Stem cells: characteristics, types, and applications

Stem Cells

Without a doubt, one of the most controversial topics of popular discourse is stem cell research. Indeed, one would be hard pressed to peruse the newspaper or magazine stand without encountering some reference to the global stem cell debate -- but what, exactly, are stem cells, and why are they so controversial?

Stem cells intended for use in human applications are harvested from humans, umbilical cords and embryos. The reason these cells are so valuable is because of their capability to produce or "become" other cell types -- for example, brain cells, heart cells, skin, etc. In short, these are "master cells," holding the ability to divide in cultures, and to be manipulated allowing it to transform into any type of cell. Of course, this is extremely important due to the fact that scientists can use this capability to either create organs (thereby helping to meet the tremendous shortage of donor organs), or to create tissues to treat various diseases and disorders.

The reason the discourse surrounding the topic of stem cells these cells is so controversial is due to the fact that the most promising source of stem cells is human fetal tissue. Of course, in order to harvest the cells from such a source, the embryo, itself, must be destroyed. Because of this, many who hold anti-abortion views find this practice to be highly immoral and repugnant. However, the reason embryo stem cells are used at all is because of their ability to transform themselves into virtually any type of cell found in the body. The specific way this works is best described according to the process of normal embryonic development.

Of course, most people know the origin of human life begins with the sperm fertilizing the egg. After this, a single cell is created that holds all of the genetic information needed to form the entire human body. This cell divides and redivides over several days until these cells (known as totipotent, or as having "total potential") begin to specialize into the formation known as the "blastocyst," which has a hollow sphere of cells, and a cluster of inner cells (the inner cell mass). While the outer cells of this blastocyst proceed to form the placenta, the cells within the inner cell mass go on to form virtually all of the tissues and organs of the human body. It is these cells that are harvested to research stem cells.

It is also true that stem cells can be found in humans, children as well as adults. These stem cells can be found in the blood (the blood stem cell), where they are found in the bone marrow (hence, the "bone marrow transplant"). In this capacity, the function of blood stem cells is to continuously replenish the body's supply of red blood cells, platelets, and white blood cells. Without the blood stem cells in the marrow, the human body cannot survive.

Another main source of stem cells is found in the umbilical cord. So called "cord blood" is an incredibly rich source of the types of stem cells that make up the blood as well as the immune system. These cells can differentiate into blood cells (red, white, platelets), so successfully that some patients with Leukemia, Sickle Cell Anemia, and non-Hodgkin's lymphoma, have been completely cured. In addition, many scientists believe that the stem cells harvested from the umbilical cord could have a tremendous impact on the research and treatment of diseases and disorders such as Alzheimer's, cancer, and many brain disorders (particularly pediatric).

The problem with umbilical cord stem cells, however, is the small amount that can be harvested from any particular cord. Because this is the case, the use of these cells for transplants is normally reserved for pediatric patients or very small adults. However, there are emerging new methods by which these stem cells can be expanded. For example, the American Society of Hematology has discovered a way to expand cord blood cells, and has proven that these cells are every bit as successful as non-expanded cord blood cells. Not only is this development good for those in desperate need of transplantation, but because cord blood is harvested without damaging the fetus, the controversy surrounding its use is minimal. (Laino, 1)

It is true that adult stem cells can be used for research. These cells are found throughout the human body, and they, too, have the capacity to develop into different types of cells -- however, they pale in comparison to the ability of embryonic cells to differentiate into specialized cells. As many researches believe, adult stem cells are more "rigid" in their ability to grow and replicate. However, there is promising research that these cells can be successfully harvested and used.

As previously stated, the controversy surrounding stem cell research is primarily due to the use of embryos. Not only could using cord blood and adult stem cells end the moral outcry, but in expanding the amount of cells, many with immune and blood disorders could be helped. However, there is another side to the coin -- for just as there are millions against the use of embryonic stem cells for research and development, so, too are there millions in favor of their use due to their tremendous potential.

It is true that embryonic stem cells are superior to cord blood and adult stem cells. After all, although cord blood has the capability to generate healthy blood and immune cells, it does not hold the boundless possibility of embryonic cells to produce virtually every organ and tissue within the body, including blood. Indeed, it is as if the embryonic stem cell holds the magic key to the whole of the body.

For this reason, there are many who strongly advocate using aborted fetuses (which, they argue, are usually thrown in the garbage, anyway), or unused embryos in fertility clinics. Many even go so far as to assert that embryos could be created expressly for medical purpose.

However, those who do believe in the importance of using embryonic stem cells (and creating embryos for this purpose), face tough opposition. In fact, on August 9, 2001, President George Bush announced that experiments should be conducted from existing cell stocks, and that the government would not financially support laboratories that use embryos specifically created for research. Interestingly, this pleases neither side of the debate. Of course it is obvious that those in favor of the creation of embryos for stem cell harvest would oppose the President and his view. However, the anti-embryo harvest camp would like the practice to be halted on all embryos -- even the ones that exist now.

As controversial as this all is, ongoing research with laboratory animals demonstrates the immense good that therapy using stem cells can accomplish. For example, experiments involving mice have shown that it is possible to insert specific genes into stem cells that can work to "activate" the immune system. The ramifications of this ability are staggering -- for, if this is the case, in theory, such cells can be utilized to fight cancer, help facilitate transplant acceptance, as well as in curing immune disorders, including AIDS.

In addition, further uses of stem cells indicated by animal experimentation include the treatment of Parkinson's disease, damaged heart tissue, as well as spinal cord injuries -- even to the degree of paralysis.

Morally, however, the use of stem cells is uncharted territory. After all, many people believe that using all human embryos -- aborted fetuses or left over embryos, constitutes the destruction of human life, and is therefore, wrong. These people not only advocate the use of adult and cord blood stem cells, but actively lobby against the use of embryonic sources.

It is important to note that this stem cell controversy is not limited to the United States, alone, but is of high importance throughout the world. Indeed, some countries show no hesitation in stem cell research. For example, in England, scientists not only may conduct research on existing donated embryos, but they are allowed to create new ones for research by cloning them. However, many other countries, including Austria, France, Ireland, and Germany prohibit all embryo research, while others still allow research (like the United States), but with strict limitations (Finland, Spain, Japan, and Denmark).

Arguably, one of the most interesting aspects of the stem cell debate is the amount of political and governmental influence applied to the issue. Indeed, it is fascinating that what is, essentially, a medical and scientific practice, and is as such, governed by medical and scientific standards of ethics, is considered fair game for politicians and governments, worldwide. Although many consider that political and governmental intervention in the stem cell debate is appropriate, many believe that politicians and governments are "meddling" in areas where they neither have expertise, nor jurisdiction.

An excellent example of this attitude is included in Supreme Court Justice Louis Brandeis' opinion that each state should regulate stem cell research, and not the federal government. He writes," Where no national consensus exists and the debate is polarized, the states should be allowed to act as 'laboratories of democracy'."(Rosenberg) By this, Brandeis means that individual states should come up with their own laws regulating stem cell research and the therapies and treatments it can provide. In other words, the states would act as individual "laboratories," that can, through their experiences, develop precedents and protocols that can later be implemented nationally.

Of course, ethical considerations are a part of any decision to be reached on the stem cell issue -- especially as it relates to the use and creation of embryos. For example, Ben Mitchell, a senior fellow at the Center for Bioethics and Human Dignity writes, "It's a question of ethics and morality." (Hall) This means that many hold that the standard of ethics (especially as espoused by ethical philosophers such as Kant), prohibits the "killing" of embryos as a means to a greater good. Further, some more religiously minded individuals view the research in itself as slightly immoral -- almost as if those who peruse stem cell therapies are attempting to cure all humankind from disease, and, eventually, death. What, then, of religion?

In addition to the pro-life stance on stem cell research, other moral and economic factors impact the advancement of the practice as well. Who, for instance, will be able to afford stem cell therapies? Will the procedure become an option only for those who "can afford it?" -- in effect, leaving most of the population of the earth in the cold? How will the practice affect the insurance industry, and what of those who have no insurance? Will those who are paralyzed and poor, for example, watch the likes of Christopher Reeves once again playing the role of the able-bodied Superman, while they remain wheelchair bound?