Age-related macular degeneration (AMD) is the leading cause of vision loss in people over 60. It affects 10 million Americans. That’s more than cataracts and glaucoma combined. The causes of AMD are not known but are believed to involve a mixture of hereditary and environmental factors. There is no treatment for it.
Now, in a CIRM-funded study, researchers at UC San Diego (UCSD) have used stem cells to help identify genetic elements that could provide some clues as to the cause, and maybe give some ideas on how to treat it.
Before we get into what the researchers did let’s take a look at what AMD does. At a basic level it attacks the retina, the thin layer of tissue that lines the back of the eye. The retina receives light, turns it into electrical signals and sends it to the brain which turns it into a visual image.
The disease destroys the macula, the part of the retina that controls our central vision. At first, sight becomes blurred or fuzzy but over time it progresses to the point where central vision is almost completely destroyed.
To try and understand why this happens the team at UCSD took skin samples from six people with AMD and, using the iPSC method, turned those cells into the kinds of cell found in the retina. Because these cells came from people who had AMD they now displayed the same characteristics as AMD-affected retinal cells. This allowed the researchers to create what is called a “disease-in-a-dish” model that allowed them to see, in real time, what is happening in AMD.
They were able to identify a genetic variant that reduces production of a protein called VEGFA, which is known to promote the growth of new blood vessels.
In a news release Kelly Frazer, director of the Institute for Genomic Medicine at UCSD and the lead author of the study, said the results were unexpected.
“We didn’t start with the VEGFA gene when we went looking for genetic causes of AMD. But we were surprised to find that with samples from just six people, this genetic variation clearly emerged as a causal factor.”
Frazer says this discovery, published in the journal Stem Cell Reports, could ultimately lead to new approaches to developing new treatments for AMD.
CIRM already funds one clinical trial-stage project targeting AMD.