The Controversy over Stem Cells and Parkinson's Disease

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Biology 202
2003 First Web Paper
On Serendip

The Controversy over Stem Cells and Parkinson's Disease

Melissa Osorio

Without any thought, without even noticing it happens, when one has an itch, they scratch it. The arm moves up to the face, the fingers reach down and move across the skin. This series of actions, which many of us do everyday is something individuals with Parkinson's disease struggle with every moment of their lives. Simple movements are replaced by frozen limbs that they or their nervous system can not move. Described by many as a type of momentary paralysis, the disease causes gradual degeneration in patients until they are no longer able to perform the most basic bodily functions, such as swallowing or blinking.

Parkinson's disease is a neurological disorder that is named after "the English physician who first described it fully in 1817" (4). The disease causes disturbances in the motor functions resulting in patients having trouble moving. Other characteristics that are not always present in every patient are tremors and stiffening of limbs. All of these characteristics, of the disease are caused by "degeneration of a group of nerve cells deep within the center of the brain in an area called the substantia nigra" (5). Dopamine is the neurotransmitter for these cells to signal other nerve cells. However as the cluster of nerve cells fail to operate, the dopamine can not reach the areas of the brain that affects one's motor functions (5). On average Parkinson's patients have "less than half as much dopamine in their systems as healthy people do" (8). The problem and controversy that arises from this disease is in the cure. Researchers, for years, have been attempting to unravel the mystery of what causes Parkinson's disease and how it can be treated and or cured. While many medications have been developed the most controversial treatment is the use of stem cells, which has raised debate not only in the scientific realm, but in political and religious circles as well.

In the past twenty years, many drugs have been developed to treat the disease. Although the cause of Parkinson's disease is still unknown, scientists have been developing methods of treatment and therapy. The idea is to replace dopamine in the brain, which is accomplished, to some extent, with the administration of L-Dopa. In conjunction with other drugs, L- Dopa "inhibits the enzymes that break down L-dopa in the liver, thus making a greater part of it available to the brain" (5). This treatment is very successful, but it only hinders the disease for a time and it is by no means a cure. That leaves us with stem-cells and the role they play in treatment of Parkinson's disease.

There are many different types of stem-cells which can be implanted in patients to regenerate or replace the damaged or abnormal cells caused by not only diseases like Parkinson's but also Alzheimer's and spinal cord injuries (2). A specific example in relation to Parkinson's is the harvesting of embryonic stem cells. These human embryonic stem cells can be transplanted into the brain to replace and create dopamine neurons. The controversy is in how one can obtain these stem cells. During fertilization, in humans, the embryo is hollow and contains cells that eventually develop into a fetus (1). Researchers have discovered, as recently as 1998, that the cells in the embryo contain all the tissues types, therefore becoming any cell in the body. Thus the stem cells can be transplanted into patients with diseases dealing with cell abnormality (1).

Many religious groups argue that stem cell research should be discontinued by the federal government, because the killing of the embryos is just as heinous as abortion. Stem-cells are extracted from a few different sources, either from surplus embryos created for infertile couples, umbilical cords, and from elective abortions. For pro-lifers the embryos used to extract the stem cells are equal to human lives being destroyed (6). The other side of the argument is that embryonic cells are not living- they do not have a soul. Much of this debate is rooted and overlaps with the debate over whether abortion, of any form should be lawful. Scientists have also argued that many of the embryos used would have been destroyed at some point anyway, so why not use them for furthering the good of the human race. Consequently, political debate over whether federal funds should be used to support the further research of stem cell transplantation continues to this day. An example of the relevance and immediacy of this issue is the speech President Bush gave in the summer of 2001, in which he approved funding from the government on research of 64 human embryonic cells (7) (1).

These arguments are all valid and much debated however there are other reasons, less explored that account for the reason some feel stem cell research should not be pursued. Much of the time when stem cells are inserted into the brain "they grow into every cell type and form tumor-like masses called teratomas, eventually killing there hosts" (1). The problem is not that stem cells fail to become dopamine neurons; the failure is in controlling the growth of these cells. While there has been research completed with successful control of the stem cell growth, the percentage is small and inconsistent (1). Therefore, at this stage it is still too early to attempt these transplantations of stem cells on human patients. However these studies represent a ray of light and hope for Parkinson's patients who could benefit greatly by the transplantation of stem cells into their brain and the resulting production of dopamine neurons.

There are no easy answers when it comes to a cure or a treatment for Parkinson's patients. The most promising cure is in stem-cells. Not only does the research and implantation of these cells into a treatment raise debate with religious groups, but it extends into the political realm as well. These debates all hold merit, but the bigger more important issue that is rarely talked about is that of whether stem cells can actually be effective in humans. Can researchers learn to harness the growth of these cells and if they can what does that mean for the future of these type of stem cell therapies? What moral and ethical implications does this process pose? While these questions are unanswerable at this point the only way to prove one way or another, whether these cells will be effective is to be able to research them, so that maybe one day Parkinson's disease can be an aliment of the past.

References

WWW Sources

1)articles from the National Academy of Sciences,particularly an article about embryonic cells by Curt Freed

2)title, encyclopedia of biological terms and articles, search under key word stem cells.

3)title,a Parkinson's disease society page that gives basic information.

4)title,

5)title, encyclopedia of biological terms and articles, search under key words Parkinson's Disease.

6) title,site that deals with religious views on stem cell research.

7)title,

8)title,science news archive with articles relating to current science issues.

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