Scientists have turned back the hands of a biological clock to rejuvenate ageing and damaged human heart cells.
Using stem cells, they reset a molecular mechanism that determines the rate at which cells age.
Although the work on human cells was confined to the laboratory, the same technique has been successfully tested in mice and pigs.
Researchers in the US managed to get new heart tissue to grow in the animals in just four weeks.
They hope the advance will lead to new treatments for heart failure, which often follows a heart attack.
"Modifying aged human cardiac cells from elderly patients adds to the cell's ability to regenerate damaged heart muscle, making stem cell engineering a viable option," said lead scientist Dr Sadia Mohsin, from San Diego State University in California.
During heart failure the damaged heart is not strong enough to pump blood around the body efficiently, leading to rapid exhaustion.
In the laboratory studies, Dr Mohsin's team worked on heart tissue surgically removed from elderly patients.
Stem cells from the samples were treated with a growth protein called PIM-1.
The effect was to boost activity of an enzyme called telomerase, which has a direct impact on ageing.
The enzyme increases the length of telomeres, "caps" on the ends of chromosomes that shorten each time a cell divides.
Would you be able to spot the first signs of heart trouble?
"A dull ache or burning sensation in the epigastrum (upper part of the abdomen). Not all pain typically occurs in the centre of the chest," explains Dr Sanjay Sharma. "The blockage in the heart could cause symptoms similar to indigestion (like fullness, bloating and problems swallowing). If these symptoms longer than two days, seek medical advice."
"Severe pain or pressure sensation around the jaw and neck only could be a sign," says Dr Sanjay Sharma. "If it starts off as a mild discomfort but gradually worsens, seek medical advice immediately."
"Pain in the centre of the upper back is often mistaken for muscular pain, but could be a 'silent heart attack' symptom," says Dr. Sanjay Sharma. "If in doubt, speak to a medical professional as soon as possible."
"Being suddenly short of breath, without any chest pain could be a sign of a herat attack - although it's more likely to occur in elderly people or diabetics. The chest pain could be due to the lack of oxygen to the heart muscle," says Dr Sanjay Sharma. "The breathlessness is often due to the fact that the heart is no longer pumping properly causing the lungs to fill up with fluid."
Dizziness and sweating is a common sign," says Dr Sanjay Sharma. "The sweating is a normal reaction to severe pain and the loss of consciousness may be due to a drop in blood pressure the heart going into a very slow, or very fast electrical rhythm, due to the effects of lack of oxygen."
"If chest pain spreads to your left or right arm, that could be another sign you're having a heart attack. We've heard from heart attack survivors who thought they'd pulled a muscle and waited until the following day before getting themselves to hospital," adds Ellen Mason, senior cardiac nurse from the British Heart Foundation.
Eventually the chromosomes become so short that their DNA is scrambled and cell division is halted. Cells in this "senescent" state not only stop growing but undergo age-related changes which may, for instance, lead to wrinkled skin.
Keeping telomeres long effectively holds back the ageing process.
The research was presented at a meeting of the American Heart Association in New Orleans and published in the Journal of the American College of Cardiology.
"Since patients with heart failure are normally elderly, their cardiac stem cells aren't very healthy," said Dr Mohsin. "We modified these biopsied stem cells and made them healthier. It's like turning back the clock so these cells can thrive again."
She added: "This is an especially exciting finding for heart failure patients. Right now we can only offer medication, heart transplantation or stem cell therapies with modest regenerative potential, but PIM-1 modification offers a significant advance for clinical treatment."