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."National Institutes of Health, "[Stem Cell Basics]," July 19, 2004.

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

Contents

1 Stem Cell Types

1.1 Potency
1.2 Sources

2 Treatments
3 Controversy surrounding stem cell research
4 Key events in stem cell research
5 End material

5.1 Notes
5.2 External links

5.2.1 Peer-reviewed journals
5.2.2 Peer-reviewed references
5.2.3 Guides
5.2.4 News

Stem Cell Types

Potency

Stem cell potency 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 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

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 could possibly be overcome by gaining the acceptance of the public and through years of intensive research.

Controversy surrounding stem cell research

There exists a 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. Proponents of the research point out that stem cells are taken from a blastocyst, typically four or five days old, which is a hollow microscopic ball of cells at that ageNational Institutes of Health, "[link]. 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. In contrast, medical researchers in the field point out that blastocysts, used by fertility clinics for in vitro fertilization, are destroyed after a couple conceives a child, unless they are adopted and implanted in a human female. Furthermore, proponents argue that embryonic stem cell research should be pursued because the resultant technologies might lead to medical breakthroughs. However, many other scientists argue that a focus on embryonic stem cell research takes away money and resources from other types of stem cell research that have already developed into successful treatments, e.g., adult and cord blood stem cell research. The ensuing debate has prompted national and international authorities to seek suitable regulatory frameworks and highlighted the fact that stem cell research represents a social, ethical and political controversy.

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
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 demonstrate that muscle stem cells retain both template DNA strands during cell division, resulting in conservative rather than semiconservative DNA replication. Entrez PubMed [16799552]

End material

Notes

External links

Peer-reviewed journals

[STEM CELLS® (Impact Factor = 6.094)]

Peer-reviewed references

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
Sources - Embryonic stem cells \| Adult stem cells \| Cancer stem cells
Related articles - Stem cell treatments \| Stem cell controversy \| Stem cell line \| Progenitor cell \| Cell differentiation

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