Sickle cell disease or sickle cell anemia is a chronic hereditary blood disorder that is difficult to treat, and that causes episodes of extreme pain in patients as well as a range of other health problems. Up until recently there were no effective treatment options, especially not for adult patients, but the advent of stem cell transplants has been a gamechanger. This treatment has been in used to treat sickle cell patients in the USA, and recently the Amsterdam UMC in the Netherlands has started treating patients in this manner. However, Dutch scientists have adapted the American practice in such a way, that patients weren’t only cured from their sickle cell disease, but also did not need to take immunosuppressants for the rest of their lives. So far, ten patients have been completely cured in this manner. In Belgium, stem cell transplants are not yet offered as a treatment for sickle cell disease.
Sickle cell disease is caused by a genetic mutation. This causes stem cells in the bone marrow to produce red blood cells in the shape of a crescent or sickle. Because of this shape, blood cells tend to get entangled and can end up jammed in the smaller blood vessels, causing all kinds of adverse reactions. Tissues and organs end up receiving too little oxygen and can get damaged as a result. The blockages can also cause severe pain that can last for days. On top of this, sickle cells do not live as long as normal blood cells, which leads to chronic anaemia in sickle cell patients. All these factors combined result in a lower life expectancy for patients: on average sickle cell patients only live to be 54 years old.
Stem cell therapy is basically a technique where ‘wrong’ stem cells are replaced by healthy ones from a donor, usually a sibling. This therapy is implemented mostly in the treatment of leukaemia in children. In order to prevent the immune system from attacking the new ‘alien’ stem cells, it is imperative that the patient’s immune system is disabled before the actual transplant. This is usually done by a heavy dose of chemotherapy. This is the reason why stem cell therapy is rarely performed on adult sickle cell patients. Since their organs have already become damaged over time, chemotherapy is too risky. In the USA adult patients receive a combined treatment of antibodies and low dosage radiation in order to prepare the body for the new stem cells.
The results in the USA leave room for improvement. In 85% of cases, the stem cell transplant is a success, but in 15% of cases the stem cells are rejected by the patient. Another downside of this treatment is the fact that the patients’ immune system must be suppressed for the rest of their lives. This means that they need to take strong immunosuppressant medication –with many side effects such as joint pain, high cholesterol levels and acne- and also need to make lifestyle choices that impact their quality of life, because they are extremely susceptible to infection.
The scientists at the Amsterdam UMC have added a so-called preconditioning phase to the American protocols. In this phase, the patient first receives medication that reduce activity in the bone marrow and calm the immune system down. Ten patients have undergone this enhanced treatment in Amsterdam over the last two years, and so far results are promising: the stem cell transplants have succeeded in every case. Furthermore: all patients have been weaned off the immunosuppressant medication. The ten patients remain to be followed by the Dutch scientists in order to monitor long term effects and whether damaged organs will in some way recover.
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