Researchers using the gene editing system CRISPR-Cas9 have demonstrated that gene editing is a viable cure for sickle cell disease
Sickle cell disease (SCD) is a group of severe, recessive inherited disorders affecting red blood cells and causing an unusual sickle-like shape. The different mutation types impair haemoglobin function and typically lead to clumping which blocks blood vessels and causes a number of serious health problems. It is particularly prevalent in African American and Sub-Saharan populations, but affects hundreds of thousands of people worldwide.
CRISPR as a solution
Gene editing is an appealing and elegant solution to these types of genetic disorders, as correcting each mutation should effectively cure the condition (as long as permanent tissue damage has not already happened). In contrast to mutations that cause widespread dysfunction throughout the body, sickle cell disease is rooted in blood cells which are derived from bone marrow stem cells. This means they're easier to target specifically with gene therapy or gene editing, because you don't have to flood the entire body with the therapy and correct a huge and wide variety of cells.
A promising development
A team from multiple universities used CRISPR-Cas9 to correct these mutations in hematopoietic stem cells in mice which reside in the bone marrow. They did this outside of the body (ex vivo) and then transplanted these cells in sufficient number into mice with SCD. The study lasted for 4 months, and by the end these cells were still present. More importantly, they were functioning correctly and producing healthy haemoglobin, suggesting that this solution could be a long term treatment.
"This is an important advance because for the first time we show a level of correction in stem cells that should be sufficient for a clinical benefit in persons with sickle cell anemia. Sickle cell disease is just one of many blood disorders caused by a single mutation in the genome. It's very possible that other researchers and clinicians could use this type of gene editing to explore ways to cure a large number of diseases. There is a clear path for developing therapies for certain diseases. It's very gratifying to see gene editing technology being brought to practical applications"
While the study is a great boost for gene editing technology, it will take a considerable amount of work to translate the progress into humans, with larger animal studies and safety checks in humans. It could represent a significant improvement over current approaches however and could be applicable to many other rare blood disorders too like β-thalassemia and severe combined immunodeficiency (SCID).
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