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Sunday, 17 June, 2001, 00:42 GMT 01:42 UK
Sickle cell transplant hope
Cells in the condition take on a distinctive shape
Cells in the condition take on a distinctive shape
Giving "mini" bone marrow transplants to sickle cell anaemia sufferers could offer hope of a cure.

Researchers in the United States have carried out tests where they transplanted 40% of the usual amount of normal bone marrow into mice, successfully treating the condition.

UK expert, Dr Phil Darbyshire, who has carried out full bone marrow transplants on sickle cell anaemia patients, said the US work could offer a safer treatment for some patients.

He told BBC News Online: "They are trying to use less invasive treatment. It may also reduce the complications of the procedure."


Even a small amount of normal marrow can result in drastic reductions in abnormal red cell counts

Dr Robert Iannone,
John Hopkins Children's Center
Sickle cell anaemia (SCA) is a congenital disease which mainly affects people of Afro Caribbean and West Indian descent, and can prove fatal.

Some people are carriers of sickle cell, but do not have the condition itself, so scientists know people can have disordered cells, but still be healthy.

The key is what proportion of healthy cells are needed to treat the symptoms of sickle cell anaemia.

The US research, carried out by John Hopkins Children's Center in Baltimore, Maryland successfully treated SCA in mice with the modified bone marrow transplant.

Ongoing trials with two human patients are also going well.

Balance

Dr Robert Iannone, who led the team, said once it was known the amount of normal bone marrow required to prevent complications from sickle cell anaemia, "mini" transplants could be given which could treat the condition, but reduce the risk of the donor tissue being rejected.

In the experiment, the normal bone marrow of the mice was genetically destroyed and different combinations of healthy and sickle cell making marrow were transplanted into them.

After four months the scientists checked the mice.

Dr Iannone found a "mini-transplant" of just 40% was enough to reduce anaemia and organ damage, symptoms of SCA, in the mice.

Those with 25% of normal bone marrow had 90% or more normal red blood cells in their system. The damaged cells they did have were too few to cause sickle cell symptoms of severe oxygen deficiency and tissue damage.

The mice who had 15% or more of the sickle cells suffered the symptoms of the condition, but that figure could be reduced with a transplant of less than 25% normal bone marrow, said the scientists.

Dr Iannone said: "Even a small amount of normal marrow can result in drastic reductions in abnormal red cell counts."

Sickle cell anaemia is named after the distinctive shape formed by red blood cells.

The cells' shape is affected because a protein within it - haemoglobin which carries oxygen from the lungs to the rest of the body - is different to normal.

This means sickled cells stick together and cannot get through small blood vessels as easily as healthy cells. This can stop oxygen getting through, and cause damage organs, or in some cases, strokes.

There is currently no cure for sickle cell widely available, but doctors can manage the condition.

Risk

Dr Darbyshire, a paediatric haematologist at Birmingham Children's Hospital, has himself carried out full bone marrow transplants on sickle cell patients, but says the operation is risky, and is not suitable for all patients with the condition.

Fifteen operations have been carried out in the UK, and one patient has died.

He said the US "mini transplant" would pose fewer risks for patients, needing less chemotherapy, and having a better chance of succeeding because there would be less bone marrow for the patient's body to accept.

"A (full) bone marrow transplant does cure the patient, but at a price. Some patients become infertile, and there are other complications," he said.

There can also be problems finding a suitable donor, something he said could still be a problem with a "mini transplant".

The research is to be published in the journal Blood.

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