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Posted on Wednesday, June 20, 2012

Hearing Loss Solutions on the Rise

Two men discuss the latest hearing loss solutions

Normally a person has up to 50,000 hair cells within the inner ear that help conduct sound to the brain, but age, noise, and ototoxicity all contribute to breakage of these hair cells, causing hearing loss that up until a short while ago was considered irreversible. Now, researchers on different fronts have hope that they might disprove this belief. Or rather, in one case, transplant it.

It’s been repeated so many times, it seems indelible—once damaged the delicate hair cells of the inner ear cannot grow back. Startling new research is challenging the long held belief that humans, unlike birds and amphibians, cannot regenerate hair cells. By transplanting stem cells and coaxing them to behave like the hair cells of the inner ear researchers have been able to restore, in varying degrees, hearing in mice. This is only one of the exciting new therapies it is hoped will bring relief to people with hearing loss.

Startling new research challenges long held beliefs on the correctible nature of certain types of hearing loss.

Of the 36 million people with hearing loss, a majority of them have sensorineural hearing loss. For most, this means the hair cells of the inner ear or cochlea have been damaged and can no longer transmit sound to the auditory nerve. Damage to these 50,000 cells happens naturally over time, but can also be the result of trauma either through instantaneous and explosive noises, long-term exposure to loud noise, ototoxcity—the destruction of hair cells through drug therapies, or a genetic abnormality.

Studies into relieving hearing loss using stem cells are now being conducted. One such study using one particular type of stem cell might come as a surprise to some people. According to the California Institute of Regenerative Medicine, “…in 2011 Australian scientists showed - for the first time in mice - that nasal stem cells injected into the inner ear have the potential to reverse or restore hearing during early onset hearing loss.”

Studies that support hair cell regeneration findings along with research are being conducted worldwide and on both coasts of the United States.

A 3.6 million dollar Bertarelli grant given to Harvard researchers will support research to delve into how we hear, gene therapy, and restoration of hair cells. According to the Harvard website getting hair cells to regenerate is only the first part of the problem, "Once scientists learn to regenerate sensory cells in the laboratory, it is still a huge leap to make this happen in a human patient. The right drugs or chemical factors must be delivered to the inner ear, held in the right place, and released slowly over months, all without damaging the delicate sound-sensing structures."

Private research is only one of the ways that hearing health is moving into the future.

The National Institute of Health is also delving into the study of hair cell regeneration to help alleviate hearing loss. According to the NIH website, NIH-supported scientists are:

• Conducting studies to coax immature hair cells generated from stem cells to develop into a more mature state by mimicking the environment that developing hair cells would normally experience.
• Exploring how to encourage newly-generated hair cells to send appropriate signals to the hearing centers in the brain.
• Using their knowledge of hearing genetics to generate new hair cells.
• Gaining a better understanding of the cellular and molecular mechanisms the body uses to protect auditory hair cells against damage, with the hope of developing methods to enhance survival of hair cells following trauma or disease.

Other researchers are focusing on a gene in mice that appears to allow them to regenerate hair cells.

According to BBC Health News, "The discovery that deleting the pRb gene 'switches on' the ear's ability to continue generating hair cells is a significant step towards the goal of restoring hearing."

These and other exciting new neuronal cell therapies are still years away from widespread trials, but limited trails on children between the ages of 6 weeks and 18 months who have sensorineural hearing loss not related to genetics have already begun. This research uses stem cells from the blood of the children’s own umbilical cord. These trials will be completed in 2015.

The foreseeable future offers hope that one day cochlear hair cells can be reconstructed and hearing loss, if not reversed, can at least be restored enough to provide greater sensory information to deaf and hard of hearing individuals who can then receive supportive assistance from hearing aids. Don't wait for the future to take care of your hearing loss. Hearing technologies have advanced greatly in the last few years, providing patients with more control and omnidirectional microphones.

If you'd like to learn more, see your hearing health provider. If you need help finding a hearing health provider click HERE to be connected with the largest network of trusted hearing health professionals in the nation!

Resources

Bauman Neil, PHD. Hearing Loss Help » Human Hair Cell Regeneration Clinical Trial Using Stem Cells Begins October 5, 2011 extreacted on Nov 21, 2011 taken from http://hearinglosshelp.com/weblog/human-hair-cell-regeneration-clinical-...

Keerthana Devarajan 1, Hinrich Staecker 2 and Michael S. Detamore. A Review of Gene Delivery and Stem Cell Based Therapies for Regenerating Inner Ear Hair Cells J. Funct. Biomater. Sept 2011, 2, 249-270; doi:10.3390/jfb2030249

N/A Hearing Loss Help. Hearing loss cures: Regrowing Inner Ear Hair Cells Research June 21, 2010 extracted on Nov 21, 2011 taken from http://www.healthyhearing.com/content/articles/Research/Cures/47482-Hear...

National Institute of Health

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