For some creatures, a lost body part is not necessarily a permanent affair. Salamanders can regrow limbs and zebrafish can rebuild their retinas. Yet mammals — including humans — are largely stuck with what they’re born with. When vision is lost to degenerative diseases like retinitis pigmentosa, it stays lost.

But a team of scientists in South Korea may have found a way to change that.

In a discovery that could reshape how we treat blindness, the researchers at the Korea Advanced Institute of Science & Technology (KAIST) have developed a therapy that restores vision by prompting the retina to heal itself. The treatment, tested in mice, triggered long-term regeneration of nerve cells in the retina — something previously thought impossible in mammals.

Why Our Eyes Can’t Heal Themselves

Inside our eyes, a special kind of cell called Müller glia keeps watch. These cells protect the retina, maintaining its structure and supporting its neurons. In fish and amphibians, they do even more. They can transform into new neurons, repairing retinal damage. In mammals, however, that regenerative process is switched off. Once the retina is harmed, it stays that way.

Why can’t our Müller glia do the same? The answer, it turns out, may lie in an unexpected molecular stowaway.

The new study, published in Nature Communications, zooms in on a protein called Prox1. In mammals, this protein appears to travel between cells and land inside Müller glia, where it acts like a molecular handbrake, preventing these cells from reprogramming into neuron-generating machines.

The same protein is nowhere to be found in the retinal Müller glia of fish, which regenerate readily. “The PROX1 protein secreted from damaged retinal nerve cells moves to Müller glia, inhibiting dedifferentiation into neural progenitor cells and neural regeneration,” the team explained.

The Antibody That Unlocks Sight

To sidestep this molecular roadblock, the researchers developed a compound that acts like a sponge for PROX1. The treatment — based on a neutralizing antibody called CLZ001 — binds to PROX1 outside the Müller glia, intercepting it before it can enter the cells. Once freed from PROX1’s grip, the Müller glia dedifferentiate, divide, and begin producing new neurons.

The results were not fleeting. Mice treated with the antibody regained retinal structure and function that lasted for half a year — the equivalent of several decades in human lifespan.

The treatment was also administered via AAV2-Anti-PROX1 gene therapy, a common viral delivery method. In models of retinitis pigmentosa, a genetic disorder that slowly robs people of vision, the therapy restored both the photoreceptor layer and the mice’s ability to see.

The scientists were actually able to provide observable proof of regenerated photoreceptor cells — the light-sensing neurons lost in many retinal diseases — lining the retina once more.

Cautious Optimism

Though the leap from mouse to human is a large one, the findings have stirred cautious optimism.

More than 300 million people worldwide suffer from retinal diseases that can lead to blindness. Conditions like age-related macular degeneration and retinitis pigmentosa have no cure. Treatments can slow progression, but they cannot recover lost sight.

The KAIST team aims to change that. “We will proceed with administration to retinal disease patients,” said Dr. Lee Eun-jeong from Celliaz, a spin-off startup from KAIST, “and strive to make a practical contribution to patients at risk of blindness without appropriate treatment.”

Celliaz Inc. is now preparing for clinical trials, expected to begin by 2028. Before that, researchers plan to fine-tune the antibody’s efficacy and evaluate safety in other animal models.

The work may eventually extend beyond the retina. PROX1 is also found in other neural tissues, like the hippocampus and spinal cord, raising questions about whether a similar strategy could be applied elsewhere in the body.