Gene therapy of retinitis pigmentosa
Geneticists have learned how to fix damaged genes and restore vision
Anna Govorova, Infox.ru
Bioengineers from Cedars-Sinai Medical Center (USA) managed to fix damaged genes directly in the adult body, Infox reports.
They cured retinitis pigmentosa in rats, a dangerous hereditary disease that leads to blindness, using the CRISPR/Cas9 system – a "genetic scalpel", removing the damaged DNA section and inserting a healthy one in its place.
"So far, our research has been conducted on animals. But we are confident that if we work on this method further, it will be possible to use genome editing based on the CRISPR/Cas9 system for the treatment of hereditary retinitis pigmentosa in humans," says lead author of the study Dr. Shaomei Wang [in a press release Gene Editing Technique Improves Vision in Rats with Inherited Blindness – VM].
Retinitis pigmentosa is a rare but dangerous disease that leads to vision loss. It is a form of retinal dystrophy and is associated with abnormalities of photoreceptors (rods and cones) or retinal pigment epithelium. Currently, unfortunately, there are no methods of treating this serious disease.
Gene editing using the CRISPR/Cas9 system is based on a molecular mechanism that allows some bacteria to incorporate DNA from the external environment into their genome. It is based on the Cas9 protein, which cuts the double-stranded DNA chain of the cell so that the desired segment can be inserted there. With the help of RNA guides, short guide sequences of RNA, it is possible to show Cas9 the place where the incision needs to be performed.
This method of genome editing appeared not so long ago – about five years ago. But a lot has already been achieved in this direction.
At first, the method was used only on cell cultures. But in 2014, geneticists from the Massachusetts Institute of Technology managed to use it to edit the DNA of mice suffering from severe hereditary liver disease. Scientists injected intact sections of DNA directly into the animals' bodies, removing the mutant ones. And the animals were cured.
Another example: more recently, a young Chinese molecular biologist Junjiu Huang from Sun Yat-sen University in Guangzhou has alarmed the entire scientific community with his research in the field of editing the genome of the human embryo.
The team under his leadership also managed to use the CRISPR/Cas9 system to rid the embryo of a mutation that causes a fatal violation of the hematopoiesis system – beta-thalassemia. Many considered such studies, though promising, but unethical.
In the current study, American bioengineers worked with rats suffering from retinitis pigmentosa. They intravenously injected a CRISPR/Cas9 system into the body of sick animals, configured in such a way as to remove the damaged section of DNA and insert a healthy one. As the test showed, the rats' vision improved significantly after that.
"For the first time, we were able to use the CRISPR/Cas9 system to prevent vision loss directly in the adult body. And this makes it possible to continue further research in this area, and in the future we can talk about the possibility of introducing this method into clinical practice," says one of the authors of the study, Clive Svendsen.
The authors report on the results of their research in the latest issue of the journal Molecular Therapy (Bakondi et al., In Vivo CRISPR/Cas9 Gene Editing Corrects Retinal Dystrophy in the S334ter-3 Rat Model of Autosomal Dominant Retinitis Pigmentosa).
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11.01.2015