Stem cells from donated bone marrow might be capable of repairing damaged lungs, intestines and skin as well as other organs and tissues, according to a report published today.
Researchers at the Johns Hopkins Oncology Center and two other institutions say the finding gives hope that the cells - easy to harvest and free from ethical concerns - could be used for a wide variety of therapeutic purposes.
"The study shows that there is a cell in bone marrow that is capable of reconstituting all these different organs," said Dr. Diane Krause, a stem cell researcher at Yale University.
"If you want to try to repair the body after injury, this could be the vehicle for doing it."
Experiments on lab mice
The experiment, reported in today's issue of the journal Cell, involved mice that had been given whole-body radiation that destroyed their bone marrow and the lining of the lungs, intestines and other organs.
Dr. Saul Sharkis, a Hopkins cancer researcher, injected each mouse with a single bone-marrow stem cell.
The natural function of stem cells is to produce bone marrow, which in turn generates red and white blood cells.
Eleven months later, Yale scientists examined the mice and found offspring of the stem cells not only in the bone marrow but in the other organs as well.
The stem cells, in effect, had taken on other tasks, traveling to other injured parts of the body where they produced the appropriate types of cells.
"It is possible that stem cells are summoned to sites of injury by factors secreted by the damaged organ," Sharkis said.
The science is still in an early stage, but Sharkis said he can imagine using bone marrow stem cells to help cancer patients recover from radiation.
A patient with lung cancer, for instance, might receive stem cells after treatments that damaged noncancerous tissues outside the tumor.
This might also enable patients to tolerate higher doses of radiation, Sharkis said.
The cells might also prove useful in treating other diseases characterized by tissue and organ damage, including cystic fibrosis and diabetes, he said.
The first evidence that bone marrow stem cells might have multiple uses came in 1998, when Italian scientists found they could induce them to produce muscle cells.
Later, other studies found that the stem cells could spawn cells of the brain, liver and heart.
Promising research field
Stem cell biology has become one of the hottest areas of medical research, with scientists racing to find ways to use the cells to repair injury caused by a wide variety of illnesses.
One intriguing possibility is using stem cells from discarded embryos or fetuses - true "master cells" that exist to produce every type of cell in the human body.
Some scientists say these might be the most useful because they are the most "plastic," capable of producing whatever the body needs.
They believe that the offspring of embryonic stem cells are more likely to function properly - to become a working part of an organ.
However, those cells are harder to obtain and have raised objections from people who believe that such therapies exploit human life, even if the cells are derived from embryos or fetuses that were going to be discarded anyway.
According to Krause, the principal advantage of bone marrow stem cells is that they are easy to obtain. Already, people donate stem cells to patients undergoing cancer therapy.
The cells are sometimes extracted from the hip or, in a simpler procedure, from blood.
"It's readily available, replenishes itself rapidly and [the procedure is] relatively noninvasive," she said.
Scientists from New York University were also involved in the study.
Sharkis said he injected one cell per mouse for technical reasons, but also to show that a single cell could spawn a large number of offspring.
Though bone marrow stem cells are relatively easy to obtain, individuals don't have a large supply of them.
In human therapy, more than one cell would be injected into the bloodstream - but the study suggests that a small number are needed.