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Latest revision as of 01:24, September 19, 2011
What Are Stem Cells?
The human body is made of billions and billions of cells, which have specific shapes, particular structures, and different functions. Cells of the same type make tissues, and tissues make organs. Cells, tissues, organs, and systems make the human body. No matter how simple or complex an organism is, the cell remains the structurally and functionally basic unit of life (there are even unicellular organisms, like bacteria.)
Some cells (but not all) have the ability to multiply by division. Most of the diseases known to medical science are due to the malfunction of cells, to premature cell death, or to cells' wrong multiplication rates.
Stem cells are a particular kind of cells, with two major characteristics:
- they are unspecialized cells that can divide over and over for very long periods of time;
- under certain conditions, they can be induced to become cells with special functions (like muscle cells, liver cells, neurons, etc.).
Stem cells are naturally occurring in the human body (and other living organisms) at all levels of development. As organisms develop, stem cells become specialized types of cells. They are harder to find and lose much of their ability to differentiate. Stem cells are the way the organism generates all the specialized cells needed for development and functioning.
There are two kinds of stem cells used in biomedical research:
- Embryonic Stem Cells - which occur only in early development;
- Adult Stem Cells - occurring in adult organisms.
In the fetus, stem cells in developing tissue give rise to the multiple specialized cell types that make up the human body. In some adult tissues, such as bone marrow, muscle, and brain, discrete populations of adult stem cells generate replacement cells. While both types of stem cells are very important for biomedical research, the use of embryonic stem cells raises most of the bioethical issues.
Stem cells originating in human embryos can be categorized as either embryonic stem cells or embryonic germ cells. While there are many similarities between the two, there are also some significant differences.
After fertilization, the zygote (fertilized egg) divides several times. Any of the cells resulted from these divisions can give rise to all the cells needed to make up an adult organism. Basically, any of these cells can “act as an embryo.” These cells are called totipotent stem cells.
After 3 to 5 days, prior to implantation into the uterine wall, the embryo achieves a stage called blastocyst. In the interior of the blastocyst, there is a cluster of about 30 cells called the inner cell mass. The cells that form the inner cell mass of the blastocyst are called pluripotent stem cells. They have lost the ability to differentiate to all cell types needed for a complete embryo development (up to 14 days post-fertilization).
As embryonic development proceeds, stem cells lose their pluripotency. In adults, the remaining stem cells only differentiate into cell types specific to the tissue in which they reside (some recent studies seem to prove the contrary.)
Embryonic germ cells share many of the characteristics of the embryonic stem cells but differ in significant ways. They are derived from the primordial germ cells, which occur in a specific part of the embryo/fetus called the gonadal ridge. The gonadal ridge normally develops into mature gametes (eggs and sperm). Germ cells do not proliferate as long as stem sells. Under certain conditions, germ cells do differentiate into specialized cells. Germ cells and stem cells also differ with respect to their growth characteristics in vitro and their behavior in vivo.
Adult stem cells give the body its ability to repair and replace the cells and tissues of some organs. Adult stem cells are rare, and their origin in mature tissue is not yet completely understood. It is supposed that they are somehow set aside during fetal development and restrained from differentiating. Adult stem cells are dispersed in tissues throughout the mature organism and behave very differently depending on the local environment. Some recent studies focus on the plasticity of the adult stem cells, which is the ability to differentiate in specialized cells of another tissue.
The embryos used in stem cell research come from three major sources:
- In Vitro Fertilization - some of the embryos used in human stem cells research were initially created for infertility purposes through in vitro fertilization procedures. When they were no longer needed for that purpose, they were donated for research with the informed consent of the donor.
- Somatic Cell Nuclear Transfer - embryos can be created by transferring the nucleus of a donor cell into an enucleated oocyte. The embryo will be genetically identical to the donor.
- Embryonic Germ Cells are obtained from aborted fetus tissue.
The stem cell extraction procedure ends the ability of the embryo to develop through implantation in the uterus. The removal of the stem cells brings the existence of the embryo to an end. Stem cell research promises not only to clarify some of the fundamental processes of life, but also some very interesting therapeutic possibilities. Nowadays scientific medicine is based on drug therapy. It is dominated by antibiotics, chemotherapy, antipsychotic agents and other pharmaceuticals.
The scientific medicine of the future will be probably based on cell therapies, focused on repair and regeneration of tissues by cell transplants. In a rough way: instead of administering lots of chemical substances in an attempt to prevent cell malfunction or premature cell death, why not just replace the cells in question? Many scientists take the view that the benefits which might flow to humanity from this form of research are so great that it is important that it be allowed to proceed.
Moral status of the embryo
The debate around embryonic stem cells research is sensitive and controversial. Is it ethically acceptable to destroy the blastocyst? Many Christians believe that it is not, and in order to respect every one of God’s children, they sustain that each created zygote is completely deserving of protection and ought not to be destroyed. To destroy a developing human at any stage is then comparable to murder. Most of the ethical debate around embryonic stem cell research is centered on the moral status of embryos and fetuses, as well as the significance of the source of embryonic or fetal material. Use of adult stem cells seems morally unproblematic from this point of view.
Opponents of embryonic stem cell research have argued that it involves the deliberate destruction of an embryo and that this is morally wrong, because embryos have the same moral status as human persons. When Robert Edwards (one of the pioneers of in vitro fertilization) saw Louis Brown, the world's first baby to be conceived by in vitro fertilization, he stated: "The last time I saw her she was just eight cells in a test-tube. She was beautiful then, and she is still beautiful now!" This shows the continuity of the person he knew “then” and the person he knows “now.” Therefore, the human life begins at conception. Concerning the use of fetal tissue, opponents argue that use of this tissue is morally problematic because it comes from abortive procedures.
Orthodox Christianity’s viewpoint is that the human person is created in the image and likeness of God and the purpose of life is theosis, which is God-likeness in union and communion with others. St Gregory of Nyssa stated:
- "'Let us make man in our image, after our likeness.' We possess the one by creation; we acquire the other by free will. In the first structure it is given us to be born in the image of God; by free will there is formed in us the being in the likeness of God. … But it is proper that one part is given you, while the other has been left incomplete: this is so that you might complete it yourself and might be worthy of the reward, which comes from God."
Both the embryo as well as the adult are potential human persons in different phases of development, growing in the image of God and trying to reach the likeness of God. As a result, the Orthodox understanding is that unborn human life should have the same opportunity to grow in the likeness of God as those already born.
The Orthodox Church believes that the person is body and soul and experimentation on the body, including embryonic stem cell research, will presume fleshly authority over the soul. The body and soul were formed at the same time—not one before and the other afterward (Louth, p.53). Stem cell research cannot be summarized as a scientific technique on a biological organism. The Orthodox Church considers that human beings should be treated with dignity and respect. Father Demopulos stated: “We must treat the developing embryo with dignity and respect, because we do not know when it becomes a person.” Since the Orthodox Church believes that human life begins at conception, the dignity and respect owed to the person should be extended to the human embryo.
The Orthodox Church promotes therapeutic advances in medicine, but not at the expense of human life. For the Orthodox life begins at conception and continues behind death. Without giving consideration to the various possible outcomes that this embryonic stem cell research will have on certain members of society, such as the Orthodox Church, science and society will continue to take diverging paths. There will be no answers found which will solve the problems that are arising because of embryonic stem cell research. Serious discussion concerning the ethical and moral dilemmas surrounding this research can only take place when consideration for the premise that humanity is created in the image and likeness of God is the paramount concern.
- Breck, John. The Sacred Gift of Life. New York: St Vladimir's Seminary Press, 1998.
- Louth, Andrew. Ancient Christian Commentary on Scripture. Downers Grove, Illinois: Inter Varsity Press, 2001.
- Ruse, Michael & Christopher A. Pynes. The Stem Cell Controversy. New York: Prometheus Books, 2003.
- Snow, Nancy. Stem Cell Research. Notre Dame, Indiana: University of Notre Dame Press, 2003.