Stem cell primer
Everything you wanted to know about stem cells but were afraid to ask
(PDF
version of the primer)
The why of it
The embryonic stem cells currently available to most scientists are close
to useless.
They fall short for research because they carry the genes of only a narrow
cross section of people.
They're inadequate for disease study because they're from
healthy people and, as a result, lack the mutations predisposing people
to most illnesses.
They are potentially dangerous for use in therapy because they have been
exposed to contamination by mouse viruses.
Given these limitations, scientists would prefer to use nuclear transfer
to customize new embryonic stem cell lines for research and therapy.
Research
By studying how embryonic stem cells develop into mature cells, such
as those that make up our bone, blood and skin, researchers can learn
how those cells function and what goes wrong when they are diseased.
Therapy
Doctors hope to use embryonic stem cells to replace cells damaged from
injury or disease. This approach could help patients with conditions including
Alzheimer's or Parkinson's diseases or spinal cord injury
Disease study
Researchers can use embryonic stem cell lines derived from people with
genetic diseases such as diabetes, cardiovascular disease or various types
of cancers to better understand and treat the diseases.
The basics
What's a stem cell?
A stem cell is a master cell that can create the more specialized cells
in an animal or human. Stem cells from human embryos have the potential
to create any type of human cell. Stem cells from mature humans (often
called "adult stem cells") can create only a subset of cell
types. For example, blood-forming stem cells can make blood cells but
not brain or liver cells.
What's a cell line?
A cell line is a population of identical cells that all originated from
a single cell. Because cell lines multiply, scientists can grow the cells
for their own research and to share with colleagues.
What's at stake?
Government funding restrictions set in 2001 thwart attempts to use stem
cells to develop cures and to learn more about how humans develop. A bill
supported by President Bush and passed twice by the House of Representatives
would criminalize the creation or use of new stem cell lines with a $1-million
fine and 10 years in jail.
What's the controversy?
The stem cells that many scientists consider especially promising for
research and medicine come from early stage embryos called blastocysts.
However, the harvesting process destroys the blastocyst, leading some
people to liken the procedure to the taking of a life.
What does stem cell research have to do with cloning?
The only connection is that creating a new line of stem cells and attempting
to clone an animal have the same first steps: replacing the nucleus of
an egg cell with the nucleus of a mature human cell and stimulating that
egg to form a blastocyst.
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