Chinese researchers say they have created a gene-editing method that could return sight to people afflicted with inherited retinal diseases. Those close to the project say the breakthrough could assist with research into other rare genetic disorders.
An estimated two million people suffer from some form of retinal disease, for which there are no known cures, according to the South China Morning Post. However, Professor Robert McLaren, from the Nuffield Laboratory of Ophthalmology in Surrey, England, believes that figure is closer to 75 million.
Many of these diseases, such as retinitis pigmentosa, are caused by faulty genes within the retina’s cells. Symptoms typically occur in childhood but vary from person to person. They include impaired night vision, loss of peripheral sight or tunnel vision, and in some of the most aggressive cases, blindness.
Chinese Academy of Sciences Tianjin Institute of Industrial Biotechnology researchers, Bi Changhao and Zhang Xueli, in collaboration with Wang Xiaolin and Sun Xiaodong of the National Clinical Research Centre for Eye Diseases, believe they may have found a gene-editing technique that could offer hope to millions of visually impaired and blind people worldwide.
Current gene therapy techniques, which involve injecting healthy copies of the affected gene into the damaged retinal cells, do not guarantee full recovery for the subject as artificial DNA has a propensity to degrade with time, according to the team’s research paper, published in the blue ribbon scientific journal, Nature Communications.
To improve this, Zhang and his fellow researchers opted to transform the pathogenic gene itself using a standard Adeno-associated virus (AAV) as a vector to deliver a base editor – whose function is to modify mutated genes – into the retinal cells of the subject.
AAVs, which infect human beings as well as several other primate species, are considered a relatively safe delivery platform as the virus is small and triggers little to no immune response in infected individuals.
In fact, human eyes and other sites within the human system, like testes, foetuses, placentas and brains, possess ‘immune privilege’, a characteristic where the immune system limits its inflammatory response, making them particularly attractive research subjects for geneticists.
The research unit found that after just a single injection, their method accurately modified the afflicted genes of all mice in the study. According to their findings, the novel technique had a 49 per cent correction rate, prolonging the lifespan of the photoreceptor cells within the subjects.
Their work also revealed that similar technologies could assist with the treatment of other rare genetic disorders, such as sickle cell disease and thalassemia.
Despite the positive results, Zhang and his colleagues warn that further research and development is needed before clinical trials on human subjects can begin.