"All stem cells -- regardless of their source -- have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise to specialized cell types." (NIH, Unique) Being unspecialized means that stem cells have no tissue-specific structures, and it can't work with other cells to perform functions, yet stem cells do give rise to cells that are specialized. Stem cells also replicate many times, called proliferation, which is unique from other kinds of cells. Differentiation is the process by which stem cells give rise specialized cells such that those found in muscles and organs. (NIH, Unique)
However, there are actually two basic kinds of stem cells: embryonic stem cells and adult stem cells. Adult stem cells will generally only generate cells like those found in the tissues that contain the stem cells; an adult stem cell found in the blood will generate blood cells such as platelets or red blood cells. (NIH, Unique) Embryonic stem cells are those which are derived from embryos. They are usually obtained from blastocysts that are only a few days old and created in a lab; embryonic stem cells are not obtained from eggs fertilized within the body under most circumstances. Adult stem cells may have some plasticity to become any type of specialized cell, but overall embryonic stem cells are far more able to become any type of cell desired. It is also easier to grow large amounts of embryonic stem cells in cultures, and adult ones are much more rare and difficult to obtain or grow. One potential advantage to using adult stem cells is that a patient could be treated with his or her own cells, but embryonic stem cells must come from a donor which could cause transplant rejection. (NIH, Similarities)
Stem cell research has come a long way, but there is a lot more that is still not understood about how they work or how they can best be used for medical advancements. Some people feel that there is a moral problem with experimenting on stem cells, and that they may not actually offer any valid medical advancements. However, others feel that stem cells are not entitled to human rights protection, and that the end definitely justifies the means as they can be used for helping many people. There are two kinds of stem cells, embryonic and adult, each of which have different potential for use in medical situations.
Bell, H. (2000) "Case Study: The Uninsured" American Medical Student Association.
Calafut, T. (2000) "Emerging Applications in Human Stem Cell Therapy." Chemical Market Reporter, March 20.
Celia, F. (2001) "Stem Cell Controversy Heats Up Amid Advances in the Field." Medical Laboratory Observer, April. http://www.findarticles.com/cf_dls/m3230/4_33/74268498/p1/article.jhtml
Fraser, R. (2003) "AMA says use of stem cells for biomedical research is consistent with medical ethics" AMA Media Relations.
Green, R. (2001) The Human Embryo Research Debates: Bioethics in the Vortex of Controversy. London: Oxford Press.
Lindsay, C. (2002) "Medical Bioethics." Nurse Week.
NIH. "What Are Adult Stem Cells?" Stem Cell Basics. Stem Cell Information. National Institute of Health. 2004.http://stemcells.nih.gov/info/basics/basics4.asp
NIH. "What Are Embryonic Stem Cells?" Stem Cell Basics. Stem Cell Information. National Institute of Health. 2004. http://stemcells.nih.gov/info/basics/basics3.asp
NIH. "What Are the Similarities and Differences Between Embryonic and Adult Stem Cells?" Stem Cell Basics. Stem Cell Information. National Institute of Health. 2004. http://stemcells.nih.gov/info/basics/basics5.asp
NIH. "What Are the Unique Properties of All Stem Cells?" Stem Cell Basics. Stem Cell Information. National Institute of Health. 2004. http://stemcells.nih.gov/info/basics/basics2.asp
Richards, T. (2000) "Stem cell research: the UK government should sanction carefully regulated research." British Medical Journal, December 9.