2009 Annual Report: Spotlight on Macular Degeneration

Spotlight on Blindness: Macular Degeneration

On April 29, 2009 the CIRM governing board heard a Spotlight on Macular Degeneration featuring reseachers and a patient speaking about their hope for stem cell research. These are their stories.

Sharon Hayes
Pasadena, CA

The images on the playing cards wouldn’t come into focus, but Sharon Hayes kept trying to play bridge, making bidding mistakes as the game went along.

Finally, another bridge player had enough. “She said, ‘Sharon, you’ve got to go to the doctor right now.’ And we literally put down the cards and we went,” Hayes said.

That’s how the Pasadena-area woman learned she had wet macular degeneration in her left eye. But her eye had deteriorated beyond treatment. Leaky blood vessels growing beneath the retina left her with a gray cloud where people’s faces should be — at the very center of her vision.

Her other eye had the dry form of the disease. It advances more slowly, but is untreatable. When it converted to the wet form, her doctor injected it with a drug called Avastin, which stopped the vessel growth. Within five days, the sight in her right eye was 20/25 again, allowing her to continue painting and running her landscaping business.

She puts her hope in studies to find new and better treatments.

“The research is the most wonderful thing in the world. It’s going to be the answer to so many things,” she said. “If something new came out, I would try it in a heartbeat.”

CURING MACULAR DEGENERATION

Every day the cells essential for vision, called photoreceptors, shed their outer layer. And every day, a layer of cells just below these photoreceptor cells consumes the discarded shells. But in Macular Degeneration a sinister cycle emerges.

With age, the cells below the photoreceptors, called the retinal pigment epithelium, lose cleaning efficiency, and in some 2 million Americans with macular degeneration, the loss is disruptive.

As the retinal pigment epithelium cells fall behind in house cleaning, toxins from the discarded shells build. The accumulation further damages the epithelial cells. Eventually, sections of epithelia die. Without the support of these cells, the photoreceptor cells necessary for vision die, too. Vision blurs at the very center of the eye. Over time, these blurry patches expand.

That’s how dry macular degeneration takes eyesight, leaving the patient with an expanding blank spot in the center of his vision. This often turns into “wet” macular degeneration, in which leaky blood vessels quickly destroy sight.

Unlike wet macular degeneration, “Dry macular degeneration has no effective therapy,” says Dr. David Hinton, M.D., a professor of pathology, neurosurgery and ophthalmology at the University of Southern California Keck School of Medicine. “That’s where we’re putting our efforts.”

To attack the problem, Hinton grows sheets of retinal pigment epithelium cells derived from human embryonic stem cells. The hope is that these sheets can be used to rescue the photoreceptor cells losing their natural RPE.

So far, the lab-grown RPE layers function very similarly to natural cells. “There’s evidence that what looks like RPE cells are RPE cells,” Hinton said. In multiple tests, the lab-grown layers of epithelia secrete the same growth factors, provide the same nourishment and disposal processes, and express the same genes.

“They’re not 100 percent identical, but they’re very similar to normal RPE,” he said.

Dr. Mark Humayun, M.D., Ph.D., has worked out how to get the new cells into the eye. The professor of ophthalmology, biomedical engineering, and cell and neurobiology at USC recently received a CIRM disease team award to pursue this work and is preparing for animal trials to test the concept.

“The cells are growing well in culture and exhibit most, if not all, of the important characteristics of normal RPE,” he said. “So we remain very optimistic.” If animal trials succeed, he hopes to see the procedure tried in humans in a few years.