| Revision as of 19:41, 20 July 2006 edit69.117.236.210 (talk) →Definition← Previous edit | Revision as of 20:20, 20 July 2006 edit undoJu66l3r (talk | contribs)Extended confirmed users5,250 edits reworked the article to try and keep focus on ESCs and not on the controversy that has its own page refered in the stem cell infobox..pls see my comments in the discussionNext edit → | ||
| Line 2: | Line 2: | ||
| ] | ] | ||
| ] | ] | ||
| '''Embryonic stem cells''' (ESCs) are stem |
'''Embryonic stem cells''' (ESCs) are ]s derived from the inner cell mass of a ], which is an early stage embryo - approximately 4 to 5 days old in humans - consisting of 50-150 cells. Embryonic stem cells are ], meaning they are able to ] into all derivatives of the three primary ]s: ectoderm, endoderm and mesoderm. In other words, they can develop into each of the more than 200 cell types of the adult ] when given sufficient and necessary stimulation for a specific cell type. When given no stimuli for differentiation, ESCs will continue to divide ''in vitro'' and each ] will remain pluripotent. The pluripotency of ESCs distinguishes them from adult stem cells or progenitor cells, the latter two only having the capacity to form a more limited number of different cell types. | ||
| Because of their unique combined abilities of unlimited expansion and pluripotency, embryonic stem cells are a potential source for regenerative medicine and tissue replacement after injury or disease. To date, no approved medical treatments have been derived from embryonic stem cell research. This is not irregular for a new medical research field, given that the first human embryonic stem cell line was only first reported in 1998. | |||
| ==History== | |||
| Embryonic stem cells were first derived from mouse embryos in 1981 by two independent research groups (Evans & Kaufman and Martin). The breakthrough in embryonic stem cell research came in November 1998 when a group led by ] at the ] first developed a technique to isolate and grow the cells derived from human blastocysts. Normally, blastocyst-stage embryos that are left over after successful in vitro fertilization would not be used but be destroyed. Scientists are only allowed to use these discarded blastocysts after assessment by specialized committees that thoroughly check the research goals of these scientists. Of course, scientific research using those blastocysts may be conducted when it contributes to a better understanding of how to generate cells and tissues that can cure a patient's disease or be used to treat severe injuries. Currently, in the United States, scientific research is limited by a ban on the use of federal funds for research with embryonic stem cells derived after August 9th, 2001. Embryonic stem cell researchers are currently attempting to grow the cells in the laboratory (i.e. in culture flasks: "in vitro") beyond the first stages of cell development. It is important to make sure the embryonic stem cells are fully differentiated into the desired cell type (i.e. tissue) before they are transplanted into the patient, as undifferentiated embryonic stem cells may develop into a ] after transplantation. Further more, scientists are trying to develop techniques to prevent rejection of implanted cells by the patient (i.e. host-versus-graft response). | |||
| ⚫ | ==Research History and Developments== | ||
| ⚫ | One of the possibilities to prevent rejection is by creating embryonic stem |
||
| Embryonic stem cells were first derived from mouse embryos in 1981 by two independent research groups (Evans & Kaufman and Martin). A breakthrough in human embryonic stem cell research came in November 1998 when a group led by ] at the ] first developed a technique to isolate and grow the cells when derived from human blastocysts. | |||
| A major development in research came in May 2003, when researchers announced that they had successfully used embryonic stem cells to produce human egg cells.{{fact}} | |||
| ⚫ | The online edition of ''Nature Medicine'' published a study on ], ] 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 ] in the growth media was found to compromise the potential uses of the embryonic stem cells in humans, according to scientists at the ]. | ||
| ==Controversial Aspects== | |||
| {{main|Stem cell controversy}} | |||
| Stem cells are taken from a ], typically four or five days old, which is a hollow microscopic ball of about 150 cells , slightly larger than the period at the end of this sentence. After 14 days a nervous system begins to develop and it is called an embryo. | |||
| ⚫ | A study was published in the online edition of ''Lancet Medical Journal'' on ], ] that 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 ]s. These properties were also successfully maintained (for more than 30 passages) with the established stem-cell lines. | ||
| Blastocysts, used by fertility clinics for ], may be destroyed after a couple conceives a child, frozen (for future pregnancy attempts), or the couple can consent for them to be donated for medical research. But due to their own ethical dilemmas, many couples are unable to make a "dispensation decision" and as a result there are many frozen embryos in fertility clinics.] In a few cases, where couples have given permission for the embryos to be adopted, the embryos have been implanted and have grown to full-term babies (see ]). | |||
| ⚫ | Recently, in California, researchers have injected embryonic stem cells into mice as they developed in the womb. Upon maturing, it was found that some of the human ESCs had survived and two months after injection, the researchers found that the HESCs had undertaken "the characteristics of mouse cells" . | ||
| ⚫ | ==Developments== | ||
| A major development in research came in May 2003, when researchers announced that they had successfully used embryonic stem cells to produce human egg cells. These egg cells could potentially be used in turn to produce new stem cells. If research and testing proves that artificially created egg cells could be a viable source for embryonic stem cells, they noted, then this would remove the necessity of starting a new embryonic stem cell line with the destruction of a blastocyst. Thus, the controversy over donating human egg cells and blastocysts could potentially be resolved, though a blastocyst would still be required to start each cycle. | |||
| ⚫ | Scientists in Australia have grown human prostate tissue in mice through the use of ESCs. The research involved combining human ESCs with mouse prostate cells, and then using a mouse as the host to grow the human prostate. The researchers were able to show the resulting tissue was also functional as a human prostate. This work may enable medical researchers to use a prostate derived in this manner as a model for studying prostate cancer and disease and analysis of future prostate-related drugs. | ||
| ⚫ | The online edition of ''Nature Medicine'' published a study on ], ] which stated that the human embryonic stem cells available for federally funded research are contaminated with |
||
| ⚫ | Research is also ongoing into reducing the potential for rejection of the differentiated cells derived from ESCs once researchers are capable of creating an approved therapy from ESC research. One of the possibilities to prevent rejection is by creating embryonic stem cells that are genetically identical to the patient. This can be achieved by fusing an ] (]), the nucleus (containing the genetic material: ]) of which is removed, with the nucleus from another of the patient's cells. The fused cell produced, similar to a ], is allowed to begin dividing based on the instructions available within the materials originating in the oocyte ]. At an early blastocyte stage, embryonic stem cells can be extracted. Because they are genetically identical to the patient, the patient's immune system will not reject differentiated cells derived from these embryonic stem cells. An alternative solution for rejection by the patient to therapies derived from non-cloned ESCs 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. | ||
| ⚫ | A study was published in the online edition of ''Lancet Medical Journal'' on ], ] that detailed information about a new stem |
||
| ⚫ | Recently, in California, researchers have injected embryonic stem cells into mice as they developed in the womb. Upon maturing, it was found that some of the human ESCs had survived and two months after injection, the researchers found that the |
||
| ⚫ | Scientists in Australia have grown human prostate in mice |
||
| {{Stem cells}} | {{Stem cells}} | ||
Revision as of 20:20, 20 July 2006
Definition
Embryonic stem cells (ESCs) are stem cells derived from the inner cell mass of a blastocyst, which is an early stage embryo - approximately 4 to 5 days old in humans - consisting of 50-150 cells. Embryonic stem cells are pluripotent, meaning they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm and mesoderm. In other words, they can develop into each of the more than 200 cell types of the adult body when given sufficient and necessary stimulation for a specific cell type. When given no stimuli for differentiation, ESCs will continue to divide in vitro and each daughter cell will remain pluripotent. The pluripotency of ESCs distinguishes them from adult stem cells or progenitor cells, the latter two only having the capacity to form a more limited number of different cell types.
Because of their unique combined abilities of unlimited expansion and pluripotency, embryonic stem cells are a potential source for regenerative medicine and tissue replacement after injury or disease. To date, no approved medical treatments have been derived from embryonic stem cell research. This is not irregular for a new medical research field, given that the first human embryonic stem cell line was only first reported in 1998.
Research History and Developments
Embryonic stem cells were first derived from mouse embryos in 1981 by two independent research groups (Evans & Kaufman and Martin). 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.
A major development in research came in May 2003, when researchers announced that they had successfully used embryonic stem cells to produce human egg cells.
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.
A study was published in the online edition of Lancet Medical Journal on March 8, 2005 that 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. (Lancet Medical Journal)
Recently, in California, researchers have injected embryonic stem cells into mice as they developed in the womb. Upon maturing, it was found that some of the human ESCs had survived and two months after injection, the researchers found that the HESCs had undertaken "the characteristics of mouse cells" .
Scientists in Australia have grown human prostate tissue in mice through the use of ESCs. The research involved combining human ESCs with mouse prostate cells, and then using a mouse as the host to grow the human prostate. The researchers were able to show the resulting tissue was also functional as a human prostate. This work may enable medical researchers to use a prostate derived in this manner as a model for studying prostate cancer and disease and analysis of future prostate-related drugs.
Research is also ongoing into reducing the potential for rejection of the differentiated cells derived from ESCs once researchers are capable of creating an approved therapy from ESC research. One of the possibilities to prevent rejection is by creating embryonic stem cells that are genetically identical to the patient. This can be achieved by fusing an egg (oocyte), the nucleus (containing the genetic material: DNA) of which is removed, with the nucleus from another of the patient's cells. The fused cell produced, similar to a zygote, is allowed to begin dividing based on the instructions available within the materials originating in the oocyte cytoplasm. At an early blastocyte stage, embryonic stem cells can be extracted. Because they are genetically identical to the patient, the patient's immune system will not reject differentiated cells derived from these embryonic stem cells. An alternative solution for rejection by the patient to therapies derived from non-cloned ESCs 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.
| Stem cells | |
|---|---|
| Sources/types | |
| Cell potency |
|
| Related articles | |
