More MS news articles for Aug 2001
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What can stem cells really do?
http://www.boston.
lly_do_+.shtml
By Raja Mishra, Globe Staff, 8/21/2001
READING - Inside the Fertility Center of New England in Reading are
several waist-high freezers. Inside the freezers are hundreds of
pinpoint-thin straws. And in the straws are human embryos, each
smaller than the period at the end of this sentence.
Some will be implanted in women. Most end up in the trash. The
ongoing national debate on stem cells begins there.
''See these little gray circles - that's them,'' said lab supervisor
May Fung as she held microscope-enhanced photos of the embryos,
whose rough textures resemble moon rocks.
Fung goes about her task - helping impregnate women - quietly,
shuffling from freezer to microscope to incubator. But the debate
has been anything but quiet, especially since President Bush earlier
this month allowed limited taxpayer funds to support research on
embryonic stem cells. Supporters claim the new field has boundless
potential for medicine. Opponents equate it with murder.
Much of the public is confused about this quite new sliver of
biology - and scientists have not always helped clarify the issue,
mingling optimistic predictions with firm facts. What follows is a
primer on stem cells.
What is a stem cell?
Every person begins as a single cell - the fertilized egg - and
grows into an enormously complex machine, a unified network of
billions and billions of cells. Stem cells are behind this
transformation.
Within that initial cell is all the information needed to create a
person. Hours after fertilization, the cell divides. Then it divides
again and again. Within five days, there is a cluster of about 150
cells called the blastocyst. In the inner core of the blastocyst are
embryonic stem cells.
As time passes, they will receive genetic signals to change. Some
will become bone cells. Some heart cells. Others will form the cells
of the brain.The body has more than 200 types of cells. The stem
cells in the blastocyst are called ''pluripotent'
any one of those types.
And as long as they remain stem cells, they can divide indefinitely.
Once they start to specialize, they cannot.
Scientists extract the mass of stem cells from the blastocyst for
research. They store them in such a way that they do not specialize.
Instead, they keep dividing, producing a mass of stem cells with the
same DNA, called a ''line.'' As long as the line continues to
reproduce, many researchers can draw from this supply for their
experiments.
But, in the process of extracting the cells, the blastocyst is
destroyed.
Is a blastocyst a person?
Many believe that life begins the moment the egg and sperm fuse to
form the first cell. At this point, they believe, the cell is given
a soul, otherwise known as ''ensoulment.
By this reasoning, the blastocyst is morally just like a person,
endowed with the same basic human rights. To destroy the blastocyst
is murder, in their view. And stem cell research, whatever benefit
it may have, comes at the expense of this slaughter, they feel.
Supporters of embryonic stem cell research fall into two camps.
There are those who believe that an embryo should not be considered
a human life until well into a pregnancy. Some say after three
months; others after six. A smaller group believes life starts at
birth.
There are also stem cell researchers who believe ensoulment occurs
quite early, but later than the blastocyst stage. They point out
that a blastcyst still has potential to become twins. How, then, can
it have a soul? They believe as soon as the stem cells start on
their missions and the faint signs of a person appear, then
ensoulment occurs. In this camp, many believe three weeks into a
pregnancy, when the spine emerges, is the magic threshold.
How can stem cells cure disease?
Most major diseases involve the destruction of cells - Parkinson's
disease, diabetes, liver disease, cancer, spinal injuries, burns,
multiple sclerosis and Alzheimer's disease, to name a few.
Scientists theorize they can coax stem cells to become whatever new
cells a patient needs. A Parkinson's victim can get new brain cells.
A burn victim, new skin cells. And so on.
Does this really work?
We know plenty about embryonic stem cells - in mice.
In 1981, scientists first successfully removed mouse stem cells and
stored them in a lab. It wasn't until 1998 that this was repeated
with human cells.
In mice, scientists have used the cells to cure paralysis, diabetes
and brain disease. This has generated enormous hope among
researchers. But mouse cures do not mean human cures.
Researchers have had limited success in coaxing human stem cells to
become pancreatic cells, cardiac cells and blood cells.
How close are the answers?
In reality, we know surprisingly little about stem cells.
Fundamental questions remain: What is the mechanism by which they
specialize? How can we control what they become? How can we deliver
them to patients with precision?
Even if stem cell research takes off in the coming years,
researchers estimate it will be at least five years before the first
clinical tests begin. And many of these will fail.
Can scientists use the existing stem cells?
Bush said in his televised address that only stem cell lines already
in existence as of three weeks ago could be used for taxpayer-funded
research. No new embryos could be destroyed for federal research.
Bush said that 60 or so stem cell lines exist around the world. But
that doesn't mean researchers will have access to all 60 lines.
Some researchers believe the true number is far lower. The ownership
of many of the lines are shrouded in secrecy. And researchers
suspect that many of the lines Bush is counting on are unusable. The
Wisconsin lab that harvested the first five lines of embryonic stem
cells has acknowledged that two of those lines cannot be used for
research.
What happened?
To keep stem cells from specializing requires a carefully controlled
lab environment, all the more difficult because scientists don't
know exactly what makes these cells specialize. Sometimes the stem
cells researchers cultivate spontaneously start specializing. Their
ability to multiply then ends, and the line dies out.
The other problem is a common one in labs - contamination. A
infectious organism can render a line scientifically useless. And
sometimes lines die out for reasons unknown.
What about adult stem cells?
The blastocyst is not the only place in which stem cells are found.
In fact, from conception to death, stem cells are present.
Stem cells with potential to become bone marrow cells are found in
umbilical cord blood, which is usually discarded after birth.
Already, these cells are used to treat leukemia victims and other
severely ill patients whose immune systems are crippled by
chemotherapy.
Many types of stem cells exist in adults. Embryonic stem cell
opponents have seized on this, stating that embryos do not have to
be destroyed to get the cells.
Scientists have identified adult stem cells in bone marrow, the
brain, blood vessels, bone, skin, eyes, teeth, liver and several
other tissue types. But they are very difficult to find and isolate.
Adult and embryonic stem cells differ in fundamental ways. Embryonic
stem cells can multiply indefinitely, enough to potentially treat
disease. Their adult counterparts proliferate less, limiting their
supply.
Adult cells also have a more limited ability to specialize.
Embryonic cells can become any of the 200 or so body tissues. But
adult cells appear limited by their environment. For instance, adult
stem cells in the blood can transform only into cell types related
to blood. Scientists have had limited success in coaxing adult stem
cells to transform into other types of cells, with skin stem cells
appearing to have great promise. But much of the work has been done
in mice.
Some have proposed that adult stem cells can be coaxed ''backward''
into embryonic stem cells. This has not been proved.
There remains much research to be done into both adult and embryonic
stem cells. Most scientists are uncertain what they will find.
Does the Bush decision mean that no embryos will be destroyed?
No. Bush's decision did not outlaw any stem-cell work. He simply
declared that no federal research money could go to scientists who
either create or use fresh lines of embryonic stem cells.
And since the advent of test-tube fertilization in the 1980s, modern
fertility science has been creating unneeded extra embryos.
On a recent morning, Fung at the Reading fertility clinic prepared
for the moment of truth. A woman had come in for implantation.
Earlier, seven of her embryos were frozen. Then they were exposed to
her husband's semen. They were placed in an incubator that mimics
the conditions inside a woman and, within days, three appeared to
develop promisingly.
The team decided to implant two. This would increase the chances
that one would take. But implanting all three might result in a
multiple pregnancy, which the fertility center discourages.
The woman lied on the operating table as a team of embryologists
brought the precious cargo to the implantation doctor. Later, the
woman would throw the leftover embryos in the trash.
Until the stem cell debate erupted recently, this simple act
occurred thousands of times a year, mostly unnoticed.
For more information on stem cells, visit:
http://www.nih.
http://www.news.
http://packages/
http://www.stemcell
This story ran on page C1 of the Boston Globe on 8/21/2001.
© Copyright 2001 Globe Newspaper Company
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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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