Hair cells are essential to hearing, but once damaged they cannot regrow, causing hearing loss. In fact, damaged hair cells are one of the leading causes of hearing loss in the United States. Now an exciting new discovery by researchers at MIT, Brigham and Women’s Hospital, and Massachusetts Eye and Ear1 may lead to the eventual regrowth of damaged hair cells.
Why are hair cells important?
There are 15,000 hair cells in each ear and they play one of the most important roles in hearing function. They are the part of the ear that detects sound and sends it to the brain. When an individual experiences sustained exposure to loud noises, it can irreparably damage the hair cells and cause hearing loss (referred to as noise-induced hearing loss or NIHL). While other parts of the ear may be repaired with cochlear ear implants and tubes to widen the eustachian tubes, solutions to repair or regrow damaged hair cells have never been available.
The recent body of research conducted at MIT, Brigham and Women’s Hospital and Massachusetts Eye and Ear discovered a combination of drugs that “expands the population of supporting cells in the ear and induces them to become hair cells, offering a potential new way to treat hearing loss.”
Research changes the landscape
The way in which scientists made the discovery is nearly as interesting as the discovery itself. The research began with an effort to regenerate cells in intestinal linings. They found that they could grow large quantities of these cells and then stimulate them to grow into different types of cells. Researchers then realized that hair cells in the ear had some of the same characteristics as the stem cells they were successfully manipulating for the intestine. That’s when they decided to find out if they could use the same clinical approach to grow hair cells. They grew a mouse cochlea (part of the inner ear that captures sound) in a lab and exposed it to molecules that make cells multiply at a rapid rate. Then they added certain drugs to direct the cells to differentiate and grow into hair cells. That is when researchers discovered they could “generate about 60 times more mature hair cells than the technique that had previously worked the best.”
Once they discovered they could actually grow hair cells things became even more exciting. When they added cells to a real mouse cochlea, (as opposed to one grown in a lab), they found that they did not need to add drugs to direct the cells to become hair cells. Once the first set of supporting cells were formed, they found that signals from the cochlea would naturally direct the cells to grow into hair cells. Scientists had just discovered that if they could encourage supporting cells to grow and proliferate, the body would naturally cause a portion of those cells to grow into hair cells in the ear.
Then, researchers turned their attention of the application to human beings. According to researchers, “…drugs could be injected into the middle ear, from which they would diffuse across a membrane into the inner ear (to grow hair cells). This type of injection is commonly performed to treat ear infections.”
This discovery may also lead to improved drug development for health problems in the inner ear. Drug development has been limited because there have never been enough hair cells to use for study. However, if those cells can be grown in a lab and are plentiful for research, then they can support the studies of hair cells to find new treatments for hearing loss.
These revolutionary findings pose fascinating potential for future treatments for hearing loss. We’ll keep you updated on new findings as they occur.