Studies Show More Potential of Stem Cells

Thu Jun 20, 2002
By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - Two studies published on Thursday show the potential of stem cells in medical treatments and even organ transplants and, scientists said, show why research should not be limited despite moves in the U.S. Congress to do so.

One study shows that embryonic stem cells, taken from a newly fertilized egg, can be used to create the kind of cells that would treat Parkinson's disease ( news - web sites), an incurable brain disorder, and a second found bone marrow cells can be coaxed into forming a wide variety of different cells in the body.

Both experiments, published in the science journal Nature, were done in rodents, but stem cell experts said they were important steps toward someday treating people.

In one experiment, Dr. Catherine Verfaillie and colleagues at the University of Minnesota found cells in the bone marrow of mice that could be infused into tiny mouse embryos and would spread to tissues throughout their bodies as they grew.

Verfaillie said in test tubes these cells, which she called multipotent adult progenitor cells, or MAPCs, started looking and acting like nerve cells, liver cells, and endothelial cells -- the cells that line the gut and blood vessels.

"We have been waiting for a couple of years for this paper," Dr. John Gearhart, a stem cell researcher at Johns Hopkins University in Baltimore, told reporters.

Verfaillie's cells are not quite adult stem cells, but are one step further along that road.

When an embryo is conceived, it first forms a ball of cells, some of which can be taken out in the first week and which are called embryonic stem cells.

As the embryo develops these cells start to differentiate, to make up the different types of cells in the body. When they form tissue they are called fully differentiated cells.

In the past few years an intermediate form of cell has been found, called an adult stem cell. It is not fully differentiated but has potential to form a number of different kinds of cells, such as one of the three kinds of nerve cell.

And experiments have shown that these adult stem cells, under the right conditions, might be induced to change form even further -- a blood cell into a nerve cell, for instance.

Verfaillie's cells are mesenchymal stem cells, destined to form muscle and bone. What she showed in her paper was that they can be made to form other tissues, too.

It is an early step to being able to take bit of a patient's bone marrow, perhaps add in a gene or two to correct a fault, and reinfuse the cells to treat a disease such as hemophilia.

The earliest stem cells, if infused right into the body, grow into a kind of tumor called a teratoma. Stem cells have to be manipulated in the lab before they can be safely used.

But Verfaillie's cells, if caught at the right moment, seem to be safe to use with little manipulation, she said. They also may lack the markers that activate the immune system, which may mean cells from one person could be used in another.

One problem is that the cells are very rare, and Verfaillie said she has to show that the cells actually do something once they migrate throughout the body.

DO THE CELLS WORK?

"Will they be functional or just decorative?" asked Dr. Curt Civin, another Johns Hopkins stem cell expert.

In the second experiment, Dr. Ron McKay of the National Institute of Neurological Disorders and Stroke, one of the National Institutes of Health, and colleagues got embryonic stem cells to treat a Parkinson's-like disease in mice.

They cultivated cells from early mice embryos in lab dishes with certain proteins that made them become neurons. "Eighty percent of the neurons are the type of neuron that we want," McKay told a news conference.

These are the neurons in the midbrain that produce dopamine -- a key message-carrying chemical linked with movement. In Parkinson's, the body destroys these cells for unknown reasons and patients eventually lose the ability to control movement.

McKay's group damaged the brains of rats on one side to mimic Parkinson's. These rats move in a circle.

When treated with these cells, the rats moved more normally, McKay said. "This is not a cure for the animals, McKay said. "But it is absolute, definitive evidence that these cells work in the brain."

Parkinson's patients have been treated with cells taken from the brains of aborted or miscarried fetuses, but McKay said it does not always work and it would be better to have a source of cells that could be grown in in the lab.

"This is a major step," Gearhart said of the McKay paper.

Both Verfaillie and McKay said their studies show that all kinds of stem cell research should continue. There have been moves in Congress to limit stem cell research, especially so-called therapeutic cloning, which uses cloning technology to create embryonic stem cells.

"These studies are intertwined and should go on in parallel," Verfaillie said.