Biologists have succeeded in inserting the gene for the light-sensitive protein substance MCO1 into the retinal nerve cells of rodents who have lost their sight.
The researchers inserted the gene into a viral object and introduced it into the organs of vision of mice suffering from retinitis pigmentosa . The new protein substance did not provoke an inflammatory response, and the rodents successfully passed visual tests.
During the perception of a picture visible to the eye, light beams are focused in the area of the retina, equipped with photoreceptors - the well-known cones and rods. The receptors contain the photosensitive protein opsin, which reacts to the photon flux and causes intrareceptor generation of a nerve impulse. The impulse is transmitted to the bipolar nerve cells of the retina, after which it is sent to the brain.
But such a scheme does not always work: in patients with retinitis pigmentosa (there are about 1.5 million of them in the world), photoreceptors lose their ability to respond to light, which is associated with changes in the genes of photosensitive opsins. This hereditary pathology causes a severe decline in visual function, up to a complete loss of vision.
Drug therapy for retinitis pigmentosa is complex and involves not restoration, but only the preservation of the functional ability of the surviving receptors. For example, retinol acetate preparations are actively used. It is possible to restore vision only through complex and expensive surgical intervention. However, not so long ago, optogenetic techniques came into practice: specialists embed photosensitive protein substances directly into the nerve cells of the retina, and after that they begin to respond to the light flux. But before the current study, a response from genetically modified cells could only be obtained after a powerful signaling effect.
Scientists have injected a substance into bipolar nerve cells that reacts to daylight. A DNA fragment was created to highlight the opsin, which was then inserted into a viral particle that had lost its pathogenic abilities: its purpose was delivery and packaging into a genetic construct. The particle was injected into the eye of a sick rodent: the DNA fragment was integrated into the neurons of the retina . Under microscopic control, the scientists noticed that the genes reached the limit of activity by 4 weeks, after which the level stabilized. To check the quality of vision after the procedure, the rodents were given the task: to find a dry illuminated island among the water, while being in the dark. The experiment demonstrated that the vision of mice really and significantly improved as early as 4-8 weeks after the manipulation.
It is quite possible that the developed gene therapy of the rodent retina, after a number of other tests, will begin to be adapted for the treatment of humans. If this happens, then there will be no need for expensive surgical interventions, for connecting special devices to amplify the photo signal. Only one or more injections of the protein substance will be required.
Read more about the study in the journal Gene Therapy, as well as on the Nature page.