Scientists 'seed' cells, make new organs

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(CNN) -- Engineering organs begins with something missing -- a phantom organ in the body that causes a patient incredible discomfort, dysfunction or pain. It ends with a Star Trek-esque feat of engineering where missing organs are replaced using cells culled from a patient's own body.

In a small pilot study, published Monday in the Lancet, scientists reported successfully reconstructing urethras in five young patients, using their own cells.

"We were able to create patients' own tissue that actually belongs there," said Dr. Anthony Atala, lead author of the study and director of the Institute for Regenerative Medicine at Wake Forest University School of Medicine. "If the tissue is supposed to be there, hopefully we will do better by the patient."

Patients had their engineered urethras implanted between March 2004 and July 2007 at the Federico Gomez Children's Hospital in Mexico City. Their urethras continued to function after several years' follow-up.

The urethra is a narrow tube that connects the bladder with the genitals, providing a conduit to usher waste out of the body. When it is damaged -- sometimes congenitally, or as result of disease, pelvic fractures or other traumas -- it is usually replaced using tissue harvested from the lining of a patient's cheeks or using skin grafted from another area of the body, according to Atala.

"Unfortunately for the narrow structures in the body (like urethras), they are kind of complex because they tend to collapse," said Atala, who added that conventional urethra replacement fails more than half the time. "Every organ has its own challenges."

The first step for engineering a new urethra is to take a very small piece of the patient's own tissue (around half the size of a postage stamp) from the bladder area. Cells are scraped from the biopsied tissue, allowed to multiply, after which muscle cells are separated from urethral cells.

It is the next few steps in the process that sound like science fiction. When there are a sufficient number of cells, scientists "seed" them -- much like you would seed a new lawn -- onto a mesh scaffold that is shaped like a urethra. The inside of the mesh is coated with urethral cells while the outside gets muscle cells.

"It's like baking a layer cake, but doing it one layer at a time," said Atala.

The seeded structure is placed in an incubator for about two weeks, in a "cooking" process that Atala says simulates how cell growth occurs inside the body. After that, the newly engineered urethra is ready to be implanted into the patient.

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