British scientists have grown part of a human heart from stem cells for the first time.
Entire organs could be grown from stem cells
Heart surgeon Sir Magdi Yacoub, who led the team, said doctors could be using artificially grown heart components in transplants within three years.
His researchers at Harefield hospital managed to grow tissue that works in the same way as human heart valves.
Sir Magdi told the Guardian newspaper a whole heart could be produced from stem cells within 10 years.
The team who spent 10 years working on the project included physicists, pharmacologists, clinicians and cellular scientists.
Researchers will see their achievement as a major step towards growing entire organs for transplant.
Stem cells have the potential to turn into many different types of cell.
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.
He said he hoped that soon an entire heart could be grown from stem cells.
He added: "It is an ambitious project but not impossible. If you want me to guess I'd say 10 years."
His team extracted stem cells from bone marrow and cultivated them into heart valve cells.
After they were placed in scaffolds formed from collagen, 3cm-wide discs of heart valve tissue were formed.
Later in the year, these will be implanted into animals such as sheep or pigs to see how well they fare.