Gene therapy could return sight to people who are blind
The eye disease glaucoma destroys the optic nerve that connects the eye to the brain’s centre of vision. According to new experiments, a protein can repair the damage.
Scientists from the UK’s University of Cambridge have demonstrated that it is possible to restore optic nerves which have been destroyed, causing blindness. In experiments with mice, the scientists have used gene therapy to activate the gene that is responsible for producing the protein protrudin. This is involved in the composition of both nerve cells’ dendrites that receive signals from the eye’s visual cells, and of axons, which pass the signals on. The axons run all the way from the eye’s retina through the optic nerve to the centre of vision that is located at the back of the brain.
Glaucoma is one of the most common causes of blindness in older people. The disease occurs when axons are damaged and fail to regenerate because the protein is not present in fullygrown axons. By stimulating nerve cells to produce an excess quantity of the protein, the scientists managed to make the axons grow as if the nerve cells were very young. The scientists first cultured the nerve cells in culture dishes, cutting their axons in two by means of laser. Subsequently they stimulated the production of protrudin, making the axons regenerate.
When the scientists subsequently tested the method on living mice with damaged optic nerves, the axons from the nerve cells grew considerably over the following two weeks.
The experiments showed that protrudin works in two ways. First it produces a skeleton that controls the extension of the axon. Subsequently it attracts the building blocks for reconstruction.
The new results, which will require extensive trials, hold some hope that people who have become blind due to glaucoma could regain eyesight via increased protrudin activity.
Glaucoma is caused by damage to the optic nerve between the eye and the centre of vision. The exact cause is unknown, but the disease has to do with the fluid pressure in the eyeball becoming too high. Around 2% of the world’s population suffer from the disease, which comes in two versions:
Open-angle glaucoma:
this is age-related and can appear without any prior symptoms. When the patient discovers that vision of one eye is impaired, the damage to the optic nerve has often built up over several years.
Closed-angle glaucoma:
this is acute and often affects people of 40+ years with small, long-sighted eyes. The vision is periodically clouded, and patients feel pain over their eyebrows. Without treatment, the patient could go blind in a matter of a few days.