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STEM CELL RESEARCH HISTORY
AND DEVELOPMENT
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). Researchers
learned that primordial embryonic germ cells (EG cells) could be
cultured and stimulated to produce many different cell types.
Embryonic stem cells (ES cells) were first derived from mouse embryos in
1981 by two independent research groups. 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.
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.
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.
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.
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.[8]
This technical achievement would potentially enable scientists to work
with new lines of embryonic stem cells derived using public funding.
There are currently significant restrictions on federal funding of
embryonic stem cell research that limit publicly-funded research to
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. Dr. Lanza states that "he never intended
to say more than that he had proved a principle"[10]. 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.
Though theoretically very promising, the principle has yet to be
demonstrated on an embryo that is to be carried to term. 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.
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What
is a stem cell?
Research history and
developments
Isolation and in vitro culture
Production of male gametes
Contamination by reagents used in cell culture
Reducing donor-host rejection
Potential method for new cell line derivation
Stem cell therapies
Controversy of
Embryonic stem cell research
Arguments for cell research state these reasons:
Arguments against embryonic stem cell research
Stem cells without embryonic destruction
Patents covering human
stem cell research
International policy
context
US policy debate
Origins of policy debate in the U.S.
Congressional response
References |