Once the researchers had grown enough cells, which takes about a month, the scientists distributed them in layers over an artificial framework—a process that Atala compares to making a layer cake.
The organ "cake" was then "baked"—or more precisely, incubated—in an oven designed to mimic normal body conditions.
When the tissues had matured, the organ was implanted into the patient. The framework was gradually absorbed by the body, which replaced it with a layer of collagen.
Nerves and blood vessels also grew into place, allowing the new bladder to function normally.
No More Waiting?
Lab-grown bladders have been successfully used in seven young patients, some of whom have been followed now for more than seven years.
Atala refers to this process as regenerative medicine and hopes it may someday be an alternative to long waits for organ donations. One major advantage is that the organ's cells are the body's own.
"[With cells] coming from the same patient, you have no rejection issues," he said.
Rejection is a process in which the body's immune system attacks transplanted tissue as though it were an invading germ. In severe cases, this can cause transplants to fail.
The new procedure also has advantages over techniques using stem cells—unspecialized cells that can grow into any type of cell in the body—because the cells being used already "know" they are bladder cells.
"You don't have to coax these cells to become something else," Atala said.
Atala's team is currently working on growing about 20 other types of tissues and organs, ranging from blood vessels to the kidney, liver, pancreas, and heart.
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