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Written Statement prepared by Mark E. Westhusin
Presented to the U.S.
House of Representatives Committee on Energy and Commerce, Subcommittee on
Oversight and Investigations, March 28, 2001.
Subject: Human Cloning
Man
has long been interested in nuclear transplantation both as a tool to study
developmental biology and as a means for producing genetically identical
animals. The basic technique involves the transfer of a nucleus from one cell
to another cell which has had its own nucleus removed. For cloning animals this entails
transferring the nucleus of a cell obtained from the individual to be cloned
into an unfertilized ovum that has had its chromosomes removed. If successful, the transferred nucleus is
re-programmed so to direct development of a new embryo that is genetically
identical to the animal from which the cell was obtained. This embryo can then
be transferred into a surrogate mother for gestation to term and birth of a
clone.
In recent years, nuclear transplantation
has been employed to clone a number of different animals. The most acclaimed example is of course the
report by Wilmut et al (1997), which was the first to demonstrate cloning of
adult mammals was possible. Nuclei of
cultured mammary epithelial cells derived from an adult ewe were transferred
into enucleated sheep ova, ultimately resulting in the birth of a cloned lamb
(Dolly). The demonstration that adult
cells could be used for cloning mammals sparked enormous new interest in exploring
the potential of cloning animals. As a
result, in just the past three years, cloned cattle, sheep, goats, pigs, and
mice have been reported (Wilmut et al. 1997; Cibelli et al. 1998; Wakayama
et al, 1998; Baguisi et al. 1999; Wells
et al. 1999a; 1999b; Polejaeva et al. 2000; Onishi et al. 2000; Hill et al.
2000).
The
potential benefits animal cloning will afford mankind are far-reaching, and
undoubtedly, many more applications and benefits are yet to be imagined. A
current utility includes the production of transgenic animals for use as living
bioreactors to produce pharmaceuticals.
Several products produced in milk of transgenic sheep and goats are
already in clinical trials (Factor IX, P.P.L., Inc.; anti-thrombin III, Genzyme
Inc.; Baguisi et al. 1999;
Schnieke et al. 1997), and the estimated market
value of pharmaceutical production in the milk of transgenic animals currently
exceeds $3 billion per year. A number of other products are targeted for
production in milk from transgenic livestock including both nutriceuticals and
vaccines. Genetic engineering animals for protein production in milk promises
to result in a wide variety of products for human use, many of which will be
less expensive and more effective (Stice
et al. 1998; Wall, 1996). Other applications of cloning to produce transgenic animals
include the production of livestock that are that are genetically resistant to
devastating diseases such as those currently causing major concern throughout
the world i.e. Mad Cow Disease and Foot and Mouth disease. Agricultural applications of animal cloning
will result in increased quality and decreased costs for food and fiber (Stice SL et al. 1998; Wall, 1996). In addition, animal cloning provides for rapid genetic gain in
animal breeding programs and could potentially have a great beneficial impact
on the conservation, preservation and propagation of endangered species (Wells et al. 1999a).
Anticipated future
applications of cloning procedures are nothing short of phenomenal. These include such things as the production
of human embryonic stem cells for tissue transplantation and/or gene therapy
and treatments for mitochondrial diseases, just to name a few. Human cells could potentially be utilized as
nuclear donors for transplantation into oocytes, resulting in cell lines that
may be useful for human therapy to treat conditions such as Alzheimer’s or
Parkinson’s disease (Zawada et al. 1998).
With
animals representing 5 different mammalian species now having been produced by
somatic cell nuclear transfer, cloning has been proposed as a tool for assisted
reproduction in humans i.e. a means for producing a human baby. Experiments from our laboratory and others
provide strong evidence that the current procedures used for mammalian cloning
are not safe and many times result in abnormal development. This can ultimately lead to death of the cloned
offspring and the surrogate mother. (Campbell et al. 1996;
Cibelli et al. 1998; Hill JR et
al. 1999; Kato Y et al. 1998; Schnieke et al. 1997; Vignon X et al. 1999; Wakayama et al. 1998; Wells et al. 1997; Wilmut et al. 1997).
Based on
these observations and evidence from studies in mice which demonstrate
incompatibilities between nucleus and cytoplasm from different strains (Latham, 1999), cloning as an approach to
human assisted reproduction is at present both risky and extremely
irresponsible.
Although
animals can be cloned by nuclear transplantation using somatic cells as nucleus
donors, the efficiency of the technique is still extremely low. In cattle where the majority of the work has
been completed, problems with early embryonic development do not seem to be a
major factor affecting the efficiency of cloning, as development rates to the
blastocyst stage in vitro are similar
to those of normal embryos produced by in
vitro fertilization. Maternal
recognition and the establishment of pregnancy as indicated by pregnancy rates
at 35 days of gestation are also similar between normal embryos and those
produced by nuclear transplantation.
However, after 35 days of gestation, pregnancy loss is dramatic and very
few fetuses survive to term.
Approximately 90% of the pregnancies are lost and abort between days 35
and 90 of gestation (the first trimester).
The most common developmental malformation observed to date is aberrant
placentation (Hill et al. 1999; Stice et al. 1996). Of those calves that do
survive, most exhibit placental edema and a reduced number of enlarged
placentomes. These placental
abnormalities pose serious health risks not only to the developing fetus and
offspring but also to the surrogate mothers carrying the pregnancies. In several cases involving cattle, both the
surrogate mother and the bovine fetuses have died during late gestation due to
a variety of complicated health issues related to the abnormal pregnancy. Moreover, even if the cloned offspring
survive to term, many of the resulting calves exhibit developmental
abnormalities and die at birth or shortly thereafter, normally a result of
cardiopulmonary abnormalities (Cibelli et al. 1998; Garry et al. 1996; Kato et al. 1998; Kruip et al. 1997; Renard et al. 1999;
Vignon et al. 1999; Wilson et al. 1995; Hill et al. 1999). In general, regardless of the species, only 1%-5% of cloned
embryos survive to term.
In
our laboratory we have utilized nuclear transfer to try and reproduce the
genotypes of several different animals, selected for cloning based on their
inherent genetic value. Results we have
obtained to date are similar to those reported by other laboratories regardless
of the species involved. The first case
involved a Brahman steer named “Chance”, known to be at least 21 years
old. Adult fibroblasts were obtained
from a skin biopsy and expanded in culture using standard methods for tissue
culture prior to being frozen and stored in liquid nitrogen. When nuclear transfer was performed using
the fibroblast cells derived from Chance, 28% of the fused couplets (53 of 190)
developed into blastocysts in culture.
Twenty-six of these were transferred into 11 recipient cows resulting in
6 pregnancies. Three of these continued
to develop through 90 days of gestation but only one survived to term. “Second Chance” is now over a year old and
appears normal and healthy for his age.
However during the first week of life he required intensive monitoring
and therapy to treat lung dysmaturity and pulmonary hypertension. At 7 days of age he was also diagnosed and
treated for Type 1 insulin-dependent diabetes, which is extremely rare in
cattle. He also lacked the expression
of an important T-cell antigen CD45, indicating his immune system was in some
way abnormal (Hill et al, 2000).
The second and third
attempts at reproducing desired genotypes by cloning involved two middle-aged
cows, one Brangus and one Charolois.
These were selected based on being top performers in the herd. Fibroblasts were again obtained from skin
biopsies. Development rate to the
blastocyst stage following nuclear transfer and embryo culture averaged 16%. Thirty-seven blastocysts derived from the
Charolois cow were transferred into 13 recipients. Six of these were diagnosed as pregnant at 30 days of gestation
but only 4 remained pregnant through 60 days.
One of these pregnancies was subsequently lost. In two cases the fetus was removed for
research purposes. The final pregnancy
was allowed to proceed to term resulting in twin heifers. However, both calves died between 7-10 days
after birth due to complications related to the cloning procedure. Forty-three blastocysts derived from the
Brangus cow were transferred into 14 recipients resulting in 3 pregnancies. However none of these survived past 90 days
of gestation.
Our
most recent attempt at cloning a specific animal has involved a deceased Black
Angus bull previously shown to be naturally (genetically) resistant to
Brucellosis. Of the oocyte-fibroblast
couplets fused and cultured, 44% developed to the blastocyst stage. Thirty-nine blastocysts were transferred
into 20 recipients resulting in 10 pregnancies at 35 days of gestation. One of these survived to approximately 150
days of gestation and was then lost.
Another single pregnancy survived to term resulting in a healthy bull
calf.
Prior
to any attempt to use nuclear transplantation/cloning as a means of human
assisted reproduction, it is imperative that many additional animal studies
evaluating the safety of somatic cell cloning be carried out. These studies
should also include efforts to evaluate the safety of applying nuclear
transplantation procedures for treatment of human disease or infertility by
manipulating oocyte cytoplasm and/or genetically modifying human cells prior to
cloning. Proponents of human cloning
as a means of assisted reproduction have pointed out that even with accepted
practices of assisted reproduction such as in vitro fertilization, success
rates are low and pregnancy losses higher than in natural reproduction. This is indeed the case, but hardly to the
extent seen in cloning where only 1-5% of the procedures performed result in
offspring, and a significant number of these either die at birth or require
intensive care for several weeks to keep them alive.
Moreover,
the claim that cloned embryos could be screened prior to embryo transfer so to
select those that will develop normally is simply not a possibility at this
time. Research conducted in our
laboratory and several others now points very strongly to the fact that
problems seen in cloned embryos/pregnancies are likely epigenetic effects
brought on by the cloning techniques themselves and causing abnormal expression
of important developmental genes.
Techniques to evaluate for these abnormalities are simply not yet
available and it will likely be years before such diagnostics do become
available. Procedures to determine
whether cloned embryos and fetuses appear to have normal and the right number
of chromosomes are woefully inadequate as there is no indication to date that
abnormal karotypes are a problem i.e. chromosomes in cloned embryos appear
normal. If one wanted to screen for
abnormal gene expression, which of the tens of thousands of genes would one
screen for? There is no solid data yet to point to one gene/cause for
developmental failure. In addition,
given the small size and few cells available, current techniques will not allow
any type of adequate analyses of an embryo so to determine in fact that it is
normal. At best, with ultrasound, one
could determine that the fetus is dead, which based on animal studies is likely
to be the situation in 90% of the cases during the first trimester of
pregnancy.
Finally,
even the apparently healthy animals that are produced by cloning should be
studied and observed for a number of years to evaluate their long-term health
status prior to any applications in humans.
Considerable evidence has now been accumulated to suggest that insults
occurring during the critical period of embryo and fetal development may have
long-term effects on the health of offspring and resulting adults. Cloned animals produced to date have not yet
lived long enough to evaluate this potential risk. Undoubtedly it would be a devastating case to produce cloned
humans only to find out that they all developed serious disease/health problems
and/or died during childhood or adolescence or even early in their adult
life. At this point it is simply
impossible to eliminate this potential disastrous outcome.
Ethical Concerns Involving Human Cloning:
I
have previously been quoted in the popular press as saying that while there are
enormous beneficial applications to cloning animals, “I have never met a human
worth cloning”. Although my wife may
take some exception to this statement, I still stand behind it. In part, this is due to the fact that as
human beings, none of us are perfect.
Also, expectations of what a human clone would be or do are many times,
exaggerated. Cloning animals by nuclear
transplantation is simply a technology that can be used to produce another
individual with the same genetic make up.
What cloning absolutely is not, is a means of resurrection. I think it
best we leave this business to God as we have enough problems to deal with just
trying to be decent human beings. It
is indeed extremely troubling to me however, that with the successful cloning
of animals, many people in society still seem to have no understanding of the
difference between “reproduction” and “resurrection”. A significant number of requests for human cloning involve the
utilization of cells from “beloved family members” that are in fact
deceased. Undoubtedly, those requesting
such services, whether they would admit it to themselves or not, in some way believe
cloning is a form of resurrection, not reproduction. It is deeply concerning that individuals offering human cloning
services could take advantage of highly emotional situations involving the
death of a loved one by selling resurrection vs reproduction.
With
time and education, society will eventually understand the difference between
resurrection and reproduction. I will
also predict that given the current state of various assisted reproduction
techniques that are already being utilized by humans and readily accepted as
ethical, such as in vitro fertilization and intracytoplasmic sperm injection,
cloning by nuclear transplantation will eventually also be thought of as simply
another form of assisted reproduction, and individuals employing techniques of
nuclear transplantation will not be accused of “playing God”. In short, I predict that humans will someday
be cloned. When this happens, the sky
will not fall and the world will not come to an end. Scenarios such as that seen in “The Boys from Brazil” and armies
of clones will remain in the movies.
The number of human babies that would ever be produced by cloning will
be infinitesimally small compared to children born by natural reproduction, and
will hardly be noticed. The person (s)
that come into this world by way of cloning will be new and unique
individuals. Moreover, I have
confidence and a personal faith in God that they will be blessed with a unique
spirit and soul. To think otherwise is
to suspect that God hasn’t blessed the thousands of babies already born by
other forms of assisted reproduction with a soul, and neither the
tens-of-thousands of genetically identical twins that live in this world. This begs the question, what is it that
really makes human cloning so (as it is often referred to) repugnant? Is it the word “clone” itself and/or the
horrendous stories that have been written, or movies that have been made that
always depict cloning as a terrible thing leading to a terrible outcome? Would it be impossible to write a story about
human cloning that had a happy ending, or is it just the fact that it wouldn’t
sell and therefore no profit would be gained?
Surely it is not the fact that a clone would have a genetically
identical copy, either still alive or deceased? How would this be that much different than an identical twin?
Consider
the following scenario. A skin cell
from a human male is inserted into an enucleated human ovum (nuclear
transplantation) so to create a cloned human embryo. However, instead of transplanting this embryo into a surrogate
mother, the embryo is placed into culture and treated in such a way that it
develops into embryonic stem cells.
Given the enormous and promising success that has been achieved in
recent years involving the production of human embryonic stem cells, it is
easily conceivable that in the not to distant future, these stem cells could
then be directed in culture to undergo gameteogenesis and develop into cell
types that represent gametes (sperm and eggs) containing a haploid number of chromosomes
(half of that in a normal somatic cell), and the genes will have been
rearranged, as occurs during normal gamete development. Once this has occurred, two of the gamete
cells could be selected and using nuclear transfer a second time, placed into another
enucleated ovum resulting in a normal embryo that could then be transferred
into a surrogate mother for development to term. While this scenario may be difficult for some to follow, here’s
the punch line. It is entirely
conceivable that a single cell originally derived from a single male, with the
aid of technology, could be used to produce a new human baby. This new human being would not at all be a
clone, because of the natural process of gene rearrangement that occurs during
gamete development, and in fact, could turn out to me a girl!
If
cloning a human being is unethical, would this procedure also be unethical even
though the new baby would not be a clone at all but simply derived from an
elaborate assisted reproductive technology?
Given the state of currently accepted practices for treating human
infertility, I doubt it, but with one caveat.
It would certainly be considered highly unethical and completely
irresponsible if 90% of the pregnancies resulted in abortions, the surrogate
mother was put in serious health risk, and a significant portion of the
offspring that resulted were developmentally abnormal and many died.
So we are back to square one. Is
nuclear transfer to produce a human clone a reasonable thing to consider
attempting at this time? In my opinion
absolutely no! Ethical issues and moral
issues aside, at present, cloning is just too risky, many times resulting in
serious health problems and/or death the developing fetus, surrogate mother,
and resulting offspring.
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