A study of pigs given protein therapy after heart attacks found it lifted the animals’ chances of survival by 40 per cent.
The protein, derived from human blood, also made the damaged heart tissue grow back stronger and better able to carry blood vessels, according to the paper published in US journal Science Translational Medicine.
Associate Professor James Chong, from the University of Sydney’s Westmead Institute of Medical Research, said the findings were “really exciting” given how little modern medicine could do until now to “change scar for the better”.
“There’s a subset of patients that I treat quite regularly who either didn’t know they were having a heart attack or had a delay coming to the hospital,” Professor Chong, who led a team of researchers from across Australia and New Zealand, said.
“They live with very damaged hearts from a very large heart attack and they don’t have a lot of hope.
“There’s not many treatments that can regenerate the heart function, and we found that this protein therapy almost did that.”
Professor Chong said researchers hoped to commercialise their findings to begin human trials.
Irreversible damage from undetected heart attacked
The successful trial used pigs — which have hearts of a similar size to human hearts and beat at a similar rate — comes after more than a decade of work that began with mice and the assumption that researchers would use stem cells.
Instead, the breakthrough involved the protein known as rhPDGF-AB (recombinant human platelet-derived growth factor AB), which was grown in a laboratory dish and fed to pigs intravenously over seven days.
Professor Chong said while there were good current heart-attack treatments, this offered hope for many who suffer irreversible damage from undetected heart attacks.
In those cases, the scar tissue is weak and can lead to heart failure, with few drugs able to help.
“Most people are surprised that heart attacks often don’t feel like pain in the normal sense,” he said.
“It’s a chest discomfort or most commonly, people describe a heavy weight on their chest, sometimes it’s only arm discomfort or neck discomfort.
“So because of that, they don’t go to the hospital quickly, so we can’t restore blood flow to that section of heart and then that region of the heart dies.”
The study found a measure of heart function, left ventricular ejection fraction, was up 11 per cent in pigs that received rhPDGF-AB.
Professor Chong said it was possible the protein could regenerate other kinds of scar tissue, with implications for burns victims and those with other kinds of organ damage.
“Scar is seen as the bad guy quite often, and we can’t do a lot to make scar better, but scar is the way that most organs repair,” he said.
“People will know if you cut your skin, you get a scar forming and if you take a big gash out of your skin then [that] scar doesn’t heal that well.
“So if we could give something that creates a better scar, it could be potentially used for things as diverse as skin wounds, kidney scarring, liver scarring.
“[Those are] all possibilities that need to be tested. But we were very excited about what we found in the heart.”
The study found the protein therapy can also lower the chance of sudden death from dangerous heart rhythms known as ventricular tachycardia, a leading killer among those who have suffered heart attacks.
“That’s a big thing,” Professor Chong said, adding it could provide an alternative to implantable cardiac defibrillators.
“We are very encouraged about that as well and we’re doing specific studies to look at the mechanisms of that.”
Heart attacks induced in pigs
Like much medical research, the study raised issues around ethical treatment of animals.
To study how the pigs recovered, the researchers first had to induce heart attacks in them before injecting the protein into their veins.
Pioneering animal rights philosopher Peter Singer is among those who have said that harming animals for medical research that could save the lives of many people can be justified ethically if there is no alternative.
“Animal research is something that we need to do in medical research. We don’t take it lightly,” Professor Chong said.
“I’m a cardiologist, I treat humans and I try and create treatments for my own patients and before I come up with something, I need to know that it’s going to be safe.
“I don’t want to give it to my grandmother, [or] my mother, without knowing that it is safe.