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Somatic Cell Nuclear Transfer
In the last 50 years, human ingenuity has moved faster than ever before. We have
delved into the atom, built computers almost as smart as ourselves, touched the surface of
our moon, and sequenced every letter in our own biological blueprint. We are on the
brink of yet another major advancement in the sciences of human health, in the form of a
single cell with almost infinite potential. Therapeutic cloning, the use of stem cells to
repair or replace an individual’s damaged tissues, promises potential uses and cures
which could be used in the future to cure conditions which were formerly untreatable, yet
major technological and moral barriers remain which will require a great deal of further
research before widespread and meaningful contributions to humanity will be realized.
Until there is an accepted legal definition of when a potential organism is truly an
organism, there will be morally based laws opposing therapeutic cloning.
Therapeutic cloning is a complicated idea. Essentially in a process called Somatic
Cell Nuclear Transfer (SCNT), doctors could harvest a somatic cell (skin, hair, bone, etc.:
any cell in the body but sperm or egg) from the individual in need of treatment and use
that cell to create an embryo of that person. The nucleus of the somatic cell is removed
and inserted into a donated de-nucleated egg cell. The scientist then triggers this hybrid to
start dividing into an embryo by chemical or electrical stimulus. Once the embryo reaches
a certain state, the embryonic stem cells (ESC) inside are harvested. These ESCs are
pluripotent, meaning they can become one of any number of somatic cells (NIH).
Therefore these cells can be stimulated through chemical signal sequences (called
protocols) to begin forming any organ or tissue or mass of cells to be introduced into a
patient. (Solter and Gearhart, par. xii-xiii).Other techniques in therapeutic cloning are
similar. Adult stem cells, rare cells which exist into adult years can be harvested and
coaxed into becoming one of a limited number of cells. These adult cells are not nearly as
useful as ESCs because they cannot differentiate with the same variety or live as long in
culture, but they have the advantage of being less regulated and better accepted by public
opinion (National Institutes of Health).
Therapeutic cloning is a subcategory to a type of medicine called “cell therapy”,
which is the use of whole cells to treat diseases, usually these are genetic conditions and
they are often serious and fatal. Cell therapy does not necessarily mean it uses stem cells,
for example it is used to treat immunodeficient individuals so that they can have a
somewhat normal resistance to common pathogens, by simply extracting a few immune
cells from the individual and growing a large population of them in vitro (literally Latin
for in glass and refers to events which happen in a Petri dish or lab setting) then
introducing this larger population back into the patient. The types of disease treatable by
therapeutic cloning are notable because they are often very frustrating and difficult to
combat. Some conditions can be treated in ways besides therapeutic cloning, while some
conditions currently have no approved treatment or cure at all (NIH). Potentially,
therapeutic cloning has 3 main areas of use: organ and tissue structure replacement,
autoimmune disease repair, and neurological gene therapy (Singec et. al. 317).
Currently, a patient in need of a new organ or structure (heart valve, skin layer,
etc.) must either have a synthetic replacement installed, or find a donor structure from
another person. Even with these two options, the risk of rejection and infection is always
present. ESC and adult stem cell technology might someday give doctors the ability to
grow almost any structure, even something as complicated as a jawbone, and implant it
into the patient with virtually no complications (Gronthos 735). Previously untreatable
malformed or missing body parts might even be replaced with correctly grown versions
soon after birth. While this is a promising idea, today’s technology only allows us to
guarantee the ability to rejuvenate existing organ structures with ESC technology (Solter
and Gearhart, par. xii), but current research is on the brink of creating whole organs by
incubating stem cells on scaffolds shaped to encourage the formation of healthy organs
outside the patient (Graham, par. ii-iii). The major advantage of creating structures like
this is that they are almost genetically identical to the cells already in the patient, and
therefore won’t be attacked by the patient’s immune system (NIH). Another advantage is
that patients will be on life support and donor list only as long as it takes to grow an
organ or tissue (Wikipedia).
Autoimmune conditions like type I diabetes, some kinds of arthritis, and multiple
sclerosis develop from an attack of a person’s own immune system attacking and
destroying an important group of cells in the body (Wikipedia). In almost the same
process as with tissue growth, nuclei are replaced ESCs are harvested and then are
directed to divide and differentiate into whatever cells are needed: anything from
pancreatic insulin-producing cells to myelin sheaths for nerve cells can be produced with
the right differentiation protocols, some research even shows that the death of cells in
vivo can stimulate introduced ESCs into replacing them (Singec et. al. 317-318). ESCs
also last roughly three years in culture before losing their therapeutic value and so make
repeated treatments of autoimmune diseases possible without need to harvest somatic
cells every time (Hochedlinger and Jaenisch, section viii). This subset of cloning-
treatable diseases is specifically notable as these types of diseases are mostly incurable
and affect at least 5% of the population (Wikipedia).
The last major use of therapeutic ESCs is in neurological gene therapy. As
previously stated, ESCs are virtually identical genetically to the cells of the individual
from which they were originally derived. Also previously stated, this means that these
cells would be safe from immune attack and can be introduced into the patient. What is
different about this type of therapy is that these ESCs can be genetically modified to
contain a slightly different compliment of genes than those of the patient (Singec et. al.
318). This trait allows treatment of potentially fatal inherited conditions in which the
patient has no healthy gene and therefore is doomed; ESCs derived from this same patient
are genetically modified to carry a functional form of the gene, are then introduced into
the body, where they function to make up for the patient’s lack of gene function. In this
treatment, the ESCs act more as a vector to deliver a healthy gene copy without eliciting
an immune response than as a replacement cell (Hochedlinger and Jaenisch, section x).
While these therapies sound promising, they are still years away from even the
first clinical trials (NIH). Researchers have shown potential for ESC mediated gene
therapy in mice, as well as repair of organ and nervous tissue. Currently scientists have
been unsuccessful in creating human ESC via SCNT. Research shows that ESCs of other
primates are also difficult to create and are very temperamental when developing (Yang
et. al. 300). Currently, more research is required to ensure correct differentiation of ESCs,
their survival in the patient, appropriate function, and the assurance that they do not cause
any harm to the individual (NIH).
On the other side of the issue, several moral and religious groups rightly claim
that stem cells made this way have the full compliment of human DNA and so should be
treated as viable life. These organizations also claim that adult stem cells should be the
main focus of therapeutic study as they are almost as promising as ESCs, yet do not
require an artificial human embryo to be destroyed. Further they claim that therapeutic
cloning research will inadvertently lead to advances in reproductive cloning and the
amoral creation of human life. These organizations have the upper hand in political
representation in the debate. Current federal policy bans research on ESCs. A few states
sponsor it within their jurisdiction, but research is progressing much slower than it could.
A legal definition of a viable organism would alleviate much of the problem over
this issue, either therapeutic use of ESCs would become completely illegal, or there
would be no legal grounds for not funding it; either way, a decision should be made to
finally decide the issue.
Atala, Anthony. “Technology Insight: applications of tissue engineering and biological
substitutes in urology.” Nature Clinical Practice Urology. 2.3 (2005): 143-149
Cowan, Chad A, et al. “Nuclear Reprogramming of Somatic Cells After Fusion With
Human Embryonic Stem Cells.” Science 309 (Aug 2005): 1369-1372
Gearhart, John, and Davor Solter. “Putting Stem Cells to Work” Science 283 (Mar 1999):
Graham, Sarah. “Scaffold May Help Stem Cells Grow into Organs” Scientific American.
15 Oct. 2003
Gronthos, Stan. “Reconstruction of human mandible by tissue engineering.” The Lancet.
364. (Aug 2004). 735-736
Hochedlinger, Konrad, and Rudolf Jaenisch. “Nuclear transplantation, embryonic stem
cells, and the potential for cell therapy.” The New England Journal of Medicine.
349.3 (Jul 2003): 275-287
National Institutes of Health. “Stem Cell Basics.” Accessed 4/10/07,
Singec, Ilyas, et al. “The Leading Edge of Stem Cell Therapeutics.” Annual Review of
Medicine. 58 (2007) 313-328
Wikipedia, Keywords: autoimmune disease, cloning, therapeutic cloning. Accessed
Yang, Xiangzhong, et al. “Nuclear reprogramming of cloned embryos and its
implications for therapeutic cloning.” Nature Genetics. 39.3 (Mar 2007) 295-302