Explained by Senior Fellow at Culture of Life Foundation
By E. Christian Brugger
WASHINGTON, D.C., 24 MARCH 2009 (ZENIT)Given the new Presidential
order allowing federal funds for research using human embryonic stem
cells, it might be helpful for readers to become more familiar with the
terminology used in any discussion of controversies surrounding
embryonic stem cell research.
What is a Stem Cell?
A stem cell, whether of the adult or embryonic type, is an
undifferentiated cell (i.e., a cell that has not yet specialized into a
particular cell type, e.g., liver cell, pancreatic cell, or cardiac
cell) with two unique capacities: the first, for rapid and prolonged
self-multiplication into daughter cells identical with itself; and the
second, for development and differentiation into specific types of cells
such as liver and cardiac cells.
What is a Stem Cell’s Potency?
A stem cell’s “potency” refers to its capacity for differentiation, that
is, for developing into particular kinds of human cells, e.g. liver,
kidney, blood, etc. Different types of stem cells have different scopes
to their potency: e.g., totipotent, pluripotent, multipotent or
unipotent. A totipotent cell is capable of differentiating into every
tissue in the human body, including extra-embryonic support tissues
necessary for human gestation (e.g., placenta, umbilical cord, amniotic
sac); a single-celled embryo, also called a zygote, possesses the
capacity of totipotency; also, the individual cells of an embryo’s body,
called blastomeres, in the first few days of the embryo’s life are
totipotent; if a blastomere splits off from the embryo’s body, it has
the capacity for complete human development, which is how we get
identical twins. A pluripotent cell is capable of differentiating into
almost all the tissues of the human body, but not the extra-embryonic
support tissues; embryonic stem cells are pluripotent. Stem cells can
also be multipotent (capable of differentiating into the cells of a cell
group type, e.g., blood cells) and unipotent (unable to differentiate
into any other cell type than itself).
What are the Differences between Embryonic and Adult Stem Cells?
Embryonic stem cells (ESCs) are undifferentiated, self-renewing,
pluripotent cells. They are harvested from the bodies of embryos at
approximately day five of human development. At day five the embryo’s
body takes the shape of a hollow sphere (the embryo at this time is
called a “blastocyst”). The blastocyst has an outer cell layer and an
inner cell mass (picture a basketball with a small group of marbles
clumped together on the inside). The cells of the inner cell mass will
eventually differentiate into the varied tissues of the person’s body;
and the outer cell layer will develop into the placenta and other
support tissues. But it is important to understand that at this point,
both the outer cell layer and inner cell mass constitute the embryo’s
body. The inner cell mass can be understood to be the embryo’s internal
organs. These cells are what we call embryonic stem cells and have the
capacity of pluripotency; they are coveted by ESC researchers precisely
because of their pluripotency. Just as harvesting all the internal
organs of an adult would kill the adult, harvesting the stem cells of an
embryo kills the embryo.
Adult stem cells (ASCs) also have the capacities of self-proliferation
and differentiation, but are not derived from the bodies of embryos.
They are ‘adult’ not because they’re found only in adults, but because
the tissue in which they’re found is differentiated tissue (as opposed
to the undifferentiated tissue of an embryo’s body). Thus ASCs can be
found in newborn tissue. In fact, some of the most clinically valuable
ASCs are found in umbilical cord blood. Although some ASCs have been
found with the capacity of pluripotency, most are only capable of
differentiating into the tissue type or related group type of the tissue
in which they’re found.
Ethical controversy surrounding stem cell research
Every reasonable person agrees that the clinical end being sought in
stem cell research is praiseworthy
—
namely, finding clinical solutions for remediating serious illnesses.
Controversy surrounds the means by which that end is pursued. The
familiar ethical question raised by ESC research is this: Is it
justifiable to kill human embryos in order to explore potentially
healing remedies for other persons? Those who judge human embryos to be
human beings, albeit at an early stage of development, think it’s wrong.
Those who believe embryos are “pre-human” entities, developmental
precursors to whole human beings, think it sometimes can be
justified.[1]
ASC research avoids this ethical problem by avoiding research on embryos
altogether. The ethical questions surrounding ASC research then are
similar to those involved with all research on human subjects: Do the
benefits promised by the research outweigh the burdens imposed by it for
the human subjects of the research? Is fully informed consent being
secured? Is truthfulness in reporting of data being maintained? Are
unwarranted promises of benefit being eschewed? And so on. If the answer
to these is yes, then one may proceed with confidence that the research
is legitimate. In fact, the Vatican and the United States Conference of
Catholic bishops have consistently supported research on stem cells that
does not exploit or destroy human embryos[2]. This support is reaffirmed
in the new Vatican document on bioethical questions, Dignitas
Personae[3].
Don’t current findings demonstrate that ESC research is clinically
unnecessary?
This is a very important question and should be asked often of
scientists and public officials. Let me elaborate it: since ASCs have
already proven remarkably effective in treating serious diseases,
including formerly untreatable diseases[4], and since ESC research,
despite billions of dollars spent, has produced nothing but failures on
the clinical front, and even human tragedies[5], and since the desire to
develop clinically useful patient-specific pluripotent stem cells is
being rapidly and efficiently fulfilled by the new and remarkable
Induced Pluripotent Stem Cells (iPSCs)[6], why aren’t embryonic stem
cells obsolete in the minds of scientists? Why does the scientific
community insist on greater liberties for embryo-destructive
experimentation when both moral reasoning and cutting edge science point
in another direction? Why this lust for the embryo?[7]
I don’t have a satisfactory answer to this. Some researchers obviously
believe that embryonic stem cells, despite current evidence, promise
benefits that ASCs and iPSCs do not. I’m also told that many of the best
researchers are turning away from ESCs because of the mounting problems
they pose, and turning towards research with iPSCs. If this is the case,
then the questions posed above need to be put frankly to our
politicians, because some still seem to think that the future of stem
cell research lies with ESCs.
In the shadow of President Obama’s executive order overturning the Bush
stem cell policy, the House Majority Leader Steny Hoyer (D-Md.) stated
on the House floor that the U.S. House will take up a bill in early
April to overturn the 1996 Dickey-Wicker Amendment prohibiting federal
funding from research involving the creation or destruction of human
embryos [8]. With all we now know, why is Congress bent on spending
taxpayer money for embryo destructive experimentation? Isn’t that
scientifically retrogressive and economically wasteful, not to mention
morally unjust to the embryos killed as a result of the decision and to
taxpayers who object to public funds being used for such research when
alternatives are available?
Postscript:
Some might be wondering what distinguishes the “Bush stem cell policy”
(Aug. 2001) from the restrictions imposed by the Dickey-Wicker amendment
(1996). Dickey-Wicker was passed before ESC research was launched in
1998 by the first successful isolation of ESCs by James A. Thomson’s lab
at the University of Wisconsin, Madison. It simply restricted funding on
research that created or destroyed human embryos. After 1998, pressure
was exerted on the Clinton administration to free up funds for this new
‘promising’ type of research. But Dickey-Wicker stood in the way. Thus,
to sidestep the restrictions Clinton, as he was leaving office (2000),
approved federal guidelines permitting the NIH to fund research on stem
cells derived from ‘spare’ embryos slated for destruction at fertility
clinics. Do you see the slight of hand? By the time stem cells are
derived, the killing is over. If private funds paid for the killing,
then the federal government would fund the subsequent research.
Clinton’s lawyers argued that his guidelines conformed to Dickey-Wicker,
and legalistically construed, they did. At once, the NIH began accepting
grant proposals from scientists bent on embryo destructive research.
Aware of the loophole, newly elected President George W. Bush passed an
executive order permitting federal funds for ESC research only on
certain pre-approved stem cell lines created by that date. Since stem
cells can self-proliferate indefinitely, these sixty lines, he thought,
would provide subject matter for years of viable research. But under the
new policy, funding would be prohibited from all stem cell lines derived
after August 2001. NIH grant proposals thereafter were carefully
reviewed to ensure that federal funds would not be used to facilitate
harm to human embryos. Obama’s recent presidential order overturned the
Bush restrictions. Dickey-Wicker however still stands. But for how long?
Notes:
[1] I critiqued several of the most prominent theoretical arguments
against the personhood of human embryos in my June 2008 CLF Brief
entitled “Arguments for and Against the Personhood of the Embryo”, so I
do not intend to engage that question here.
[2] See Pontifical Academy for Life, Declaration on the Production and
the Scientific and Therapeutic Use of Human Embryonic Stem Cells (August
25, 2000); Catholic Online, “American Bishops Reaffirm Church Support
for Adult Stem-Cell Research,” www.catholic.org, June 26, 2006,
www.catholic.org/national/national_story.php?id=20275.
[3] See Congregation for the Doctrine of the Faith, Instruction Dignitas
Personae (On Certain Bioethical Questions) (2008), nos. 24, 31, 32.
[4] For an enlightening updated summary of clinical successes using ASCs
prepared by the Family Research Council, see
http://www.frc.org/insight/adult-stem-cell-success-stories-2008-update-july-december
[5] Recall the recent tragic story of the 9 year old Israeli boy, who
received embryonic stem cell injections in Russia for a lethal brain
disease, and contracted as a result tumors on his brain and spinal cord;
see CBS News report, “Study: Stem Cell Injections Caused Tumors: Israeli
Researchers Say Fetal Stem Cells Led To Benign Tumors For Boy With Rare
Genetic Disease,” Feb. 17, 2009; available at
http://www.cbsnews.com/stories/2009/02/17/health/main4808339.shtml?source=RSSattr=Health_4808339
[6] Induced pluripotent stem cells are differentiated cells such as a
skin cell that are “reprogrammed” back to a state of pluripotency. They
were first reported in research with human cells in November 2007. I
describe their advent and initial promise in my CLF Brief from January
2008, “A Moral Tsunami”. Since then dozens of studies have been carried
out (and published) perfecting the initiate technique. For example,
researchers at the Whitehead Institute in Cambridge, Mass., recently
converted skin cells from patients with Parkinson’s disease into the
type of neuron destroyed by the disease. Although the technique needs
perfecting, it promises to provide a therapy one day that replaces the
damaged neural tissue of Parkinson’s sufferers with healthy tissue
derived from the patient’s own body, and therefore with no risk of
immune rejection. See the NY Times on line report, “Converting Cells
Shows Promise for Parkinson’s”, March 6, 2009, available at
www.nytimes.com/2009/03/06/health/06parkinsons.html
[7] See Bernadine Healy’s piece in US News and World Report on line,
“Why Embryonic Stem Cells Are Obsolete” March 04, 2009, available at
http://health.usnews.com/blogs/heart-to-heart/2009/3/4/why-embryonic-stem-cells-are-obsolete.html
[8] The exchange between Hoyer and House Minority Whip Eric Cantor (R-Va.)
on the floor of the U.S. House of Representatives on March 12, 2009 can
be read in the Congressional Record, House, page H3376, March 12, 2009.
* * *
E. Christian Brugger is a Senior Fellow of Ethics at the Culture of
Life Foundation and is an associate professor of moral theology at St.
John Vianney Theological Seminary in Denver, Colorado. He received his
D.Phil. from Oxford in 2000.
[Article published with permission of the Culture of Life Foundation
(http://culture-of-life.org)]
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