Science News - October 9, 2010

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 stem cells.

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.

ImPerfect
Reprogramming may not produce
exact embryonic stem cell replicas
mimics

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.