A new treatment for the most severe form of advanced, dry age-related macular degeneration (AMD) has shown promise in an animal study. Researchers hope the treatment, which involves using a patient's own stem cells to replace lost retina cells, will soon be tested in humans.
There are two forms of AMD: dry and wet. About 80% of people who have AMD have the dry form, and there are several kinds of dry AMD. There is currently no way to treat any kind of dry AMD.
In dry AMD, cells called retinal pigment epithelium (RPE) cells die. These cells nurture light-sensing cells in the retina called photoreceptors. Once the cells die, the photoreceptors also eventually die. This cell death results in the most severe form of dry AMD—called geographic atrophy. Geographic atrophy can lead to blindness.
The new experimental treatment is designed to replace the dying cells with cells that have been created from a patient's blood cells. In the lab, the researchers convert the patient's cells into induced pluripotent stem cells (iPS) cells. These can become any kind of cell in the body.
In this study, researchers programmed human iPS cells to become RPE cells. The lab-made cells were grown in tiny sheets that were one cell thick. The researchers then inserted the cells into the retinas of rats and pigs. Ten weeks after the cells were implanted, the researchers conducted imaging studies that showed the lab-made cells were integrated within the retina.
The transplanted cells functioned properly, the researchers reported in the journal Science Translational Medicine. These healthy new cells could stop any further vision loss from dry AMD and might even be able to return some lost vision.
"Being able to reprogram stem cells to become missing RPE cells is really exciting technology," said Pravin U. Dugel, MD, an ophthalmologist at Retinal Consultants of Arizona in Phoenix.
"It's still very early and there are a lot of challenges ahead,” he said. "Just because it works in rats and pigs doesn't necessarily mean it will work in humans. But we don't have any treatment for dry AMD, so this is something to watch out for."
Dr. Dugel noted that a key concern with any stem cell therapy is that changing the nuclear structure of the cell has the potential to cause cells to multiply uncontrollably and become cancerous. The researchers said they genetically analyzed the RPE cells derived from stem cells and found no genetic mutations linked to tumor growth. "Although it was not seen in this animal study, it always remains a possibility, and that has to be overcome," Dr. Dugel said.
The researchers have started to plan a Phase I clinical trial to test the safety of the treatment in humans. The U.S. Food and Drug Administration must still approve the trial before it can begin.
"If the clinical trial moves forward, it would be the first ever to test a stem cell-based therapy derived from induced pluripotent stem cells for treating a disease," lead researcher Kapil Bharti, PhD, of the National Eye Institute said in a news release.