Research Seeks to Expand Use of Stem Cell Transplants

Technology could be used to treat a variety of diseases, experts say

WEDNESDAY, Oct. 19, 2005 (HealthDay News) -- A new way of manipulating stem cells may expand the donor pool for a variety of diseases and offer new hope to people suffering from a number of malignant and non-malignant disorders.

In fact, the technology might mean that every patient who needs a stem cell donor would get one, the authors of a new study state.

"We are at the moment now that we have the possibility to include non-identical donors into the donor pool," said lead investigator Dr. Rupert Handgretinger, who is affiliated both with St. Jude Children's Research Hospital in Memphis, Tenn., and University Hospital, in Tuebingen, Germany.

"Normally, we use one of the parents as a donor. For this approach we can identify a donor for almost every child who needs a transplant," Handgretinger said.

The findings were presented Tuesday at the Bone Marrow Failure Scientific Symposium, a conference organized by the Aplastic Anemia & MDS International Foundation, and sponsored by the U.S. National Institutes of Health. The symposium was held in Washington, D.C. This particular research was done at St. Jude.

Handgretinger said the technology is already being used at St. Jude and at various facilities across Europe.

In stem cell transplantation, doctors introduce stem cells that are intended to grow into cells to replace malfunctioning cells, such as white blood cells in leukemia patients.

Stem cell transplantation is often the only chance for patients with different malignant and non-malignant diseases, including leukemia and other cancers of the blood. On average, however, there is only a 25 percent chance of finding a matched donor within your family. In some ethnic groups, that chance plummets to 10 percent.

When non-matched donors are used, the chances of developing graft-versus-host-disease (GVHD) -- when the donor's immune cells attack the patient's body -- increase.

"The main problem with all stem cell transplantations is GVHD, which occurs in up to 30 percent of cases," said Dr. Gary Kleiner, an assistant professor of pediatrics at the University of Miami School of Medicine.

Scientists have been trying various methods to reduce the odds of developing GVHD. Last week, one of Kleiner's patients, an 11-month-old baby with a rare disorder called osteopetrosis and GVHD, was given an experimental stem cell drug that has given the infant another chance at life.

Another way to prevent GVHD is to remove the donor's T-cells before doing the stem cell transplantation, but this requires giving the patient immunosuppressant drugs. And that has a considerable downside.

"The relapse rate of leukemia is much higher, it takes a long time for the immune system to develop and the patient is susceptible to viral infection," Kleiner said.

As a result, researchers have been trying to engineer a stem cell graft that causes less GVHD without interfering with reconstitution of the immune system.

The technique featured in this study involves removing the donor's T-cells, which are programmed to attack foreign substances, then adding back the donor's natural killer cells. While killer cells, like T-cells, are part of the body's immune system, they are different in molecular structure.

"If it's as effective and you do have good immune reconstitution, it will open up the donor pool in terms of who can be a donor," Kleiner said. "Right now, it's experimental, but it shows a fair amount of promise. The data isn't that tight yet."

More information

The National Marrow Donor Programhas more on GVHD.

SOURCES: Rupert Handgretinger, M.D., Ph.D., St. Jude Children's Research Hospital, Memphis, Tenn., and University Hospital, Tuebingen, Germany; Gary Kleiner, M.D., Ph.D., assistant professor, pediatrics, University of Miami School of Medicine; Oct. 18, 2005, presentation, Bone Marrow Failure Scientific Symposium, Washington, D.C.
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