Human vision restored for the first time with gene therapy

For the first time, doctors were able to partially restore the patient’s vision using optogenetic therapy. Previously, this method has been successfully applied only to animals.

Optogenetics is a fairly young method that allows you to control neurons using light-sensitive proteins. This successful application of optogenetic therapy is a major breakthrough in restorative medicine.

The study, published in Nature Medicine, describes progress in treating a patient from Paris who was diagnosed with retinitis pigmentosa 40 years ago. It is a progressive neurodegenerative disease that destroys light-sensitive cells in the retina and leads to blindness. Mutations in 71 genes are the cause of retinitis pigmentosa, so it is extremely difficult to develop a gene therapy that would successfully “repair” all the broken protein bonds.

Therefore, the researchers approached the treatment of this disease from a completely different angle. Instead of sequentially repairing each damaged gene in the photoreceptors that transmit signals to nerve cells, the scientists decided to directly activate the nerve cells themselves. This is where the optogenetic tools came in handy.

The researchers injected into the patient’s eye an injection containing an adeno-associated virus vector (often used in gene therapy). This harmless virus has been used to deliver light-sensitive proteins to retinal cells. These proteins react to light by changing their shape and allowing the flow of ions to pass through the cell.

However, these proteins are only sensitive to light of a certain wavelength. To correct the rays of light falling on the retina, the researchers used special glasses. They transform the light that bounces off objects, much like a projector transmits an image onto a screen in a movie theater.

During the experiment, the patient recognized objects on the table in front of him.
Photo by Sahel et al. / Nature Medicine, 2021.

With the help of gene therapy and these glasses, the patient was able to see real objects for the first time in many years, albeit under special experimental conditions. The researchers simultaneously read the activity of the patient’s neurons using EEG. Thus, they became convinced that optogenetic therapy of the retina really allowed to activate the primary visual cortex of the brain. It is into it that the signal from the retina enters, that is, this path of information transmission has been successfully restored.

The adaptation period to the new equipment took several months. After that, the patient was able to see (and even count) the white stripes at the pedestrian crossing and gradually learned to distinguish more and more different objects outside the laboratory.

Of course, this method of restoring vision is still at an experimental stage, and a lot of time will pass before it becomes available to a wide range of patients.

However, in the long term, this successful experiment opens the way for the treatment of a wide variety of neurological diseases, including epilepsy and Parkinson’s disease.

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