Thursday August 9 9:41 PM ET
"Stem Cells Offer Therapeutic Promise"
Stem Cells Offer Therapeutic Promise
WASHINGTON (Reuters) - President Bush (news - web sites) announced on Thursday
that he supported federal funding of research on stem cells but
said such studies should be restricted to 60 existing stem-cell
Following are answers to some common questions about stem
-- What are stem cells?
Stem cells are master cells that have the ability to
transform themselves into other cell types, including those in
the brain, heart, bones, muscles and skin.
-- What are embryonic stem cells?
Embryonic stem cells are cells contained in embryos that
have the ability to transform themselves into virtually any
other type of cell in the body. They are called pluripotent. It
is this quality that enables the tiny embryo to develop into a
fully formed body. About five days after fertilization, the
human embryo becomes a blastocyst -- a hollow sphere of about
100 cells. Cells in its outer layer go on to form the placenta
and other organs needed to support fetal development in the
uterus. The inner cells go on to form nearly all of the tissues
of the body. These are the embryonic stem cells used in
-- What are adult stem cells?
The name is a misnomer because they are harbored in mature
tissue -- in the bodies of children as well as adults. Adult
stem cells are more specialized than embryonic ones and give
rise to specific cell types. They are called multipotent. The
mature body uses these cells as "spare parts" to replace other
worn out cells. For example, certain stem cells in the bone
marrow spawn red blood cells, white blood cells and blood
platelets. Recent research has suggested adult stem cells can
turn into many more cell types than once believed possible.
-- What is the source of embryonic stem cells?
Scientists generally harvest embryonic stem cells from
embryos left over in fertility clinics after in vitro
fertilization techniques. These "test-tube baby" techniques,
used to help infertile couples have a baby, involve fertilizing
a woman's egg cells with a man's sperm cells in a laboratory
dish. Several embryos are created at a time, and not all are
implanted into the mother's womb to create live births. Embryos
left over by the couple are slated for destruction by the
fertility clinic. These can serve as the source for deriving
stem cells, a process that involves removing the blastocyst's
inner cells and destroying the embryo.
-- What are the possible medical uses for stem cells?
Scientists hope to harness the transformational qualities
of stem cells to provide treatments for a variety of diseases
affecting millions of people worldwide. Because stem cells can
turn into many other cell types with the right prompting,
doctors may be able to replace tissues and organs damaged by
disease or injury to restore healthy function. For example, in
people with Parkinson's disease (news - web sites), injecting stem cells into the
area of the brain that controls muscle movement, where the
disease kills nerve cells, might regenerate the neurons and
reverse the illnesses. This procedure would be called a stem
cell transplantation. Therapeutic applications of stem cells
potentially also could treat illnesses including: diabetes;
Alzheimer's disease (news - web sites); stroke; heart attack; multiple sclerosis;
blood, bone and bone marrow ailments; severe burns by providing
skin grafts; spinal cord injuries, and cancer patients who have
lost cells and tissue to radiation and chemotherapy.
-- What other medical uses are possible?
Using stem cells, researchers would be able to test a
drug's therapeutic effects and toxic side effects in human
tissue without using a laboratory animal as a proxy. Sometimes
the reaction of laboratory animals to a given drug does not
match the human reaction to the drug. In addition, stem cells
could be harnessed and packaged to deliver gene therapies to
specific targets in the body to treat genetic problems.
-- Are embryonic stem cells better than adult stem cells?
It is too early to say. Embryonic stem cells boast two
important qualities: they can become almost anything in the
body and they can be grown in culture in an unlimited quantity.
The disadvantages are that a patient's immune system might
reject transplants of embryonic stem cells just as some organ
transplants are rejected, and that runaway growth of embryonic
stem cells could produce tumors. Because adult stem cells would
be taken from the very patient who would receive them later in
treatment, there are no rejection issues. Disadvantages in
adult stem cells include: doubts about whether they can
transform themselves as readily as embryonic stem cells;
difficulty in growing them in culture at the quantity needed to
facilitate transplants, and worry that years of exposure to
toxins, radiation and DNA replicating errors could leave them
with genetic abnormalities.
-- What's the controversy?
For some people, the destruction of any embryo is
tantamount to murdering a human being. Leaders of the Roman
Catholic Church and some other religious and political figures
hold this view.
-- Has the federal government ever funded research
involving human embryonic stem cells?
No, it has not. Human embryonic stem cells were first
isolated in 1998, but a 1995 law banned federal funding for any
research "in which a human embryo (is) destroyed, discarded or
knowingly subjected to risk of injury greater than that allowed
on fetuses in utero," or in the mother's womb.
In January 1999, the Department of Health and Human
Services (news - web sites) (HHS) general counsel's office issued a legal opinion
that the earlier law did not apply to stem cells derived using
private money from spare embryos at fertility clinics because
the stem cells themselves were not embryos and the destruction
of the embryos was not financed by the government.
The National Institutes of Health (news - web sites), the government agency
that funds medical research and had requested the opinion in
1998, released guidelines on Nov. 21, 2000, for federal funding
of embryonic stem cell research. Two key conditions included
were that federally funded researchers cannot derive the stem
cells, a process that involves destroying an embryo, and the
source of the embryos that gave rise to the stem cells must be
embryos created for in vitro fertility treatment.
Shortly after being sworn into office in January, President
Bush ordered HHS to reconsider its legal opinion. In April, HHS
Secretary Tommy Thompson directed the NIH to cancel its first
scheduled meeting to consider research proposals submitted by
scientists seeking federal funds for work involving human
embryonic stem cells.
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