Nanopackaging for genomic editor
CRISPR-Cas9 Genomic Editor adapted to fight blood diseases
Due to this, patients with sickle cell anemia and other similar diseases will get a chance for treatment
Molecular biologists have created nanoparticles with which the CRISPR/Cas9 genomic editor can be used to treat sickle cell anemia and other blood diseases that are associated with the appearance of dangerous mutations in genes involved in the production of hemoglobin. An article with the results of their first experiments was published by the scientific journal Science Advances (Yang et al., .
"The results of our work have shown that nanoparticles can be used to deliver CRISPR/Cas9 to blood stem cells, which are quite difficult to infect with the help of viruses traditionally used for these purposes. We hope that with the help of our approach, it will be possible to combat a variety of forms of hemoglobin disorders," the researchers write.
According to statistics from the World Health Organization (WHO), about 420 million people worldwide suffer from sickle cell anemia and other diseases that are associated with a mutation in the HBB gene responsible for hemoglobin synthesis. So far, scientists have no effective methods of combating these diseases, except for suppressing their symptoms and various external manifestations.
Chinese and American molecular biologists, led by Professor Donald Cohn of the University of California at Los Angeles (USA), took the first step towards creating a therapy that would allow patients to get rid of such mutations. The key element of their method was the CRISPR/Cas9 genomic editor.
It was opened in early 2010 by future Nobel laureates Emmanuel Charpentier and Jennifer Dudna in the study of bacteria. CRISPR/Cas9 consists of two parts – the Cas9 protein, which cuts the DNA of cells, as well as a set of short RNA molecules that this enzyme uses as a kind of "templates" for recognizing those sequences of nucleotides that need to be cut from the genome.
As a rule, Cas9 molecules and "templates", strands of the so-called "guide RNA", are introduced into human or animal cells using special viruses purified from dangerous contents. In the case of blood stem cells and their progenitors in the bone marrow, this is quite difficult to do because of the large size of Cas9 and the high cost of reagents.
Cohn and his colleagues wondered whether it was possible to use nanoparticles that penetrate human cells to deliver Cas9 molecules, "templates" and correct copies of the HBB gene to blood stem cells. Similar methods have already been successfully used for fairly simple procedures involving the removal of damaged DNA sections, but so far scientists have not used nanoparticles to replace one copy of a gene with another.
Cohn and his colleagues solved this problem by creating porous polymer nanoparticles that consist of three different organic components. Such structures, as experiments on cell cultures show, easily penetrate into them and decompose there, releasing their contents into their cytoplasm.
Having created two different types of similar nanoparticles, the scientists filled them with copies of the Cas9 protein, copies of the HBB gene, as well as RNA templates. The latter forced the enzyme to cut out one of the sections of junk DNA in the nineteenth chromosome, which is not related to the vital functions of the body.
The scientists tested the work of these nanoparticles on blood stem cell cultures obtained from patients suffering from sickle cell anemia. These experiments showed that nanoparticles penetrated about 21% of cells and successfully edited their genome by inserting instructions for the production of a luminous version of hemoglobin into them. The probability of this, as the researchers note, was significantly increased when using different nanoparticles to deliver the genomic editor and copies of the HBB gene.
Scientists injected some of these "reprogrammed" stem cells into mice and monitored their reproduction. It turned out that the stem cells did not lose a new copy of HBB and showed no abnormalities in their vital activity.
The successful completion of these experiments, according to Cohn and his colleagues, opens the way for the use of CRISPR/Cas9 not only for the treatment of sickle cell anemia, but also other diseases associated with mutations in HBB. These include, for example, beta-thalassemia, which occurs as a result of the appearance of several mutations in HBB at once. In the near future, geneticists plan to conduct experiments of this kind on mice.
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