May 3, 2001 -- Researchers have at last found a cell that may be able to repair any part of the body. The breakthrough finding -- from mouse studies -- offers hope for treating human diseases now considered incurable.
"The amazing finding is that there are cells in the bone marrow that can be all of these things -- liver and lung and gut and skin and more," lead study author Diane S. Krause, MD, PhD, tells WebMD. Krause is director of the Yale University Frisbee Laboratory for Hematopoietic Graft Engineering in New Haven, Conn.
"We are a long way from using these to treat people, but now we can start to think about ways to test these cells in injury/repair models of a lot of important diseases such as diabetes, cystic fibrosis, and myocardial infarction," co-author Saul Sharkis, PhD, tells WebMD. "These purified, special cells may very well be able to be used in an approach to human disease. That is extremely exciting for all of us."
Sharkis is director of the experimental hematopoiesis program at Baltimore's Johns Hopkins University.
"The big news is that with all the recent stuff about adult stem cells having a wider range of potential, this is the first time anyone has shown an adult stem cell is capable of giving rise to any portion of the body," says co-author Neil D. Theise, MD, associate professor of pathology at New York University Medical School.
Other researchers are excited about the findings, too -- although as scientists, they would like to see more proof.
"The study ... raises the very interesting and potentially important possibility that transplanted [blood] stem cells may give rise to a wide variety of cell types in different organs," Sean J. Morrison, PhD, tells WebMD. "If so ... this might open new avenues for repairing ... tissues or for performing gene therapy outside the [blood] system."
Morrison is assistant professor of internal medicine and cell and developmental biology at the University of Michigan in Ann Arbor.
"Krause [and his colleagues] have demonstrated that a single bone-marrow-derived cell can make significant donor-derived contributions to ... multiple tissues after transplantation," Gerald Spangrude, PhD, tells WebMD. Spangrude, a stem-cell expert, is assistant professor at the University of Utah's Huntsman Cancer Institute.
A New Rule Book
All of this is impossible, according to the current rules of biology.
The textbooks say that only an embryo has stem cells that can turn into any type of cell. Adults are only supposed to have more mature stem cells destined to become specific organs or types of tissue.
But what was in the original piece of tissue? Maybe there were cells in the batch that were already destined to be another type of organ. To rule this out, scientists have to find the single adult cell capable of changing into another type of adult cell. Nobody has been able to do this -- and then Sharkis came up with an idea.
Sharkis knew that the adult stem cell everyone has been looking for has an interesting property: When placed in the body, it quickly goes back to its home in the bone marrow. So he took bone marrow from a male mouse and injected it into a female mouse whose own marrow had been destroyed by radiation.
After two days, he looked inside bone from the female mouse and found some of the cells he had injected. He then gave 30 new marrow-depleted female mice a transplant with just one of these male cells. The transplant rescued five of the animals.
The male cells divided quickly and repopulated the females' marrow. They also turned into cells that, to a greater or lesser extent, repopulated the animals' lungs, liver, skin, and digestive tract. The greatest repopulation was seen in the lung -- possibly because the cells were repairing damage caused by the original radiation.
"This is the final nail in the coffin of the idea that cells have such rigid restrictions on what they can do," Theise says. "A new paradigm is required to accommodate this data."
If these versatile stem cells exist in mice, they should exist in humans. But if we already have them, why don't they repair damaged organs?
Probably they do. But researchers hope that if they can figure out what makes these cells tick, they can make them do even more repair work.
"Maybe we can get these cells to go to the damaged organs and repair them -- that's the trick," Theise says. "They are doing this as we speak, but in some cases they don't accomplish the job. If we can figure out what the mechanisms are that make them do this, we could stimulate the body to repair itself in a way it wouldn't otherwise."
For people whose organs are damaged too much for repair, the new cells could be used as part of an artificial organ. And the possibilities are enormous for people with genetic diseases.
"You could take the cell from a patient, put in a gene or correct a defective one, and then put it back in the patient," Theise speculates. "Gradually, through normal cell turnover, you could correct genetic defects in one or more organs."
Not the End of Fetal-Cell Research
Even though the new adult cells can do things once thought impossible, it doesn't mean there isn't more to learn from research into the ultimate stem cell: the embryonic cell.
"I don't want our data to be used as an argument against continuing fetal cell research," Krause says. "I don't think you will find a single person in our field who will say we are finished with this kind of research. This is a beginning -- an exciting beginning, but a beginning all the same."