By Dennis Thompson
WEDNESDAY, April 4, 2018 (HealthDay News) -- A new stem cell transplant might help preserve or even restore vision being lost to the dry form of age-related macular degeneration, a new pilot clinical trial has shown.
In the experimental therapy, a specially engineered sheet of stem cells is transplanted into the back wall of the eye to replace a layer of cells destroyed by age-related macular degeneration (AMD).
Vision loss appeared to halt in four of the first five people treated with the implant cells, researchers reported in the April 4 issue of the journal Science Translational Medicine.
The fifth patient actually experienced some improvement in vision, and was able to read 17 additional letters off a standard eye chart, said lead researcher Dr. Amir Kashani. He is assistant professor of clinical ophthalmology at the University of Southern California's Keck School of Medicine.
"We didn't really anticipate or expect dramatic improvement in vision," Kashani said. "That was a very encouraging sign."
Two other patients displayed improvement in their ability to focus or fixate on a target better than before surgery, he added.
"They could guide their vision to look at a certain location," Kashani said. "That's one of the prerequisites for being able to read or look somebody in the face, or doing those high-acuity kinds of tasks, so that was also very encouraging."
There currently is no cure or treatment for the dry form of AMD, which accounts for 80 percent to 90 percent of all cases, he noted.
The retina -- the light-sensitive tissue along the back of the eye wall -- is slowly destroyed as a result of AMD. As light-sensing cells die off, people's vision becomes blurry and distorted, and they begin to lose their central vision.
Age-related macular degeneration currently affects approximately 1.7 million Americans, and is projected to affect almost 3 million by 2020. It's a leading cause of severe visual impairment in adults older than 65.
The dry form of AMD involves the loss of a thin layer of cells beneath the retina called retinal pigment epithelium (RPE) cells, Kashani said.
"The function of the RPE cells is to support the overlying retina and its photo sensor cells," Kashani said. Without the nourishment provided by the RPE layer, the retina cannot function normally and begins to die off, permanently damaging vision.
To halt the advance of vision loss, Kashani and his team engineered in the lab a fresh sheet of RPE cells created from embryonic stem cells.
The researchers then implanted the new sheet of cells into the eyes of five patients with long-term dry AMD, in a stage I clinical trial that ultimately will include a total of 20 people.
There were no serious side effects or unanticipated problems in the transplant, Kashani said.
Patients required only a small amount of immune suppression to make sure the body didn't reject the implant. That's because the retina is considered an extension of the brain, and the immune system typically does not target the brain or its related structures, he explained.
"The body doesn't really mount immune responses as we understand them in those areas," Kashani said.
The researchers already are planning a larger series of trials, which they hope will get underway within the next couple of years.
Dr. Avnish Deobhakta is a retina surgeon at the New York Eye and Ear Infirmary of Mount Sinai in New York City. "This type of technology is very exciting considering that it aims to replace the precise layer of cells that are progressively damaged in a form of macular degeneration that affects millions of people and is one of the major causes of irreversible blindness in the U.S.," he said.
"At present, we do not have any effective treatments for the dry form of macular degeneration that results in this sort of retinal atrophy, so this therapy has the potential to change the way we look at this disease and possibly give patients hope that at the very least we can stem the tide of disease progression," Deobhakta added.