Pod people may look a lot like the real thing, but — as the fictional town of Santa Mira finds out in Invasion of the Body Snatchers
— they are disastrously different. The
same may be true for reprogrammed
These cells are designed to mimic
embryonic stem cells and are grown in
lab dishes by researchers, not pods by
aliens. But scientists now worry that
reprogrammed cells, like the duplicates
that invaded Santa Mira, may not be
wholly satisfactory replacements.
New research suggests that impor-
tant differences may separate the two
kinds of cells. Such differences could
impair the ability of reprogrammed
cells to make other cell types, which doc-
tors hope to use to repair diseased and
damaged tissues. Other limitations of
the reprogramming process could leave
transplanted cells more susceptible to dis-
eases such as cancer, some scientists fear.
Not like the other
Embryonic stem cells are pluripotent,
meaning they can become any type of
cell. But isolating stem cells destroys the
embryo from which they come, raising
ethical concerns and funding barriers.
Reprogramming may not produce
exact embryonic stem cell replicas
In 1996, the Dickey-Wicker Amendment banned federal funding for
research that harmed human embryos.
President George W. Bush allowed
researchers to work with a small number of existing human embryonic stem
cell lines, and President Barack Obama
later opened research on newly created
lines, provided they were made with
private money. Now a federal court is in
the midst of deciding whether Obama’s
policy violates Dickey-Wicker.
When scientists learned that a few
proteins could reprogram a skin cell into
a cell that appeared indistinguishable
from a stem cell ( SN: 11/24/07, p. 323),
there was great hope that the ethical
considerations swirling around embryo-derived stem cells could be bypassed.
Many expect that research on these new
induced pluripotent stem cells, or iPS
cells, might eventually lead to replacement tissue for sick and injured patients,
no embryo needed.
“There’s a fever to make progress and
translate this into clinical applications,”
says bioinformaticist James Cooper of the
University of California, Santa Barbara.
Teams have already made iPS cells
from skin and blood cells and then
coaxed those iPS cells into becoming
heart muscles and brain and spinal cord
neurons (along with other cell types) in
the lab. Eventually, scientists would like
to transplant tissues grown from these
cells into the body to replace tissues
damaged by heart attacks, accidents or
diseases such as Alzheimer’s.
Reprogramming offers another possibility: Researchers could revert skin
cells from people with a disease into iPS
cells and then study the development of
that disease in a petri dish.
But these hopes all bank on the premise that reprogrammed stem cells are as
versatile and safe as embryonic stem cells.
And niggling differences are making some
scientists question that assumption.
Recent studies show that reprogrammed stem cells carry a molecular
Scientists are starting to question
whether reprogrammed stem cells (col-
ony shown) can fully forget their past.