Mending a broken heart (revisited)

Around 1.4 million people alive in the UK today have survived a heart attack, but survivors can suffer from debilitating heart failure, because the heart is damaged during the attack. Ten years ago The Naked Scientists spoke to Professor Sian Harding from Imperial College London about some promising new “heart patches” that could be grown in the lab. Ten years on, production is more reliable and plentiful, and Harding hopes that safety trials on humans will begin within the next couple of years.

The heart loses about a billion cells during a heart attack and the rate that the heart regenerates is not nearly fast enough to cope with such a large loss. This can result in shortness of breath and fatigue because the heart is not pumping blood around the body as effectively as it should. Harding’s idea is to put muscle back into the heart in the form of heart patches which can be sewn onto the damaged parts of the heart, a bit like a plaster!

Normal cells taken from a patient can be re-programmed into pluripotent stem cells, which have the ability to grow into any kind of cell in the human body. "We can turn (the stem cells) very efficiently into cardiac muscle cells" says Harding, "we can see them beating in the dish as they turn into muscle cells". About 20 million cardiovascular muscle cells are needed to make a 2 by 3 cm heart patch. The cells are suspended in a gel and as the cells expand they meet and grow into a unified sheet. The sheet grows around some “bendy support posts” and after about a week the sheet begins to expand and contract, or beat like a heart. The beating sheet bends the supports and "in doing that they excercise themselves - like you might excercise your muscles picking up weights" says Harding. Over a few weeks the sheets get stronger and after about six to eight weeks they are ready to be implanted in the heart.

The patches have been successfully tested in rabbits. Harding has also tested how they interact with tissue from human hearts, which can be taken from the hearts discarded after a heart transplant.

Crucially, as the patches can be grown from the patient’s own cells, they shouldn't be rejected by the immune system of the patient. However, Harding acknowledges that this may not always be practical in every situation. Therefore Harding and her team are now trying to genetically modify the stem cells to reduce the risk of rejection. If this is successful it would be possible to make large quantities in preparation for when they were needed.

In the UK a patient is admitted to hospital due to a heart attack every five minutes. Harding hopes that within the next ten years the heart patches will have been shown to be a safe and effective treatment for heart attack survivors.