May 20, 2003
Different Stem Cell Types Really The Same?

Researchers at Genzyme published some results last fall that suggesd that two different types of adult stem cells extracted from different parts of the body may not be different from each other.

Date: October 28, 2002

Genzyme Biosurgery (Nasdaq: GZBX), a division of Genzyme Corporation, today announced the publication of a research paper that casts new light on the nature of adult stem cells. In a paper published in the Oct. 28 issue of Tissue Engineering, scientists in Genzyme's Stem Cell Biology Research Laboratory demonstrate that many adult stem cells that have been claimed to be unique are actually "virtually indistinguishable" from one another in the laboratory, sharing many of the same physical and functional properties. The finding helps to clarify the many competing claims about the potential use of adult stem cells in a range of therapeutic applications.

In recent years, a growing number of researchers have reported that through a variety of proprietary methods they could generate cells with the potential to differentiate into a variety of specialized cell types, including nerve, cartilage, muscle, and endothelial cells. What has not been clear in these individual studies is whether the adult stem cells themselves are actually distinct, or whether they gained their distinction in the laboratory.

To help answer this question, Genzyme's study team systematically tested the approaches taken by various companies and laboratories. The Genzyme team isolated mesenchymal stem cells derived from the bone marrow of adults, and subjected them to a variety of the laboratories' research protocols used to develop cells capable of differentiating into nerve, cartilage, muscle, and endothelial cells. They found that regardless of the protocols used to isolate and propogate these cells, they were "virtually indistinguishable" from one another in several important ways. Each cell, for example, expressed the same or similar cell surface markers, or antigens. They also showed a common ability to undergo differentiation into nerve, cartilage, muscle, and endothelial cells based on culture conditions. The researchers concluded that although these stem cell populations were previously reported to be distinct from one another, on closer analysis they are not.

"We have shown that we can reproducibly isolate and propogate adult stem cells and demonstrate their potential to differentiate using a variety of methods," said Ross Tubo, PhD, director of Genzyme's Stem Cell Biology Research Laboratory. "These results give a strong indication that adult stem cells are robust and have great therapeutic potential for use in tissue regeneration. These findings help to clarify the complex and many times confusing literature surrounding adult stem cells."

Commenting on the findings of the Genzyme study, Dr. Diane Krause, associate professor of laboratory medicine at Yale University said: "The finding that these cells are very similar in their surface phenotype and their ability to differentiate into chondrocytes and neural-type cells helps us to make sense of the diverse literature in this field, paving the way for uniform isolation and propagation of mesenchymal stem cells for tissue engineering."

If adult cells from different reservoirs in the body that get used for different purposes are (at least in some cases) essentially the same as stem cells in other parts of the body then that would make it easier to get stem cells to use to develop various types of therapeutic treatments. It might turn out to be easier to, for instance, get some stem cells that would make good starters for growing replacement organs. This would be good.

The New Scientist has just picked up on this report and their story includes quotes from scientists who voice doubts about the conclusions which Genzyme researchers are drawing from their work. Some other stem cell researchers do not view the 12 chosen surface protein markers as definitive indicators of the type of a stem cell.

But not everyone agrees. Looking at 12 markers and two cell fates does not justify conclusions of such magnitude, says stem cell biologist Leonard Zon of Harvard University. "It's far from settled," he says. "I'd love for it to be simple, but it's not."

The other major point of contention has to do with how the cells were grown:

There is also debate over a seemingly small, but potentially important change in the method that Genzyme used to obtain MAPCs. A key step in obtaining MAPCs, according to Ohio-based Athersys, the company that has licensed the technology, is to grow bone marrow cells at a very low density. Yet Tubo's team obtained nothing this way and instead grew cells at a high concentration.

My guess is that it will be necessary to check a lot more markers (especially by measuring the expression of a large number of genes) to find out whether these stem cell types are really the same. If, for instance, growing stem cells at different densities changes what kinds of stem cells they are then what is really being demonstrated by these results might be just another way to change adult stem cell types into other adult stem cell types.

The bigger mystery continues to be just how difficult will it be to make stem cells into useful medical therapies? The potential payoffs include replacement organs, treatments for degenerative neurological disorders, and revitalization of aged stem cell reservoirs with youthful replacements. All of these uses of stem cells will eventualy help to reverse the aging process.

Share |      Randall Parker, 2003 May 20 08:45 PM  Biotech Organ Replacement


Comments
student said at November 1, 2003 3:41 AM:

after stem cells being divide into different cell types,that have the same genitic seq
what control speed or rate of cell divition for different cell typers?

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