Listen Up: A stem cell-based solution for hearing loss

Can you hear me now?

If you’re old enough, you probably recognize this phrase from an early 2000’s Verizon Wireless commercial where the company claims to be “the nation’s largest, most reliable wireless network”. However, no matter how hard wireless companies like Verizon try, there are still dead zones where cell phone reception is zilch and you can’t in fact hear me now.

This cell phone coverage is a good analogy for the 5% of the world population, or 360 million people, that suffer from hearing loss. There are many causes for hearing loss including genetic predispositions, birth defects, constant exposure to loud noises, infectious diseases, certain drugs, ear infections and aging. There is no cure that fully restores hearing, but patients can benefit from hearing aids, cochlear implants and other hearing devices.

But listen to this. A new stem cell-based technique developed by the Massachusetts Eye and Ear Infirmary may restore hearing in patients with hearing loss. The team discovered that stem cells in the inner ear can be manipulated in a culture dish to expand and develop into large quantities of cochlear hair cells, which make it possible for your brain to detect sound. Their work was published this week in the journal Cell Reports.

In a previous study, the Boston team found that stem cells in the inner ears of mice could be directly converted into cochlear hair cells, but they weren’t able to generate enough hair cells to fully restore hearing in these mice. Building on this work, the team isolated these stem cells, which express a protein called LGR5, and developed an augmentation technique consisting of drugs and growth factors to expand these stem cells and then specialize them into larger populations of hair cells.

A new technique converts stems cells into hair cells. Image credit Will McLean, Albert Edge, Massachusetts Eye and Ear

A new technique converts stems cells into hair cells. Image credit Will McLean, Albert Edge, Massachusetts Eye and Ear.

From a single mouse cochlea, they made more than 11,500 hair cells using their new augmentation method, which is more than 50 times the number of hair cells they made using a more basic method.

In a news release, senior author on the study, Dr. Albert Edge, explained the importance of their findings for patients with hearing loss:

Albert Edge

Albert Edge

“We have shown that we can expand Lgr5-expressing cells to differentiate into hair cells in high yield, which opens the door for drug discovery for hearing. We hope that by stimulating these cells to divide and differentiate that we will improve on our previous results in restoring hearing. With this knowledge, we can make better shots on goal, which is critical for repairing damaged ears. We have identified the cells of interest and have identified the pathways and drugs to target to improve on previous results. These clues may lead us closer to finding drugs that could treat hearing loss in adults.”

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