Nanoparticles instead of viruses

Viruses did not live up to expectations: delivery of CRISPR tools will be entrusted to nanoparticles

Yulia Vorobyova, Vesti

CRISPR gene editing technology opens up new opportunities for researchers, including those that could only be dreamed of before. However, even the best tools can and should be improved, scientists are sure.

So, in the case of DNA editing, it is very important to deliver the genetic material to exactly the right place. This will help not only to increase the effectiveness of the method, but also to avoid non-target mutations, which so far occur quite a lot when genes are changed.

A team from the Massachusetts Institute of Technology, together with colleagues from the Russian Skoltech, has developed a new way to transfer the CRISPR tool to the target region of the genome.

Previously, viruses were used for this. However, experts believe that because of them, patients may develop resistance to treatment. Therefore, it was proposed to use nanoparticles instead of viruses.

Let us explain that the CRISPR technique is useful in the treatment of many diseases. The genetic mutations that cause the disease are cut out of the patient's genome and replaced with "correct" sequences. This is the task of the Cas9 enzyme: it cuts a strand of DNA and a short RNA that "tells" where to make a "cut" (the RNA guiding the enzyme is called an RNA guide). A harmless virus serves as a "courier" for the delivery of such "scissors".

However, this approach has its drawbacks. The fact is that the patient's immune system can develop antibodies against this virus. So the effectiveness of repeated therapy will noticeably decrease. Scientists have proved that it is possible to avoid these problems if you use another "deliverer" instead of the virus.

First, the team chemically modified the RNA so that it would not be destroyed by enzymes in the body. These modified RNA guides, together with Cas9, were "packed" into lipid nanoparticles, which were sent to the liver cells of adult mice. In addition, the animals were also injected with nanoparticles containing mRNA that encoded the Cas9 enzyme.

As a result, the enzyme "cut out" the intended sections of genes in about 80% of cells. This indicator for the CRISPR tool when working with adult animals has become a record.

The enzyme was chasing the Pcsk9 gene, which is responsible for regulating cholesterol levels. Mutations in this gene cause liver disorders and contribute to the accumulation of "bad" cholesterol. When this gene was removed, the production of the protein it encoded decreased so much that the proportion of "bad" cholesterol in rodents decreased by 35%.

"We have shown that nanoparticles can be used for permanent and accurate DNA editing in the liver of an adult animal. I believe that fully synthetic nanoparticles can become a powerful tool not only for changing the Pcsk9 gene. They will also help in the treatment of other diseases," says Daniel Anderson, the head of the work.

Now his team plans to "incite" nanoparticles on other genes, mutations in which cause serious diseases. First, the research will continue specifically with liver cells, and then, probably, scientists will try out a new method of delivering "scissors" on other organs.

A scientific article describing the innovative method has been published in Nature Biotechnology.

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