An End to Deafness?
By Tracie White
Editor: You may remember Stefan Heller as the researcher who
identified stem cells within the inner ear back in 2002. Following his
discovery, the idea of treating hearing loss using stem cells really
took off. Dr. Heller has just moved his lab to Stanford to take
advantage of California's progressive views on stem cell research.
Here's the press release, which includes a good overview of his current
work and his plans for future research.
~~~~~~~~~~~~~~~~~
Stefan Heller, whose reflection can be seen in the droplet, will be
testing some 100,000 drugs over the next decade in his new lab to see if
any will yield an ear drop that alleviates hearing loss.
His dream is to someday use ear drops to cure deafness. On a recent
morning, Stefan Heller, PhD, explained this by tilting his head to the
side and squeezing imaginary drops into his right ear.
Heller's eyes light up. The cure could be that simple.
As a leader in stem cell-based research on the inner ear, Heller,
newly arrived at the School of Medicine direct from the Harvard faculty,
has a step-by-step plan for making this dream come true. It will, at the
very least, take another decade or so, but if anyone can do it, he's the
guy to place your bets on.
"Heller's a world-class scientist and originator in this
field," said Robert Jackler, MD, the chair of the otolaryngology
department who helped recruit Heller to spearhead research into possible
cures for deafness. "He came here to assemble a team around his
vision."
Heller's vision is to work together with the many experts on the
Stanford campus to come up with a variety of possible cures for deafness
from drug therapy treatment-which could be as simple as an application
of ear drops-to stem cell transplantation into the inner ear to remedy
hearing loss.
"Everyone asks 'How long before we do this?'" said Heller,
associate professor of otolaryngology, whose accent still bears the
trace of his native Germany. "I tell them the devil is in the
details."
But even at the national level, those in the research community
remain hopeful that Heller's work will reap successes sooner rather than
later.
James Battey, MD, director of the National Institute on Deafness and
Other Communication Disorders, lauded Heller as "one of the leading
auditory neuroscientists" and points to his stem cell regeneration
research as a "high priority" for the institute. Dean Philip
Pizzo, MD, described Heller's work as "enormously promising."
The goal, both Jackler and Heller agreed, is to see possible
treatments within five to 10 years, though the early experimental
approaches to therapy have to be tested extensively on laboratory
animals first.
Heller gained international attention for having first identified
stem cells that reside within the inner ear in 2002. Since then, his
research has focused on using these stem cells to regenerate critically
needed hair cells in the inner ear. It's these cells that convert the
mechanical energy of sound into electrical impulses that are sent to the
brain so that we can hear.
Humans are born with 15,000 hair cells per ear. When a significant
number of these cells are lost or damaged, hearing loss occurs. Unlike
in other species such as birds, humans are unable to spontaneously
regenerate these hearing cells.
"There are no deaf birds," observed Heller. "This is
hopeful because it means the genetic program for regeneration exists
somewhere in the vertebrate family."
This explains why Heller has centered his research on stem cells as
the key to unlocking future cures for hearing disorders. Following the
identification of the stem cells in the ear, his research group reached
another significant milestone: the team demonstrated in 2002 that it is
possible to coax embryonic stem cells in a test tube to differentiate
into hair cells-and then also to differentiate after transplantation in
chicken embryos' ears.
"Embryonic stem cell-based approaches are probably the linchpin
to finding a drug-based treatment for deafness," said Heller. He's
been working on developing the necessary technology to go forward with
his drug therapy research, which will entail screening about 100,000
drugs on progenitor hair cells that he has successfully grown in the
lab, converted from embryonic stem cells. After pinpointing any drugs
found to be promising candidates, clinical tests will follow, also to be
conducted on the Stanford campus.
Heller's hope is to cure deaf mice using drug therapy within the next
five to eight years and next move on to humans. At the same time, Heller
has a grant from the McKnight Endowment Fund for Neuroscience to
continue his research into stem cell transplantation.
While potential cures for deafness are, in fact, as variable as the
many causes of hearing loss, Heller said, the simple use of ear drops to
cure the most common causes of deafness, such as the natural aging
process and exposure to loud noises, is currently his favorite plan.
"The ear is good for drug treatment," Heller said.
"You can do local treatment without affecting the whole body."
This idea has been at the back of his mind since he began researching
the inner ear 10 years ago, and it has become more plausible as a result
of his lab's successes in the field of stem cell research over the past
four years.
"Treatment may not be as broad as people think," Heller
said. "It may help some people and not others." For some
people with genetically caused hearing disorders, he explained, no drug
is likely to help. "For them, stem cell transplantation may be the
answer," he said.
But for the majority of those with hearing loss, particularly in the
aging population, drug therapy could be the answer. As the population
has aged and noise pollution has grown more severe, health experts now
estimate that one in three adults over the age of 65 has developed a
handicapping hearing loss.
An unassuming man of 40, Heller spent his first few weeks at Stanford
after arriving in October dashing around campus in shorts, unpacking
boxes, helping his wife (who is also his lab manager) set up shop, and
helping his team of researchers, six who followed him here from Harvard,
cope with the daunting Silicon Valley real estate market.
"Everyone's found housing," said Heller with a relieved
sigh.
On weekdays the team works on cures for deafness. On weekends they
play soccer together, including Heller's two bearded collies, Sepp and
Kalle. "We're almost like a family," his wife and high school
sweetheart Sabine Mann said of the research team.
Moving to Stanford wasn't an easy decision, because it meant
uprooting so many people, Heller added. But the advantages of both
California's support of stem cell research with the passage of
Proposition 71, the state's $3 billion stem cell initiative, and what he
calls the "collaborative" atmosphere on the Stanford campus
ultimately won out.
"I am very much interested in basic research," Heller said.
"But deafness is a clinical problem. I would like to connect basic
science with potential clinical applications. I think this, now more
than ever, is the future of medicine."
