What are embryonic stem cells, and why are scientists so interested in them?
Embryonic stem cells, as their name suggests, are derived from embryos. As scientists look for cures for many diseases that plague humans, they are specifically interested in human embryonic stem cells because stem cells have the ability to divide (self replicate) for indefinite periods….Under the right conditions, or given the right signals, stem cells can give rise (differentiate) to cell types that make up the organism. Scientists envision drawing from “lines” of stem cells – colonies of similar cells that can replicate for long periods – to create new specialized cells for transplant into patients, to repair or replace tissues that disease and disability have damaged.
The embryos from which human embryonic stem cells are taken have been created in a laboratory process known as in vitro fertilization. These embryos are typically four or five days old and are a hollow microscopic ball of cells called the blastocyst. The blastocyst includes three structures: the trophoblast, which is the layer of cells that surrounds the blastocyst; the blastocoel, which is the hollow cavity inside the blastocyst; and the inner cell mass, which is a group of approximately 30 cells at one end of the blastocoel. For further information about the process of in vitro fertilization and how these cells are differentiated into skin cells, nerve cells, or heart muscle cells, click here. However, one must remember, that when scientists remove stem cells from a human embryo, the embryos dies in the process. This is the ethical and moral problem we face when we decide to use human embryos for scientific research.
In addition to taking stem cells from embryos created through in vitro fertilization, scientists also want to clone embryos for scientific research. Cloning human embryos requires that scientists take eggs or female gametes from women who have volunteered to take high does of hormones in order to mature their eggs. As many as ten eggs are then removed from the woman’s ovaries with the insertion of a long needle. There is risk of scar tissue forming in the woman’s ovaries from this removal procedure, which can result in infertility for the woman making the donation. Then an adult skin cell is removed from another donor. The nucleus of the donated egg is removed and the nucleus of the adult skin cell is also removed and transferred into the enucleated egg cell in a procedure known as somatic cell nuclear transfer. This is how Dolly the sheep was cloned. It is a very technical procedure that often fails to produce the desired clone. However, if and when science successfully clones a human embryo, this human being will have the entire DNA of the person who donated the skin cell, becoming his or her identical twin. This human embryo cannot grow into anything other than a human baby if it is implanted into a woman’s uterus. Removing its stem cells would kill the cloned human being in the process. Are we willing to cross that ethical line where we actually allow scientists to create human life for scientific research that will cause the death of the human life?
Where will scientists get all the stem cells necessary for embryonic stem cell research?
It is estimated that 133.9 million Americans suffer from diseases some claim may be helped by cloning human embryos in order to remove their stem cells for scientific research. If just 10 percent were eligible for therapies derived from human cloning, the potential patient pool would be 13.4 million people. To provide genetically matched material to treat such numbers, one would need at least 670 million eggs to clone. Where would the eggs come from? Well, if each female donor provided 10 eggs, 67 million women donors would be needed. Each would be subjected to high levels of hormonal stimulation, followed by laparoscopic surgery to remove the matured eggs. The removal of the eggs can sometimes cause scarring of the ovaries, which can result in infertility. Senator Mary Landrieu (D-LA) put it rather succinctly: women would simply become egg factories.
The issue of the large numbers of eggs needed to create human clones was addressed in the recent scandal surrounding the claims of human cloning by the South Korean scientist Dr. Hwang Woo Suk. Hwang claimed that he used 242 eggs to clone the first human embryo in 2004 and 273 to clone the 11 alleged embryos in 2005. However, MBC (South Korean news agency) reported that he actually used over 1,600 eggs from 86 women for both experiments, paying many of the women (which is against international scientific protocol). The television station also claimed that 20% of the women experienced side effects from the egg extraction.
For further information on stem cell research, check the following web sites:
The Center for Bioethics and Human Dignity http://www.cbhd.org