In the basement at the Panum-building at the University of Copenhagen, Denmark, you will find a little piece of India. Everyday, the sun slowly rises around 8 AM and sets again around 10 PM. The humidity is high and the room temperature is a constant 26° C while the blue water is 28° C. The only ones taking a swim in the windowless room though, are the approx. 10,000 zebra fish that fill the approx. 1.000 aquariums lining the walls.
In order to give the fish optimal conditions, the electric light is switched on and off to indicate dawn and twilight, resulting in 14 hours daylight a day and complete darkness for 10 hours each night.
The aquariums have just been placed in the newly decorated rooms and food is delivered by way of a small robot that drives up and down the lanes between the aquariums, depositing precise doses of dry fodder and tiny crustacean.
“It’s part of what makes this place unique. You can programme the exact amounts of food you want to be distributed. We can even log-on and feed the fish from home,” Pia Rengtved Lundegaard explains. She is in charge of the zebra fish facilities and affiliated with the Department of Biomedicine at SUND.
A beating heart in 25 hours
The black/blue and white-striped fish, fully grown at approx. 5 cm, are the laboratory’s new stars and in only a few years, they have become a preferred laboratory animal globally.
“It may sound strange, but zebra fish are actually remarkably similar to humans”, says Associate Professor Elke Ober with a smile.
She is affiliated with the Danish Stem Cell Center, DANSTEM, at the University of Copenhagen, and she has used zebra fish in her research for more than 15 years.
“Their organs are more or less the same. Like humans, they have a liver, a pancreas and intestines. In 2014, the genome of zebra fish was mapped out completely, and 70% of their genes are also found in humans. And if you only look at disease-related genes, the number is as high as 82%,” Elke Ober states.
Which is also why zebra fish have become highly popular laboratory animal, second only to mice, in countries such as the US, the UK and Germany.
“The advantage is that they are easy to manipulate genetically. You can easily model diseases in the fish because the larva are transparent, which enables you to see, literally, what goes on in their brain by making proteins and cells fluorescent”, Elke Ober elaborates.
Time and money are two other factors that have made the zebra fish popular among researchers.
“This fish grow really quickly. It only takes 25 hours to have one cell grow into a beating heart. After 48 hours, they move about and after five days, they are completely mobile. And this is without any nourishment besides the yoke. After this they are fed externally and after 2-3 months they are sexually mature and able to breed,” Pia Rengtved Lundegaard says as she indicates the size of an A-5 page with her thumbs and index fingers.
“You can place 96 foetuses on one sheet, which enables you to test many different substances at the same time. Furthermore, their tiny size means reduced amounts of test-substances. A foetus lives in approx. 300 micro litres of water – less that what’s in a thimble”, Pia Rengtved Lundegaard elaborates.
Cancer, Alzheimer’s and anxiety
The zebra fish can be used in research into diseases such as Alzheimer’s and different types of cancer as well as anxiety and various addictions. Furthermore, the fish are used in research into so-called repurposing – where you test whether already approved drugs can be used for other diseases than originally intended.
“Zebra fish are a good place to start. It’s cheaper to test drugs on zebra fish, and if they’re no good, there’s no reason to move on to mice, as they are more expensive,” Elke Ober states.
And if you look further into the future, there is a point when humans hope to pick up one of the most important of the zebra fish’s tricks.
“If you cut off part of its fin, or even its heart, new live tissue will grow to make up for what’s lost. We would really like to find out what enables it to do that, and why mammals can’t. When a human suffers a heart attack, by way of example, some of the heart’s tissue usually dies, and this cannot be replaced or brought back to life. Finding out whether the zebra fish’s ability is transferrable to humans is a huge challenge,” Pia Rengtved Lundegaard states.
The scientists have high expectations for the little fish.
“The technology here is world class, and we aim to live up to that,” Elke Ober concludes.
The new zebra fish aquariums officially open on September the 10th.
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