Retinitis pigmentosa is a degenerative disease that destroys the eye’s photoreceptors, light-sensitive neurons that are probably one of the most specialized and sensitive cells in the human body. Now, a novel gene therapy could help alleviate the effects of this pathology: the first step, a clinical trial published in the journal Nature Medicine that reports partial restoration of sight in a 58-year-old man, has already been taken . The technique used is called optogenetic therapy, and it uses flashes of light to control gene expression and the activation of neurons. Additionally, it is being investigated as a potential treatment for pain, blindness, and brain disorders.
As explained in the journal Nature , in a healthy retina, photoreceptors detect light and send electrical signals to the retinal ganglion cells (RGC), which then transmit the signal to the brain. The optogenetic therapy employed completely bypasses the damaged photoreceptor cells by using a virus to deliver light-sensitive bacterial proteins into the RGCs , allowing them to detect images directly bypassing the photoreceptors.
In the case study, the researchers injected the virus into the eye of a man with retinitis pigmentosa and waited four months for protein production by retinal ganglion cells to stabilize. The researchers then designed a prototype of glasses that capture visual information and optimize it for detection by bacterial proteins. The trial participant had to train with the glasses for several months before his brain adapted to interpret the points correctly. Finally, he was able to make out high-contrast images, including objects on a table and the white stripes on a crosswalk. When the researchers recorded your brain activity, they found that your visual cortex reacted to the image in the same way that it would if you had normal eyesight. Of course, because the retina contains around a hundred times more photoreceptors than RGCs, the resolution of the images detected by RGCs will never be as good as natural vision.
Limitations of this work
Although the trial has been completed in just one person, six others have been injected with the same light-sensitive proteins, but the pandemic has delayed their training and the researchers hope to see results soon. We will have to wait to find out if these results are replicable, since the results cannot be generalized since it is a single person. “This is a high-quality study, which is carried out and controlled with great care,” James Bainbridge, professor of retinal studies at London Global University , explains to the Science Media Center. . “ The problem is that the findings are based on laboratory tests performed on one person, so more work will be needed to find out if this technology is really useful. The press release describes an improved recognition of the objects, but there is no evidence in the results of the study ”, he clarifies.
