Article: Stem cell

Mouse embryonic stem cells. More lab photos

Stem cells in animals are primal undifferentiated cells that retain the ability to divide and differentiate into other cell types. In higher plants this function is the defining property of the meristematic cells. Stem cells have the ability to act as a repair system for the body, because they can divide and differentiate, 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 there is general agreement that, "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

The potency specifies the differentiation potential (the potential to differentiate into different cell types) of the stem cell.

• 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 differentiate into embryonic and extraembryonic cell types.

• Pluripotent stem cells are the descendants of totipotent cells and can differentiate into cells derived from the three germ layers.

• Multipotent stem cells can produce only cells of a closely related family of cells (e.g. hematopoeietic stem cells differentiate into red blood cells, white blood cells, platelets etc.).

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

Sources

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 throughout the body that divide to replenish dying cells and regenerate damaged tissues. Also known as somatic (from Greek Σωματικóς, of the body) stem cells, they can be found in children, as well as adults.

• 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).

• Cord blood stem cells are derived from the blood of the placenta and umbilical cord after birth.

Treatments

Main article: Stem cell treatments

Medical researchers believe that stem cell research has the potential to change the face of human disease. 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 could possibly be overcome by gaining the acceptance of the public and through years of intensive research.

Controversy surrounding stem cell research

Main article: Stem cell controversy

There exists a widespread controversy over stem cell research that emanates from the techniques used in the creation and usage of stem cells. Embryonic stem cell research is particularly controversial 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 instrumentalization of a potential human being. Contrarily, some medical researchers in the field argue 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 challenge.

Key events in stem cell research

• 1960s - Joseph Altman and Gopal Das present evidence of adult neurogenesis, ongoing stem cell activity in the brain; their reports contradict Cajal's "no new neurons" dogma and are largely ignored
• 1963 - McCulloch and Till illustrate the presence of self-renewing stem cells in mouse bone marrow
• 1968 - bone marrow transplant between two siblings successfully treats SCID
• 1978 - haematopoietic stem cells are discovered in human cord blood
• 1981 - mouse embryonic stem cells are derived from the inner cell mass
• 1992 - neural stem cells are cultured in vitro as neurospheres
• 1995 - President Bill Clinton signs into law the Dickey Amendment which makes it illegal for Federal money to be used for research where stem cells are derived from the destruction of the embryo.
• 1997 - leukemia is shown to originate from a haematopoietic stem cell, the first direct evidence for cancer stem cells
• 1998 - James Thomson and coworkers derive the first human embryonic stem cell line at the University of Wisconsin-Madison.
• 2000s - several reports of adult stem cell plasticity are published
• 2004-2005 - Hwang Woo-Suk claims to have created several human embryonic stem cell lines from unfertilised human oocytes. The lines are later shown to be fabricated
• 2006 - Pasteur Institute scientists provide evidence that muscle stem cells might retain both template DNA strands during cell division, resulting in conservative rather than semiconservative DNA replication.^[2]
• July 19, 2006 - President George W. Bush vetoed a bill which would have allowed Federal money to be used for research where stem cells are derived from the destruction of the embryo.

End material

Notes

1. ^ National Institutes of Health, "Stem Cell Basics," July 19, 2004.
2. ^ Shinin V, Gayraud-Morel B, Gomes D and Tajbakhsh S (2006). "Asymmetric division and cosegregation of template DNA strands in adult muscle satellite cells". Nat Cell Biol 8 (7). Entrez PubMed 16799552

External links

• International Society for Cellular Therapy
• International Society for Stem Cell Research
• Progenitor Cell Therapy
• Video Archive: The Stem Cell Controversy
• Stem Cell & Cord Blood implications
• Scientific American Magazine (June 2004 Issue) The Stem Cell Challenge
• Scientific American Magazine (July 2005 Issue) The Future of Stem Cells
• Scientific American Magazine (July 2006 Issue) Stem Cells: The Real Culprits in Cancer?
• The American Society for Cell Biology
• California Institute for Regenerative Medicine

Peer-reviewed journals

• STEM CELLS® (Impact Factor = 6.094)

• Cytotherapy
• Cloning and Stem Cells
• Stem Cells and Development

Peer-reviewed references

1. Shostak S (2006). "(Re)defining stem cells". Bioessays 28 (3): 301-8. PMID 16479584.

Guides

• UMDNJ Stem Cell and Regenerative Medicine Literature Reviews of Stem Cell Research.
• 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 dedicated to advancing stem cell research by "raising awareness and promoting education".
• Virtual Stem Cell Laboratory Cause cells to differentiate and learn about stem cell research through this interactive feature.

News

• STEM CELLS® YOUNG INVESTIGATOR AWARD
• STEM CELLS® (Impact Factor = 6.094)
• Cell Therapy News.
• Do No Harm: The Coalition of Americans for Research Ethics
• Congressional Research Service (CRS) Reports regarding Stem Cell Research
• Stem Cells & Cloning Club (SCCC) - online community dedicated to the provision and discussion of information related to stem cell, cloning and cell therapy research; news, articles, interviews, business, discussion and more....
• Stem cell Research - Biology News Net.
• Stem Cell Research Blog - updated daily with latest stem cell news.
• Latest Advances In Stem Cell Research.
• New Scientist's list of stem-cell and cloning related articles it has covered.
• Stem Cell News.
• Latest cell therapy progress.
• Stem Cell Research