Scientists, including one of Indian-origin, have successfully grown a functional human vocal cord tissue in a lab, an advance that could lead to treatments for those who have lost their voice to cancer or other diseases.
Although such implants likely would not be ready for human testing for years, creating the tissue, known as a vocal fold, and showing it was functional in dog larynges and was not rejected by a mouse model of the human immune system are significant steps, researchers said.
"We never imagined that we would see the impressive level of function that we did - and that this engineered tissue, created with actual human vocal fold cells, would have such strong potential as a therapy," said Nathan Welham, a University of Wisconsin-Madison speech language pathologist and leader of the research team.
About 20 million Americans suffer from voice damage at any given time. Many of the problems go away on their own, but injury, cancer, nerve damage and other conditions can cause permanent harm, Welham said.
The scientists faced a formidable task in trying to engineer a replacement tissue for the vocal cord. Such tissue must be soft and pliable enough to create waves of vibration but strong enough to withstand rapid acceleration and stress.
The researchers, including Sundaram Gunasekaran, a professor at UW-Madison, took healthy vocal cord tissue from a person who had just died and four patients who had their larynges removed for reasons other than cancer.
They isolated and purified two types of cells - fibroblasts and epithelial cells - and grew them in a dish on a 3D scaffold.
In about two weeks, the cells formed tissue that produced many of the same proteins as normal vocal cord cells.
"They're effectively talking to each other and producing the structural proteins that make this special tissue capable of vibration," said Brian Frey, a UW-Madison associate scientist in chemistry.
To see if the tissue could make sound, the researchers transplanted it onto larynges removed from dead dogs and attached to artificial windpipes.
When humidified air blew through the model, the tissue produced sound like the musical instrument kazoo - similar to what the human voice sounds like before it is modulated by the throat, mouth and nose, Welham said.
The engineered tissue performed better than tissue taken from inside the cheek, the researchers said.
To see if the human body would reject such an implant, the scientists placed it in two kinds of mice - one engineered to have the larynx cell donor's immune system and one with other human immune systems.
The engineered tissue grew in the mice and was not rejected, though the it was a relatively short-term test.
The study was published in the journal Science Translational Medicine.
