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Stemming Sickle Cell (con't)Chris Hartlove

Stemming Sickle Cell (continued)

Death’s Crescent

Sickle cell is among the most common disorders caused by a single genetic defect, and it can be devastating.

People with the disease produce crescent-shaped red blood cells that are stiff, sticky and prone to piling up or breaking apart, clogging small vessels. These misshapen cells only live about one-tenth as long as normal blood cells, and a patient’s bone marrow can’t make replacements fast enough to keep delivering sufficient oxygen to the body.

Clogged vessels often trigger attacks, called “crises,” that produce acute pain in the back, chest, arms or legs and can last for hours or days. Patients may suffer leg ulcers, small strokes, blindness, and kidney failure and be prone to lethal infections.

The disease is found in certain populations around the world but is most common in Africa, parts of the Middle East, India, Central America and the Caribbean. It affects an estimated 90,000 to 100,000 people in the U.S., including about 1 in 500 African Americans.

The mutation that causes the disease is thought to have evolved in the tropics. For those carriers of a single gene (said to have “sickle cell trait”), most do not have symptoms of sickle cell disease but do have some protection against malaria.

In the U.S., the universal screening of newborns and early, aggressive treatment of sickle cell disease with blood transfusions, antibiotics and other drugs have helped reduce infant mortality and prolong lives. But the disease can still have a devastating impact on patients: Life expectancy in the U.S. for women with the disorder is still only about 48 years. For men, it’s 42.

In recent years, doctors have cured sickle cell disease in a few hundred patients using a technique that combines stem cells from healthy donors with bone marrow transplants. But the procedure is expensive and risky, Chandrasegaran says, while matching patients with healthy donors can be very difficult.

So Ramalingam and Chandrasegaran, working with Civin, are trying a different approach. Instead of using donors, they plan to take a sickle cell patient’s own stem cells, repair the faulty gene, and turn the repaired stem cells into blood and blood-producing cells. The hope is that these healthy cells, put back in the body, will outlast and replace the diseased ones without the need for a bone marrow transplant.

The aim is to make the repair of a patient’s sickle cell gene safer, simpler and cheaper, putting the procedure within the reach of more patients. “We’d like everybody to have access to it, so we want to make it as inexpensive as possible,” says Chandrasegaran.

If the technique works, the senior researcher says it could have wide applications. The biotech company Sangamo Biosciences of California has licensed some of Chandrasegaran’s work and is using a similar strategy to knock out a gene known as CCR5 with zinc finger nucleases, eliminating a route HIV uses to invade and hijack the body’s immune system.

Comments

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  • AFOLABI WASIU

    NIGERIA 10/14/2012 07:31:10 AM

    Congratulations to these scientists for daring to take up this challenge. I can only wish them success as humanity will never forget anyone that will rid the world of these deadly scourges. There will be light at the end of the tunnel

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