Mexican fish that can repair its OWN HEART could hold hope for millions of patients

A Mexican fish that can repair its own heart offers clues for future treatments in humans, according to new research.

Scientists discovered a gene that may hold the key to the fish’s ability to regenerate its heart tissue.

The same gene, called Irrc10, is present in humans, and researchers at Oxford University say their new findings hold potential to change the lives of heart attacks patients.    

Over half a million people in the UK are living with heart failure, often as a result of a heart attack, according to the British Heart Foundation, who funded the research.

The cave-dwelling Mexican tetra fish evolved to losing their sight and colour from being in the dark

Scientists at Oxford University compared Mexican tetra fish that either live in rivers (left), or caves (right). The former can repair it’s own heart with the lrrc10 gene playing a key role

People suffering from heart failure can’t regenerate their damaged hearts, and often the only cure is a heart transplant. 

The new evidence about these remarkable fish, called tetra fish, suggests we could one day be able to heal human hearts in much the same way.    

HOW HAVE FISH BEEN USED IN HEART STUDIES BEFORE? 

The zebrafish has been studied by The British Heart Foundation before. They have given funding for the following:

  1. The zebrafish embryo is transparent, which makes it ideal to study how the heart first starts to grow and beat. The development of its heart also begins in a similar way to humans. Scientists at the University of Glasgow are using a bespoke microscope to create a 3D movie image at different stages as the fish develops.
  2. Researchers at the University of Birmingham are trying to find better drugs for irregular heart rhythms, which can increase the risk of blood a stroke. Thousands of drugs can be tested in detail on  zebrafish embryos because they have a very similar electrical profile to that of humans.
  3. Changes in a protein called Popdc have been linked with heart rhythm problems and muscular dystrophy, a group of genetic conditions. Imperial College London’s research into how changes in Popdc proteins in zebrafish hearts can lead to conditions such as heart rhythm disorders, holds hope for humans.
  4. When blood vessels become damaged, cardiovascular conditions such as coronary heart disease or stroke can develop. The University of Sheffield has the largest number of zebrafish heart researchers in the UK. Here, they are looking at how zebrafish grow new vessels, which could help humans do the same once theirs is damaged.
  5. People who survive a heart attack may have heart tissue damage that can lead to debilitating heart failure. Scientists across the UK are looking at how zebrafish turn stem cells into heart muscle cells, remove scar tissue and repair their hearts.  

 Source: British Heart Foundation

For this study, publised in Cell Reports, Dr Mathilda Mommersteeg and her team studied two types of Mexican tetra fish – river-dwellers (Astyanax mexicanus) and cave-dwellers (Pachón) 

Both types once lives in the rivers of Northern Mexico. The now called cave-dwelling fish were washed into caves by floodwaters about 1.5 million years ago and evolved, losing their sight and colour because of living in darkness.

The cave fish lost the ability to repair their hearts, whereas the river fish are still able to do so. 

Comparing the two types of tetra fish, researchers found two genes – lrrc10 and caveolin – were much more active in the river fish following heart injury. 

The lrrc10 gene is already linked to a human heart condition called dilated cardiomyopathy (DCM). 

Studies in mice have previously shown that this gene is involved in the way that heart cells contract with every heartbeat. 

Having discovered this, they switched off the lrrc10 gene in a different species of fish with self-healing abilities, the zebrafish, native to the Himalayas.

With this gene no longer working properly, the zebrafish became unable to fully repair its heart without scarring.   

Dr Mommersteeg, who’s associate professor of developmental and regenerative medicine, said: ‘We have discovered that, like zebrafish, the river surface fish regenerate their heart, while, cavefish cannot and form a permanent scar, similar to the human injury response after a heart attack. 

‘This finding is important as it allows to directly compare a ‘fish-like’ regenerative response with a ‘human-like’ scarring response within the same species.’

Scar tissue stops the heart muscle from contracting properly and reduces the heart’s ability to pump blood around the body.  

The study authors say their findings suggest it will one day be possible to regenerate damaged hearts in people by artificially modifying how these and other genes function. 

This could be done either with drugs or by modifying DNA.  

Zebrafish, that can also repair their own hearts, struggled to repair their hearts when the lrrc10 gene was turned off in the study

Zebrafish, that can also repair their own hearts, struggled to repair their hearts when the lrrc10 gene was turned off in the study

‘We’ve been able to pick apart the genes responsible for heart regeneration’, said Dr Mommersteeg. ‘It’s early days but we’re incredibly excited about these remarkable fish and the potential to change the lives of people with damaged hearts.’

But she said more work is needed to find other key genes that may be involved in the heart regenerating.

Prof Metin Avkiran, associate medical director at the British Heart Foundation, said: ‘Survival rates for heart failure have barely changed over the last 20 years, and life expectancy is worse than for many cancers.

‘Breakthroughs are desperately needed to ease the devastation caused by this dreadful condition.’ 

 

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