Scientists at the National Eye Institute have advanced a stem cell therapy to treat an eye disease known as geographic atrophy, a leading cause of blindness in the United States. Photo by Laitr Keiows/Wikimedia Commons

Jan. 2 (UPI) -- Researchers made advances toward creating stem cell-derived retinal cells used to treat a leading cause of blindness, scientists at the National Eye Institute said.

NEI scientists found that tiny tube-like protrusions called primary cilia on a layer of cells in the back of the eye, known as the retinal pigment epithelium, are essential for the survival of the retina's light-sensing photoreceptors, according to a new study published in the journal Cell Reports.


The discovery has advanced scientists' ability to use induced-pluripotent stem cells to create adult RPE for transplants to treat patients with geographic atrophy -- or dry age-related macular degeneration -- a leading cause of blindness in the United States.

"We now have a better idea about how to generate and replace RPE cells, which appear to be among the first type of cells to stop working properly in AMD," Dr. Kapil Bharti, lead investigator on the study, said in a press release.

The RPE cells of patients with geographic atrophy die, causing photoreceptors to degenerate and ultimately causing vision loss.

Bharti and his colleagues hope to halt such degradation by replacing dying and diseased RPE with cells made in a lab, but stem cells programmed to become RPE cells regularly got stuck in development.

"The cells frequently fail to mature into functional RPE capable of supporting photoreceptors. In cases where they do mature, however, RPE maturation coincides with the emergence of primary cilia on the iPSC-RPE cells," Bharti said.

Researchers then tested three drugs that modulate the growth of primary cilia on stem cell-derived RPE and found the two known to enhance cilia growth improved the maturation of the RPE stem cells, while one that inhibited growth severely disrupted structure and functionality.

The RPE cells formed using the drugs to enhance cilia growth all oriented properly and engulfed the tips of photoreceptor outer segments, a pruning process that keeps photoreceptors working properly.

Bharti said the developments have been incorporated into the group's protocol for making clinical-grade stem cell-derived RPE cells and will also inform the development of disease models in future research of age-related macular degeneration.