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A step closer to human voice transplants: Working vocal cords that produce sound are grown in laboratory for the first time

Scientists grew multi-layered cells on a scaffold to produce elastic tissue
Tissue was able to vibrate hundreds of times per second to create sound
Gives hope to people whose voices have been lost due to cancer or injury
But scientists say the first vocal cord implants are still some years away

By Ellie Zolfagharifard For Dailymail.com

Published: 15:40 EST, 18 November 2015 | Updated: 00:31 EST, 19 November 2015

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Functional vocal cords with a 'voice' have been grown in the laboratory for the first time.

The research offers hope to people whose voices have been lost due to cancer or injury, although scientists say the first vocal cord implants are still some years away.

Vocal cords are made up of two flexible folds of muscle lined with a delicate membrane, or mucosa, that vibrate hundreds of times per second to create sound.

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Researchers have grown human vocal cords in the laboratory that appear capable of producing sound — in hopes of one day helping people with voice-robbing diseases or injuries

HOW WAS IT DONE?

The team started with some rare donations of vocal cords from four patients who had had their larynx removed.

The researchers culled two types of cells that made up most of the tissue, and grew a large supply of them.

Then they arranged the cells on 3-D collagen scaffolding, and the two cell types began mixing and growing.

In 14 days, the result was tissue with the shape and elasticity of human vocal cords, and with similar chemical properties.

They took a larynx that had been removed from a large dog after its death and attached it to a plastic "windpipe" that blew in warm air to simulate breath.

The sound made was similar to that produced by the remaining natural dog vocal cords.

Scientists in the US have manged to grow multi-layered cells on a 3D scaffold to produce strong, elastic tissue similar to that of natural vocal cords.

Tests on the lab-grown tissue transplanted into voice boxes removed from deceased dogs proved that it could produce the same kind of sound generated by its 'real' counterpart.

Lead researcher Dr Nathan Welham, from the University of Wisconsin-Madison, said: 'Voice is a pretty amazing thing, yet we don't give it much thought until something goes wrong.

'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.'

The tissue was grown from healthy connective and surface lining cells taken from the vocal cords of four patients.

These patients voice boxes had been removed for non-cancer medical reasons, and one deceased human donor.

In two weeks, the two kinds of cells self-assembled into layers that closely resembled the structure of natural vocal cords, the researchers reported in the journal Science Translational Medicine.

The tests involved implanting the artificially grown cord tissue into one side of cadaver dog voice boxes attached to artificial windpipe.

When warm, humidified air was blown over the tissue it vibrated.

Analysis showed that the sound made the same acoustic characteristics as that produced by the remaining natural dog vocal cords.

Millions of people suffer from voice impairments, usually the temporary kind such as laryngitis from a virus or a singer who overdoes the performing. But sometimes the vocal cords become too scarred and stiff to work properly, or even develop cancer and must be removed. Pictured is a healthy larynx and vocal folds

More work revealed that the tissue was not rejected when transplanted into mice engineered to have human immune systems.

'It seems like the engineered vocal cord tissue may be like cornea tissue in that it is immunoprivileged, meaning that it doesn't set off a host immune reaction,' said Dr Welham.

The lab-grown tissue had a fibrous structure that was less complex than that of adult vocal cords.

But the researchers say this is not surprising since human vocal cords continue to develop for at least 13 years after birth.

Because cancer-free vocal cord tissue is rare, medical applications will require cell-banking or the use of stem cells, say the scientists.

Stem cells could be primed to differentiate into vocal cord cells by exposing them to vibration and stretching forces in a 'laryngeal bioreactor', according to the team.