Building a bladder: patients for the first time benefit from lab-grown organs.

The humble bladder is now the world's first bioengineered internal organ to work in people. Several years after surgery, seven young patients who received lab-grown bladders are doing just fine, according to a new report.

"Bladders are a complex organ," and bladder tissue is difficult to replace, says urologist Anthony Atala of Wake Forest University Baptist Medical Center in Winston-Salem, N.C.

A bladder acts as a muscle to expel its contents, while having "natural elasticity" that limits fluid pressures on the bladder walls, Atala notes. Without that elasticity, high pressure could force fluids back into the kidneys, damaging those organs.

Doctors currently use a century-old method to repair bladders, which may be damaged by injury, illness, or congenital defects such as multiple sclerosis or spina bifida. In the traditional procedure, a surgeon rebuilds a bladder by stitching in pieces of intestine, stomach, or other tissues. However, those tissues can cause complications. For example, using intestinal tissues, which absorb nutrients rather than just hold fluids, can alter the body's metabolism and lead to kidney stones and osteoporosis.

Searching for an alternative to that surgery, Atala designed a biodegradable scaffolding that his team covers with a patient's own cells. The team identified young people, ages 4 to 19, who had severe bladder malfunction from spina bifida. Because the spine doesn't close completely in people with this condition, nerve damage disrupts the flow of signals between brain and bladder, and the organ becomes flaccid or spastic and begins to leak.

In a surgical procedure, the researchers removed most of the damaged bladder tissue from each patient and collected healthy bladder-wall and muscle cells. The team grew the cells in the lab and then covered the outside of the bladder-shaped scaffold with muscle cells and the inside with bladder-wall cells.

After incubating the construction for 4 days, the researchers surgically attached the faux bladders to what was left of the original organs. In four of the patients, the team also wrapped the entire implant with blood vessel-rich abdominal tissue to ensure adequate blood supply.

After monitoring the patients for 2 to 5 years, the researchers found that all the engineered bladders functioned as well as traditionally repaired bladders, and, furthermore, lacked any of the negative side effects of the standard procedures, they report in an upcoming Lancet.

"We're pleased with the results, but we have to go slowly," Atala says. The next step, he says, will be a series of long-term clinical trials with many more patients.

The success of the bladders is "a huge milestone," representing the first time a working organ has been created using tissue engineering, says urologist Steve Chung of St. Margaret's Hospital in Spring Valley, Ill. Even better, Chung adds, the new procedure is less invasive than traditional bladder repair because it leaves other organs intact.

Depending on the results of the next series of clinical trials, it may be 5 to 10 years before implanting tissue-engineered bladders becomes commonplace, Chung says.

In the meantime, this study may motivate scientists attempting to engineer other organs. Chung says that the new findings show that "it definitely can be done."