Understanding a Pressure Relief Valve in the Inner Ear

By Ian Swinburne, Ph.D.

The inner ear senses sound to order to hear as well as sensing head movements in order to balance. Sounds or body movements create waves in the fluid within the ear. Specialized cells called hair cells, because of their thin hairlike projections, are submerged within this fluid. Hair cells bend in response to these waves, with channels that open in response to the bending. The makeup of the ear’s internal fluid is critical because as it flows through these channels its contents encode the information that becomes a biochemical and then a neural signal. The endolymphatic sac of the inner ear is thought to have important roles in stabilizing this fluid that is necessary for sensing sound and balance.

This study helps unravel how a valve in the inner ear's endolymphatic sac acts to relieve fluid pressure, one key to understanding disorders affected by pressure abnormalities such as Ménière’s disease.

While imaging transparent zebrafish, my team and I found a pressure-sensitive relief valve in the endolymphatic sac that periodically opens to release excess fluid, thus preventing the tearing of tissue. In our paper published in the journal eLife June 19, 2018, we describe how the relief valve is composed of physical barriers that open in response to pressure. The barriers consist of cells adhering to one another and thin overlapping cell projections that are continuously remodeling and periodically separating in response to pressure.

The unexpected discovery of a physical relief valve in the ear emphasizes the need for further study into how organs control fluid pressure, volume, flow, and ion homeostasis (balance of ions) in development and disease. It suggests a new mechanism underlying several hearing and balance disorders characterized by pressure abnormalities, including Ménière’s disease.

Here is a time-lapse video of the endolymphatic sac, with the sac labeled “pressure relief valve” at 0:40.

2017 Ménière’s Disease Grants scientist Ian A. Swinburne, Ph.D., is conducting research at Harvard Medical School. He was also a 2013 Emerging Research Grants recipient.

In Memoriam: David J. Lim, M.D.

By Nadine Dehgan

Credit: UCLA Head and Neck Surgery

We recognize with profound sadness the recent passing of David J. Lim, M.D., who was pivotal to the establishment of Hearing Health Foundation (HHF) and remained committed to our research throughout his life.

As a member of our Council of Scientific Trustees (CST)—the governing body of HHF’s Emerging Research Grants (ERG) program—and as a Centurion donor, Lim worked tirelessly to ensure the most promising auditory and vestibular science was championed.

Prior to his appointment to the CST, “Lim contributed to our understanding of the mechanics of hearing through his excellent scanning electron micrographs of the inner ear,” says Elizabeth Keithley, Ph.D, Chair of the Board of HHF. Lim pursued this critical work in 1970 through his first of many ERG grants.

“Lim was also one of the founding members of the Association for Research in Otolaryngology (ARO) and served as the historian of this esteemed scientific organization,” says Judy Dubno, Ph.D., of HHF’s Board of Directors. “Along with HHF, he cared deeply about ARO and will be missed by many.”

Most recently, Lim was a surgeon-scientist and a director of the UCLA Pathogenesis of Ear Diseases Laboratory, where he was considered an authority on temporal bone histopathology, morphology and cell biology of the ear, and the innate immunity of the middle and inner ear.

We, the HHF community, are grateful to have known and to have benefited from Lim’s wisdom, good humor, and kind spirit. HHF will honor his legacy by continuing our mission, knowing we are indebted to his leadership and dedication to advancements in hearing health.

ReSound HearSay: Be The Voice of Hearing

By Tom Woods

"A journey of a thousand miles begins with a single step.” For many individuals who know—or suspect—they have a hearing loss, the first step in their journey to better hearing can prove difficult.

It took more than two years for Francine Murphy of Peoria, Arizona to take action. She says, “I was in denial and I was concerned that it would not help, especially if the sound quality was poor. Start with acknowledging that there may be an issue and start with your family doctor. The best resource I found was my audiologist.”

ReSound hearing aid user Francine Murphy.

Francine is clearly not alone. For many, the delay is due to uncertainty, apprehension, and lots of questions. In the U.S. alone, more than 25 million people who could benefit from hearing aids have yet to take that first step. 

We believe that hearing is fundamental to life. When it starts to decline, it’s imperative that everyone understands, and has access to, the best hearing technology.

That’s why we created ReSound HearSay, an online resource that gives people who are successfully managing their hearing loss an opportunity to lend their voice to educate and inspire others to seek care.

We think that peer-to-peer information sharing is critical in this learning process.

“Get your hearing tested now,” urges John Chynoweth from Orlando, Florida. “Determine exactly what your hearing is like now (get a baseline). Work with a hearing specialist to determine the environments where you struggle to hear. Try different types of hearing aids to find the right ones for you.”

I’m reaching out to readers of this blog to share their hearing journey. Just like Francine and John, you can help those who are just starting to realize hearing loss or considering a hearing aid, and may be hesitant or unsure where to start.

Through posts, you’ll encourage others into action by addressing common concerns and questions, giving them practical advice to help navigate the process, from diagnosis to hearing aids. And you’ll help them understand the important role of the hearing care professional.

Be the “Voice of Hearing” and help others on the path to better hearing. Please take time today to visit ReSoundHearSay.com to share your insights and experience.

Tom Woods is President, ReSound North America.

Advancing Accessibility in the Audiology Profession

By Lauren McGrath

Born with a profound sensorineural hearing loss, Jessica Hoffman, Au.D., CCC-A, never believed she could become an audiologist. In fact, she didn’t consider the profession until her final year as a biopsychology undergraduate at Tufts University.

By then, Dr. Hoffman was the recipient of successful hearing loss intervention and treatment for two decades. Diagnosed at 13 months, she was fitted with hearing aids by age two, practiced speech and hearing at the New York League for the Hard of Hearing (today the Center for Hearing and Communication) until five, and learned American Sign Language (ASL) at 10. She pursued a mainstream education since preschool with daily visits from a teacher of the deaf. Dr. Hoffman received cochlear implants at ages 14 and 24, respectively and, in college and graduate school, enjoyed a variety of classroom accommodations including ASL interpreters, CART, C-Print, notetakers, and FM systems.

After Tufts, Dr. Hoffman worked as a lab technician at Massachusetts Eye and Ear as her interests in studying hearing began to grow. But she doubted her abilities to perform key tasks in audiology, like speech perception tests and listening checks with patients. After speaking with others in the field with hearing loss, she became less apprehensive. Engaging with mentors like Samuel Atcherson, Ph.D., and Suzanne Yoder, Au.D., who have greatly advanced opportunities for individuals with hearing loss in audiology, further cemented Dr. Hoffman’s self-confidence. In 2010, she completed her Doctor of Audiology from Northwestern University.

Today, Dr. Hoffman is happy to work with both children and adults at the ENT Faculty Practice/Westchester Cochlear Implant Program in Hawthorne, NY. She takes pride in helping her patients realize that they are not alone with hearing loss and that technology, like her own cochlear implants, can provide immense benefits to communication. Dr. Hoffman is motivated to help her patients understand that hearing loss does not define who one is and can be viewed as a gain rather than as a limitation.

Dr. Hoffman’s career is not exempt from challenges. Fortunate to receive accommodations as a child and young adult, she is disappointed by the tools that are missing in a field that serves those with hearing loss. Though she credits her own workplace as being very understanding, Dr. Hoffman points out the difficulties she experiences during team meetings and conversations with patients who speak English as a second language. She is grateful to have considerate colleagues who will repeat themselves as needed or offer to facilitate verbal communication with non-native English-speaking patients.

At audiology conferences, however, necessities like CART, FM systems, and/or interpreters are often lacking for professionals with hearing loss. Dr. Hoffman and others with hearing loss in the audiology field have petitioned to encourage accessibility at such events. She has had to take on the responsibility of finding CART vendors for conference organizers to ensure her own optimal listening experience. She reports being brushed off by meeting leaders and a sense of doubt in her abilities and those of her colleagues with hearing loss.

Dr. Hoffman also wishes to see greater accessibility in audiology offices nationwide, including recorded speech perception materials, captioning for videos or TV shows in the waiting room, and email exchanges with patients, rather than phone calls. She’d like all audiology staff to be well-versed in communicating with people with hearing loss and to have a strong understanding of the Americans with Disabilities Act (ADA) as it pertains to hearing loss. Dr. Hoffman also thinks facilities would benefit from hiring ASL interpreters or Cued Speech transliterators as needed. Her ideas would help professionals like her and patients alike.

Accommodations for people with hearing loss and other disabilities in academics, public sectors, and the workforce—audiology included—should be provided without question, says Dr. Hoffman, who has had the burden of reversing many people’s misconceptions about her capability to thrive independently in her career. “The self-advocacy never ends, but it has made me stronger and more confident in my own abilities as a deaf person. I am proud to have a hearing loss because it has shaped me into the person I am today.”

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How One Institution is Changing South Africa’s Approach to Pediatric Hearing Loss

By Vicky Chan

Carel du Toit Center (CDT) has been at the forefront of hearing loss education for the past 45 years—offering a mainstream education and speech development programs for children aging from infancy to 10 years old in Cape Town, South Africa. Although an estimated 6,000 babies are diagnosed annually with permanent bilateral hearing loss in the country, early detection and intervention programs are extremely uncommon. CDT is one of the only institutions in the area that offers an early intervention program for children with hearing loss and their parents.

A young student with hearing loss. Credit: Carel du Toit.

Because the damaging effects of hearing loss are widely dismissed by South African legislation, 72% of the nation’s hospitals do not offer any form of hearing tests and fewer than 1% plan to implement newborn hearing screenings. Consequently, 90% of newborns do not have access to a hearing test and families do not receive information about pediatric hearing loss.

Hearing loss is usually detected only after the child’s caregiver notices unusual behavior or speech and language delays. The average age of diagnosis for a child with hearing loss in South Africa is 31 months old, and the typical age at which one is first fitted with hearing aids is 39 months. This is well beyond the critical time period for a child's speech and language development, which depends immensely on the brain’s responses to hearing in the first two years of life.

To help parents understand their child’s hearing loss, the school provides a family-centered early intervention program in their CHAT (Children Hear And Talk) Centre. Coaching families about how to cope with hearing loss is a key component in teaching a child to talk. Parents are encouraged to attend weekly sessions at the CHAT Centre where they are taught to incorporate speech into their family’s daily routine so their child can continue to develop language and social skills at home. The CHAT also provides weekly sessions for children who are too young for school so they can be enrolled in an early intervention program as soon as possible.

“This is your journey with your child and you are absolutely equipped to teach your child to talk through listening,” one teacher says of CHAT. “It may not have been what you were expecting—but embrace it.”

The school employs more than 60 staff, including teachers, early interventionists, social workers, audiologists, psychologists, and speech therapists, who strive to create a natural environment that promotes listening experiences and intensive speech training. Students are fitted with the appropriate hearing technology and learn with the support of the school staff and their parents.

“I had a passion for special needs children and ended up in deaf education,” reflects an CDT educator. Echoing this sentiment, another teacher comments, “Teaching a child a new word or concept everyday makes it very rewarding. You are changing their lives on a daily basis.”

CDT understands that early diagnosis and intervention is the cornerstone for obtaining the best outcome for infants with hearing loss, which is why the center also partners with social services and South Africa’s State Health Department to provide equipment and personnel to test high-risk babies in the largest hospital in West Cape. With a mission to ensure all children in South Africa can function optimally in a hearing world, CDT is making strides to change outcomes for those with hearing loss nationwide.

For more, visit http://careldutoit.co.za/.

A Powerful New Bioinformatics Tool

By Stefan Heller, Ph.D.

Our paper describing a new bioinformatics tool—and to showcase the software, a very detailed investigation as to how inner ear hair cells assemble their hair bundles—appeared in Cell Reports on June 5, 2018.

The creation of the CellTrails tool was supported in part by Hearing Health Foundation’s Hearing Restoration Project (HRP) but moreover, it is the product of recognizing existing limitations of data analysis, going back to the drawing board multiple times, and finally getting to a “product” that is going to be the workhorse to analyze a good part of the bioinformatics data that the HRP has been accumulating for years.

An image taken at 40x magnification using a confocal microscope in the Stefan Heller lab shows a 7-day-old chicken cochlea. Credit: Amanda Janesick, Ph.D.

The ideas came from conversations between HRP scientific director Peter Barr-Gillespie, Ph.D., and me and our getting stuck with trying to make sense of all the data—so the tool is the direct product of interactions through the HRP.  It follows on our work utilizing single-cell gene expression analysis to examine the genetic instructions allowing individual cells to differentiate (change) into other types of cells, such as inner ear supporting cells that turn into hair cells in species other than mammals, and thereby restoring hearing.

The tool helps us pinpoint where specific single cells are located in an organ, and their trajectories as they undergo transformations, information that was lost or fuzzy before. With it we can create a more robust, visually rendered gene expression landscape. Two postdoctoral fellows in my lab were instrumental in CellTrails: bioinformatics researcher Daniel Ellwanger, Ph.D., the tool’s primary developer, and Mirko Scheibinger, Ph.D., who validated its predictions.

I hope many researchers make use of CellTrails, accessible online, to analyze their own mountains of data. As I told Stanford’s SCOPE Blog, “Single cell transcriptome analysis and reconstruction of spatial and temporal relationships among cells is an exploding new technology. A lot of labs are faced with the challenge of analyzing the data from single cells. This study is a rather extensive study that goes beyond the inner ear field because it provides a new way to analyze single cell transcriptomic data.”

I truly feel that the seeds that were planted years ago are now growing into sizable plants—we have a massive "chick regeneration inner ear plant” that is starting to thrive!

Find the tool at hellerlab.stanford.edu/celltrails.

Stanford University’s Stefan Heller, Ph.D., is a member of HHF’s Hearing Restoration Project, where Oregon Health & Science University’s Peter Barr-Gillespie, Ph.D., is the scientific director.

Empower the Hearing Restoration Project's life-changing research. If you are able, please make a contribution today.

HHF Attends HLAA 2018 Convention

By Nadine Dehgan

I was fortunate to attend my very first Hearing Loss Association of America (HLAA) Convention last week in Minneapolis, MN with Hearing Health Foundation (HHF)’s Program Associate, Maria Bibi.

Nadine Dehgan and Maria Bibi at HLAA 2018.

We spent much of our time serving as resources to the highly engaged attendees. In the exhibit hall at our HHF booth, we answered questions related to our critical research and awareness programming. Maria and I were humbled to learn of the deep appreciation for our work from our booth’s visitors.

Several educational sessions were held beyond the exhibit hall. I was particularly grateful to witness John Brigande, Ph.D., and Ronna Hertzano, M.D., Ph.D., speak about HHF’s Hearing Restoration Project (HRP), the international scientific consortium dedicated to identifying better treatments and cures for hearing loss and tinnitus. Here, I met a supporter of HHF, who said, “[Drs. Brigande and Hertzano] were both informative, encouraging, and enthusiastic about their work and the possible outcomes. I will continue to follow their progress even more closely now.”

HHF Emerging Research Grants (ERG) 2018 recipient Evelyn Davies Venn, Au.D, Ph.D, also delivered a compelling presentation. An Assistant Professor at the University of Minnesota, Dr. Venn’s research focuses on a highly personalized hearing technology to help individuals better understand speech in noise. She discussed a new hearing aid in concept phase that will convert the sense of touch into sound electricity.

A shift from typical days in our quiet New York City office, the four-day convention connected us with many inspirational people—folks with hearing loss and scientists alike. Buzzing with energy, optimism, and knowledge about hearing loss, the convention was an important representation of how HHF’s work impacts so many individuals.

Uncovering a Signaling Molecule That Modulates Avian Hair Cell Regeneration

By Rebecca M. Lewis, Au.D., Ph.D., and Jennifer Stone, Ph.D.

Mammals including humans cannot regenerate hair cells, but other species such as birds and fish readily regenerate hair cells after damage to restore auditory function. The gene ATOH1 produces a protein that pushes supporting cells—cells that neighbor hair cells—to either directly convert into a hair cell or to divide and form a new hair cell. However, ATOH1 expression (when the gene is turned on) does not guarantee that hair cells develop in birds or mammals, which suggests that there are factors that prevent supporting cells from changing into hair cells. Identifying these factors in birds may help us better understand the lack of hair cell regeneration in mammals.

This schematic depicts our current ideas for how BMP4 regulates ATOH1 expression and therefore hair cell regeneration in the avian hearing organ. It shows (from left) typical hair cells, hair cell damage, and hair cell regeneration. Typical hair cells secrete BMP4. When hair cells die, BMP4 signaling is reduced, which allows ATOH1 to be expressed in supporting cells and pushes supporting cells to turn into hair cells. The newly regenerated hair cells secrete BMP4, suppressing ATOH1 in supporting cells and restoring the normal condition.

We examined the avian auditory system to characterize a potential inhibitor to ATOH1 during hair cell regeneration: bone morphogenetic protein 4 (BMP4). Bone morphogenetic proteins are secreted signaling molecules that regulate cellular processes in many regions of the body, including the nervous system. We found that BMP4 localizes to hair cells of the mature avian hearing organ and disappears when hair cells die or sustain damage. From this, we hypothesized that BMP4 may prevent ATOH1 expression in supporting cells and loss of BMP4 when hair cells die may enable ATOH1 to be expressed in supporting cells, driving them to convert into hair cells.

When we exposed avian auditory organs to BMP4 after selectively killing hair cells, this prevented ATOH1 expression and hair cell regeneration. When we antagonized BMP4 using an inhibitor, we found a generally opposite result: an increase in the number of regenerated hair cells.

We conclude that BMP4 is a potent inhibitor of ATOH1 and therefore suppresses hair cell regeneration. We recommend that BMP4 be explored further in studies of mammalian hair cell regeneration.

Published in Hearing Research on May 2, 2018, this study detailing BMP4’s negative effect on ATOH1 expands our knowledge of signaling molecules that suppress hair cell regeneration in birds and may also modulate hair cell regeneration in humans.

Rebecca M. Lewis, Au.D., Ph.D., is a clinical audiologist and auditory neuroscientist at Massachusetts Eye and Ear/Harvard Medical School in Boston. HRP researcher Jennifer Stone, Ph.D., is the director of research in the department of otolaryngology–head and neck surgery at the Virginia Merrill Bloedel Hearing Research Center at the University of Washington.

Empower the Hearing Restoration Project's life-changing research. If you are able, please make a contribution today.