Issues in Stem Cell Research
Posted by Justine Johnson, 7/29/02 at 7:28:12 AM.

1.- A rising political debate in America is the use of embryonic stem (ES) cells in research. It is possible that this research could lead to cures for type 1 diabetes, Parkinson‚s disease and Alzheimer‚s. Despite these exciting possibilities, there are many who oppose the research because the stem cells are only harvested through the destruction of human fetuses or embryos. Some of those opposed to ES cell research suggest that adult stem cells could be used with just as much, if not greater, usefulness than ES cells. Adult stem cell research does not bring up any of the ethical debates and recently has proven to be a more viable option than previously thought. However, many scientists feel that there is still too much to learn from ES cells to move exclusively to adult stem cells. There are currently 64 ES cell lines, which were made eligible for federal funding. This debate will likely go on for some time and as new discoveries are made, new questions will arise.

2.- Stem cells are cells, which are capable of self-renewal and differentiation (Weissman, 2002). This means they give rise to more stem cells and generate tissue cells. Embryos have pluripotent stem cells, which are capable of producing all types of cells, in the human body. These cells will eventually differentiate into all the needed tissue types for the fetus. These cells can be isolated and grown into embryonic stem cell lines. In adults, there are stem cells within organs which repair and regenerate tissue. These stem cells only produce one type of cell. It has recently been found that these stem cells can undergo transdifferentiation, meaning they can be moved to another tissue and produce cells for a different type of tissue.

3.- When working with these two types of cells, there are many differences that must be considered. Embryonic stem cells multiply easily in vitro and are more easily coaxed into producing specific cell types. Unfortunately, they can also more easily generate cells out of control. Normally stem cells are kept in check by T lymphocytes, which destroy stem cells when they are no longer needed. When embryonic stem cells are transplanted, they are not under the protection of these T cells and are at risk for developing into tumors (Labat, 2001). Therefore, while ES cells are easier to grow in the lab they are riskier to transplant. Adult stem cells, which come from bone marrow, brain tissue, fat, skin and gut, are less proliferative, but also pose little risk of tumors. They have more difficulty growing in vitro; however, as scientists have further studied stem cells, they have been able to grow them without difficulty. Currently, only adult stem cells are actually being used in clinical trials. The embryonic stem cells are being used to gather information about how stem cells grow and differentiate.

4.- By transplanting stem cells into people with genetic diseases, they could begin growing new tissue or the cells could theoretically be induced to differentiate into specific types of tissue, which could then be used for transplants. Stem cells are thought to hold the key to treating many diseases, which have for years seemed incurable. Normal pancreatic islet cells could be given to diabetics whose own pancreases do not produce insulin. Neural cells could be transplanted to help Alzheimer‚s patients, or brain tissue for those suffering from Parkinson‚s disease.

5.- Until recently, it was thought that only ES cells could be used for this purpose. New research, which has discovered that adult stem cells can reprogram themselves to take on a new function when they are in a new environment, changes this notion. The first report of this was stem cells from the brain being transplanted into the bone marrow of mice and the subsequent production of blood cells (Science, 1999). This process takes longer than using ES cells which may be due to the cells having to return to their unspecialized state and then learn a new function. This finding in mice may or may not apply to humans.

6.- Stem cells are also useful for cloning which is the transplantation of a nucleus from the cell of one organism to another. Thus the second organism ends up with identical genetic material to the first. Cloning is another area of research, which we previously thought to be exclusively accessible through ES cells, but we are now finding out differently. There is evidence that adult stem cells could be used for cloning by putting the nucleus of the stem cell into an ovum donor cell resulting in embryonic stem cells which can be manipulated to become all the types of tissue an embryonic cell could. By using a patient‚s own stem cells the new tissue would be a genetic match. The cells can then be cultured to possibly produce tissues to treat diabetes, or spinal cord injury (Science, 2002). This process, however, is 10 times less efficient than simply using ES cells because the adult stem cells cannot be easily isolated. The House of Representatives has voted to ban this cloning procedure, called therapeutic cloning, along with human reproductive cloning (Weissman, 2002).

7.- Stem cell research is a controversial subject in America today largely because of the differing views on when a human life begins. As in the abortion debate, many believe that human life should be protected from conception on, while others believe it should only be protected after the embryo becomes a fetus or until after birth. Since beginning a cell line requires destroying an embryo, this has been considered unethical by many pro-life advocates. Once a cell line is begun, it can replicate indefinitely and provide many cells for use in research. Recently, the debate has centered on whether the federal government should fund research on embryonic stem cells. The decision made by President Bush last year allowed research to be funded only for 64 cell lines which were already in use. This was a fairly even compromise because it allowed research to be federally funded without promoting the destruction of any more embryos.

8.- This solution, however, is only temporary. Scientists know the available lines will only give them so many cells and some may not be viable. The available cells do not necessarily provide a diverse gene pool. In order to study cures for certain diseases from these lines, it would be necessary to get many embryos with the same genetic defects. This will probably not be possible with the limited number of cell lines available, but would be conceivable through the process of therapeutic cloning (Weissman, 2002).

9.- The politics of this debate seem to come down to when does a human become a human being or a „person‰. There is a basic agreement among both pro-life and pro-choice advocates that an embryo is a living cell with a complete set of human DNA with the potential of becoming a human being. Among the pro-choice advocates however the human is not considered a human being until they can survive independent of a „host‰ (mother), and therefore believe personhood starts at birth. Some believe it starts when a fetus is able to live outside the womb at about 24 weeks. The fetus is then considered viable. Many pro-life advocates believe that the embryo is immediately to be given the rights of a human being at the time of conception when the DNA of two germ cells form a new and unique sequence of DNA, which if undisturbed will become a person. There are also those who believe personhood starts at various times during pregnancy (Robinson, 2002). As it is related to the issue of embryonic stem cells, we are primarily concerned with those who believe full rights should be given at the time of conception because the stem cells usually come from very young embryos (four days old). At four days the embryo is a 16-cell organism not yet implanted in the mother‚s uterus. When embryonic stem cells are harvested from an embryo, it is destroyed and prevented from developing into a child. Whether or not this is too large a price to pay for a possible cure to chronic and terminal diseases depends largely on one‚s political and religious views. This is likely a conflict that will continue to be battled for many years.

10.- This is a debate which science can help us understand but it will only take us so far. Questions such as does the embryo have a soul and our beliefs about God and the sanctity of human life all come into play and confound any simple explanation of when a life becomes a human being. The desire to heal the infirm and the desire to uphold certain principles pull at each other and stir up conflicting conclusions. Careful thought must be put into each person‚s decision as to whether embryonic stem cell research is justifiable.