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Where
do the different cells and tissues in your body come from? Incredible
as it seems, every cell was produced by mitosis from a small number
of cells called stem cells. Stem cells are unspecialized cells that
have the potential to differentiate—to become specialized
in structure and function—into a wide variety of cell types.
In early embryonic development, stem cells produce every tissue
in the body. Evidence indicates that stem cells also are found in
adults. Stem cells in the bone marrow, for example, produce more
than a dozen types of blood cells, replacing those lost due to normal
wear and tear.
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Stem
Cells in Medicine
Although
your body produces billions of new cells every day, it is
not always able to produce the right kind of cell to replace
those damaged by injury or disease. For example, the body
is not able to produce new neurons to repair serious spinal
cord injuries, such as those that cause paralysis. Because
of this, at present, there is no way for doctors to restore
movement and feeling to people who are paralyzed.
Stem
cells may be the perfect solution to this problem. Recently,
researchers have found that implants of stem cells can reverse
the effects of brain injuries in mice. There is hope that
the same will hold true for humans and that stem cells might
be used to reverse brain and spinal cord injuries. It also
may be possible to use stem cells to grow new liver tissue,
to replace heart valves, and to reverse the effects of diabetes.
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Sources
of Stem Cells
Human embryonic stem cells were first isolated in 1998 by scientists
in Wisconsin. Many scientists are now experimenting with ways to produce
such cells by transferring adult cell nuclei into the cytoplasms of
egg cells. However, since these techniques use or produce early human
embryos, they also raise serious moral and ethical questions. Because
of such issues, embryonic stem cell research is highly controversial.
Researchers
have also found that nerve, muscle, and liver cells sometimes can
be grown from adult stem cells isolated from the bone marrow and
other tissues in the body. Experiments such as these, although still
in the early stages of development, may usher in a new era of therapy
in which replacement tissue is grown from a person's own stem cells.
Research
and Decide
Use library
or Internet resources to learn more about stem-cell research. Then,
write a brief report on how this technology will impact the future
of medicine |