The mice have seen the light
Gene therapy restored vision to blind mice
Sergey Vasiliev, Naked Science
It was quite easy for laboratory mice to regain their eyesight. Scientists from the team of UC Berkeley Professor Ehud Isacoff (Ehud Isacoff) the gene encoding the receptor protein opsin, sensitive to green color, was introduced to the animals, and after a month the rodents were able to navigate the maze, relying on the restored eyes. According to the authors, the mice's vision was not perfect, but sharp enough to distinguish the letters on the tablet screen. The authors hope that in a few years the method will begin to be tested on humans: "An intraocular injection of modified viral particles is enough," says Professor Isakoff, "and in a couple of months the patient will be able to see something."
In fact, diseases and inevitable age-related changes lead to retinal degeneration. According to scientists, every tenth person over the age of 55 suffers from it, and this condition still remains poorly curable. About 1.7 million more people worldwide suffer from congenital blindness caused by retinal degeneration due to mutations in any of the hundreds of genes important for its development. In some severe cases, the only option for them is the installation of visual implants – which are still very far from perfect.
Most of these disorders lead to the mass death of photosensitive cells of the eye, rods and cones. On the other hand, other types of retinal cells, including ganglion cells, which normally receive a signal from photoreceptors, and bipolar cells, which collect signals from ganglion cells and send them further to the brain, usually remain unaffected by degradation. Gene therapy allows to give them additional photosensitivity functions.
Gene therapy for retinal degeneration uses modified virus particles as a "vector" to deliver genes to target cells. Previously, they had to be introduced with jeweler's precision into the layers below the retina itself (below), now an injection into the vitreous body (above) is enough / ©John Flannery, Berkley University.
American geneticists used particles of the adenoassociated virus (AAV), which does not cause serious diseases in humans, but is able to integrate into our genome. Scientists have modified AAV so that it has the ability to selectively bind to retinal ganglion cells.
Anchored on the surface, they introduce DNA encoding the opsin gene into the cell, which is normally contained in photoreceptors and makes them sensitive to light from the green and yellow parts of the spectrum. The operation on mice was successful, and after the injection of such particles, their ganglion cells began to synthesize a sensitive protein, register light and again transmit visual signals further down the chain.
Tracks of the first minute of moving mice in an unfamiliar cage: at the top – an animal blind from birth; in the middle – an animal with restored vision; at the bottom – a healthy control mouse / ©John Flannery, Ehud Isacoff, Berkley University.
"Within the limits that tests allow us to judge, the behavior of mice with restored vision was no different from the behavior of completely healthy ones," the authors of the work add. However, the claimed effectiveness needs to be confirmed in humans. After all, our retina contains hundreds of times more photoreceptors and ganglion cells. A person will need an injection of a much larger number of viral particles, and only full-fledged clinical studies will show how much they will restore his vision.
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