LONDON (AP) - Doctors have created urethras using patients' own cells for the first time - another example that scientists may be able to grow replacement body parts one day.
"It's not so much science fiction anymore to think we can grow replacement organs," said Patrick Warnke, a tissue engineering expert at Bond University in Australia.
American doctors made the urethras for five boys in Mexico, aged 10 to 14, after they were injured in accidents.
The urethra is a thin tube that carries urine out of the body from the bladder; cells from both organs are very similar. Tissue grafts are normally used in such cases, but there's a less than 50 percent success rate.
After removing a postage stamp-sized piece from the boys' bladders, scientists put the cells into a special mixture in a laboratory to speed their growth. They then fashioned a tiny mesh tube out of the same material used for dissolvable stitches in surgeries to act as a scaffold.
After that, the scientists alternately coated the tube with muscle cells on the outside and lining cells on the inside.
Dr. Anthony Atala, a professor of surgical sciences at the Wake Forest University School of Medicine in North Carolina, described the process as "very much like baking a layer cake."
He said the new structure is put into an incubator for several weeks before being implanted into the patient, in the knowledge that the scaffold will eventually disintegrate, leaving the boys' own cells as a new urethra.
Up to six years after having their new urethras implanted, Atala said the boys' organs are fully functional and no major side effects were reported.
"It's like they now just have their own urethras," Atala said. He said the techniques used might be applied to create more complicated tubular structures in the body, like blood vessels. Atala and her colleagues have previously made bladders using patients' own cells.
The urethra research was paid for by the National Institute of Diabetes and Digestive and Kidney Diseases and the National Institutes of Health. It was published online Tuesday in the medical journal, Lancet.
In recent years, doctors have made new windpipes for patients partly from their own stem cells. Warnke's team has grown a replacement jaw and is now working on an eye.
Warnke also thought it was possible that children - who heal faster than adults - might be better candidates for such procedures in the future, though that could raise ethical dilemmas. "Tissue regeneration is much faster in children, but my gut feeling tells me not to do it," he said. "If you mess it up in a child, it will be horrific."
Other experts said using science to reconstruct body parts was the ultimate medicine.
"When an organ or tissue is irreparably damaged or traumatically destroyed, no amount of drugs or mechanical devices will restore the patient back to normal," said Chris Mason, chair of regenerative medicine bioprocessing at University College London, in a statement.
"If the goal is cure, then cell-based therapies are the answer."