Stem cells, show your face
By Patrick BarryWeb edition : Sunday, August 24th, 2008 Text Size A
new test distinguishes embryonic stem cells and those with equal
therapeutic potential from other, less capable stem cell types.Stem
cells' unassuming, bloblike appearance makes them hard to identify,
but new research offers a way to blow their cover.
The technique can distinguish embryonic stem cells — which are
pluripotent, meaning they can become any kind of cell in the body —
from "adult" stem cells that reside in people's organs and have a
much more limited repertoire.
Using the new test, Jeanne Loring of the Scripps Research Institute
in La Jolla, Calif., and her colleagues provide fresh evidence that
stem cells made by "reprogramming" a person's skin without ever
making or destroying an embryo are truly pluripotent, just like
embryonic stem cells.
The findings, reported online August 24 in Nature, suggest that these
reprogrammed, embryonic-like stem cells could be used for future stem
cell therapies in place of embryonic cells, which are more
controversial because they are extracted from embryos.
Scientists have debated whether reprogrammed cells truly have all the
abilities of cells taken from embryos.
"You can do a pretty simple test now and discover if it's
pluripotent, and you couldn't do that before," Loring says.
To distinguish adult stem cells from pluripotent cells, Loring's team
compared the gene activity of about 150 stem cell samples of various
types, including reprogrammed cells, embryonic stem cells and neural
stem cells. Out of this comparison popped 299 interacting genes that
form what the researchers call a pluripotency network, or PluriNet.
Measuring the activity of these genes could reliably distinguish the
different kinds of stem cells, the team reports.
"This is an exhaustive documentation of the essential gene expression
features of pluripotency and will be a helpful roadmap for scientists
working in this hot new area of biomedical research," says George
Daley of the Harvard Stem Cell Institute.
The way scientists have been testing the pluripotency of reprogrammed
mouse cells is to add reprogrammed cells to mouse embryos and see
whether the cells give rise to every type of body cell in the newborn
pups. Such tests are difficult to perform with human cells for
ethical reasons.
"People are always arguing about the differentiation potential and
therapeutic potential of each of the various stem cells," says Robb
MacLellan, a cardiologist at the UCLA David Geffen School of
Medicine. The new test is "going to help and speed up the development
of this whole field."
In 2006, Japanese researchers discovered a set of four genes that
when injected into skin cells reprogram those cells into an embryonic-
like state. Many of the 299 PluriNet genes encode proteins that are
activated by this process, Loring says.
The test also found distinctions among neural stem cells that
scientists had thought were the same, MacLellan notes. "There was a
lot of divergence in terms of what other people were calling neural
stem cells," he says. Identifying these previously unrecognized
subtypes could help scientists better understand the various roles
that the cells play in creating new nerve cells for the brain. "This
test will help to clarify some of that."
http://www.sciencen
w_your_face
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StemCells subscribers may also be interested in these sites:
Children's Neurobiological Solutions
http://www.CNSfoundation.org/
Cord Blood Registry
http://www.CordBlood.com/at.cgi?a=150123
The CNS Healing Group
http://groups.yahoo.com/group/CNS_Healing
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