Girl receives bioengineered windpipe
April 30, 2013 10:20 AM

PEORIA, Ill. — Using plastic fibers and human cells, doctors have built and implanted a windpipe in a 2 1/2-year-old girl — the youngest person ever to receive a bioengineered organ.

The surgery, which took place on April 9 here at Children’s Hospital of Illinois and formally announced today, is only the sixth of its kind and the first to be performed in the United States. It was approved by the Food and Drug Administration under rules that allow experimental procedures when otherwise the patient has little hope of survival.

Dr. Paolo Macchiarini, a specialist in the field of regenerative medicine who developed the windpipe and led the complex nine-hour operation, said the treatment of the Korean-Canadian toddler, Hannah Warren, made him realize that this approach to building organs may work best with children, by harnessing their natural ability to grow and heal.

“Hannah’s transplant has completely changed my thinking about regenerative medicine,” said Macchiarini, a surgeon at the Karolinska Institute in Stockholm. He said he would like to proceed with a clinical trial in the United States, something that critics of his approach have called for.

Hannah was born without a windpipe, or trachea — an extremely rare condition that is eventually fatal in 99 percent of cases — and had lived since birth in a newborn intensive care unit in a Korean hospital, breathing through a tube inserted in her mouth. Because of other developmental problems, she cannot eat normally and cannot speak.

Nearly three weeks after the surgery, the girl is acting playfully with her doctors and nurses, at one point smiling and waving goodbye to a group of visitors. Dr. Mark Holterman, a pediatric surgeon at the hospital, said that Hannah was breathing largely on her own, although through a hole in her neck, not through her mouth yet. “She’s doing well,” he said. “She had some complications from the surgery, but the trachea itself is doing great.”

Macchiarini described a look of befuddlement on the child’s face when she realized that the mouth tube was gone and she could put her lips together for the first time. “It was beautiful,” he said.

The goal of regenerative medicine, or tissue engineering, is to create or regrow tissues and organs to ease transplant shortages or treat conditions that do not have an effective cure. After years of scant progress, tissue engineers have begun to make advances as they have gained a better understanding of the role that stem cells — basic cells that can become tissue-specific ones — play in signaling the body to grow and repair itself.

Still, only a few relatively simple organs have been made and implanted, and the science-fiction-inspired goal of ready-made hearts or other complex organs remains far off. Until now, the youngest recipient of a tissue-engineered organ was a 4-year-old spina bifida patient who received a bladder.

Macchiarini has performed the five other windpipe implants similar to Hannah’s. One patient, an American man who was operated on in Stockholm, has died. An Eritrean man has lived the longest so far, surviving for about 2ᄑ years since the surgery.

To make Hannah’s windpipe, Macchiarini’s team made a half-inch diameter tube out of plastic fibers, bathed it in a solution containing stem cells taken from the child’s bone marrow and incubated it in a shoebox-size device called a bioreactor.

Doctors are not sure exactly what happens after implantation, but they think that the stem cells signal the body to send other cells to the windpipe, which then sort out so the appropriate tissues grow on the inside and outside of the tube. Because the windpipe uses only the child’s own cells, there is no need for drugs to suppress the patient’s immune system to avoid rejection of the implant.

Dr. David Warburton, director of the regenerative medicine program at the Saban Research Institute in Los Angeles, who was not involved in the windpipe work, said that “guarded optimism with a major dash of skepticism is the watchword” for such experimental approaches. “The challenges will be making a wind pipe that functions better than a temporary fix,” he said.

While one-of-a-kind operations like this are ethically justified given the desire to save the life of the patient, some experts say that regenerative medicine would be better served by clinical trials that could, through analysis of more data, provide a better understanding of how effective these kinds of implants are and how they function.

“No doubt large trials are critical,” said Martin Birchall, a professor at University College London who used to work with Macchiarini but has switched to using donor tracheas from cadavers, which he strips of their original cells.

Macchiarini said he was now ready to go ahead with a clinical trial in the United States, and the Peoria hospital said it would like to arrange one if it could gain FDA approval.

The toddler faces a long rehabilitation process as she breathes normally for the first time. Doctors hope that with additional operations she will be able to eat through her mouth and speak.

As the girl grows, she will also need a bigger windpipe. Macchiarini estimated that she might need a new one in four years, but said his team tried to delay a replacement for as long as possible by oversizing the implant and including some biodegradable plastic, which may allow it to stretch.

The girl’s parents, Darryl and Young-Mi Warren, said that shortly after Hannah was born they were told there were some treatments, but that the odds of her living past age 6 were very slim.

Darryl Warren did some Internet research two years ago and discovered Macchiarini’s work. He shared it with Holterman, who happened to learn about Hannah while on a business trip to South Korea. Holterman and the hospital’s chief surgeon, Dr. Richard H. Pearl, persuaded Macchiarini to come to Peoria to do the procedure.

Warren said he was amazed that it all worked out. “It actually is unbelievable,” he said. “The fact that they’re doing this, at this time, when Hannah needed it the most.”

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