For the first time, scientists havesuccessfully grown vocal cords in the lab, with tests showing theengineered tissue to be functional, with the ability to transmitsound. While the research is just the first step on a long pathtowards clinical use, the results are very promising, providing asolid basis for future study.
While vocal cord issues are verycommon, with around 20 million people in the US suffering from someform of voice impairment, it's a very tricky area of study. Vocalcord tissue is extremely specialized, being flexible enough tovibrate, but strong enough not to be damaged by thousands of hours ofuse, the cords colliding with one another hundreds of times every second. Asengineered replacement tissue would have to exhibit these sameproperties, the task of creating it in the lab is a difficult one.
For the new study, conducted at theUniversity of Wisconsin, the researchers worked with vocal cordtissue taken from four patients who had previously had their laryngesremoved, as well as samples from a cadaver. The tissue cells weregrown from the mucosa, before being transferred to a 3D collagenscaffold.
After two weeks of growth on thescaffold, the team tested the qualities of the resulting tissue,finding that a pliable lower layer had formed underneath an uppercovering of layered epithelial cells. Further testing revealed thatmany of the same proteins found in natural vocal cords were present,and a membrane was found to be forming that helps create a barrieragainst irritants and pathogens in the airway. Overall, the resultswere similar to what you'd expect from naturally-grown tissue.
The next step was to see if thebioengineered tissue was actually able to transmit sound. To do so,the team transplanted it onto larynges removed from canine cadavers,passing air through attached artificial wind pipes. Once again, theresults were promising, with sound being produced and high-speedimaging revealing that the engineered tissue vibrates in a similarway to its natural counterpart.
Continuing their testing, thescientists then grafted the tissue onto laboratory mice engineered tohave human immune systems. Once again, the results were positive,with the tissue growing normally and not being rejected.
However, despite the success of thestudy, perhaps unsurprisingly, the engineered vocal cord tissue isn't quite as good as thereal thing. Most notably, its fiber structure is less complex than innatural tissue in adults, which develop over much longer periods oftime, for at least 13 years after birth.
According to the researchers, years offurther study will be required before clinical applications couldbe considered, particularly to assess the safety and long-termfunction of the tissue. That said, given how rare a commoditycancer-free vocal cord tissue is, the research provides a very strongbasis for future study.
The results of the study were recently publishedin the journal Science Translational Medicine.
Source: University of Wisconsin
