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Sickle cell anemia is a disease that affects 500 million people around the world annually. The disease is caused by a mutation in the gene that makes hemoglobin. The abnormal hemoglobin causes an individual's red blood cells to sickle and clump which clogs blood vessels causing the characteristic debilitating symptoms and pain. The pain affects an individual's day to day life and as such researchers are constantly working on ways to alleviate the symptoms or cure the disease.
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Bone Marrow & Umbilical Cord Stem Cells Transplant
Bone marrow transplants have been used as a safe permanent cure for sickle cell anemia. In a study that appeared in the journal Biology of Blood and Marrow Transplantation in 2008 researchers performed reduced intensity conditioning (a less toxic procedure) bone marrow transplants that are safer and more effective for people afflicted with severe sickle cell anemia. Traditional bone transplants can be a life-threatening procedure for patients whose health is already compromised by the sickle cell disease. Generally speaking transplants are rare because of the difficulty of finding a compatible donor but this may be a hurdle of the past because of a new transplant procedure called sickle cell unrelated transplants (discussed below).
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Researchers are studying and identifying the genes that are related to the abnormal hemoglobin production in patients suffering from the disease. This new treatment's precept is based on the fact that it may be possible to repair the damaged gene or restore the function of the gene used to produce fetal hemoglobin. Fetuses produce a type of hemoglobin called fetal hemoglobin which has a high affinity for oxygen and is found in individuals with both the normal and abnormal adult hemoglobin gene. In sickle cell anemia patients whose bodies continued producing fetal hemoglobin, disease symptoms were not as severe. Normally, fetal hemoglobin disappears soon after birth, and in an individual with the sickle cell anemia, disease symptoms start appearing. Gene therapy can be used to allow the body to continue producing fetal hemoglobin which can alleviate the disease associated symptoms. In another study that appeared in the journal Molecular Therapy, December 2008, a group of scientists used gene therapy to introduce the normal gene into the mice’s hemoglobin genetic code to produce fetal hemoglobin. This procedure still requires more testing before it can be attempted in the human population.
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Future Sickle Cell Therapies
In another study that appeared in the journal Science in December 2008 researchers suppressed the gene BCL11A which lead to an increase in fetal hemoglobin production. The newly discovered gene promises to be a target site for future gene therapy. Increasing levels of fetal hemoglobin have successfully alleviated symptoms associated with sickle cell anemia. Advances in transplant cures are also coming down the pike; a recent US National Phase II clinical trial, donor marrow and umbilical cord from an unrelated individual will be transplanted into patients with severe sickle cell disease. The results of this study will hopefully pave the way for Sickle Cell Unrelated Transplants (SCURT) cutting the wait time for suitable bone marrow matches.
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Lakshmanan Krishnamurti, Sandhya Kharbanda, Melinda A. Biernacki, Wandi Zhang, K. Scott Baker, John E. Wagner, Catherine J. Wu Stable Long-Term Donor Engraftment following Reduced-Intensity Hematopoietic Cell Transplantation for Sickle Cell Disease Biology of Blood and Marrow Transplantation November 2008 (Vol. 14, Issue 11, Pages 1270-1278)
Pestina TI, Hargrove PW, Jay D, Gray JT, Boyd KM, Persons DA.Correction of Murine Sickle Cell Disease Using gamma-Globin Lentiviral Vectors to Mediate High-level Expression of Fetal Hemoglobin. Mol Ther. 2008 Dec 2
Sankaran VG, Menne TF, Xu J, Akie TE, Lettre G, Van Handel B, Mikkola HK, Hirschhorn JN, Cantor AB, Orkin SH. Human Fetal Hemoglobin Expression Is Regulated by the Developmental Stage-Specific Repressor BCL11A. Science. 2008 Dec 4.
Children's National Medical Center (2008, August 19). Landmark Sickle Cell Disease Trial To Investigate Unrelated Donor Marrow And Umbilical Cord Blood Transplants. ScienceDaily. Retrieved December 29, 2008, from http://www.sciencedaily.com /releases/2008/08/080818183946.htm