British scientists claim a major breakthrough after they successfully develop part of a human heart from stem cells.
They now believe that artificially grown heart components could be used in transplants within three years.
A team led by Sir Magdi Yacoub, at Harefield hospital have been able to grow a tissue that works in the same way as human heart valves.
Sir Magdi said that a whole heart could be produced from stem cells within 10 years.
The team spent 10 years working on the project and included physicists, pharmacologists, clinicians and cellular scientists.
Many scientists believe it should be possible to harness the cells' ability to grow into different tissues to repair damage and treat disease.
Previously, scientists have grown tendons, cartilages and bladders, which are all less complex.
Sir Magdi, professor of cardiac surgery at Imperial College London, had been working on ways to address a shortage of donated hearts for patients.
His team extracted stem cells from bone marrow and cultivated them into heart valve cells. Discs of heart valve tissue were obtained in turn from them.
Later in the year, these will be implanted into animals such as sheep or pigs to see how well they fare.
Dr Stephen Minger, a stem cell expert at London's King's College, said Sir Magdi's team were at the forefront of tissue engineering for cardiac disease.
"If the valves they've engineered prove successful in experimental animals, this could open the door to generating complex tissues from stem cells for a wide variety of clinical application.
Heart disease is the UK's biggest killer. More than 200,000 people died from heart disease and strokes in 2004.
And in 2003 nearly 10,000 people needed surgery to replace heart valves with artificial ones.