Embryonic Stem Cell

Information about Embryonic Stem Cell

Human embryonic stem cell colony.

Pluripotent, embryonic stem cells originate as inner mass cells within a blastocyst. The stem cells can become any tissue in the body, excluding a placenta. Only the morula's cells are totipotent, able to become all tissues and a placenta.

Embryonic stem cells (ES cells) are stem cells derived from the inner cell mass of an early stage embryo known as a blastocyst. Human embryos reach the blastocyst stage 4-5 days post fertilization, at which time they consist of 50-150 cells.

ES cells are pluripotent. This means they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm. These include each of the more than 220 cell types in the adult body. Pluripotency distinguishes ES cells from multipotent progenitor cells found in the adult; these only form a limited number of cell types. When given no stimuli for differentiation, (i.e. when grown in vitro), ES cells maintain pluripotency through multiple cell divisions. The presence of pluripotent adult stem cells remains a subject of scientific debate, however, research has demonstrated that pluripotent stem cells can be directly generated from adult fibroblast cultures.^[1].

Because of their plasticity and potentially unlimited capacity for self-renewal, ES cell therapies have been proposed for regenerative medicine and tissue replacement after injury or disease. However, to date, no approved medical treatments have been derived from embryonic stem cell research (ESCR). Adult stem cells and cord blood stems cells have thus far been the only stem cells used to successfully treat any diseases. Diseases treated by these non-embryonic stem cells include a number of blood and immune-system related genetic diseases, cancers, and disorders; juvenile diabetes; Parkinson's; blindness and spinal cord injuries. Besides the ethical problems of stem cell therapy (see stem cell controversy), there is a technical problem of graft-versus-host disease associated with allogeneic stem cell transplantation. However, these problems associated with histocompatibility may be solved using autologous donor adult stem cells or via therapeutic cloning.

Research history and developments

Isolation and in vitro culture

Stem cells were discovered from analysis of a type of cancer called a teratocarcinoma. In 1964, researchers noted that a single cell in teratocarcinomas could be isolated and remain undifferentiated in culture. These types of stem cells became known as embryonic carcinoma cells (EC cells).^[2] Researchers learned that primordial embryonic germ cells (EG cells) could be cultured and stimulated to produce many different cell types.

Growing cells in a laboratory is known as cell culture. Human stem cells are isolated by transferring the inner cell mass into a plastic laboratory culture dish that contains a broth known as culture medium. What are embryonic stem cells? . In Stem Cell Information [World Wide Web site]. Bethesda, MD: National Institutes of Health, U.S. Department of Health and Human Services, 2006 [cited Tuesday, April 10, 2007] Available at <http://stemcells.nih.gov/info/basics/basics3>

Embryonic stem cells (ES cells) were first derived from mouse embryos in 1981 by Martin Evans and Matthew Kaufman and independently by Gail R. Martin. Gail R. Martin is credited with coining the term 'Embryonic Stem Cell'.^[3]^[4] A breakthrough in human embryonic stem cell research came in November 1998 when a group led by James Thomson at the University of Wisconsin-Madison first developed a technique to isolate and grow the cells when derived from human blastocysts.^[5]

Production of male gametes

Researchers at the Whitehead Institute announced in 2003 that they had successfully used embryonic stem cells to produce haploid, male gametes. They found embryonic stem cells that had begun to differentiate into embryonic germ cells and then further differentiated into the male haploid cells. When injected into oocytes, these haploid cells restored the somatic diploid complement of chromosomes and formed blastocysts in vitro.^[6]

Contamination by reagents used in cell culture

The online edition of Nature Medicine published a study on January 23, 2005 which stated that the human embryonic stem cells available for federally funded research are contaminated with non-human molecules from the culture medium used to grow the cells. It is a common technique to use mouse cells and other animal cells to maintain the pluripotency of actively dividing stem cells. The problem was discovered when non-human sialic acid in the growth media was found to compromise the potential uses of the embryonic stem cells in humans, according to scientists at the University of California, San Diego.^[7]

However, a study was published in the online edition of Lancet Medical Journal on March 8, 2005 detailed information about a new stem cell line which was derived from human embryos under completely cell- and serum-free conditions. After more than 6 months of undifferentiated proliferation, these cells demonstrated the potential to form derivatives of all three embryonic germ layers both in vitro and in teratomas. These properties were also successfully maintained (for more than 30 passages) with the established stem cell lines. ^[8]

Reducing donor-host rejection

There is also ongoing research to reduce the potential for rejection of the differentiated cells derived from ES cells once researchers are capable of creating an approved therapy from ES cell research. One of the possibilities to prevent rejection is by creating embryonic stem cells that are genetically identical to the patient via therapeutic cloning.

An alternative solution for rejection by the patient to therapies derived from non-cloned ES cells is to derive many well-characterized ES cell lines from different genetic backgrounds and use the cell line that is most similar to the patient; treatment can then be tailored to the patient, minimizing the risk of rejection.

Potential method for new cell line derivation

On August 23, 2006, the online edition of Nature scientific journal published a letter by Dr. Robert Lanza (medical director of Advanced Cell Technology in Worcester, MA) stating that his team had found a way to extract embryonic stem cells without destroying the actual embryo.^[9] This technical achievement would potentially enable scientists to work with new lines of embryonic stem cells derived using public funding. Federal funding is currently limited to research using embryonic stem cell lines derived prior to August 2001.

In the experiments, Lanza's team used a single-cell biopsy technique to pluck out a single cell when the embryo was at the 8-to-10 cell stage. This is the same stage used for preimplantation genetic diagnosis, which also requires the removal of a single cell from the blastocyst. As with times where preimplantation genetic diagnosis is used, excising a cell at this point does not interfere with the embryo's development and the excised cell can be used for both purposes at the same time. Using this method, Lanza and his team managed to get two stable human embryonic stem cell lines that behaved like conventional embryonic stem cell lines.

Quickly after its publication, this paper came under some criticism for its representation of the facts. Examination of the paper revealed that the described process was highly inefficient, and in addition, no embryos survived the process. ^[10] Dr. Lanza states that "he never intended to say more than that he had proved a principle"^[11]. The goal of the paper was to demonstrate that an embryonic stem cell line could be derived from a single cell from the inner mass. Given that the embryos in the study were not medically or legally eligible for implantation, more than one cell was removed from the inner cell masses - each to be used in a separate experiment.

At the 2007 meeting of the International Society for Stem Cell Research (ISSCR) ^[12], Dr. Lanza announced that his team had succeeded in producing three new stem cell lines without destroying the parent embryos. "These are the first human embryonic cell lines in existence that didn't result from the destruction of an embryo." Lanza is currently in discussions with the National Institutes of Health (NIH) to determine whether the new technique sidesteps U.S. restrictions on federal funding for ES cell research ^[13]. Advanced Cell Technology has pledged cooperation with WiCell Research Institute to derive new stem cell lines using the principle of the Lanza paper, pending federal approval and further research. ^[14]

Professor Yamanaka, Japan’s leading genetics researcher, had a recent breakthrough in which the skin cells of laboratory mice were genetically manipulated back to their embryonic state.

References

1. ^ Department of Stem Cell Biology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto,Induction of Pluripotent Stem Cells from Mouse Embryonic and Adult Fibroblast Cultures by Defined Factors, August 25, 2006
2. ^ Andrews P, Matin M, Bahrami A, Damjanov I, Gokhale P, Draper J (2005). "Embryonic stem (ES) cells and embryonal carcinoma (EC) cells: opposite sides of the same coin.". Biochem Soc Trans 33 (Pt 6): 1526-30. PMID 16246161.
3. ^ Evans M, Kaufman M (1981). "Establishment in culture of pluripotential cells from mouse embryos.". Nature 292 (5819): 154-6. PMID 7242681.
4. ^ Martin G (1981). "Isolation of a pluripotent cell line from early mouse embryos cultured in medium conditioned by teratocarcinoma stem cells.". Proc Natl Acad Sci U S A 78 (12): 7634-8. PMID 6950406.
5. ^ Thomson J, Itskovitz-Eldor J, Shapiro S, Waknitz M, Swiergiel J, Marshall V, Jones J (1998). "Embryonic stem cell lines derived from human blastocysts.". Science 282 (5391): 1145-7. PMID 9804556.
6. ^ [1]
7. ^ [2]
8. ^ [3] (Lancet Medical Journal)
9. ^ Klimanskaya I, Chung Y, Becker S, Lu SJ, Lanza R. (2006). "Human embryonic stem cell lines derived from single blastomeres.". Nature 444 (7118): 481-5. PMID 16929302.
10. ^ 'Ethical' stem-cell paper under attack
11. ^ [4]
12. ^ [5]
13. ^ [6]
14. ^ [7]

External links

Understanding Stem Cells: A View of the Science and Issues from the National Academies
Tell Me About Stem Cells
Health MSN article on new stem cell extraction
http://humanEScellbook.com Harvard Stem Cell Institute's guide to growing and manipulating human embryonic stem cells
National Institutes of Health
Stem Cell and Cord Blood information database

Pluripotent (cell biology)

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Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a "type". The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions.
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germ layer is a collection of cells, formed during animal embryogenesis. Germ layers are only really pronounced in the vertebrates. However, all animals more complex than sponges (eumetazoans and ) produce two or three primary tissue layers
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The ectoderm is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers.

What forms from it (general)?

Nervous system
Outer part of integument

What forms from it (vertebrates)?

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Endoderm is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm.

The endoderm consists at first of flattened cells, which subsequently become columnar.
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The germ layer mesoderm forms in the embryos of animals more complex than cnidarians, making them triploblastic. Mesoderm forms during gastrulation when some of the cells migrating inward to form the endoderm form an additional layer between the endoderm and the ectoderm.
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The human body is the entire physical structure of a human organism. The human body consists of a head, neck, torso, two arms and two legs. The average height of an adult human is about 1.6 m (5 to 6 feet) tall. This size is largely determined by genes.
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Multipotent progenitor cells can give rise to several other cell types, but those types are limited in number. An example of a multipotent stem cell is a hematopoietic cell — a blood stem cell that can develop into several types of blood cells, but cannot develop into brain
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The term progenitor cell is used in cell biology and developmental biology to refer to immature or undifferentiated cells, typically found in post-natal animals. While progenitor cells share many common features with stem cells, the term is far less restrictive.
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In vitro (Latin: (with) in the glass) refers to the technique of performing a given experiment in a test tube, or, generally, in a controlled environment outside a living organism. In vitro fertilization is a well-known example of this.
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Cell division is a process by which a cell, called the parent cell, divides into two cells, called daughter cells. Cell division is usually a small segment of a larger cell cycle. In meiosis however, a cell is permanently transformed and cannot divide again.
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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
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There is widespread controversy over stem cell research largely due to techniques used in the creation and usage of human embryonic stem cells. Some opponents of the research argue that this practice is a slippery slope to reproductive cloning and fundamentally devalues the
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Graft-versus-host disease
Classification & external resources

ICD-10 T 86.0
ICD-9 996.85

DiseasesDB 5388

eMedicine med/926 ped/893 derm/478
MeSH D006086 Graft-versus-host disease
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Histocompatibility is the property of having the same, or mostly the same, alleles of a set of genes called the major histocompatibility complex. These genes are expressed in most tissues as antigens, to which the immune system makes antibodies.
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In biology, autologous refers to cells, tissues or even proteins that are reimplanted in the same individual as they come from. Bone marrow, skin biopsy, cartilage, and bone can be used as autografts.
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somatic cell nuclear transfer (SCNT) is a laboratory technique for creating an ovum with a donor nucleus (see process below) . It can be used in embryonic stem cell research, or in regenerative medicine where it is sometimes referred to as "therapeutic cloning.
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Germ cell tumor
Classification & external resources

ICD-10 C 56. , C 62. , D 27. , D 29.2
ICD-9 183 , 186 , 220 , 222.0
ICD-O: 9060-9100

eMedicine med/863 Germ cell tumor (GCT) is a tumor (neoplasm) derived from germ cells.
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Martin Evans

Born 1 January 1941
Stroud, Gloucestershire, England
Nationality British
Field Developmental biology
Institutions University College London
University of Cambridge
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In 1981 Matthew H. Kaufman and Martin Evans at the University of Cambridge in England and Gail R Martin in America were the first to derive embryonic stem cells (ES cells) from mouse embryos.^[1]^[2]

He is an authority of mouse development.
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James "Jamie" Alexander Thomson (born in Oak Park, Illinois) is an American developmental biologist who also serves as a professor of anatomy in the University of Wisconsin School of Medicine and Public Health and as the chief pathologist at the Wisconsin National Primate Research
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University of Wisconsin–Madison (also known as UW–Madison, Madison, Wisconsin, University of Wisconsin, or UW) is a highly selective public research university located in Madison, Wisconsin, USA.
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Founded in 1982, the Whitehead Institute for Biomedical Research is a non-profit research and teaching institution located in Cambridge, Massachusetts. The Whitehead Institute was founded as a fiscally independent entity from Massachusetts Institute of Technology, and its members
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A gamete (from Ancient Greek γαμετης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilisation (conception) in organisms that reproduce sexually.
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A germ cell is part of the germline and is involved in the reproduction of organisms. Germ cells should not be confused with "germs" (pathogens).

Germ cells includes all stages of gametogenesis, i.e. gametogonia, gametocytes, gametids and gametes.
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