A new genetic study carried out by researchers at the Johns Hopkins University School of Medicine, Maryland, has identified a pair of proteins that precisely control when sound-detecting cells, known as hair cells, are born in the mammalian inner ear. 

 

The study published in the latest issue of the eLife journal, reported that the findings may hold a key to future therapies to restore hearing in people with irreversible deafness.

 

Hearing is based on two types of sound-detecting cells, inner and outer hair cells, which convey sound information to the brain. Unlike their counterparts in other mammals and birds, human hair cells cannot regenerate. So, once hair cells are damaged, hearing loss is likely permanent. Problems with hair cells are responsible for 90 percent of hearing loss. 

 

The first step in hair cell birth starts during the fetal development. Here, the immature cells found in the outer cochlea transform into fully mature hair cells. Then, the cells' production moves from the outer cochlea to the inner ear.

 

Although scientists had much information on hair cells growth, the molecular cues that control the process remained unclear. However, in this study involving mice, the researchers managed to determine two of the proteins responsible for this growth: Activin A and follistatin. 

 

To figure out how exactly Activin A and follistatin coordinate hair cell development, the researchers studied the effects of each of the two proteins individually. 

 

In a report published on the university's website on August 9, Angelika Doetzlhofer, associate professor of neuroscience at the Johns Hopkins University School of Medicine, said that knowing more about how they develop will help us figure out ways to replace hair cells that are damaged.

 

"Further studies on animals are needed before stepping into clinical trials on humans. By providing a solution for an incurable problem, this discovery would lead to a revolutionary treatment."