Stem Cells
What Are Stem Cells?
By Jeanna Bryner - Live
Science Managing Editor
The term "stem cells" has become
part of the mainstream lexicon, likely to be overheard in conversations
anywhere from a baseball game to cocktail get-togethers.
Along with phrases such as "that's just
immoral" or "stem cells could be the end-all cure," one could
easily weave in some technical tidbits about these microscopic, yet
significant, cells.
Stem cells are considered the
"engine" cells of regeneration in that they are self-renewing and
able to duplicate, or clone, themselves.
These special cells are used in the rapidly
growing field of regenerative medicine to halt or even reverse chronic
diseases.
Regenerative medicine seeks to repair or
replace tissues or organs that have been damaged by trauma, disease or
congenital defects, according to the McGowan Institute for Regenerative
Medicine at the University of Pittsburgh.
Embryonic stem cells are considered
pluripotent, meaning they can give rise to all of the cell types that make up
the human body.
Cord and adult stem cells are multipotent,
which means that they are able to develop into more than one cell type, but
they are more limited than pluripotent cells, according to NYSTEM (New York
Stem Cell Science).
In the United States, cord and adult stem
cells are the only ones used in regenerative medical procedures.
Due to ethical controversy, embryonic stem
cells are not used in clinical practice but can be used for research purposes.
Adult stem cells
Adult stem cells — which can be taken from
bone marrow, blood or fat — are mostly free of ethical controversy, but they
have limited potential.
As we get older, not only do our stem cells
lose functionality, but we have far fewer of them. Researchers estimate that
newborns have 40 times more stem cells in their bone marrow compared to a 50-year
old, according to a 2009 study in the Journal of Pathology.
In addition, adult stem cells may be subject
to DNA abnormalities caused by sunlight, toxins and errors associated with making
more DNA copies over the course of a lifetime, according to the National
Institutes of Health (NIH).
Cord stem cells
Cord stem cells can be harvested from the
umbilical cord after birth with the mother's permission.
This tissue, which is typically discarded,
can be donated to science for use in research or medicine, or placed in a cord
bank in case the mother or child may need it one day.
Cord stem cells are much more efficient at
replicating once removed from the body compared to adult stem cells.
For example, when placed in a petri dish with
the proper nutrients, one cord stem cell will multiply into 1 billion cells in
30 days, whereas one adult stem cell will multiply into only around 200 cells
in 30 days, according to a 2011 study published in the journal Orthopedics.
Doctors use cord stem cells to treat
autoimmune conditions, such as lupus, rheumatoid arthritis and multiple
sclerosis, as well as chronic infections such as HIV, herpes and Lyme disease,
according to AMA.
Embryonic stem cells
Embryonic stem cells hold the most promise
for treating diseases, but heated debate abounds over the ethics of using them.
Human embryonic stem cells are derived from
eggs fertilized in vitro (outside of the body) and are somewhat pristine.
These pluripotent stem cells are prized for
their flexibility in being able to morph into any human cell.
The resulting batch of cells is referred to
as a stem-cell line.
The NIH said 64 embryonic stem-cell lines
existed as of August 2001 when President Bush announced the federal policy
describing the constraints on funds for stem-cell research.
In March 2009, however, President Obama
officially removed the restrictions placed by President Bush on federal funding
for research on embryos.
Although it's been contested, the policy
remains in effect with strict guidelines in place by the NIH.
Induced pluripotent stem cells
Scientists can now reprogram adult stem cells
to become more like embryonic stem cells.
These are known as induced pluripotent stem
cells (iPSCs). But since iPSCs are still adult stem cells, they carry the risk
of having abnormalities.
Much more research is needed on iPSCs, but scientists hope to use them in transplantation medicine, according to the NIH.
Jeanna
Bryner
Live
Science Editor-in-Chief
Jeanna
is the editor-in-chief of Live Science. Prior to this role, she served as the
site's managing editor, and before that a reporter for both Live Science and
Space.com. Previously she was an assistant editor at Scholastic's Science World
magazine. Jeanna has an English degree from Salisbury University, a Master's
degree in biogeochemistry and environmental sciences from the University of
Maryland, and a science journalism degree from New York University.
https://www.livescience.com/32369-what-is-a-stem-cell.html
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