Exclusive: Whatever Happened to the Mouse with the Ear on Its Back?

Mouse lacking an immune system with an engineered ear on the back. Courtesy of the Laboratory for Tissue Engineering and Organ Fabrication, Massachusetts General Hospital, Boston, MA, USA, Dr. Joseph P. Vacanti, Director.

You may have seen it in a textbook or on TV: a mouse with a human ear on its back. You might have thought that the mouse was genetically engineered, or deformed, or the result of mad scientists "playing God." Twenty years ago, Harvard surgeons Joseph and his brother Charles Vacanti, along with MIT engineer Bob Langer, experimented with techniques to create human body parts in the lab. They implanted the shape of a human ear in the back of a mouse as part of research to better understand how they could help grow body parts for humans. They published their results in 1997. After BBC aired a documentary on tissue engineering, the world saw the bizarre animal: The Vacanti Mouse.

Throughout the public consciousness, the mouse is still an icon of the power of science. On the 20th anniversary of this noteworthy development, Newsweek spoke with Joseph Vacanti to hear what he has to say about the mouse, looking back two decades later.

This interview has been edited for length and clarity.

How do you refer to this mouse? It's alternately called "The Vacanti Mouse" and "the ear mouse."
I just say "the mouse with the ear on its back."

Did you name the mouse?
My brother and I called it "Euriculosaurus," because when you looked at it from the side it kind of looked like a dinosaur.

Why did you put this ear on its back?
In the mid-80's, I was a pediatric surgeon and I was trying to address the organ shortage. I thought, "well why don't we do what humans do when we need something—we design it and we make it."

Then, when I was getting ready to go into the operating room with my friend, a well-known pediatric plastic surgeon, I asked him, "What is the worst problem you have as a reconstructive plastic surgeon in children?" And he said it was the ear: they couldn't construct a good one.

We were making cartilage, and we could make it in specific shapes, so we decided that maybe we could make the specific shape of an ear. We developed a way to fashion a scaffolding in the shape of a human ear.

How did the mouse get the ear on its back?
The whole process involved making a scaffold that has the shape and the size of an ear. The material is man-made, biocompatible and bioabsorbable; it disappears over time. Once you've made the ear-shaped scaffolding, then you seed it with cartilage cells and put it all in an incubator. Then you remove it from the incubator and implant the now-living structure in an animal.

How did the mouse become so famous?
In 1997 the BBC wanted to do a special on this emerging field of tissue engineering. Several of us were contacted to be interviewed and filmed. That included me, Bob Langer at MIT and my brother Chuck.

The true story is, I thought the visual image of having a human ear on the back of a mouse would be too controversial. So I asked my brother, people in my lab, and Bob not to bring up the mouse with the ear on its back so that we wouldn't create controversy.

Bob and I didn't bring up the mouse with BBC. When they went to my brother's lab at the University of Massachusetts, he showed them everything he was doing, and said "I've got this really cool thing to show you," which was the mouse with the ear on its back.

So the BBC trailers for the program have that iconic shot with the interviewer and the mouse. It took on a life of its own over time and the world became intrigued with the image. It became a metaphor for both the good and bad things about the human condition, and the controversy about what it could generate in the future.

What happened to the mouse in the photo?
Many people had children asking those questions, and so what we would say is, we removed the ear, and the mouse lived out a happy, normal life. It was not harmed by our work, so I think that's the answer that I would like to give. In the world of medicine, there's a massive controversy about the use of animals. We're hoping to eliminate the need to use animals because we can now generate human structures and tissues using human cells and we can study them without the use of animals. That's our long-term goal.

It didn't actually live happily ever after, did it?
Of course it did. The happy little mouse. That little mouse was very pleased that he could contribute in some way and make people's lives better.

Mouse lacking an immune system with an engineered ear on the back. Courtesy of the Laboratory for Tissue Engineering and Organ Fabrication, Massachusetts General Hospital, Boston, MA, USA, Dr. Joseph P. Vacanti, Director

What did you think of that advertisement with the mouse on it that warns people about science going too far? The one that says " Who Plays God in the 21st Century? "
I think that the fundamental messages of that ad were the concern about new technologies and how they might impact the human condition in a negative way. Those are appropriate questions. We've got similar questions today.

In point of fact, if you read the detail of that article, they misunderstood what had been done in terms of the genetic engineering. Scientifically it was very inaccurate, and that's one of the problems when the genie comes out of the bottle. Anyone can comment on it. But in that era that image created an immense amount of controversy.

If I lost my ear today, would I be able to get a new one using tissue engineering and regenerative medicine?
Today you still would not be able to get one. But if we had roughly another million dollars in funding we could do the final large animal experiments that could lead to a human trial.

Why do you think this mouse was important?
I don't have the specific numbers, because those numbers are very difficult to get your hands on, but I would estimate that well over a billion people on planet earth need new organs. Most of the people in Asia who have advancing liver disease from infection and cirrhosis are going to die from it. So the notion that we can help all those people with just what we currently do is not correct.

Not only do we need to have these organs available, but also we need to manufacture them like cell phones. That's the dream, that's what originally motivated us with this mouse.