Friday November 23 2007
Lab techniques may not be useful in humans
“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” reported The Daily Telegraph. The conditions “caused when the immune system becomes faulty” can be “cured” by transplanting stem cells to “effectively transplant the donor’s immune system and cure the condition.”
Currently, when people receive bone marrow transplants (which contain the stem cells needed to create new blood cells) they need to be treated with radiation or chemotherapy first, to kill off their own bone marrow. However, this radiation has a damaging effect on tissues other than bone marrow, and can have long lasting effects such as brain damage, or an increased the risk of cancer. The Guardian reports that scientists have come up with a new technique in mice that means it “might be possible to perform bone marrow transplants without needing risky therapy beforehand”.
The newspaper story is based on a study carried out in mice. Although this research opens up a new prospect for avoiding the drastic pre-treatment needed for people receiving blood-forming stem cell transplants, it is only at its early stages. It is not yet clear whether the same technique would work in humans, what side effects it might have, or for what diseases it may have a use.
Where did the story come from?
Dr Agnieszka Czechowicz and colleagues from the Stanford University School of Medicine in the US carried out this research. The study was funded by the US National Institutes of Health the Medical Scholars Program at Stanford University School of Medicine, the Cancer Research Institute, and a Hope Street Kids Award. One of the authors declared that they owned stock in Amgen, cofounded and consulted for Systemix, cofounded and is director of Stem Cells Inc., and co-founded and is a director of Cellerant Inc. The study was published in the peer-reviewed journal: Science.
What kind of scientific study was this?
This was a laboratory study carried out in mice to see whether removing the mouse’s own blood stem cells would give transplanted blood stem cells a better chance of thriving.
First, the researchers transplanted blood stem cells from one type of mouse into another. After injecting the cells, they looked to see if the donated stem cells were producing a particular type of new white blood cell and calculated what proportion of the new blood cells came from the transplanted stem cells.
They then looked to see whether they could stop the mouse’s own blood stem cells from working by injecting a blocking antibody. They looked at whether doing this reduced the number of stem cells the mouse had, and how long it took the numbers of stem cells to recover after this treatment.
After this, they injected various doses of donor blood stem cells into a group of mice that had been treated with the antibody, and another group of untreated mice. The scientists then measured the resulting stem cell levels.
What were the results of the study?
The researchers found that they could successfully transplant blood stem cells into mice, but that these donor stem cells only produced about 3% of the recipient mouse’s new white blood cells. They found that antibody treatment drastically reduced the number of blood stem cells for about 23 days, after that, the number of stem cells went back to normal. If antibody treated mice received donor blood stem cells while their own stem cells were reduced, the proportion of new white blood cells that came from the donor cells increased. They found that they could achieve up to 90% of the recipient’s new white blood cells being generated from the donor cells when they used the highest dose of donor cells.
What interpretations did the researchers draw from these results?
The researchers concluded that in mice, the transplant recipient’s own blood stem cells occupy “niches” that block the success of the donated blood stem cells. Temporarily removing a mouse’s own blood stem cells using an antibody opens up these “niches” for the donor stem cells, and makes the transplant more successful. The researchers suggest that this method may avoid the need for the drastic treatments that are currently used in humans to suppress their immune systems before receiving transplants.
What does the NHS Knowledge Service make of this study?
This study gives hope that in the future people receiving donor blood stem cell transplants may not need to have drastic pre-transplant treatment to kill off their own immune system. However, this research is at the early stage of studies on mice. It is not yet clear whether the same technique would work in humans, or what the side effects might be. Blood-forming stem cell transplants are not currently used in the treatment of autoimmune diseases and therefore it seems unlikely that this advance will mean that this type of approach will be commonly used for these diseases in the near future.
Sir Muir Gray adds...
The technology will have an impact on medicine, but it may take at least five years to reach the bedside.