How to mend a broken heart: Rat study heals heart attack scars

A study in male rats has discovered that a single injection of a protein was able to make muscle damaged by a heart attack ‘stretchier’ and improve the way the heart was able to contract.

Researchers are hoping that this might lead to a method to reverse the loss of elasticity of damaged heart tissue following heart attacks.

“Following a heart attack part of the heart muscle dies and is replaced by a stiff collagen scar,” Dr Robert Hume, a University of Sydney heart regeneration researcher told Cosmos.  “This prevents the heart from contracting as effectively.”.

“We found that by injecting the protein tropoelastin into the heart wall four days after a heart attack, we were able to reduce the size of the scar and also increase its elasticity/flexibility. This improved the heart’s ability to contract and pump blood more effectively than without the treatment.”

Hume conducted the research – which has been published in Circulation Research – at the Westmead Institute for Medical Research in Sydney along with senior author Associate Professor Dr James Chong.

A small number of male rats had a heart attack (or a myocardial infarction) induced, and then they were split into groups. Four days later, eight were given a saline solution and seven given tropoelastin.

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The paper’s visual abstract. Credit: Hume et al. 2022

Eight rats weren’t given a heart attack, and instead underwent a ‘sham’ surgery as a control.

For the injection, the researchers used a new surgical method using ultrasound to guide the needle into the heart wall, which is less invasive than previous methods.

After 28 days, the team found that the tropoelastin reduced scar size, increased scar elastin, as well as allowed more blood to pump through the heart.

“In the future, we hope that this could be administered to humans following a heart attack to reduce scar formation and increase scar elasticity,” Hume told Cosmos.

“Our published data is a preclinical study, with exciting potential and some evidence of its efficacy in lab grown human cells. However, more work is required before human trials would be considered.”

Ultrasound showing tropoelastin being introduced into the wall of the heart. Credit: Hume et al. 2022

In past studies it has been noted that men and women suffer differently from heart attacks. This could mean that scarring might be different depending on the gender as well.

This study only used male rats to cut down on variables, but more research will need to be done to determine if this is the case. 

“Future studies would use both male and female animals to understand if there are any sex differences in response to the treatment,” Hume told Cosmos.

Despite this, with heart disease currently being the largest cause of death worldwide, the research could be an exciting step forward.

“What we have found is highly encouraging,” says Chong. “We hope to continue developing the method so it can eventually be used in a clinical setting and used to treat and improve the lives of the millions of heart failure patients worldwide.”

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