It sounds like something from a carnival side show: “The Mouse With A Human Ear On Its Back.” But it’s real. It’s alive.
That mouse, and others of its kind, are at the leading edge of a science known as tissue engineering, which allows laboratories to grow skin and cartilage for transplant in humans.
The mouse in question, in the laboratory of University of Massachusetts anesthesiologist Dr. Charles Vacanti, is helping researchers refine the technology that someday will allow them to regrow ears and noses for people.
Linda Griffith-Cima, an assistant professor of chemical engineering at Massachusetts Institute of Technology who helped Vacanti grow the first ears on mice, said she did it at the request of a plastic surgeon from Children’s Hospital, Dr. Joe Upton.
“He said, ‘I see these kids who are born without ears. And I have boys who come in whose ears have been chewed off in playground fights, and I can’t sew them back on because they’re so chewed up,”’ Griffith-Cima said.
So she set about creating an ear-like scaffolding of porous, biodegradable polyester fabric. Then she and Vacanti distributed human cartilage cells throughout the form, and implanted the prototype ear on the back of a hairless mouse.
The mouse, specially bred to lack an immune system that might reject the human tissue, nourished the ear as the cartilage cells grew to replace the fiber. The mouse remains healthy and alive after the ear is removed, the researchers said.
“You end up with a piece of cartilage in the shape of an ear,” Griffith-Cima said.
Griffith-Cima’s and Vacanti’s research follows in the footsteps of Vacanti’s older brother, Dr. Joseph Vacanti, a surgeon who does liver transplants at Children’s Hospital, and his close friend Dr. Robert Langer, professor of chemical engineering at MIT.
Twelve years ago, when Joseph Vacanti became head of the hospital’s transplant program, he started searching for ways to grow new liver tissue in sick children instead of waiting for donor organs. Too many of his patients died before they could get transplants.
Now Joseph Vacanti can implant a polymer scaffolding in a diseased rat’s liver and transplant new liver cells. The new liver will grow and function for up to six weeks, he said.
Langer, the Vicantis and other scientists now have managed to grow liver, skin, cartilage, bone, ureters, heart valves, tendons, intestines, blood vessels, and breast tissue on such polymers, Langer said.
Although no such tissue products have yet become available to the public, skin products are in the advanced stages of clinical testing on humans, and heart valves are in the early phase of clinical trials.
Someday, ears and noses will be grown in a test tube using the patient’s own cells on a custom-designed polymer scaffold. Other tissues will be grown from donated cells on polymer devices placed in the patient’s body.
“Some tissues, like cartilage, we can grow all the way to perfect tissue before putting it in,” Joseph Vacanti said. “In other tissues, we only grow it for a short time, then we implant it and the body takes over.”
Dr. Michael Miller, an associate professor of plastic surgery at the University of Texas’ Anderson Cancer Center, said the technology is promising. “In fact, I think the next major advances to come in the field of reconstructive surgery are going to be due to tissue engineering,” Miller said.
The chemical engineers say their job now is to create better polymers. It’s one thing to grow cartilage that holds a shape for cosmetic surgery, another to grow cartilage that could mend a shattered knee, Griffith-Cima said.
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