Oct. 13, 2006 — Do adult and embryonic
stem cells have different therapeutic potential?
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Response
by Fernando Camargo
Whitehead Fellow |
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Human embryonic and adult stem cells each have advantages
and disadvantages regarding potential use for cell-based
regenerative therapies.
First, adult and embryonic stem (ES) cells differ in
the number and type of differentiated cells types they
can become. Embryonic stem cells are pluripotent, which
means they can become all cell types of the body. Adult
stem cells are generally limited to differentiating
into specialized cell types of their tissue of origin.
Second, ES cells have an unrestricted capacity to proliferate
in culture. In practice, this means that we could get
an unlimited number of ES cells or their differentiated
cell products for potential therapeutic applications.
Adult stem cells on the other hand, seem to be restricted
in their capacity to expand in the test tube. Alternatively,
this could mean that scientists have not identified
the right cocktail of factors that allow for the amplification
of these cells in culture. Intense research is aimed
at trying to determine the appropriate conditions for
the maintenance and expansion of different adult stem
cells.
Third, ES cells derived from a donor introduced into
a patient could cause transplant rejection. Adult stem
cells in theory could be isolated from the same patient,
then either expanded or manipulated and re-infused into
the same patient without any immunological complications.
However, a procedure known as somatic cell nuclear transfer,
commonly referred as “therapeutic cloning”
could allow for the generation of ES cells that are
a perfect genetic and immunological match to individual
patients. There is currently a great ethical and scientific
debate over the nature of this procedure.
It took approximately 25 years for adult stem cell therapy
to emerge as a routine clinical application for a narrow
range of diseases. It is not known how long it will
take for embryonic stem cells to become useful therapeutically
or whether that will ever happen. However, it would
be unwise to ignore the potential for either adult or
embryonic stem cells to result in meaningful new approaches.
Adult and embryonic stem cells are complementary subjects
of research and studying them side-by-side offers the
greatest potential to rapidly generate new therapies.
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