Researchers at the University of Minnesota and Stanford University have successfully used adult stem cells from bone marrow to replace the radiation-ravaged immune system and bone marrow of mice, giving them a healthy new blood supply.
The research, published online in the Journal of Experimental Medicine, offers the promise of new therapies for humans, the investigators said.
For decades, scientists have tried in the laboratory to expand hematopoietic stem cells, which produce the blood system. Success in this effort would mean increasing the supply of cells available for bone-marrow transplant patients.
For this research, Dr. Catherine Verfaillie, director of the University of Minnesota’s Stem Cell Institute, and colleagues used multipotent adult progenitor cells (MAPCs). These cells, which can be isolated from bone marrow, have the ability in the lab to differentiate into brain, bone and liver cells.
Dr. Verfaillie and her team isolated MAPCs from mice and grew them in the laboratory. They then transplanted the cells into mice that had undergone radiation and had no immune systems.
“The cells not only survived when transplanted, but they completely repopulated the blood system of the mice,” she said.
Dr. Irving Weissman, a professor of pathology and developmental biology at Stanford, and a collaborator in the research, acknowledged that he initially had been skeptical that MAPCs could contribute to blood formation.
So, Dr. Weissman said, he insisted on rigorous evaluation of the data and is now a believer. “Scientists must now understand that mouse MAPCs can make normal blood, and we need to explore how they do it,” he said.
If research with human MAPCs confirm the mouse findings, the researchers said those cells might be used to help reduce rejection in tissue transplants, to boost damaged immune systems and to treat blood cancers.
But Dr. Weissman cautioned that the study revealed that MAPCs “were not themselves radioprotective,” so “they alone could not be used in patients in whom the bone marrow is totally eliminated due to radiation or chemotherapy.” He added: “But it is still remarkable that they can give rise to blood cells.”
Dr. Verfaillie said the MAPCs did not transform into other cell types in the study. But she said such differentiation has been documented in other recent research. She further noted that the mice that received MAPCs in her study did not develop tumors, which have been a frequent problem in animal research involving embryonic stem cells.
Stem cells are the body’s master cells, which theoretically can give rise either to all cells and tissues in the body or to a family of cells. They are seen as potentially valuable tools in fighting many diseases of humans.
Embryonic stem cells can grow into any type of tissue, researchers say. Opponents of such research say recent studies show that adult stem cells are more flexible than scientists had thought.
Human embryonic stem-cell research is opposed by many Americans for moral reasons, because human embryos have to be destroyed to derive the stem cells. President Bush is a key opponent and hopes the answer to curing diseases such as Alzheimer’s, Parkinson’s and diabetes lies in non-embryonic stem-cell research.
Yesterday, Dr. Verfaillie joined the chorus of researchers arguing that embryonic-stem-cell research also is necessary.
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