|Human red blood cells made from bone-marrow stem cells of a patient with sickle-cell disease. The red blood cells with BetaAS3 anti-sickling vector show the normal round shape, while those that were not corrected are sickle shaped. Photo: Courtesy of Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research|
Sickle-cell disease causes the body to produce misshapen red blood cells that form like the crescent-shaped blade of a sickle, which hinders blood flow and deprives the body’s organs of oxygen. Dr. Kohn introduced an anti-sickling gene into the hematopoietic stem cells to capitalize on the self-renewing potential of stem cells and create a continual source of healthy red blood cells that do not sickle. The breakthrough gene-therapy technique for sickle-cell disease is scheduled to begin clinical trials early next year.
Dr. Kohn’s autologous gene-therapy approach is a revolutionary alternative to current sickle-cell disease treatments, which include transplanting patients with donor hematopoietic stem cells. Such transplants offer a potential cure for sickle-cell disease, but due to the serious risks of rejection, only a small number of patients have undergone this procedure, and it is usually restricted to children with severe symptoms.
Dr. Kohn and colleagues found that in the laboratory, the hematopoietic stem cells produced new non-sickled blood cells at a rate sufficient for significant clinical improvement for patients. The new blood cells survive longer than sickled cells, which also could improve treatment outcomes.
More than 90,000 patients in the U.S. have been diagnosed with sickle-cell disease. It is caused by an inherited mutation in the beta-globin gene that makes red blood cells change from their normal shape, which is round and pliable, into a rigid, sickle-shaped cell. Normal red blood cells are able to pass easily through the tiniest blood vessels, carrying oxygen to organs throughout the body. But due to their rigid structure, sickled blood cells get stuck in the small capillaries.
“ß-globin Gene Transfer to Human Bone Marrow for Sickle Cell Disease,” Journal of Clinical Investigation, July 1, 2013