Hair Cell Regeneration as a Cure for Hearing Loss
One of the promising medical technologies that could at
least partially restore hearing in some people with hearing loss is hair
cell regeneration. This process refers to the ability to cause the
cochlear hair cells to repair or replace themselves. Since the large
majority of hearing loss is caused by damage to these hair cells, this
technology offers great hope to many people with hearing loss.
April 2013 - UW Researchers Work to
Regenerate Inner Ear Hair Cells
April 2013 - Taking
Hair Cell Regeneration Up a Notch
March 2013 - Researchers Restore
Hearing and Balance in Mice
March 2013 - Forerunners of Inner-Ear
Cells That Enable Hearing Identified
February 2013 - Researchers
Regenerate Hair Cells and Restore Hearing to Noise-Damaged Ears
February 2013 -
Scientists Repair Mouse Hair Cells and Restore Hearing
January 2013 -
Regenerated Hair Cells Restore Hearing in Mice
July 2012 - Gene therapy holds
promise for reversing congenital hearing loss
May 2012 - Gene therapy for hearing loss:
potential and limitations
January 2012 -
AFA Denounces FDAs Approval of Newborn
Stem Cell Experimentation
December 2011 -
British Researchers Working to Grow Hair Cells
October 2011 - Group Seeks Cure for Hearing Loss in
September 2011 -
Growth Hormone Helps Repair The Zebrafish
September 2011 -
A Review of Gene Delivery and Stem Cell Based
Therapies for Regenerating Inner Ear Hair Cells
May 2011 -
Hair Cell Regeneration Update from Dr. Stefen
February 2011 - NIDCD Researchers Discover Unique
Protein That Appears to Control Stereocilia Length
February 2011 - UCLA and Sound Pharmaceuticals
Identify a Key Hearing Regeneration Protein in the Human Inner Ear
September 2010 - Study Suggests Avenue To Restore
Hearing Loss From Nerve Damage
August 2010 - Japanese Team Discovers Enzyme
that May Lead to Hair Cell Recovery
May 2010 -
Scientists create functional
August 2009 -
2009 HLAA Convention Research Symposium: Hair Cell Regeneration
August 2009 - Can a Tiny Fish Save Your Ears?
June 2009 - Regrowing Hair Cells in the Human
May 2009 - Hair Cell Regeneration - How It Works and
What It Means for Audiologists
March 2009 - Brain Cells Coaxed to Mimic Hair Cells
March 2009 - New Stem Cell Therapy May Lead
to Treatment for Deafness
January 2009 - HEI Researchers Report Hair Cell
November 2008 - Researchers Make in Vitro Inner Ear
August 2008 - OHSU Grows Hair Cells Involved in
November 2007 - Researchers Develop New Method of
Growing Hair Cells
September 2007 - The Hearing Regeneration
Initiative at UW
September 2007 - New Technique May be Boon for
Hair Cell Studies
June 2006 - Scientists Show Mouse Ear Holds
Potential for Cell Regeneration to Restore Hearing
April 2006 - Here's the latest report on the hair
cell regeneration work at Massachusetts General Hospital.
September 2005 - The
2005 SHHH National Convention included a wonderful panel on the current
state of hair cell regeneration.
June 2005 - Now that scientists have discovered
the gene that inhibits hair cell reproduction, the next hurdle is
developing a way to control that gene. Here's an article about a new
study that attempts to do just that!
April 2005 - Scientists from the Medical Research
Council (MRC) and the University of Hong Kong have isolated the gene
responsible for sensory development in the inner ear.
April 2005 - Work at Indiana University causes more
excitement about hair cell regeneration progress.
February 2005 - UM Scientists Restore Guinea Pig's
January 2005 - Concerned that the hype regarding hair cell
regeneration may be inflating expectations, Dr. Neil
Bauman offers his analysis of where hair cell regeneration stands and
when we can expect it to be generally available.
January 2005 - Scientists have discovered a gene
that inhibits hair cell reproduction, and have learned that turning off
the gene causes hair cell proliferation.
September 2004 - Here's some more information on
hair cell regeneration in mammals.
September 2003 - Hair cell regeneration and the related stem cell research
offer what is probably the best hope for hearing restoration in the next
few years. A reader who follows these developments just sent me four
stories, each of which discusses promising medical discoveries. Two of
the stories are late-breaking news and two are from earlier this summer.
Here are a couple of paragraphs from each story and a link to the full
June 2003 - Is this the holy grail of hair cell regeneration?
Scientists at the University of Michigan have achieved hair
cell regeneration in a mammal!
November 2002 - Deafness Discovery Showed Inner Hair
August 2002 - Hair Cells
July 2002 - From the 2002 SHHH Convention, here's a report on Dr.
Session on hair cell regeneration.
December 2000 - Adult humans are unable to regenerate
damaged hair cells. But birds are able to do it quite readily. Do our
feathered friends offer hope that we may one day be able to regenerate
human hair cells? Find out what the University of Washington
Hair Cell Research has to say.
More on this and related
The loss of cochlear mechanosensory hair cells is
the primary cause of acquired hearing impairment. In contrast with the
situation for all other vertebrates, mammals' hair cells are not
regenerated after they are lost. As a result, traumas that lead to hair
cell loss cause permanent hearing deficits. The use of hearing aids or
cochlear implants can significantly mitigate these losses, but they don't
constitute a cure. The regeneration of hair cells, on the other hand, has
the potential for permanent recovery. Activation of a well-conserved
signaling molecule, called Notch, has been shown to prevent hair cell
formation. In embryos, Notch signaling plays an important role in ensuring
that only the correct number of hair cells form, but, in adults, it had
been suggested that continued or renewed activation of this pathway,
particularly following hair cell damage, might play a role in preventing
new hair cells from forming.
Congenital hearing impairment is present in
approximately 1 in 1,000 newborns, and yet there is no physiological cure
for children who are born deaf. Most cases of congenital deafness are due
to a mutation in a gene that is required for normal development of the
sensory hair cells in the inner ear that are responsible for detecting
sound. To cure deafness caused by such mutations, the expression of the
gene must be corrected, a feat that has been elusive until recently.
Rosalind Franklin University of Medicine and Science (RFUMS) Assistant
Professor Michelle Hastings and her team, along with investigators at
Louisiana State University Health Sciences Center in New Orleans, and Isis
Pharmaceuticals in Carlsbad, Calif, have now found a way to target gene
expression in the ear and rescue hearing and balance in mice that have a
mutation that causes deafness in humans. The results of the study are
reported in the paper, Rescue of hearing and vestibular function in a
mouse model of human deafness, which was published February 4, 2013 in the
journal Nature Medicine.
A drug applied to the inner ears of adult mice can
spur the regeneration of hair cells, according to researchers at Harvard
Medical School and the Massachusetts Eye and Ear Infirmary in the United
States and the Keio University School of Medicine in Japan. The drug works
by activating a transcription factor involved in hair cell development.
The finding is a first in the field-while fish and birds can regenerate
hair cells after damage, scientists have never before shown that this is
possible in mammals. Cochlear hair cells are vital for converting sound
waves into electrical signals that inform the brain of noises. They can
become damaged or die suddenly through an acoustic injury-the sound of a
loud explosion, for example-leading to permanent loss of hearing.
Currently, such damage is treated with cochlear implants, surgically
implanted devices that convert sounds to electrical signals.
Researchers at Keele University in North
Staffordshire will be the first in the world to attempt to 'grow' new
cells in the ear that become lost and damaged with age. Age-related
hearing loss affects more than nine million people with over half of
people aged 60 and above affected to some degree. The researchers found
that in some cases hearing begins to decline when fibrocytes, cells in the
inner ear which usually manage levels of potassium and sodium, start to
degenerate. Once these cells have died and no longer function correctly,
other parts of the inner ear can become permanently damaged, leading to
increased loss of hearing and possible deafness. Dr Dave Furness, from
Keele University's school of life sciences, has been working for three
years on a study funded by Deafness Research UK and The Freemasons Grand
Charity to look into the causes of age related hearing loss. Now, Dr
Furness and his PhD student Jacqueline Tickle have begun the next phase of
the research, which will explore whether replacement fibrocytes and
fibrocyte stem cells can be successfully grown and implanted into the
ear. If successful, the research could pave the way towards the
prevention of age related hearing loss.
Abstract: Sensory neural hearing loss and
vestibular dysfunction have become the most common forms of sensory
defects, affecting millions of people worldwide. Developing effective
therapies to restore hearing loss is challenging, owing to the limited
regenerative capacity of the inner ear hair cells. With recent advances
in understanding the developmental biology of mammalian and non-mammalian
hair cells a variety of strategies have emerged to restore lost hair
cells are being developed. Two predominant strategies have developed to
restore hair cells: transfer of genes responsible for hair cell genesis
and replacement of missing cells via transfer of stem cells. In this
review article, we evaluate the use of several genes involved in hair
cell regeneration, the advantages and disadvantages of the different
viral vectors employed in inner ear gene delivery and the insights
gained from the use of embryonic, adult and induced pluripotent stem cells
in generating inner ear hair cells. Understanding the role of genes,
vectors and stem cells in therapeutic strategies led us to explore
potential solutions to overcome the limitations associated with their use
in hair cell regeneration.
Stefan Heller, Ph.D., is a professor of
otolaryngology and a professor of molecular and cellular biology at the
Stanford University School of Medicine.He is also the principle
investigator of Heller Lab in Stanford's Department of Otolaryngology.
Roughly a decade ago, Heller proposed that stem cells could be used to
create the specialized inner-ear hair cells that are critical for our
ability to hear. Unlike birds, fish, and amphibians,mammals cannot
regenerate hair cells, so once they are lost or damaged, the hearing loss
is permanent. Last May Heller reported in the journal Cell that he and his
team had successfully created mouse cells that not only resemble but also
behave like mouse inner-ear hair cells. In an interview with Hearing
Health, Heller reviewed the advances his lab has made since that
For many people, loss of hearing is irreversible.
For scientists trying to figure out what can be done about that, one
answer may lie-or swim, actually-in freshwater aquariums. About one of
every 10 Americans suffers from hearing impairment, according to a survey
conducted by the Better Hearing Institute, a nonprofit advocacy group. By
far the most common cause of hearing loss is damage to the so-called hair
cells in the inner ear as a result of excessive noise, certain illnesses
and drugs, and simple aging. The problem is that once hair cells die,
humans (like other mammals) aren't able to grow new ones. In recent years,
a research team at the University of Washington in Seattle has been
working on finding a way to resolve that problem in experiments involving
the zebrafish, a common aquarium denizen. The zebrafish, like many aquatic
creatures, has clusters of hair cells running along the outside of its
body that help sense vibrations in the water, working in a similar way to
hair cells in the human inner ear. But unlike humans, zebrafish are able
to regenerate their damaged hair cells. Researchers hope their work can
unlock secrets to protect human hair cells from becoming damaged and to
stimulate the cells to regenerate.
More than 20 years ago, Douglas Cotanche, PhD,
then at the Medical University of South Carolina and now affiliated with
Children's Hospital Boston, discovered that the hair cells within the
chick cochlea were capable of a "significant amount of recovery and
regeneration" following acoustic trauma.1 His unexpected discovery began a
cascade of research on the question of whether hair cells within the human
cochlea could someday achieve the same regenerative results. If and when
this happens, many of the causes of hearing loss in humans, from noise to
aging, can finally be resolved without the need for hearing aids or
cochlear implants. Although steady progress has been made in understanding
the mechanisms underlying hair cell regeneration, human subjects have yet
to participate in clinical trials concerned with regrowing hair cells.
Such trials may still be years away. Let's look at a sampling of the
research in 2008, which moves us ever closer to the goal of restoring
hearing in this most natural way.
Twenty years have passed since the discovery of
hair cell regeneration in birds (Corwin & Cotanche, 1988; Ryals & Rubel,
1988). The initial excitement caused by this discovery has been followed
by steady progress in understanding the fundamental mechanisms that
recently culminated in research evidence of hair cell regeneration in both
the auditory and vestibular portions of the mammalian inner ear (Kawamoto
et al., 2003; Izumikawa et al., 2005; Staecker et al., 2007). Clinical
audiologists are faced with the responsibility of translating these basic
science findings into potential patient application. They raise important
questions: When will hair cell regeneration be a reality for my patients?
What will be the measures of candidacy? What will the impact of hair cell
regeneration be in my patients who use or are candidates for hearing aids
or other amplification devices? Will hearing aids or cochlear implants
continue to be needed in the face of hair cell regeneration?
Iranian researchers managed to successfully
extract bone marrow stem cells from rodents and produce in vitro inner ear
hair cells. "In this two-year project, researchers cultured and produced
inner ear hair cells, a procedure which is not commonly performed in other
countries," research team-leader, Mohammad Farhadi told the Iranian
students news agency. Farhadi reported that injecting the resulted cells
into deaf mice has successfully tackled hearing loss in them.
Researchers at the University of Virginia have
developed a new method of growing inner-ear hair cells that will aid
research to help people regain their hearing. Dr. Jeffrey T. Corwin, a
professor of neuroscience at the UVa Health System, and Dr. Zhengqing Hu,
a neuroscience research assistant, have been growing cells from inner ears
of chicken embryos. They hope to extend that knowledge to re-grow the
inner-ear hair cells of humans. Mammals grow inner-ear hair cells only
before they are born, unlike amphibians and birds, which can re-grow
damaged or lost cells. These unique structures are lost over time as
mammals age, or if they contract certain infections or undergo trauma. The
loss of inner-ear hair cells results in hearing loss and balance
impairment. Hu and Corwin's process is able to grow chicken inner-ear hair
cells in a laboratory setting.