Stanford Medicine Newsletter Updates For the Local Community

Stem Cells Explored As Hearing Loss Treatment

Summer 2007

Stefan Heller, PhD, whose reflection can be seen in the droplet, hopes a simple ear drop may someday cure deafness.

Stefan Heller, PhD, whose reflection can be seen in the droplet, hopes a simple ear drop may someday cure deafness.

Stefan Heller's dream is to someday find a cure for deafness.

As a leader in stem cell-based research on the inner ear at the School of Medicine, he's got a step-by-step plan for making this dream a reality. It may take another decade or so, but if anyone can do it, he's the guy to bet on.

"Everyone asks, 'How long before we do this?'" said Heller, PhD, 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.

Stem cell program grows

The California Institute of Regenerative Medicine has awarded $25 million to the School of Medicine to advance its research in human embryonic stem cells. The state agency handed out its first rounds of research awards this winter, with the medical school receiving 19 awards worth $25 million -- more than any other single institution.

Among other things, the funding will launch an effort to create new stem cell lines using a process known as somatic cell nuclear transfer. These new cell lines are expected to provide insight into a variety of diseases -- from diabetes to Parkinson's disease -- and open the way to developing new therapies.

In other funded projects, researchers will work to isolate heart and blood stem cells from embryonic stem cells, and to generate inner ear cells, nerve cells or cells for tissue grafts in the heart. The research effort is led by Irving Weissman, MD, director of the Stanford Institute for Stem Cell Biology and Regenerative Medicine.

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.

Since coming to Stanford from Harvard two years ago, Heller has been focused on two paths: drug therapy -- which could be as simple as an application of ear drops -- and stem cell transplantation into the inner ear to remedy hearing loss.

Currently he's working on perfecting the steps toward eventual stem cell transplantation into humans, with the goal of first curing deafness in mice within the next five years.

His lab is also busy studying the ability of birds to regenerate the tiny hair cells in the cochlea. It's these cells that convert the mechanical energy of sound into electrical impulses that are sent to the brain so that a chicken, a mouse or a human can hear. Chickens, like all birds, have the ability to spontaneously regenerate these hair cells, which explains why there are no deaf birds.

"This is promising because it means the genetic program for regeneration exists somewhere in the vertebrate family," Heller said.

The idea of using drug therapy to cure deafness became more plausible as a result of his lab's successes in the field of stem cell research during the past seven years. Heller gained international attention in 2003 for identifying stem cells that reside within the inner ear. Since then, his research has focused on using these stem cells to regenerate the critically needed hair cells in the inner ear.

Later in 2003, his group reached another significant milestone: The team demonstrated that it is possible to coax embryonic stem cells in a test tube to differentiate into hair cells -- and then also to have the stem cells differentiate after transplantation into the ears of chicken embryos.

"Embryonic stem cell-based approaches are probably the linchpin to finding a drug-based treatment for deafness," Heller said.

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