A new breakthrough in using stem cells to regenerate delicate parts of the inner ear is good news for millions of Americans suffering from hearing loss.
Although practical applications may be many years away, the study authors say they've found a way to create critical pieces of the ear in a three-dimensional aggregate, which may lead to answers about why people lose their hearing and perhaps even ways to restore it.
The research, published just days ago in the journal Nature, explains how the scientists used embryonic stem cells from mice to develop sensory epithelia, which consist of hair cells, supporting cells and neurons.
These fragile hair cells allow a person to detect sound waves and react to head movements and gravity. The study's lead authors, Eri Hashino and Karl Koehler of the Stark Neurosciences Research Institute at the Indiana University School of Medicine, told Healthline they created the perfect “cocktail” of chemicals and proteins needed to make these hard-to-grow tissues.
Essentially, the researchers found a way to grow these important body parts in a way that mimicked the body's natural environment during the early stages of fetal development.
“Specifically, we figured out how to do this more naturally so the cells as they are developing organize in the same structure that we find in the inner ear,” Koehler said. “We were able to develop miniature inner ear organs very similar to the inner ear organs important to balance and gravity.”
Using an aggregate suspension, the researchers prodded the stem cells to differentiate into hair cells, but they were still astonished to find complete, complex hair cells growing in their solution. Hashino said that once hair cells are destroyed, they are gone forever and will not naturally regenerate. So their newfound ability to grow these cells in the lab is an exciting breakthrough, she explained.
“You can hear because you have hair cells," Hashino said. "The most prominent cause of hearing loss is sensory.” These critical pieces of the inner ear are often destroyed during surgeries, Koehler said.
These hair cells form important connections to neurons, allowing them to convert the sound waves we hear into information our brains can process. “Now we can study the hair cell-neuron connection, which is very important. It shows us how the ear forms and how things go wrong,” Koehler said.
According to National Institutes of Health (NIH), approximately 17 percent of adult Americans experience hearing loss. It is very common among the elderly, as aging, noise, disease, and genetics can all contribute to the condition.
Hearing loss contributes to other health conditions as well. Many elderly Americans have a difficult time understanding their doctor's instructions because of hearing difficulties, according to the NIH.