Gene therapy of cystic fibrosis: modest successes
The mutation leading to cystic fibrosis was corrected in 5% of cells
Alexey Paevsky, Indicator
Specialists of the genome editing laboratory of the Academician N.P. Bochkov Medical and Genetic Research Center managed to correct a mutation in the CFTR gene that leads to the development of cystic fibrosis. In the cell culture of patients with cystic fibrosis, scientists edited the genes so that the correction efficiency was 5%, that is, in 5% of cells, the mutation was corrected. This is the best result achieved by Russian scientists working with the CFTR gene. The work was supported by a grant from the Russian Science Foundation (RNF) and published in the journal PLOS One (Smirnikhina et al., P.F508del editing in cells from cystic fibrosis patients).
Cystic fibrosis is the most common of rare, orphan diseases. More than 3,000 people with this diagnosis live in Russia today. The CFTR gene encodes a protein that forms a chlorine channel in cells for the exchange of chlorine ions between the cell and the intercellular space. Mutations in the homozygous state, that is, inherited from both parents, in this gene lead to the fact that chlorine is delayed in the cell, the exchange of electrolytes is disrupted, and a hereditary disease develops – cystic fibrosis, in which the respiratory system and pancreas are particularly affected.
Cystic fibrosis is caused by hundreds of mutations in the CFTR gene, including the most frequent in European populations – F508del. Specialists of the genome editing laboratory of the Academician N.P. Bochkov Medical and Genetic Research Center, as a result of a number of experiments, managed to correct a mutation in the cell culture of patients with cystic fibrosis by genomic editing. The correction efficiency was 5%, that is, in 5% of cells, the mutation was corrected. To cure cystic fibrosis, it is assumed that it is necessary to correct a mutation in 1-15% of the patient's lung cells. Low efficiency of genomic editing is a common problem of researchers all over the world. The data of the world literature speak about the effectiveness in different cases of 2-5%.
The immortalized CFTE29o- and induced pluripotent stem cells of a cystic fibrosis patient with homozygous mutation F508del were used in the work. An immortalized cell line is, in fact, "immortal" cells capable of dividing without restrictions. Scientists often use such cell lines in their work as a model biological object. Pluripotent stem cells are skin cells of a patient with cystic fibrosis, whose memory of which particular tissue they belong to has been "erased", they have been reprogrammed into stem, pluripotent, that is, they can be "programmed" to become cells of any organ or tissue of the human body.
"CRISPR/Cas9 components were introduced into cells, the effectiveness of mutation correction was evaluated by next-generation sequencing (NGS). In the culture, the CFTE29o mutation was corrected in about 3% of cells, whereas in the culture of the patient's stem cells - in 5% of cells. These results are in good agreement with the world data demonstrating the low efficiency of correction of this particular mutation," said Svetlana Smirnikhina, Head of the Genome Editing Laboratory at the Academician N.P. Bochkov Medical and Genetic Research Center, PhD.
It is necessary to conduct further studies aimed at improving the efficiency of delivery of CRISPR/Cas9 components to cells, which will increase the efficiency of editing the F508del mutation in the CFTR gene.
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