Is That an Ear in Your Pocket?

A Unique Collaboration Revolutionizes Tissue Engineering

February 18, 2013

Most otolaryngology residents learn how to repair damaged ears and noses in the operating room. David Zopf, MD, also is learning how to grow new ones in the laboratory.

Zopf is an otolaryngology-head and neck surgery resident in the University of Michigan Health System. He spent six months of his residency doing research in a tissue engineering lab run by Scott Hollister, a professor of biomedical engineering and associate professor of surgery. Growing artificial ears and noses in a bioreactor is not part of a resident's normal training, but for Zopf, whose undergraduate work focused on biomedical engineering, it's a perfect match. "I'm very fortunate that our department provides this time for research," he says.

He's so enthusiastic about his work that he carries ears and noses around in the pocket of his lab coat to show visitors.

The ear Zopf carries is actually a scaffold on which cells and tissue are grown. Made from a biodegradable polymer that is resorbed by the body, it contains many small pores. The scaffolds are made in all shapes and sizes and line the shelves and counters of Hollister's lab. They are built layer-by-layer on a computer-controlled, 3-D printer in the lab.

After the scaffolds are fabricated and sterilized, Zopf incubates them in a bioreactor for several weeks while they soak in a cocktail of cells, growth factors, and collagen. During their time in the bioreactor, cartilage grows around and through the scaffold holes until the ear is ready to be implanted under the skin of a rat or pig. If all goes well, the scaffold will be resorbed by the animal's body, leaving healthy cartilage that looks just like a normal ear.

Zopf hopes that tissue-engineered ears and noses will one day be ready for use in human patients—children with congenital defects who are born without ears, for example, or adults whose noses or ears were destroyed by fire, traumatic injuries, or cancer.

"The current gold standard for ear reconstruction is to take rib cartilage from the patient and carve it into the shape of an ear," says Zopf. "The problem is this involves multiple operations, which increases risk, especially in a small child. It also requires carving this complex geometric shape from rib cartilage and there are just a handful of surgeons who have mastered that."

The ability to grow cartilage in a bioreactor is a big step forward in the field of tissue engineering, Hollister says. Researchers have figured out how to build polymer scaffolds that can be implanted in the body, but are still working on how to stimulate and control the growth of specific types of cells and tissue on the scaffold. No one has succeeded yet at growing a blood vessel, for example, but one of Hollister's graduate students is working on the problem.

"It's been great to have Dave here for six months," says Hollister. "We got his clinical experience and insight into clinical problems; he learned about cell cultures and rapid prototyping. It's a win-win for everyone."

Educating up-and-coming physicians like Zopf and the next generation of biomedical engineers is a major goal of the new Department of Biomedical Engineering. The department offers courses for undergraduates and graduate students that give them experience in a hospital environment and opportunities to work with physicians while they design, build, and test new types of medical devices as part of their coursework.

Sally Pobojewski

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