Stem cells can divide and differentiate into other cell types and also self-renew. There are two main types: embryonic stem cells from blastocysts and adult stem cells found in tissues. In adults, stem cells act as a repair system and in embryos can differentiate into all cell types. There are three sources of autologous adult stem cells - bone marrow, adipose tissue, and blood. Embryonic stem cells are controversial because deriving them requires destroying the embryo. Induced pluripotent stem cells generated from adult cells may eliminate this issue but more research is needed. The ethics of stem cell research centers around the moral status of embryos and whether the potential medical benefits outweigh this.

1. Stem cells are biological cells found
in all multicellular organisms, that
can divide (through mitosis) and
differentiate into diverse specialized
cell types and can self-renew to
produce more stem cells. In
mammals, there are two broad types
of stem cells: embryonic stem cells,
which are isolated from the inner
cell mass of blastocysts, and adult
stem cells, which are found in
various tissues. In adult organisms,
stem cells and progenitor cells act as
a repair system for the body,
replenishing adult tissues. In a
developing embryo, stem cells can
differentiate into all the specialized
cells[ectoderm,endoderm and
mesoderm-see induced pluripotent
stem cells] (these are called
pluripotent cells), but also maintain
the normal turnover of regenerative
organs, such as blood, skin, or
intestinal tissues.
There are three accessible sources of
autologous adult stem cells in
humans:
1. Bone marrow, which requires
extraction by harvesting, that
is, drilling into bone (typically
the femur or iliac crest),
2. Adipose tissue (lipid cells),
which requires extraction by
liposuction, and
3. Blood, which requires
extraction through pheresis,
wherein blood is drawn from
the donor (similar to a blood
donation), passed through a
machine that extracts the
stem cells and returns other
portions of the blood to the
donor.
Stem cells can also be taken from
umbilical cord blood just after birth.
Of all stem cell types, autologous
harvesting involves the least risk.
By definition, autologous cells are
obtained from one's own body, just
as one may bank his or her own
blood for elective surgical
procedures.
Highly plastic adult stem cells are
routinely used in medical therapies,
for example in bone marrow
transplantation. Stem cells can now
be artificially grown and
transformed (differentiated) into
specialized cell types with
characteristics consistent with cells
of various tissues such as muscles or
nerves through cell culture.
Embryonic cell lines and autologous
embryonic stem cells generated
through
therapeutic cloning have also been
proposed as promising candidates
for future therapies.[1]
Research into
stem cells grew out of findings by
Ernest A. McCulloch and James E.
Till at the University of Toronto in
the 1960s.[2][3]
Ethics of Stem Cell Research
First published Fri Apr 25, 2008;
substantive revision Mon Jan 28,
2013
Human embryonic stem cell (HESC)
research offers much hope for

2. alleviating the human suffering
brought on by the ravages of disease
and injury. HESCs are
characterized by their capacity for
self-renewal and their ability to
differentiate into all types of cells of
the body. The main goal of HESC
research is to identify the
mechanisms that govern cell
differentiation and to turn HESCs
into specific cell types that can be
used for treating debilitating and
life-threatening diseases and
injuries.
Despite the tremendous therapeutic
promise of HESC research, the
research has met with heated
opposition because the harvesting of
HESCs involves the destruction of
the human embryo. HESCs are
derived in vitro around the fifth
day of the embryo's development
(Thomson et al. 1998). A typical day-
5 human embryo consists of 200–250
cells, most of which comprise the
trophoblast, which is the outermost
layer of the blastocyst. HESCs are
harvested from the inner cell mass
of the blastocyst, which consists of
30–34 cells. The derivation of HESC
cultures requires the removal of the
trophoblast. This process of
disaggregating the blastocyst's cells
eliminates its potential for further
development. Opponents of HESC
research argue that the research is
morally impermissible because it
involves the unjust killing of
innocent human beings.
Scientists recently succeeded in
converting adult human skin cells
into cells that appear to have the
properties of HESCs by activating
four genes in the adult cells
(Takahashi et al. 2007; Yu et al.
2007). The reprogrammed cells—
―induced pluripotent stem cells‖
(iPSCs)—could ultimately eliminate
the need for HESCs. However, at
present, the consensus in the
scientific community is that both
HESC and iPSC research should be
pursued, as we do not yet know
whether iPSCs have the same
potential as HESCs or whether it is
safe to transplant them into
humans. Thus, the controversies
around HESC research will
continue, at least in the near-term.
While the principal source of the
controversy surrounding HESC
research lies in competing views
about the value of human
embryonic life, the scope of ethical
issues in HESC research is broader
than the question of the ethics of
destroying human embryos. It also
encompasses questions about, among
other things, whether researchers
who use but do not derive HESCs are
complicit in the destruction of
embryos, whether there is a moral
distinction between creating
embryos for research purposes and
creating them for reproductive ends,
the permissibility of cloning human
embryos to harvest HESCs, and the
ethics of creating human/non-
human chimeras. This entry
provides an overview of all but the
last two issues just listed; cloning
and human-non-human chimeras
are addressed in separate entries.

3. Stem cells hold great promise in
helping us understand and treat
many human diseases and
conditions. That's because stem cells
are quite unique compared to other
types of cells. For one thing, unlike
most normal types of cells, stem cells
are capable of dividing and
regenerating for long periods of
time. Secondly, stem cells are
unspecialized, which means they
don't have a unique function, such
as pumping blood to the heart or
supporting muscles in the legs. These
unspecialized cells can be trained,
however, which means they could
become specialized in whatever area
of the body they're needed.
Why do these properties portend
medical breakthroughs? Many of the
deadliest diseases, such as cancer,
are the result of uncontrolled
cellular division. By studying how
stem cells are able to reproduce
without causing damage, scientists
may be able to better understand
the disease and determine more
effective treatments. And the ability
to regenerate new, unspecialized
cells could revolutionize treatment
for conditions caused by cellular
degeneration. For example, during a
stroke, brain cells are irreparably
damaged; stem cells could kick-start
the regenerative process and
undergo specialization to replace the
lost cells. It's impossible to know
every possible medical use of stem
cells because scientists haven't been
able to conduct extensive research
with them, but researchers claim
that they may be the key to treating
a host of diseases and conditions,
including Parkinson's disease,
diabetes, heart disease, multiple
sclerosis, baldness and spinal cord
injuries.
Research on possible treatments has
been limited due to ethical concerns
over where the stem cells came from.
Until recently, scientists only knew
of two ways to obtain stem cells --
from embryos and from adults.
Adult stem cells are found in
various parts of the body, such as
the brain, bone marrow, blood, skin
and heart, but they tend not to
divide very often once they are
removed from the body, and there
has been some difficulty in re-
specializing these cells. Embryonic
stems cells are derived from a
blastocyst, or an embryo that's
between three and five days old.
These embryos are usually furnished
by clinics that perform in vitro
fertility treatments; for one reason
or another, they've been rejected for
implantation into a womb.
It is embryonic stem cells that cause
controversy. Removing the stem
cells requires the destruction of the
embryo, which some people liken to
destruction of a human being. The
issue comes down to the question of
when life begins: Those who believe
that life starts at the moment of
conception think that harvesting
embryonic stem cells is akin to
murder. Some critics of this
viewpoint have argued that these

4. embryos were marked for
destruction and then donated by
their owners, meaning that these
embryos would never have come to
term anyway, but others predict
that this excuse might lead to more
ethically questionable actions in the
future, such as harvesting embryos
specifically for research.
In recent years, researchers have
tried to find ways to obtain
embryonic stem cells without
destroying the embryos. One method
of deriving stem cells from mice
embryos has proven successful.
Researchers are also experimenting
with reprogramming adult stem
cells to act more like embryonic
stem cells. These cells, known as
induced pluripotent stem cells, hold
promise, but scientists would still
like the opportunity to pursue work
with the embryonic stem cells.
The ethics of stem cells
Ethical issues around stem cells
focus almost entirely on embryonic
stem cells.
Stem cells have been used in
medicine for many years - bone
marrow transplantation is a form of
stem cell therapy. Ethical concerns
have focused mainly on the use of
embryonic stem cells in research
and their possible application in
medicine.
A core issue has been the source of
embryonic stem cells. Until recently,
these were obtained from embryos
that were by-products of assisted
fertilisation attempts; these could be
voluntarily donated for use in
research.
More recently, UK law was changed
to allow researchers to create
human embryos for use in research,
so that embryonic stem cells could be
extracted. The key difference here
was that new human embryos were
being created specifically for
research. Some commentators
argued that this contravened the
principle that human life should
never be created as a means to an
end. However, embryos created for
research cannot by law be
implanted in the womb, so never
give rise to new individuals.
A key ethical concept is the moral
status of the embryo. The consensus,
enshrined in the Human
Fertilisation and Embryology Act in
1990, is that the embryo does have
moral rights but not to the same
extent as a living person. The
interpretation is challenged by some
groups, including the Catholic
Church, which holds that new life
begins at the point of conception and
hence a fetus at any stage of
development should hold full human
rights. Others, including some other
faiths, consider that the status of a

5. fetus changes as it develops, for
example as its nervous system
appears.
The rights of a fetus at any a
particular stage are balanced
against the potentially large benefits
that others may gain from research
and, ultimately, stem cell-based
treatments. This line of reasoning
has led some to argue that use of
embryonic stem cells is not justified,
because alternatives are available,
such as adult stem cells or, more
recently, induced pluripotent stem
cells. Most scientists counter that
research on embryonic stem cells is
still needed to clarify fundamental
biological mechanisms and because
it is not yet clear which types of
stem cell will prove the best bet
therapeutically. Use of pre-14-day
embryos, still little more than a ball
of cells, would therefore remain
justified.
Ethics of stem cell research
The overwhelming objection to stem
cell research is that it involves the
destruction of an embryo or foetus.
For many this constitutes
destruction of a potential human,
and conflicts with religious and
moral views held in our society. For
others, the potential for this
research to provide treatments and
possibly cures for debilitating
illnesses that have no cure and
significantly impact on our way of
life overrides this concern. Central
to any argument on this is what
actually constitutes the beginning of
life for a human. Opinions on this
vary from the moment of
conception, to a 14 day embryo, to a
living baby at birth. This issue is
highly emotive and it will always be
necessary to consider all opinions
and to balance the harm that might
be done against the potential good
this research may provide for those
suffering from debilitating diseases.
In Australia, legislation states that
no embryo may be created for the
purpose of this research or to
generate stem cell lines. The
embryonic stem and germ cells are
obtained from either donated
embryos not required for an IVF
procedure that would otherwise be
destroyed, or from pregnancies that
were terminated for medical or
social reasons.
The other major ethical issue
associated with stem cell research
ties in with the combination of
embryonic stem cell and cloning
technologies, leading to generation
of an embryo that is a genetic clone
of the donor of the nucleus (see
section on stem cells and cloning).
What is critically different in this
context as opposed to that above is
that an embryo is actually created
for research or therapeutic
purposes, and this raises a wider
range of objections, in that a
potential life is created for a specific
purpose.
Also of issue here is the purpose of
this cloning, which would be done
purely for the purpose of generating
tissue for transplantation. The

6. embryo generated could be allowed
to continue development and could
potentially lead to the birth of a new
human if implanted into a willing
mother. There are serious ethical
and medical concerns associated
with the use of somatic cell nuclear
transfer technologies to reproduce
humans and it is illegal in
Australia, UK and the USA to
conduct any research into
reproductive cloning of humans.
The Prohibition of Human Cloning
Act 2002 (Cth) prohibits all types of
human cloning by any method. The
Research Involving Human
Embryos Act 2002 (Cth) allows for
regulated use of an appropriate
number of excess ART embryos in
approved research programs. State
and Territory governments are
introducing complementary
legislation to provide nationally
consistent prohibition and
regulation of use of excess ART
embryos in research.
Some people speculate that allowing
any somatic cell nuclear transfer
will be the start of a slippery slope
into reproductive cloning.
Given these concerns, which stem
cell research should be permitted?
There are pluses and minuses
associated with the research and use
of all types of stem cells. Which ones
should research focus on?
The ethical issues surrounding the
origin of embryonic stem cells will
always be a sensitive issue. There
are strict guidelines and legislation
regarding any research involving
embryos, but for many, research on
adult stem cells is the only
acceptable alternative.
Embryonic stem and germ cells can
give rise to every cell type in the
body. Adult stem cells, however, are
multipotent, giving rise to a limited
range of cell types. This may limit
their use in cell-based therapies, and
many researchers believe research
using embryonic cells will be more
fruitful. However, recent research
has revealed that some adult stem
cells may be able to generate
different tissues under the right
conditions and this may increase
their therapeutic potential.
Embryonic stem cells have a greater
capacity for self-renewal and the
cell lines that have been established
will be useful for research into the
effects of drugs and toxins, and also
into early human development.
Their uncontrolled growth also leads
to the development of tumours
called teratomas, which may
restrict their use in cell-based
therapies. Research is continuing
into ways to control and regulate
the growth of ES cells more
effectively. Embryonic germ and
adult stem cells do not form these
tumours in culture, which may
make them better alternatives for
transplant tissue sources.
Obviously there are pros and cons to
the use of all three types of stem cells

7. and most scientists agree that it is
important to continue to pursue
research into embryonic stem and
germ cells and adult stem cells. All
scientists are aware that they must
undertake their work ethically and
within the bounds of the law, and
these can vary from country to
country. In Australia, all research
involving humans must be approved
by Human Research Ethics
Committees.