Cell transplant hope for blood diseases and Multiple Sclerosis 23 November 2007
Thousands of patients with ailments such as multiple sclerosis and sickle cell disease have been given new hope that cell transplants could offer a more effective way to treat them.
An important step towards the goal of transplanting the parent stem cells that give rise to red blood cells to treat genetic blood diseases, such as sickle cell disease, is reported by an American team.
Using the same method, it should be possible to treat a person with an autoimmune disease, such as multiple sclerosis, in which immune cells attack the person's own body.
An immune system transplant, much like a liver, kidney or heart transplant, would give the person a different set of white blood cells that might not attack the body, offering an effective treatment.
Bone marrow transplants are already used to, in effect, transplant stem cells that make healthy white and red blood cells from one person to another but it is necessary to wipe out the old bone marrow first with radiation, which damages other tissue and can cause lasting effects including infertility, brain damage and an increased risk of cancer.
Now an elegant and more efficient way to achieve the same result, by focusing only on the stem cells of the body's blood and immune system, is reported in the journal Science by researchers at the Stanford University School of Medicine, California.
The team has found a way to transplant new blood-forming stem cells from a donor into the bone marrow of mice, effectively replacing their immune systems.
Many aspects of the technique would need to be adapted before it can be tested in humans, said lead author Prof Irving Weissman but, when surmounted, the benefits are potentially huge, he said.
To avoid the need to wipe out bone marrow, Prof Weissman, Dr Deepta Bhattacharya and Agnieszka Czechowicz found a way to eliminate only the blood-forming stem cells without affecting bone marrow cells or other tissues, using a toxin that only sticks to blood-forming stem cells, effectively destroying the cells, so implanted cells can take hold.
"It is essentially a surgical strike against the blood-forming stem cells," says Prof Weissman. When the team transplanted new blood-forming stem cells into the mice, those cells took up residence in the bone marrow and established a new blood and immune system.
In this way, stem cells can be taken from one person who has a good tissue match and these donor cells implanted into a person with autoimmune disease, such as multiple sclerosis, so that the new immune system would likely no longer attack the nerves of the body.
Likewise, in people with a genetic blood disorder such as sickle cell anaemia, the new blood system would not have the genetic mutation, eliminating the cause of disease.
First, the researchers have to develop a way to carry out the same kind of surgical strike on human blood forming cells. They also need to do more animal testing to check the effects of the immune system. Although these steps will take time, Prof Weissman says he considered this work to be the beginning of research that could lead to human studies.
Dr Laura Bell, research communications officer at the MS Society, comments: "Stem cell studies are an important avenue of research which hold promise in terms of treatments for MS. This early stage study is interesting and we look forward to seeing how the work translates into studies in people with MS."
"For those whose blood stem cells contain a severe genetic defect such as that causing sickle cell anaemia, replacing them with normal stem cells would enable restoration of normal blood," comments Prof Edward Tuddenham of Royal Free Hospital, London.
"Bone marrow transplantation has been used for sickle cell anaemia with good results in children, but in adults it is difficult to get the new stem cells to take in the face of rejection by the resident stem cells and their progeny- the immune system."
"This study is clearly interesting and has great potential. It will clearly be needed to see whether these finding in mice can be translated into benefit for patients," adds Prof Lars Fugger of the Medical Research Council Human Immunology Unit and Department of Clinical Neurology, Oxford University.
Source: The Daily Telegraph © Copyright of Telegraph Media Group Limited 2007 (23/11/07)