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Stem Cell Research Q & A
Imagine having a spinal chord injury or needing a liver transplant. Instead of waiting for a donor
you just grow your own liver. Instead of living life, paralyzed, tiny cells are injected into your
spinal chord repairing any damage. Well, Scientist are working towards these goals using tiny
stem cells. These cells that have the potential to grow into a liver a heart, or maybe any part of
our body.
Provided are some frequently asked Questions of Stem Cell Research. I hope all find this
informative. Please refer to the International Society of Stem Cell Research or other
orginizations for recent findings and indepth study analysis.
Q1. How are human embryonic stem cells obtained for research, and at what stage of
embryonic development?
A. Human embryonic stem cells are derived from eggs that have been fertilized in vitro - by an
assisted human reproduction clinic - and then donated to research with the informed consent of
the donors. They are not derived from eggs fertilized in a woman's body. The embryos from
which the stem cells are derived are typically four or five days old and are a hollow microscopic
ball of cells called the blastocyst that is about the size of a grain of sand. The blastocyst includes
three structures: the trophoblast, which is the layer of cells that surrounds the blastocyst; the
blastocoel, which is the hollow cavity inside the blastocyst; and the inner cell mass, which is a
group of approximately 30 cells at one end of the blastocoel.
Q2. How are embryonic stem cells grown in the laboratory?
A. Human embryonic stem cells are isolated by transferring the inner cell mass into a plastic
laboratory culture dish that contains a nutrient broth known as culture medium. The cells divide
and spread over the surface of the dish. The inner surface of the culture dish is typically coated
with mouse embryonic skin cells that have been treated so they will not divide. This coating
layer of cells is called a feeder layer. The reason for having the mouse cells in the bottom of the
culture dish is to give the inner cell mass cells a sticky surface to which they can attach. Also, the
feeder cells release nutrients into the culture medium. Recently, scientists have begun to devise
ways of growing embryonic stem cells without the mouse feeder cells. This is a significant
scientific advancement because of the risk that viruses or other macromolecules in the mouse
cells may be transmitted to the human cells.
Over the course of several days, the cells of the inner cell mass proliferate and begin to crowd
the culture dish. When this occurs, they are removed gently and plated into several fresh culture
dishes. The process of replating the cells is repeated many times and for many months, and is
called subculturing. Each cycle of subculturing the cells is referred to as a passage. After six
months or more, the original 30 cells of the inner cell mass yield millions of embryonic stem
cells. Embryonic stem cells that have proliferated in cell culture for six or more months without
differentiating, are pluripotent, and appear genetically normal, are referred to as an embryonic
stem cell line.
Once cell lines are established, or even before that stage, batches of them can be frozen and
stored or shipped to other laboratories for further culture and experimentation.
Q3. Why not use human adult somatic stem cells instead of human embryonic stem cells in
research?
A. Embryonic stem cells are pluripotent, which means they have the ability to differentiate into
all cell types of the body. Adult somatic stem cells, however, are generally limited to
differentiating into cell types of their tissue of origin. However, there is now evidence to
suggests that some adult somatic stem cells, referred to as multipotent, may be able to create a
limited number of specialised cell types.
Large numbers of cells are needed for stem cell replacement therapies. While large numbers of
embryonic stem cells can be grown relatively easily in culture, adult somatic stem cells are rare
in mature tissues and methods for expanding their numbers in cell culture have yet to be
discovered.
Q4. Have stem cells been used to treat any human diseases yet?
A. Adult somatic stem cells such as blood-forming stem cells in bone marrow (hematopoietic
stem cells or HSCs) are currently the only type of stem cell commonly used to treat human
disease. Doctors have been transferring HSCs in bone marrow transplants for over 40 years.
More advanced techniques for collecting HSCs are now used to treat leukaemia, lymphoma and
several blood disorders.
The clinical potential of adult somatic stem cells has now also been demonstrated in the
treatment of some other diseases, including diabetes, Parkinson’s disease and advanced kidney
cancer. For example, in 1999 scientists in the USA removed 10–15 neural stem cells from a
Parkinson’s disease patient and used them to reproduce 6 million dopaminergic neural stem cells
in culture. These were reintroduced into the patient’s brain tissue, producing a 62% increase in
dopamine uptake and a 40–50% improvement in certain motor tasks.
However, these newer uses of adult somatic stem cells have involved studies with very limited
numbers of patients.
Embryonic stem cells have not been used to treat any human diseases yet, but are thought to
offer potential cures and therapies for many devastating diseases. Scientists first started studying
embryonic stem cells in the late 1990s, so this area of stem cell research is at a particularly early
stage.
Q5. How are embryonic stem cells stimulated to differentiate into specialised cells?
A. Providing the embryonic stem cells are grown under certain conditions, they remain
undifferentiated. However, if they are allowed to clump together to form embryoid bodies, they
begin to differentiate spontaneously, forming specialised muscle cells, nerve cells, and many
other cell types. Although this spontaneous differentiation is a good indication that a culture of
embryonic stem cells is healthy, it is not an efficient way to produce cultures of specific cell
types.
To generate specific types of differentiated cells — heart muscle cells, blood cells, or nerve cells,
for example — the researcher needs to control the differentiation of embryonic stem cells. They
can change the chemical composition of the culture medium, alter the surface of the culture dish,
or modify the cells by inserting specific genes. Through years of experimentation scientists have
established some basic protocols or ‘recipes’ for directing how embryonic stem cells differentiate
into some specific cell types.
If scientists can reliably direct the differentiation of embryonic stem cells into specific cell types,
they may be able to use the resulting, differentiated cells to treat certain diseases at some point in
the future. Diseases that might be treated by transplanting cells generated from human embryonic
stem cells include Parkinson's and Alzheimer's disease, diabetes, traumatic spinal cord injury,
stroke, Purkinje cell degeneration, Duchenne's muscular dystrophy, heart disease, osteoarthritis,
rheumatoid arthritis, and vision and hearing loss.
International Society of Stem Cell Research Aug 2004 http://www.isscr.org/
World Stem Cell Map. http://www.mbbnet.umn.edu/scmap.html