One good turn deserves another, they say – and when it comes to generosity these women have hearts of gold.

Katie James, Kara Terol and Hannah Sharma all received life-saving heart transplants before the age of 35 and all donated those that were removed to research.

The organs have helped scientists move a step closer to a cure for heart failure and have supported other projects, such as creating lab-grown heart valves.

Ms James, 41, Ms Terol, 38, and Ms Sharma, 35, now want other patients to consider donating their old organs for research.

Ms Sharma, who was 28 at the time of her transplant, had dilated cardiomyopathy, which is thought to have been triggered by a virus.

The condition causes the heart's main pumping chamber to stretch and thin, making it harder to pump blood effectively. 

The events manager, from Hadlow Down in East Sussex, said: 'That heart wasn't what makes me "me", and I was happy to give it to scientists who needed it.'

Ms Terol was pregnant when she was told she had restrictive cardiomyopathy, which causes part of the heart to become stiff. 

She had no idea until she volunteered to take part in a study looking at how pregnancy affects the heart.

Ms Terol said she had been having symptoms 'for years' but thought it was asthma.

Her son George was born in 2018, but three years later she was told she would need a new heart as the condition had put so much strain on her lungs.

She said: 'The donor who gave me my heart helped me more than anyone could, and so I wanted to pass that help on.'

Ms James had her heart transplant a decade ago when she was 32.

She had been diagnosed with a rare condition called arrhythmogenic cardiomyopathy when she was just 20.

It causes the heart muscle to weaken because the heart cells do not stick together properly.

Ms James, now 41, said: 'I had absolutely no hesitation about donating my heart to help advance medical knowledge.

'It is simple – I wouldn't be here without science and research, so it is the least I can offer.

'I didn't say no to donating my heart, and I don't say no to very much now. As I tell people, you only live once – or you only live twice, as I feel I have done after getting my new heart.'

Tissue from all three hearts has been used in a major heart failure study at Imperial College London, funded by the British Heart Foundation.

People with heart failure have a lack of a protein called serca, causing their heart to beat weaker than normal.

Scientists working on the project were able to add the protein back into heart cells provided by living donors, helping them to beat more strongly in a lab dish.

If the findings are replicated in humans, it could pave the way for treatments which help the heart pump stronger, reducing some symptoms of heart failure such as tiredness and breathlessness.

A new study will test this method in people using a gene therapy to deliver serca directly to heart cells.

Ms Sharma and Ms James's hearts have helped scientists at Imperial College London move closer to creating heart valves in a lab.

At the moment, patients are either given mechanical replacements and must take drugs for life to prevent clotting, or biological valves made from animal tissue that typically fail within 10 to 15 years.

Dr Najma Latif, who has led the research, said: 'These people make discoveries possible that would otherwise never be achieved, which can transform the lives of others.'

Tissue from the hearts of Ms Terol and Ms James has been studied to determine how the organ's normal electrical signals were disrupted by cardiomyopathy.

Researchers hope that by finding the specific damaged cells that cause the most disruption could help tackle the disease with more targeted treatments.

Professor Bryan Williams, chief scientific and medical officer at the British Heart Foundation, said: 'Giving the gift of an organ donation is an incredible act, and yet we rarely talk about the extraordinary living heart donors.

'These are people who look to the future and decide their old heart could help others – even as they prepare for the life-altering journey of a heart transplant and the long recovery that follows.

'Their decision to donate their heart for research opens the door to discoveries that can only be made through examination of real human tissue, allowing researchers to identify the cause of heart diseases, test new ideas and refine treatments.

'We cannot thank these people enough for the vital part they play in driving scientific innovation and progress.'

The Heart, Lung and Critical Care Biobank at Royal Brompton and Harefield Hospitals oversees the storage of tissue from heart donors.

Harshil Bhayani, the biobank's manager, said: 'These contributions are more than samples – they represent a lasting legacy that supports progress in research and benefits future generations.'