For the first time, researchers have successfully grown functional vocal cord tissue in the laboratory, a breakthrough that can help restore the voice of people whose vocal cords have been injured or damaged.

An estimated 20 million Americans suffer from voice problems, many of which involve damage to the vocal cords. Through bioengineering, researchers from the University of Wisconsin-Madison were able to construct vocal cord tissue that can transmit sound when transplanted into a voice box.

"Voice is a pretty amazing thing, yet we don't give it much thought until something goes wrong," lead study author Nathan Welham, speech-language pathologist, said in a press release. "Our vocal cords are made up of special tissue that has to be flexible enough to vibrate, yet strong enough to bang together hundreds of times per second. It's an exquisite system and a hard thing to replicate."

Working with experts from other disciplines, Welham took vocal cord tissue from a cadaver and from four patients and began growing cells from the mucosa. They applied the cells to a 3-D collagen scaffold, where the cells formed a tissue that "felt like vocal cord tissue." It had a basement membrane that blocks irritants along the airway and produced many proteins similar to that of a natural vocal cord.

To test the lab-grown tissue, the researchers transplanted it to one side of dogs' larynges, which were attached to artificial windpipes. When air was blown through them, the mucosa produced sound similar to that produced by the mucosa on the other side and vibrated in a like manner.  

The researchers also transplanted the tissue in living mice and found that the mice's immune system did not reject it. Welham said the lab-grown vocal cord tissue, like cornea tissue, could be "immunoprivileged," meaning it does not cause the host's immune system to react.

Although more testings are needed before clinical application can be done, Welham called their study a "robust benchmark" in the development of vocal cord tissue replacement.

The study was published in the online Nov. 18 issue of the journal Science Translational Medicine.