Embryonic Vs. Adult Stem Cells in Research

The successful use of adult stem cells for medical research can eliminate the destruction of embryos and lead to medical advances and potential cures for a number of diseases. An adult stem cell is a cell found in many organs with the capability to regenerate itself. Researchers have made many discoveries in recent years that will change research in this area. They have found that using adult stem cells are more effective than previously thought. Therefore, embryonic stem cells will no longer be needed for research because there is now a viable alternative. In light of this evidence, the incessant controversy between pro-life groups and researchers may conceivably be put to rest.

There is no more appropriate moment to begin calling a human "human" than the moment of fertilization (Baumgartner). This belief has halted the progress of embryonic stem cell research. Beginning in the late 1970's with in vitro fertilization "IVF" Presidents Reagan and George Bush joined the resistance a decade later to the use of embryonic stem cells. It wasn't until 1994, after the election of President Clinton, that federal funding was granted for research using both embryonic and fetal tissue. However, the National Institute of Health, NIH, was unable to convince Congress to allow funding for embryonic research. To combat the efforts of the NIH, Congress passed the Dickey-Wicker Amendment. This prohibited the creation of human embryos for research purposes. NIH responded to the actions of Congress with the argument that once a stem cell has been separated from the embryo, it is no longer considered an embryo; it is now considered a stem cell; therefore, stem cell research cannot be restricted by the Dickey-Wicker Amendment. In an attempt to clarify the types of tissue (embryonic or stem cell) that can be used for research, NIH released these Guidelines to help distinguish the type of research would be allowed federal funding. These guidelines distinguish between using an embryo already in existence and creating an embryo solely for research purposes. The first qualifies for funding; the second does not.

Former President Bush placed a ban against researching fresh stem cell lines taken from IVF surplus embryos that would have been otherwise destroyed (Stolberg). He presented a compromise in 2001 in hopes of satisfying both sides of this longstanding debate. His proposal was to allow continued research on the 21 existing stem cell lines, and to include surplus embryos created in IVF clinics that had already been destroyed (Torrisi 5). On March 14, 2009, President Obama lifted that ban, allowing researchers funding to access any stem cell line in existence; no longer restricting them to the 21 lines created before August 2001. Obama continues to stand in opposition of researchers creating new lines, as per the Dickey-Wicker amendment (Fox news).

The term in vitro fertilization derives from the Latin phrase in vitro meaning in glass. IVF clinics across the country destroy thousands of unused embryos every year. Generally, about 6-14 fertilized embryos are created for each patient, while only 2-3 are implanted. According to the Center for Disease Control and Prevention, in 2007, there were 142,415 recorded Assisted Reproductive Technology (ART cycles), only 41,343 which resulted in live births. What happened to the other 101,072 embryos? Most are frozen for later use, but surprisingly enough, the rest are often washed down the sink! Many clinics simply leave the fertilized embryos exposed to the air, allowing them to die on their own. This natural death usually takes about 3-4 days.

A pre-implanted embryo is called a blastocyst (Stem Cell Basic). Consisting of approximately 150 cells, it's arranged into a three layered sphere shape. The outer layer is called the tropoblast; if allowed to mature, it will later develop into embryonic tissue & the placenta. Inside the tropoblast, is a fluid cavity known as the blastocoel. After about 2 weeks, at the very center of the blastocyst a cluster of cells called the inner cell mass, or ICM, begins to develop. Here is where the key to the controversy lies; the ICM is where the embryonic stem cells are located. If implanted, the ICM will go through a process called gastrulation. This means that the cells will proliferate, or continuously divide, each cell creating two identical daughter cells, migrate & transform into an embryo containing three primary germ layers.

These three germ layers are the outer layer, the ectoderm; the middle layer or the mesoderm; and the endoderm in the center. The outer layer gives rise to the nervous system, sensory organs, skin & related structures; during weeks 3 and 4. The mesoderm & endoderm produce the bones, muscles, connective tissues; lungs, respiratory and digestive systems respectively. When the inner cell mass is destroyed by extracting the embryonic stem cells, these processes cease, preventing the blastocyst to develop into a fetus. According to Dr. Robert Needleman, by the end of its 8^th week of development, an embryo has all major organ systems in place, although not in their final form (Needleman). At this point the embryo is now considered a fetus, measuring about 2 inches long and weighing about 1/3 of an ounce.

Once extracted from a developing embryo, stem cells go through a process called differentiation. What this means is that the unspecialized cell acquires the features of a particular cell type such as heart, liver or muscle tissue cells. When a stem cell culture is manipulated to specify which type of cell it will become, it is called directed differentiation. During differentiation, the physical characteristics of the stem cells can drastically change while the DNA remains intact. For example, the differentiation process makes it possible for bone marrow or neural stem cells to produce blood and muscle tissue and in aiding in repairing damage from a stroke.

Using embryos can benefit research for the potential cures for paralysis, Parkinson's disease, and repairing damaged organs (Commonweal Pr2). In contrast, studies have shown that adult stem cells taken from an umbilical cord can regenerate into immune cells to treat blood disorders, and the blood type does not have to match. Adult stem cells can also be taken from amniotic fluid. The Cord Blood Registry recommends saving a segment of the umbilical cord as well as cord blood. The stem cells from each sample are slightly different, and can be used as treatment for a number of disorders such as spinal injury or leukemia. These genetically unique stem cells are also showing potential to treat incurable conditions like brain injury & juvenile diabetes. In the case of Chloe Levine, a 50% recovery from Cerebral Palsy was made possible by using stem cells recovered from the umbilical cord. "Stem cells can certainly rejuvenate tissue" (Alvarez).

Samples of adult stem cells from bone marrow have to been shown to improve blood circulation in patients with gangrene to eliminate amputation in most cases. Although they do not have the same capabilities of an early stage embryo, researchers have also found that adult stem cells taken from the human nose give rise to brain, liver, heart, kidney and muscle cells (Torrisi, 5). Since the recipient will be receiving the product of their own stem cells, they will not experience immune rejection. Acute rejection is a quick, aggresive attack against cells or tissue not recognized by the immune system. Another milder form is chronic rejection which can be sustained over longer periods of time. Although both forms of rejection can be regulated with immunosuppressive drugs, there can still many complications such as infection or death of the patient (Kadereit).

Though there are many positive things to be said about adult stem cells, there are a few negatives as well. The surgery used to collect the stem cells is significantly riskier, and expire after only a few weeks. Because they are most likely taken from a patient with an already present health condition, there is a chance that, the regenerated cells will carry the same cellular defect as the original cell. This would cause the problem to worsen exponentially. For example, cells taken from a cancer patient would regenerate into more cancer cells causing it to spread. Also, as a patient gets older, their number of salvageable cells decreases over time. The probability of DNA abnormalities due to sun exposure and toxins is greatly increased.

It has also been found that epidermal neural crest stem cells found in hair follicles have similar qualities to that of an embryonic stem cell. Cells from mouse testes also behave like an embryonic cell. In addition to the breakthroughs of adult stem cells, there should be no need to destroy an embryo for research purposes. Another disadvantage to using embryonic cells is that their uncontrolled development can lead to tumor growth.

Medical breakthroughs have proven that adult stem cells are a viable alternative to replace embryonic research. It answers the ethical questions posed by pro-life groups by eliminating the destruction of human embryos. Adult stem cells have already shown great promise in the treatment of many diseases. Federal funding can now be focused on the exploration of advancements using adult stem cell research.

Works Cited

Alvarez, Manny Dr. (2008, July 28). Chloe's Remarkable Story. Fox News Health Editor. Cord Blood Registry. < http://www.cordblood.com/cord-blood-banking-news.asp?fbid=0Xve39UCGoW>.

Baumgartner, Fritz MD (2005, April 12). Life Begins at the Beginning