Some Stem Cells May Be Less Versatile Than Thought

[antiquity]

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Some Stem Cells May Be Less Versatile Than Thought
August 22, 2002 03:29:23 PM PST, Reuters
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Although past animal research has suggested stem cells in adult bone marrow can develop into brain cells, the results of a new study in mice indicate that this is not a universal phenomenon.

The finding may take some air out of the hope that a person's own bone marrow cells could one day be used to replace brain cells damaged by diseases such as stroke--a possibility raised by some previous animal work.

"That was the promise, but our study suggests it's not that simple," lead author Dr. H. David Shine of Baylor College of Medicine in Houston, Texas, told Reuters Health.

However, that's not to say that adult bone marrow cells will not someday turn out to be a useful source of new brain cells, according to the researcher. Instead, the new findings indicate that the transformation of bone marrow cells into brain cells is "probably not a general phenomenon," Shine explained.

He and his colleagues report their findings in the August 23rd issue of Science.

In the study, the researchers transplanted bone marrow stem cells from one type of lab mouse into another. The mice used as "donors" carry a gene called LacZ in most of their cells, which allowed the scientists to weed out which cells in the recipient mice were derived from the bone-marrow-cell transplant.

Some of the mice were given brain injuries to see if the donor bone marrow cells would develop into replacement brain cells. However, Shine's team found no evidence of this--nor did they find any donor-derived neural cells in the uninjured mice.

"Of course, we were disappointed," Shine said.
However, these results are far from the final word on the potential of adult bone marrow cells in treating brain injury, according to the researcher. Instead, he noted, it emphasizes that there is much more work to be done.

SOURCE: Science 2002;297:1299.

[Jeremy]

Adult-stem-cell research shows some limits
Fri Aug 23, 9:06 AM ET
Elizabeth Weise USA TODAY

Despite earlier research that adult stem cells from bone marrow could successfully change into brain cells, research out today suggests the change isn't as easy as once believed. That could put a damper on hopes that adult cells might take the place of those from embryos in research to cure brain diseases and spinal cord injuries.

The research, reported in the journal Science, is the latest entry in the politically charged debate over stem cells. The cells are found both in embryos and grown animals, and are coveted for their ability to change, or differentiate, into any kind of tissue in the body.

Scientists are studying stem cells as possible therapies to regenerate diseased tissues in patients with Parkinson's disease ( news - web sites), Alzheimer's disease ( news - web sites) and spinal cord paralysis. However, some say research on human embryonic stem cells, which are harvested by destroying embryos, is immoral.

Those who say they believe human embryonic stem cells hold the most promise are pitted against those who say adult stem cells are just as useful and harvesting them doesn't involve the destruction of embryos.

A team at Baylor College of Medicine in Houston described its futile efforts to get adult stem cells from mouse bone marrow to produce neural cells, which are found in the brain and nervous system.

''It may work only under certain experimental conditions,'' says H. David Shine, of the Center for Cell and Gene Therapy at Baylor and senior author of the study.

Over the past three years, several researchers were able to coax mouse bone marrow cells to differentiate into neural cells, but the Baylor team was unable to replicate those findings.

The team used radiation to wipe out the bone marrow of mice and then implanted genetically marked bone marrow cells from other mice to see whether the cells would differentiate into neural cells, but none appeared.

''More research needs to be done because it would be a great resource'' to learn the conditions under which the differentiation takes place,'' Shine says. ''We're still betting it's possible.''

The study was funded by The Institute of Rehabilitation and Research in Houston, which provides rehabilitation services for the paralyzed.

Helen Blau, professor of genetic pharmacology at Stanford University in California, says there's evidence the genetic marker used by the Baylor group doesn't function as well in brain tissue. She says her group, which published one of the first papers to show adult stem cells becoming brain cells, tried using that marker for a year before switching to another, which worked better.

Blau notes that research in all types of stem cells has become complicated by the politics of research on embryonic stem cells.

She emphasizes that research should continue on both adult and embryonic stem cells. ''For certain diseases, one type of cell might be more applicable than the other.''

As is often the case with new science, the limits of what is possible are still being worked out in the realm of adult stem cells. Whether or not adult stem cells are as flexible as some scientists believe them to be is a matter of much debate in research circles, with vociferous arguments taking place in conference corridors and graduate seminars around the world.

Although papers published in the past three years have shown that adult bone marrow cells can become brain cells and that brain cells can become blood cells, other researchers, including Derek van der Kooy of the University of Toronto, have been unable to replicate those findings.

He says that although such studies may ''throw cold water'' on a number of individual examples of the apparent plasticity of these cells, ''the mass of (the studies) can't all be done poorly -- some of them have to be correct.''

Walter Low, a neuroscience professor at the University of Minnesota, says, ''We need to find out the full potential of both of these types of cells and where they are the same and where they differ. People are getting the impression that these adult cells can do everything an embryonic cell can do. They need to have a more balanced view.''

"If the wind could blow my troubles away. I'd stand in front of a hurricane."

[Wise Young]

When a field is this new, it takes time for it to settle. I agree very much with the tone of these articles. It suggests that we have to be careful about the interpretation of data because they may mislead us in many ways. Because of the huge emphasis on adult stem cells today, hundreds of laboratories are now competing fiercely with each other to be the first to show that adult stem cells can become different kinds of cells when transplanted. It is turning out to be a more difficult task making the transformation consistent. Wise.