In this short paper I will attempt to distinguish between the terms “embryonic stem cell” and simply “stem cell” in order to aptly define all the terms I will use in my research paper. The addition of a single word has some serious implications. Embryonic stem cells, as one might guess are derived from a human embryo. However there is some confusion surrounding the precise definition of “embryo” compared to a fertilized cell, also known as a zygote. A zygote is the single cell that forms the instant of fertilization commonly called conception. An embryo is formed from the process of cell division as the fertilized egg (zygote) matures. In humans the zygote forms an embryo thirteen days after fertilization (Campbell 1034). In short an embryo is a multi-celled zygote. As we can see a fertilized egg and an embryo are not the same but they are very similar but, in the thirteen days of maturation the zygote undergoes subtle changes that make the embryo so valuable in the field of regenerative medicine.
Now that the scientific definition of an embryo has been established, it is possible to examine the scientific differences between stem cells from an embryo and those harvested from other sources. There are many methods by which stem cells can be obtained including those derived from adult cells, prenatal cells (umbilical cord), and bioengineered cells (produced in a lab). The derivation of adult cells is accomplished through the removal of bone marrow or adipose (fat) tissues. Prenatal cells are taken from the umbilical cord blood cells or amniotic fluid. Bioengineered stem cells are created in a lab from somatic cells (almost all body cells) which undergo complex and arduous scientific techniques in the form of either cloning, or induced pluripotency. Cellular potency is the term used to describe the ability of a stem cell to differentiate into its surrounding cells. All of these methods require some form of alteration or procedure to yield usable stem cells, in the case of using adult cells it is often a very long and painful outpatient procedure. Embryonic stem cells differ from these types of cells in three extremely important ways. In contrast to these methods, embryonic stem cells are taken from the inner core of the embryo itself which requires little to no processing to obtain. Secondly, the stem cells taken from a human embryo are more pluripotent than other stem cells. This means that they are able to differentiate into different tissues faster and with greater accuracy. Lastly, and most importantly, embryonic stem cells have the capability to differentiate into all tissues in the human body, no other type of stem cell has this unique ability. Adult stem cells are only able to differentiate into a certain number of tissues depending on their origin and lab induced pluripotent cells still lack the pluripotency of embryonic stem cells. (Zacharias, David G. et al. pg 637-638)
To put this into more understandable terms it is easiest to look at real world examples. Adult stem cells taken from either bone marrow or adipose tissue are only capable of differentiating into either bone/cartilage cells or adipose tissue respectively. Prenatal stem cells are often useful in several applications but again lack the range that embryonic cells offer. Finally bioengineered cells can offer an alternative to embryonic stem cells, albeit an inferior alternative. The field of induced pluripotent stem (iPS) cells is far more complex than that of embryonic stem (ES) cells, which leads to a loss of efficiency in the final product cell as well as a decreased functionality as compared to ES cells. It is most useful to use stem cells derived from an embryo because they are able to create any type of tissue found in the human body.
It is important to remember that the source of the stem cell affects its properties throughout the entire life of the cell. Embryos are unique in that they contain the basis for each type of tissue in the human body, due to the fact that if they had been allowed to mature they would in fact eventually become a full human body. The importance of embryonic stem cell research as compared to other stem cell research is exemplified in a quote from a Mayo Clinic Proceedings article: “iPS researcher Juan Carlos Izpisúa Belmonte, ‘ES cells are needed to understand the basic mechanism of pluripotency and self-renewal. As such, it is out of the question to even suggest phasing them out. We will be lost without them.’” (Zacharias, David G. et al. pg 637)
In defining the types of stem cells, the political and moral angles must also be addressed. The issue that embryonic stem cells face morally and politically is that of defining exactly when a cluster of cells is called a human being. This issue is similar to that of the abortion issue which was highly debated just a few years ago. For example in almost all cases it is legal in the United States for a pregnant woman to receive a late term abortion, that is to terminate her pregnancy up to the 24th week of pregnancy, sometimes even longer. At this state of gestation limbs, eyes and organs are almost fully developed yet it is not deemed a human being and can be terminated (Campbell 1015). But the government has decided to ban any research which destroys an embryo only 13 days from fertilization. Morally defining an embryo is crucial because of the laws which initiated the ban. With almost no development save for the production of a few membranes, an embryo should not be considered a human or living in any way. With a redefining of an embryo, the government could lift its ban on embryonic stem cell research and open the gates to discovering cures for deadly diseases.
Zacharias, David G. et al. “The Science and Ethics of Induced Pluripotency: What Will Become of Embryonic Stem Cells?” Mayo Clinic Proceedings (Jul 2011), Vol. 86 Issue 7 pgs 634-638 Academic Search Premier. Web. 7 Mar. 2012.
Reece, Jane B., and Neil A. Campbell. Biology. Eighth ed. Boston: Benjamin Cummings, 2011. Pgs (1015-1034) Print.