For the first time doctors have successfully transplanted a vein grown with a patient's own stem cells, another example of scientists producing human body parts in the lab.

In this case, the patient was a 10-year-old girl in Sweden who was suffering from a severe vein blockage to her liver. Last March, the girl's doctors decided to make her a new blood vessel to bypass the blocked vein instead of using one of her own or considering a liver transplant.

They took a 9-centimeter section of vein from a deceased donor, which was stripped of all its cells, leaving just a hollow tube. Using stem cells from the girl's bone marrow, scientists grew millions of cells to cover the vein, a process that took about two weeks. The new blood vessel was then transplanted into the patient.

Because doctors used her own cells, the girl did not have to take any drugs to stop her immune system from attacking the new vein, as is usually the case in transplants involving donor tissue.

"This is the future for tissue engineering, where we can make tailor-made organs for patients," said Suchitra Sumitran-Holgersson of the University of Gothenburg, one of the study's authors.

She and colleagues published the results of their work online on Thursday in the British medical journal Lancet. The work was paid for by the Swedish government.

The science is still preliminary and one year after the vein was transplanted, it needed to be replaced with another lab-grown vein when doctors noticed the blood flow had dropped.

Experts from University College London raised questions in an accompanying commentary about how cost-effective the procedure might be, citing "acute pressures" on health systems that might make these treatments impractical for many patients.

Sumitran-Holgersson estimated the cost at between $6,000 and $10,000.

Patients with the girl's condition are usually treated with a vein transplant from their own leg, a donated vein or a liver transplant. Those options can be complicated in children, and using a donated vein or liver also requires taking anti-rejection medicines.

Since her first transplant, the girl, who was not identified, has grown 6 cm and gained weight. Her parents say she is much more focused, articulate and physically active, Sumitran-Holgersson said.

"She was always tired and hardly went to school before," Sumitran-Holgersson said. "Last week, her father said she did somersaults for the first time."

Other experts predicted that it should soon be possible for doctors to build arteries for patients.

The Associated Press