Sickle Cell  (Source: Getty Images)
Scientists are currently in the final stages of obtaining approval to start clinical trials for a gene therapy to treat and possibly cure sickle cell anemia. The CRISPR-Cas9 technology represents an important new approach that could transform research on sickle cell and lead the development of an innovative cure for this disease.

Although physicians and scientists have known the causes of sickle cell anemia for more than 60 years, treatments have been extremely slow to progress.  Until now…
Researchers from UC Berkley, San Francisco Benioff Children’s Hospital Oakland Research Institute (CHORI) have discovered a way to use the CRISPR-Cas9, genome editing technology to fix the mutated gene responsible for the sickle cell disease. The CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and associated protein enzyme (Cas-9) genes are used in molecular biology to make precise targeted changes to the genetic structure of living cells. Essentially, CRISPR-Cas9 allows medical scientists and researchers to edit and repair parts of the genetic code by replacing or adding parts to the DNA sequence. 
What is sickle cell disease?
More than 300,00 babies worldwide are born with sickle cell disease. The condition, is considered an “inherited” genetic disease because the genes are passed down from parents to children. Those who are born with sickle cell inherit two abnormal hemoglobin genes, one from each parent.
Sickle cell disease causes red blood cells, which are normally round and flexible, to become crescent shaped. These crescent or sickle shaped cells reduce the flow of blood and oxygen to nearby tissues.
As a life-long illness, children with sickle cell disease often suffer painful attacks, which can be sudden and life threatening. These crises, frequently require hospitalization, and can cause severe pain, fatigue, organ damage, stroke, and even death. The video below provides a brief overview of the problem with sickle cell disease.
See Video
CRISPR-Cas9: A Novel Gene Editing Technology
The approach to gene editing using CRISPR-Cas9 is to target a gene that keeps producing a form of hemoglobin that is made by both human fetuses and newborn babies to protect the body from disease. People normally stop making this ‘fetal’ hemoglobin after birth. Over time our bodies switch to making adult hemoglobin which is less efficient at carrying oxygen throughout the body.

Photo credit:  UC Berkley video/Roxanne Makasdjian and Stephen McNally

However, those with the sickle cell mutation that don’t develop the disease, continue to make fetal hemoglobin. Scientists discovered that the switch from fetal to adult hemoglobin is controlled by the BCL11A gene. By taking blood from patients with sickle cell anemia, they replace the genetic mutation that causes the disease and replace it with healthy DNA. This process allows the patient to use their own stem cells to continue producing fetal hemoglobin, and triggers the production of healthy red blood cells. Individuals with sickle cell are unable to produce healthy red blood cells.
Clinical laboratory test conducted with mice using genetically engineered stem cells showed that the transplanted cells continued producing healthy red blood cells at least four months after the procedure. Even though there is a lot more testing that needs to be done, the success of these initial outcomes seemed to have enough clinical relevance to be considered as a potential cure for sickle cell. 
Results were reported in the most recent issue (October 12) of the online journal Science Translational Medicine. According to co-author Mike Waters, Pediatric hematologist and Director of CHORI, “This is an important advance because for the first time we show a level of correction in stem cells that should be sufficient for clinical benefit in persons with sickle cell anemia.”. 
Clinical trials for this breakthrough genetic therapy could begin as early as next year.
Increased Survival Rates
Thankfully, adults with sickle cell disease are living on average into their 40’s and 50’s. The recent scientific advancements, combined with improvements in clinical treatments, technology and medicine have given hope of increased life expectancy to many patients with sickle cell disease. In fact, more than just increased longevity, quality of life can be improved for those who receive curative treatments.
Even as testing for current treatments is ongoing, the possibility of the successful use of gene therapy provides another ray of hope towards finding a cure for sickle cell anemia. For children and adults with this condition, experiencing life without pain means being able to return to school, work and social activities without fear of recurrent symptoms and complications from this debilitating disease.  Now that is life worth living!

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