A team of researchers at the Stanford University School of Medicine has used CRISPR to repair the gene that causes sickle cell disease in human stem cells, which they say is a key step toward developing a gene therapy for the disorder.
The team demonstrated that the modified cells could make a functioning hemoglobin molecule, and then successfully transplanted the stem cells into mice. The researchers say the study represents a demonstration in principle for the repair of blood-borne genetic diseases, such as sickle cell disease and thalassemia.
As many are aware, the sickle mutation causes the red blood cells to make an altered version of the hemoglobin that forces the red cell into a sickle shape. These cells do not flow smoothly through blood vessels; they jumble together and cause blockage. This leads to severe pain and dangerous health consequences. Sickle cell disease affects 70,000 to 100,000 Americans and millions globally.
The research team started with human stem cells from the blood of patients with sickle cell disease, corrected the gene mutation using CRISPR and then concentrated the human stem cells so that 90 percent carried the corrected sickle cell gene. The team injected the concentrated, corrected hematopoietic stem cells into young mice.The corrected red blood cells do not have to replace all of a patient's original sickle cells. If the amount of sickle cells is below 30 percent, patients have no symptoms of disease
Some may question the safety of using gene therapy. According to the article, "the team found that their corrected human hematopoietic stem cells seemed to behave like normal, healthy human hematopoietic stem cells." But there are the possibilities of problems including the alteration of the wrong sequence of DNA or unexpected immune reaction. So the effects of gene editing are really impossible to predict. For now, it looks like CRISPR is the best thing we've got.