Damaged Optic Nerves In Mice Eyes Regenerated In The Lab Through Gene Therapy

Ganglion cells make up the optic nerve and carry the signals from the retina to the brain. Richard Wingate (CC BY 4.0)

Scientists have shown that it’s possible to regenerate the damaged optic nerve cells of mice using a new gene therapy technique, offering a possible new way to treat glaucoma, one of the leading causes of blindness.

Visual information is sent to the brain through nerve cells in the retina, called retinal ganglion cells, which feature long axons that extend down the optic nerve found in the back of the eye, linking the eye to the brain. If this optic nerve becomes damaged, it can result in vision loss or even blindness, known as glaucoma. Unfortunately, nerve cells in the adult central nervous system do not usually regenerate, meaning damage to the optical nerve can result in irreversible vision loss. However, researchers might have found a new way to work around this problem.

"The causes of glaucoma are not completely understood, but there is currently a large focus on identifying new treatments by preventing nerve cells in the retina from dying, as well as trying to repair vision loss through the regeneration of diseased axons through the optic nerve," Dr Veselina Petrova of the Department of Clinical Neurosciences at the University of Cambridge, and the study's first author, said in a statement.

In the study, published in Nature Communications, the scientists show how evoking the gene responsible for the production of a protein, Protrudin, can spark the regeneration of nerve cells in the retina and protect them from cell death after injury. They also showed that Protrudin achieves this by aiding the transport of "rebuilding" materials to the site of damage.

For the first part of the research, the team grew mouse brain cells in a petri dish. After injuring the nerve cells with a laser, they noticed that increasing or activating Protrudin boosted their ability to regenerate. 

Next, they carried out the experiment on an actual mouse. Gene therapy was used to increase the amount and activity of Protrudin in the eye and optic nerve in mice who had an injured optic nerve. After two weeks, the nerve fibers (axons) of the mice had shown significant regeneration, while their retinal ganglion cells were also protected from cell death.

Finally, to confirm the protective properties of Protrudin, they took a whole retina from a mouse eye and cultured it in a petri dish. While around half of retinal neurons would typically die within three days of retinal removal, increasing Protrudin gave almost complete protection of retinal neurons.

This has only been carried out in mouse eyes so far, so there’s still a long way to go before this technique could be used to heal blindness in humans. Nevertheless, it’s a promising step forward.

“Our strategy relies on using gene therapy – an approach already in clinical use – to deliver Protrudin into the eye. It’s possible our treatment could be further developed as a way of protecting retinal neurons from death, as well as stimulating their axons to regrow,” Dr Petrova said.

However, “It’s important to point out that these findings would need further research to see if they could be developed into effective treatments for humans."

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