WASHINGTON, Nov. 19 — US researchers said Wednesday they have succeeded in growing functional vocal cord tissue in the laboratory, a major step toward restoring a voice to people who have lost their vocal cords to cancer surgery or other injuries.
Many voice disorders are due to damage to the vocal cord mucosae, the specialized tissues that vibrate as air moves over them, giving rise to voice, according to the study, published by the US journal Science Translational Medicine.
While injections of collagen and other materials can help some in the short term, not much can be done for people who have had larger areas of their vocal cords damaged or removed, it noted.
"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," said Nathan Welham, an associate professor of surgery at the University of Wisconsin-Madison.
"It's an exquisite system and a hard thing to replicate," Welham said.
Welham and colleagues began with vocal cord tissue from a cadaver and four patients who had their larynxes removed but did not have cancer.
They isolated, purified and grew the cells from the mucosa, then applied them to a 3D collagen scaffold, similar to a system used to grow artificial skin in the laboratory.
In about two weeks, the cells grew together to form a tissue with a pliable but strong connective tissue beneath, and layered epithelial cells on top.
Welham said the lab-grown tissue "felt like vocal cord tissue," and materials testing showed that it had qualities of viscosity and elasticity similar to normal tissue.
When transplanted onto one side of larynges that had been removed from cadaver dogs, the bioengineered tissue vibrated in response to air flow and generated sound much like native tissue.
In mice engineered to have human immune systems, the tissue was well-tolerated and persisted for up to three months.
In one way, the tissue was not as good as the real thing: Its fiber structure was less complex than adult vocal cords, but the authors said this was not surprising because human vocal cords continue to develop for at least 13 years after birth.
Clinical applications are still years away, but Welham said this proof-of-principle study is a "robust benchmark" along the route to replacement vocal cord tissue.(PNA/Xinhua)