Research Offers Alternative to Embryo Stem Cells
A Minnesota researcher says she has found a previously unknown type of cell in the adult body that acts much like the highly versatile stem cells from human embryos that have caused a political furor for more than a year.
Like embryonic stem cells, the cells recently discovered in adult bone marrow seem capable of turning into a wide assortment of the body’s various tissues, raising hopes that they can be fashioned into transplantable material for patients whose own cells and tissues have become faulty. Previously, scientists had documented other cells of the adult body that give rise to various tissues, but nothing nearly as versatile as these bone marrow cells.
The cells were discovered by University of Minnesota researcher Dr. Catherine Verfaillie and colleagues, who revealed new details Thursday in an online version of the journal Nature.
Antiabortion groups said that the discovery shows scientists should try to devise cures for disease using adult cells and that they do not need to use embyronic stem cells, which cannot be obtained without destroying human embryos.
“With adult cells, we may be able to do everything that embryonic stem cells have been proposed for, and without the ethical problems,” said Richard Doerflinger, a spokesman for the U.S. Conference of Catholic Bishops, which believes embryo destruction is tantamount to murder. “This shows you don’t have to forgo scientific progress when you take into account moral issues.”
Verfaillie and an array of other scientists said adult and embryonic stem cells show promise and should be vigorously investigated.
“There may be particular diseases that would be more easily treatable with one cell type than the other,” Verfaillie said. “These studies should go on in parallel.”
As evidence, she and others cited a second paper published by Nature on Thursday in which scientists used embryonic stem cells to ease the symptoms of Parkinson’s disease in rats.
These scientists, led by Ron McKay of the National Institutes of Health, turned embryonic stem cells from mice into a specific type of brain cell before transplanting them into the rats.
Transforming stem cells in this way has been largely a hit-or-miss process. But the team said it had developed a method to transform the cells reliably and in high numbers, suggesting that it could one day be industrialized to serve a large number of patients.
“We can really deliver the right cell that we need by starting with an embryonic stem cell,” McKay said. “This is a real technology now. It’s not just fooling around.”
Several scientists said that the experiment was one of the most dramatic illustrations of the potential of embryonic stem cells to treat disease but that cures were still uncertain and years away.
Once an arcane debate, the relative promise of adult and embryonic stem cells has become politically charged in recent years. The goal is to turn these cells into heart cells for cardiac patients, brain cells for Alzheimer’s patients, insulin-producing cells for diabetics, and the like.
Many scientists say that stem cells from embryos are best for the task. The cells are usually taken from embryos, about 5 days of age, that were created in laboratory dishes by fertility patients but are no longer needed. Taking the cells destroys the embryos.
Opponents of embryo research say scientists should first study the potential of creating these materials from stem cells found in adults.
Citing ethics concerns, President Bush last year barred federal funding for experiments that caused embryos to be destroyed, though he said stem cells taken from embryos before August could be used in taxpayer-funded experiments. This year, Congress is considering whether to criminalize cloning research, which also destroys embryos.
Verfaillie has found the versatile cells, called MAPCs, or multipotent adult progenitor cells, in the bone marrow of humans and other species. The first indications of her discovery were published last fall.
But in the report published Thursday, she used a more definitive test to show that the cells are truly versatile. In this test, MAPCs from mice were injected into mouse embryos. As the embryos matured, the MAPCs incorporated themselves into almost every organ of the body.
Dr. Robert Goldstein, chief scientific officer at the Juvenile Diabetes Research Foundation International, said Verfaillie had made a “pretty convincing” case for the versatility of the MAPCs.
But Larry Goldstein, a stem cell researcher at UC San Diego, said that Verfaillie would have made a stronger case if she had shown that the MAPCs were actually functioning in the mice and if they were found in higher numbers.
“This is interesting. It’s provocative....But it’s not quite there, I’d say,” he said.
One question is whether versatile MAPCs exist in the body or if Verfaillie created them unintentionally during the process of isolating and culturing them in laboratory dishes. The answer is important, though, either way, the cells could be useful in designing treatments for patients.
McKay and his team set out to turn mouse embryonic stem cells into a type of brain cell that produces the chemical dopamine. For unknown reasons, these brain cells die in Parkinson’s patients, and the lack of dopamine leads to tremors, instability and other symptoms.
The team said it could get nearly 80% of the embryonic stem cells to become dopamine-producing cells, compared with only a few percent in the past. The remaining cells were undesirable cell types. Obtaining a purified population of the brain cells is important, because scientists do not want to transplant undesired cells to patients.
McKay’s team tested its cells in rats. Chemicals were used to destroy dopamine neurons on one side of the brain, mimicking Parkinson’s disease in that region. As a result, the rats would walk in a circle, as if they were boats being rowed by a single oar.
Transplanting dopamine neurons improved the rats’ walking, McKay’s team reported. “What impresses me is that not only did he get these cells to survive but they sent out extensions to form connections with other neurons in the brain,” said Jeffrey Kordower of Rush-Presbyterian-St. Luke’s Medical Center in Chicago.
McKay said the next step is to repeat the experiment in monkeys, which would take several years.
