Choroideremia gene therapy: success is developing
Gene therapy for blindness has been successfully tested in the UK
Medical news from Oxford University: Gene therapy trial shows promise for type of blindnessWith the help of gene therapy, scientists from the University of Oxford were able to partially restore vision to people with a hereditary progressive form of blindness – choroideremia.
The researchers replaced the defective gene by giving patients a single injection of a normally functioning copy of the gene. The results of phase I clinical trials published in The Lancet (MacLaren et al., Retinal gene therapy in patients with choroideremia: initial findings from a phase 1/2 clinical trial) may in the future help in the treatment of other genetically determined diseases of the visual organ, for example, macular degeneration and retinitis pigmentosa.
With choroideremia, there is a gradual degeneration of the choroid (the vascular membrane of the eye), the pigment epithelium and the retina of the eye, which significantly impairs visual functions. Over time, rods and cones – light–sensitive cells of the retina of the eye that send signals about visual information to the brain - also degenerate, resulting in complete loss of vision. This disease develops as a result of a mutation of the CHM gene located on the X chromosome, which encodes the REP1 protein, a component involved in the processes of movement of substances through the cell membrane. Choroideremia progresses slowly: blindness overtakes most patients by the age of 40-60; there is currently no treatment for this disease.
In this study, Professor Robert MacLaren and his colleagues studied the effect of gene therapy on the visual functions of six patients aged 25 to 63 years with diagnosed choroideremia. In order to stop the death of photoreceptors, they injected a vector – a genetically engineered design of a non-pathogenic human adeno-associated virus (AAV) encoding the REP1 protein into their retina.
As the results showed, thanks to such treatment, the patients' vision partially improved without causing any undesirable consequences for their health. Six months after the manipulations, all the subjects had a stable increase in visual acuity, and two of them were able to see three lines more on the vision test table. The scientists also noted an increase in the photosensitivity of the eye that was subjected to gene therapy in all participants of the experiment.
"This is the first time that gene therapy has been used to treat patients before the appearance of clinically significant retinal thinning," said Dr. McLaren. "The results obtained open up great prospects for gene therapy in preventing vision loss in other retinal diseases, for example, in age–related macular degeneration."
According to scientists, the ultimate goal of gene therapy will be to preserve the central part of the retina from further degeneration. And even if the effect of such treatment turns out to be small, it will have a positive value, since there are additional therapeutic measures that help to preserve or restore visual functions.
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