A laboratory at Cambridge University in the United Kingdom created mouse embryos from embryonic stem cells, circumventing the traditional sperm-egg fertilization process, according to an early edition of a manuscript published Aug. 25 by Nature.
Biologists say this could offer an alternative to using natural embryos to study early development by allowing researchers to see more developmental stages in mammals than previously possible.
However, this new science raises ethical questions about the use of clones in research.
In mammals, it can be difficult to study early development as the offspring grow in the uterus of the mother, out of sight. Because of this, biologists have been developing ways to generate early embryos for study for many years.
Through this research, we have learned that as an embryo grows from a single cell to many, the cells begin with broad capability to become anything in the body. Over time, however, these cells become more “specialized” and are less able to change to a different cell type. This cycle creates the many different cell types and organs of the body, which all perform specific tasks to sustain life and its processes.
The Zernicka-Goetz Laboratory at Cambridge University is the first to show they can grow embryos past the stage of “gastrulation,” the point at which embryos go from having one layer of cells to three. This process allows for complex structures to form, such as the heart and brain.
This research group was able to achieve this by cloning embryos using stem cells from the very early stages of development. They found when certain cells are taken from an early stage embryo, they can then be combined to generate a separate clone of the original mouse embryo.
Instead of dozens of baby mice being used and then euthanized in the pursuit of science, this advance would provide the opportunity to use the “same” mouse – a clone – over and over again.
“People are even having their dogs cloned now”
This presents a few scientific and ethical questions that we need to address now, before this science is applied to humans.
Walter Low is a member of the Stem Cell Institute and a professor in the neurosurgery department here at the University of Minnesota. He pointed out that cloning of animals has been happening for many years, starting with the widely publicized cloning of Dolly the sheep in the ‘90s.
To clone Dolly, her DNA was inserted into a sheep egg cell whose own DNA had been removed. This egg was then grown inside of a sheep to produce Dolly’s clone. Cloning technology has since become more popular, Low said. “People are even having their dogs cloned now,” he said.
For Low, the ethical boundary for embryo cloning is human reproduction.
“Cloning for reproductive purposes for humans … that is the line in the sand,” he said.
While he can see this technology being used to develop cellular therapies and potentially organs, Low said human cloning is as of yet unlikely, for both technical and ethical reasons.
As a historical parallel, Low brought up the example of former University faculty member Dr. Christiaan Barnard’s completion of the first successful human heart transplant in 1967. While the initial transplant was successful, the heart recipient survived less than three weeks after the surgery.
As exciting of a moment in medical history this was, it was also cause for ethical concern. The patient’s death raised concerns over the basis of a human soul, not to mention the safety of the surgery.
“Any time when technology really advances so quickly like this, there are ethical concerns,” Low said. “People thought at that time … the heart was the seat of the soul. And how can you transplant the soul of one person into another? But look at it now.”
Indeed, look at it now. Heart transplants are being performed all over the world and are considered standard care for heart disease that cannot be treated successfully by other means.
The question of soul
While society seems to have agreed since 1967 that the human soul is not based in the heart’s physical form, questions still remain as to the source of a human soul in the physical body and, importantly, when that soul begins to exist.
Stem cell-derived embryos in humans may be far off for now, but as they have become possible in mice, we should consider the potential implications for humans.
People who share identical DNA and originate from a single embryo that “splits” are known as identical twins. We do not refer to these people as “clones” for many reasons, most of which revolve around respect for their individuality.
Identical twins are not considered to share a soul any more than they are considered to share a body, even though science has suggested that they did share a single body for a very short period of time early in development.
The human soul is often considered to be the source of our capabilities in life beyond the basic abilities of our bodies. Because of our souls, we can think with reason and morality and act as individuals to accomplish great things in life.
Perhaps what identical twins reveal to us is our souls do not reside in any piece within us, but rather they originate from the whole of us when we, and our cells, were capable of almost anything. This idea shows that there is no such thing as a clone among human beings, and there never will be.
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