Stem cells are primal cells found in all multi-cellular organisms. They retain the ability to renew themselves through mitotic cell division and can differentiate into a diverse range of specialized cell types.
ES cells are pluripotent. This means they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm. These include each of the more than 220 cell types in the adult body. Pluripotency distinguishes ES cells from multipotent progenitor cells found in the adult; these only form a limited number of cell types. When given no stimuli for differentiation, (i.e. when grown in vitro), ES cells maintain pluripotency through multiple cell divisions. The presence of pluripotent adult stem cells remains a subject of scientific debate.
Because of their plasticity and potentially unlimited capacity for self-renewal, ES cell therapies have been proposed for regenerative medicine and tissue replacement after injury or disease. However, to date, no approved medical treatments have been derived from embryonic stem cell research (ESCR).
Currently government funds can be used to research stem cells, as long as they are not embryonic stem cells.
(1) The utilitarianism argument
The benefits of stem cell research outweigh the cost in terms of embryonic "life"
* Embryonic stem cells have the capacity to grow indefinitely in a laboratory environment and can differentiate into almost all types of bodily tissue. This makes embryonic stem cells an attractive prospect for cellular therapies to treat a wide range of diseases.
* The social, economic and personal costs of the diseases that embryonic stem cells have the potential to treat are far greater than the costs associated with the destruction of embryos.
(2) The human potential vs humanity argument
The value of an embryo should not be placed on par with the value of a child or adult
This argument often goes hand-in-hand with the utilitarian argument, and can be presented in several forms:
* Embryos, while of value, are not equivalent to human life while they are still incapable of existing outside the womb (i.e. they only have the potential for life).
* Approximately 18% of zygotes do not implant after conception. Thus far more embryos are lost due to chance than are proposed to be used for embryonic stem cell research or treatments.
* Blastocysts are a cluster of human cells that have not differentiated into distinct organ tissue; making cells of the inner cell mass no more "human" than a skin cell .
* Some parties contend that embryos are not humans, believing that the life of Homo sapiens only begins when the heartbeat develops, which is during the 5th week of pregnancy, or when the brain begins developing activity, which has been detected at 54 days after conception.
(3) The consequentialism argument
The ends (i.e. new treatments and cures) justify the means (i.e. the destruction of embryos)
This can be seen as a more extreme view of the utilitarianism argument.
(4) The efficiency argument
If an embryo is going to be destroyed anyway, isn't it more efficient to make practical use of it?
* In vitro fertilization (IVF) generates large numbers of unused embryos (e.g. 70,000 in Australia alone). Many of these thousands of IVF embryos are slated for destruction. Using them for scientific research utilizes a resource that would otherwise be wasted.
* While the destruction of human embryos is required to establish a stem cell line, no new embryos have to be destroyed to work with existing stem cell lines. It would be wasteful not to continue to make use of these cell lines as a resource.
* Abortions are legal in many countries and jurisdictions. A logical argument follows that if these embryos are being destroyed anyway, why not use them for stem cell research or treatments?
(5) Arguments for the superiority of embryonic stem cells
Embryonic stem cells can be considered far more useful therapeutically than adult stem cells
This is usually presented as a counter-argument to using adult stem cells as an alternative that doesn't involve embryonic destruction.
* Embryonic stem cells make up a significant proportion of a developing embryo, while adult stem cells exist as minor populations within a mature individual (e.g. in every 10,000 cells of the bone marrow, only 10 will be usable stem cells). Thus, embryonic stem cells are likely to be easier to isolate and grow ex vivo than adult stem cells.
* Embryonic stem cells divide more rapidly than adult stem cells, potentially making it easier to generate large numbers of cells for therapeutic means. In contrast, adult stem cell might not divide fast enough to offer immediate treatment.
* Embryonic stem cells have greater plasticity, allowing them to treat a wider range of diseases.
* Adult stem cells from the patient's own body might not be effective in treatment of genetic disorders. Allogeneic embryonic stem cell transplantation (i.e. from a healthy donor) may be more practical in these cases than gene therapy of a patient's own cell.
* DNA abnormalities found in adult stem cells that are caused by toxins and sunlight may make them poorly suited for treatment.
* Embryonic stem cells have been shown to be effective in treating heart damage in mice.
(6) Fertilization is not the beginning of life
* Clones can be produced without fertilization taking place, and the clones are alive.
* Before the "primitive streak" is formed when the embryo attaches to the uterus at approximately 14 days after fertilization, the fertilized egg can split in two to form identical twins. Also, rarely, two separately fertilized eggs can fuse together to form a tetragammetic chimera - a single human individual with half of his cells being male from the original male embryo, and half being female from the original female embryo.
* Therefore before the primitive streak is formed, an individual human life does not exist at fertilization, as it can go on to split into two separate individuals. Therefore, an individual human life begins when the primitive streak is formed - beyond which the cell group cannot split to make twins - and not before. Therefore the blastocysts destroyed for embryonic stem cells do not have human life, and it is ethical to use them.
Opposing Arguments
(1) Embryos are lives
An embryo is actually a human, therefore it should be valued as highly as a human life.
The reasoning can be summed up by the fact that, once an egg is fertilized, unless inhibited, it will develop into a fully-developed adult. This opinion is often related to religious doctrines which assert that conception marks the beginning of human life or the presence of a soul. Based upon this reasoning, the subsequent argument against embryonic stem cell research is that human life is inherently valuable and cannot be involuntarily destroyed to save another life.
As an extension of this, it is argued that the tendency by some supporters of embryonic stem cell researchers to dismiss the ethical significance of embryo destruction may act to devalue human life. Moreover, it has been argued that "the line at which an embryo becomes a human life remains as arbitrary as ever".
Viability is another standard under which embryos and fetuses have been regarded as human lives. In the United States, the 1973 Supreme Court case of Roe v. Wade concluded that viability determined the permissibility of abortions performed for reasons other than the protection of the woman's health, defining viability as the point at which a fetus is "potentially able to live outside the mother's womb, albeit with artificial aid." The point of viability was 24 to 28 weeks when the case was decided and has since moved to about 22 weeks due to advancement in medical technology. If further technological advances allow a sperm and egg to be combined and fully developed completely outside of the womb, an embryo will be viable as soon as it is conceived, and under the viability standard, life will begin at conception.
(2) Alternative therapeutic options should be better explored
Embryonic stem cells should be abandoned in favor of alternatives, such as those involving adult stem cells.
This argument is used by opponents of embryonic destruction as well as researchers specialising in adult stem cell research.
It is often claimed by pro-life supporters that the use of adult stem cells from sources such as umbilical cord blood has consistently produced more promising results than the use of embryonic stem cells. Furthermore, adult stem cell and cord blood stem cell research may be able to make greater advances if less money and resources were channeled into embryonic stem cell research.
Adult stem cells have already produced therapies, while embryonic stem cells have not. Moreover, there have been many advances in adult stem cell research, including a recent study where pluripotent adult stem cells were manufactured from differentiated fibroblast by the addition of specific transcription factors. Newly created stem cells were developed into an embryo and were integrated into newborn mouse tissues, analogous to the properties of embryonic stem cells.
This argument remains hotly debated on both sides. Those critical of embryonic stem cell research point to a current lack of practical treatments, while supporters argue that advances will come with more time and that breakthroughs cannot be predicted.
(3) Scientific flaws in embryonic stem cell research
The use of embryonic stem cell in therapies may be fundamentally flawed.
For instance, one study suggests that autologous embryonic stem cells generated for therapeutic cloning may still suffer from immune rejection. The researchers note that: "Our results raise the provocative possibility that even genetically matched cells derived by therapeutic cloning may still face barriers to effective transplantation for some disorders." In other words, therapeutic cloning may not always produce matched tissues. In contrast, there are reports of adult stem cells being successfully reintegrated into an autogenic animal.
Another concern with embryonic stem cell treatments is a tendency of stem cells from embryos to create tumors. However, the tumorigenic potential of embryonic stem cells remains poorly described.
(4) Overstatement of research potential
Scientists have long promised spectacular results from embryonic stem cell research, and this has not yet occurred.
Conspicuously, such criticism has even come from researchers themselves. For example, in November 2004, Princeton University president and geneticist Shirley Tilghman said, "Some of the public pronouncements in the field of stem-cell research come close to overpromising at best and delusional fantasizing at worst." Similarly, fertility expert and former president of the British Association for the Advancement of Science, Lord Winston has warned of a public backlash against stem cell research if it fails to deliver on some of the "hype" surrounding potential treatments.
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