measuring cerebrospinal fluid flow in zebrafish

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The purpose of this application is to study the circulation of cerebrospinal fluid (CSF) in the brain ventricles of juvenile and adult zebrafish. In this project, we aim to identify how CSF is produced and circulated in the brain ventricular system to understand the function of CSF in brain development, physiology and disease. We will use zebrafish as a model system, since its external development and transparency allow to monitor and manipulate physiological processes, including CSF flow, throughout development.
Our published work revealed that, in young larval zebrafish, motile cilia, heartbeat and bodily movement contribute to the CSF flow dynamics in vivo. The zebrafish ventricular system also undergoes drastic changes at 3-4 weeks as the brain becomes more complex. We measured differences in motile ciliated cells, in the volume of the ventricles, and in the size and architecture of the CSF producing organ, known as the choroid plexus. Yet, little is known about the mechanisms underlying CSF production and circulation in the developing and adult brain and, more broadly their requirements for brain physiology and homeostasis.
In this project, we want to study the fluid dynamics properties of CSF in the brain of zebrafish, beyond 5 days post fertilization. In order to perform these analyses, we will inject fluorescent beads and dyes in the brain of anaesthetized animals at larval (2 weeks), juvenile (4-6 weeks) and adult stage (>2 months), and image the movement of particles. We will also analyze the function of the choroid plexus, which generate CSF upon uptake of water from the blood vessels, by injecting dyes intravenously and measure the diffusion of fluorescent dyes in and out of the brain ventricle.
These experiments require to immobilize the animals, to inject a solution into the brain ventricles or intravenously, and to image the ventricles using non-invasive microscopy techniques. To minimize pain and improve the welfare of the animals, all animals will be anaesthetized throughout the procedure. At the end of the experiment, all animals will be sacrificed without recovering from anesthesia.
The essential vital signs of the subject will be monitored throughout the procedure, and include the heartbeat, breathing (gill movements) and blood flow. In case of the loss of any given vital signs, the animal will be euthanized immediately according to described procedures.
We will perform these experiments in various genetic background, including transgenic animals and mutant animals with impaired cilia function. To obtain sufficient statistical power, we will analyse a total of 980 animals including various developmental stages and genetic background.
Using zebrafish, we replace mammalian animal models such as the mouse or rat. All our experiments aim to study the circulation of CSF and its function. Since such a mechanism involves multiple tissues (e.g. brain, choroid plexus and motile ciliated cells) and physiological processes (like blood flow and heartbeat), these experiments require working with living animals.
We anticipate that our results will go beyond zebrafish brain and will inspire novel knowledge about the function of CSF flow in the brain of mammals, including humans.