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Stem cells are primal undifferentiated cells which retain the ability to differentiate into other cell types. This ability allows them to act as a repair system for the body, replenishing other cells as long as the host organism is alive.

Medical researchers believe stem cell research has the potential to change the face of human disease by being used to repair specific tissues or to grow organs. Yet as government reports point out, "significant technical hurdles remain that will only be overcome through years of intensive research."^[1]

The study of stem cells is attributed as beginning in the 1960s after research by Canadian scientists Ernest A. McCulloch and James E. Till.

Stem Cell Types

Potency

Stem cells are categorized by potency, which specifies the ameliorative potential of the cell type.

Totipotent stem cells are produced from the fusion of an egg and sperm cell. Cells produced by the first few divisions of the fertilized egg cell are also totipotent. These cells can grow into any type of cell without exception.

Pluripotent stem cells are the descendants of totipotent cells and can grow into any cell type except for totipotent stem cells.

Multipotent stem cells can produce only cells of a closely related family of cells (e.g. blood cells such as red blood cells, white blood cells and platelets).

Unipotent cells can produce only one cell type, but have the property of self-renewal which distinguishes them from non-stem cells.

Sources of stem cells

Stem cells are also categorized according to their source, as either adult, embryonic or cord blood stem cells.

Adult stem cells are undifferentiated cells found among differentiated cells of a specific tissue and are mostly multipotent cells. They are already being used in treatments for over one hundred diseases and conditions. They are more accurately called somatic (Greek σωμα sōma = body) stem cells, because they need not come from adults but can also come from children or umbilical cords. Particularly interesting are adult stem cells termed "spore-like cells". They are present in all tissues (Vacanti, M. P., A. Roy, J. Cortiella, L. Bonassar, and C. A. Vacanti. 2001. "Identification and initial characterization of spore-like cells in adult mammals." J Cell Biochem 80:455–60.) and seem to survive long time periods and harsh conditions.

Embryonic stem cells are cultured cells obtained from the undifferentiated inner mass cells of an early stage human embryo (sometimes called a blastocyst, which is an embryo that is between 50 to 150 cells). Embryonic stem cell research is "thought to have much greater developmental potential than adult stem cells," according to the National Institutes of Health.^[2] However, embryonic stem cell research is still in the basic research phase, as these stem cells were first isolated in 1998 (at least for humans), whereas adult stem cells have been studied since the 1960s.^[3] Research with embryonic stem cells derived from humans is controversial because, in order to start a stem cell 'line' or lineage, it requires the destruction of a human embryo and/or therapeutic cloning, which some believe is a slippery slope to reproductive cloning and tantamount to the objectification of a potential human being. In an attempt to overcome these moral, political and ethical hurdles, medical researchers have been experimenting with alternative techniques of obtaining embryonic stem cells by extraction, which does not involve cloning and/or the destruction of a human embryo.

Cord blood stem cells are derived from the blood of the placenta and umbilical cord after birth. Since 1988 these cord blood stem cells have been used to treat Gunther's disease, Hunter syndrome, Hurler syndrome, Acute lymphocytic leukemia and many more problems occurring mostly in children. Umbilical cord blood use has become so common that there are now umbilical cord blood banks that accept donations from parents. It is collected by removing the umbilical cord, cleansing it and withdrawing blood from the umbilical vein. This blood is then immediately analyzed for infectious agents and the tissue-type is determined. The cord blood is processed and depleted of red blood cells before being stored in liquid nitrogen for later use, at which point it is thawed, washed of the cryoprotectant, and injected through a vein of the patient. This kind of treatment, where the stem cells are collected from another donor, is called allogeneic treatment. When the cells are collected from the same patient on whom they will be used, it is called autologous and when collected from identical individuals (i.e. homozygous twin), it is referred to as syngeneic. Xenogeneic

Treatments

Medical researchers believe that stem cell research has the potential to change the face of human disease and alleviate suffering. A number of current treatments already exist, although the majority of them are not commonly used because they tend to be experimental and not very cost-effective. Medical researchers anticipate being able to use technologies derived from stem cell research to treat cancer, spinal cord injuries, and muscle damage, amongst a number of other diseases, impairments and conditions.

However, there still exists a great deal of social and scientific uncertainty surrounding stem cell research, which will only be overcome by gaining the acceptance of the public and through years of intensive research.

Controversy surrounding stem cell research

Stem cell research has the potential to impact all of our lives, but it is not without controversy. Particularly, research using embryonic stem cells has proven to be an immensely sensitive topic. This is because, with the present state of technology, starting a stem cell 'line' requires the destruction of a human embryo and/or therapeutic cloning. Opponents of the research argue that this practice is a slippery slope to reproductive cloning and tantamount to the objectification of a potential human being. Contrarily, the pro-research people argues that it is necessary to pursue embryonic stem cell research because the resultant technologies are expected to have significant medical potential. The ensuing debate has prompted national and international authorities to seek suitable regulatory frameworks and highlighted the fact that stem cell research represents a moral, social and ethical minefield.

Notes

^ National Institutes of Health, "Stem Cell Basics," July 19, 2004.
^ National Institutes of Health, Stem Cell FAQ, April 13, 2005.
^ Graham, Judith and Schodolski, Vincent J., "Son of former President Reagan enters the fray with a speech at the Democratic convention." Chicago Tribune, July 27, 2004.

External links

Peer-reviewed journals

Peer-reviewed references

1. Shostak, S. 2006. (Re)defining stem cells. BioEssays 28:301-308.

Guides

Cells Limited Research, Processing & Storage of Stem Cells. Cord Blood & Bone Marrow Stem Cells.
International Society for Stem Cell Research Stem cell information for the public from a global research society
National Institutes of Health Guide
Embryoperson Web site: Showing that the human embryo is a person, and distinguishing between a sick embryo and a pseudo-embryo
A Guide to the Benefits, Responsibilities and Opportunities of Embryonic Stem Cell Research, from the British-North American Committee
Harvard College Stem Cell Society A student organization striving to educate the public about issues related to stem cell research

News

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 ==Controversy surrounding stem cell research==
 {{main|Stem cell controversy}}
-Stem cell research has the potential to impact all of our lives, but it is not without controversy. Particularly, research using embryonic stem cells has proven to be an immensely sensitive topic. This is because, with the present state of technology, starting a [[stem cell line|stem cell 'line']] requires the destruction of a [[embryo|human embryo]] and/or [[therapeutic cloning]]. Opponents of the research argue that this practice is a [[slippery slope]] to [[reproductive cloning]] and tantamount to the [[objectification]] of a potential [[human being]]. Contrarily, the pro-research lobby argues that it is necessary to pursue embryonic stem cell research because the resultant technologies are expected to have significant medical potential. The ensuing debate has prompted national and international authorities to seek suitable regulatory frameworks and highlighted the fact that stem cell research represents a [[moral]], [[social]] and [[ethical]] minefield.
+Stem cell research has the potential to impact all of our lives, but it is not without controversy. Particularly, research using embryonic stem cells has proven to be an immensely sensitive topic. This is because, with the present state of technology, starting a [[stem cell line|stem cell 'line']] requires the destruction of a [[embryo|human embryo]] and/or [[therapeutic cloning]]. Opponents of the research argue that this practice is a [[slippery slope]] to [[reproductive cloning]] and tantamount to the [[objectification]] of a potential [[human being]]. Contrarily, the pro-research people argues that it is necessary to pursue embryonic stem cell research because the resultant technologies are expected to have significant medical potential. The ensuing debate has prompted national and international authorities to seek suitable regulatory frameworks and highlighted the fact that stem cell research represents a [[moral]], [[social]] and [[ethical]] minefield.
 ==See also==