Vocal cord tissue grown in lab was able to generate sound once it was transplanted into voice boxes from animals, the researchers found in a new study.
Researchers say that tissue engineering of vocal cords may one day help patients who have voice disorders that prevent them from speaking, to restore their voice. That being said, a lot more research is needed before this technology can be applied to humans, according to the researchers.
Nathan Welham, author of the study and a speech-language pathologist at the University of Wisconsin-Madison (UW) said that because of regulatory requirements, the clinical trial in humans shall not take place any time soon.
The vocal folds, commonly referred to as vocal cords, are two flexible infoldings of mucous membrane that vibrate, modulating the flow of air that moves over the cords.
People tend to lose their voice when the mucosa is injured, because it scars and stiffens. There are treatments than can partially fix the injury, such as collagen injections. However, researchers say that those treatments only work as a short-term measure. Welham also stated that the treatments do not fix the sound output.
The new research is meant to completely replace a potential affected tissue, in situations where other existing treatments are practically useless, Welham said.
In the study – published November 19 the journal Science Translational Medicine – the researchers took vocal cord tissue from four patients who had their larynx removed for other unrelated medical reasons, and from a human cadaver. They then purified and grew cells from the tissue in a three-dimensional (3D) culture.
Two weeks after, the cells grew and formed a tissue that looked a lot like vocal cord tissue. Further tests proved that both the lab-grown tissue and real vocal cord tissue had similar elasticity and viscosity, according to Welham.
To see whether the lab vocal cords could produce sound, they transplanted the tissue to dogs’ larynges, which anatomically speaking, resemble the human larynges. The larynges were then attached to artificial windpipes.
When the researchers blew air through the artificial windpipes, they saw that the tissue vibrated and produced sound. Welham said that the sound was humanlike.
The engineered vocal cords were also transplanted to lab mice, and the tissue was well tolerated by the immune system of the mice, which had a normal lifespan after the researchers performed the transplant.
Because vocal cord tissue takes time to mature, the engineered vocal cords had a fibre structure that was less complex than the fibre structure of the real tissue, the researchers explained. Human cord tissue completes its development when a person is about 13 years of age.
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