Hair Cell Regeneration-Looking Beyond the Hype
Editor: We've met Dr. Neil Bauman in these pages on several occasions,
and we're fortunate to meet him again! He's been watching the hype
regarding hair cell regeneration and wanted to offer his thoughts on a
realistic timetable for this hearing loss "cure".
Neil is also the author of the definitive book on ototoxic drugs, as
well as a number of other works on hearing loss. More information is
available on his website www.hearinglosshelp.com .
You can also email him at firstname.lastname@example.org .
Finally, I've chosen to remove the footnotes from this article, because
superscripts don't come across well in a text document. For the complete
article (including footnotes) please point your browser to http://www.hearinglosshelp.com/HairCellHype.htm
(c) November 2004 by Neil Bauman, Ph.D.
Question: Hair cell regeneration has been in the news for some time
now. Will it soon restore hearing for the millions of hard of hearing
people? I'd love to know your thoughts about this.-J. S.
Answer: Investigation into hair cell regeneration has come a long ways
from the late 1970s when researchers first discovered that sharks could
produce hair cells throughout their lives. However, it was not until
1986-87, when researchers discovered that birds could naturally regenerate
hair cells to restore damaged hearing, that scientists got excited and
began to think, "If it works in birds, maybe we can make it work it
Since then, research on hair cell regeneration has accelerated. In the
past 3 or 4 years, researchers have made remarkable strides towards one
day being able to regenerate hair cells in people with hearing loss.
Unfortunately, every time there is another discovery or breakthrough in
this research, the media hype seems to indicate that hair cell
regeneration is just around the corner-that in just a few years hearing
loss is going to be a thing of the past. Hard of hearing people are
getting their hopes up-thinking that in a few years, they will get their
hearing back. Is this really going to happen, or are their hopes going to
be dashed once again? Let's look at the facts.
First, hair cell regeneration will not help all people with hearing
loss. For example, hair cell regeneration won't help deaf people who lost
their hearing before they acquired speech. This is because brains wire for
sound during the first 6 years of life. If a person doesn't hear any
sounds during this time, their brains never develop the necessary auditory
capability to understand speech. Thus, even if their ears could grow new
hair cells, these hair cells would be useless to them because their brains
wouldn't know how to process these new sound signals. (However, if hair
cells were regenerated in deaf children in the very first few years of
their lives, the results could be fantastic.)
Furthermore, hair cell regeneration won't help people with conductive
losses such as are caused by middle ear infections or otosclerosis, nor
will it help people with auditory nerve conditions such as acoustic
neuromas. Also, hair cell regeneration will not help people with hearing
loss if their hearing loss is caused by the absence of certain genes that
result in hearing loss even though adequate numbers of hair cells are
present. That's the bad news.
The good news is that the majority of people with hearing loss have a
sensorineural type of hearing loss that may benefit from hair cell
Second, hair cell regeneration is still a long ways off-several decades
at least. It is not just around the corner. As of 2004, the most realistic
time frame is still 20 or more years in the future. Dr. Rubel, perhaps the
leading researcher in the world today on hair cell regeneration, says,
"My most hopeful prediction is 20 years, and that's being very
optimistic." He further states, "Over 15 years of studies on
hair cell regeneration in the inner ears of birds has taught us that a
quick and easy cure for sensorineural hearing loss is unrealistic."
He adds, "It will be a long time until we have anything near a
perfect cure for hearing loss."
Third, once hair cell regeneration is possible, the public has been
lead to believe that treating hard of hearing people will result in them
having normal hearing once more. However, if you carefully read the
reports as they come out, you begin to realize that researchers are not
talking about hard of hearing people receiving normal hearing through hair
cell regeneration. They are talking about "growing enough hair cells
where hearing aids could be used more effectively and provide much more
acoustic information" than would otherwise be possible.
In fact, Dr. Rubel expects that hair cell regeneration, far from
leading to the demise of hearing aids, will actually make them even more
common and useful. He explains, "Hair cell regeneration will, if
anything, increase the population of people who could benefit from hearing
This is because a normal human ear has between 16,000 and 30,000 hair
cells, yet hair cell regeneration researchers are talking about only being
able to grow a few hundred hair cells -not the thousands upon thousands
needed for normal hearing. Obviously, regenerating a few hundred hair
cells is a drop in the bucket and will in no way restore hearing to
normal-better hearing, yes, but not normal hearing.
Did you know that even in the animals that God designed to naturally
regenerate hair cells, hearing does not return to normal? For example,
researchers used loud noise and antibiotics to produce a 70 dB loss in
chickens. When these chickens regenerated hair cells to replace the
damaged ones, their hearing returned, but not to normal. They had a
permanent 23 dB hearing loss. Most studies on birds have reported mild
permanent hearing losses and mild to moderate tuning (discrimination)
Thus, even though much hearing returns, the regenerated hair cells are
not as "good" as the originals. Before and after
photomicrographs of hair cells are revealing. Before noise damage, the
hair cells are symmetrical and beautifully ordered. Later, pictures taken
of regenerated hair cells show them as irregularly shaped and the
stereocilia (the "hairs" of the hair cells) look like they were
all hashed together-not beautifully arranged like before.
These are some of the facts. Therefore, at the present time (2004),
hair cell regeneration is nowhere near ready to be applied to humans.
However, if research into hair cell regeneration continues at the present
pace, hair cell regeneration in humans will very likely become a reality
sometime in the next few decades. Even so, it won't be a cure for hearing
loss. Rather, it will be another aid to better hearing, just like hearing
aids are today.
Neil Bauman, Ph.D., has successfully coped with a life-long severe
hereditary hearing loss. He is a hearing loss coping skills specialist,
author and speaker. Send your questions to him at: email@example.com.