London, England (LifeNews.com) -- British researchers have grown human heart tissue from adult stem cells found in a person's bone marrow. Their progress means that the ethical stem cells could be used to create hearts from scratch for transplants and show that adult stem cells can be just as effective as more controversial embryonic ones.

Ledy by Magdi Yacoub, scientists at Imperial College London said the tissue works the same way that the natural valves in the human heart do.

"We have a sort of rudimentary new valve tissue," Adrian Chester, one of the lead researchers, told AFP.

"We have been using various mechanical stimuli to cause this change in the cell function. We are still a matter of (three) years away before being able to test this in an animal," Chester added.

The animal testing is important because it would allow scientists the chance to test the tissues and see how well they hold in transplants before using the tissues in humans.

The adult stem cell-based tissues also present an advantage over embryonic stem cell research because they can involve the patient's own cells. That's important because embryonic stem cells have problems with being rejected by the immune system.

The tissues could also be used in patients with heart damage and could be a better replacement than artificial valves.

Still, with any research, scientists warn patients not to expect miracles overnight.

Professor Colin McGuckin, a Newcastle University researcher who has grown a miniature artificial human liver, told AFP that replacement tissues for implantation in animals may be obtainable within years.

But, they are "a long way off" for humans -- perhaps as much as 50 years.