Sergio Pistoi
Scientific American
Stem
cells are a bit like wild cards in the body's deck: some can become almost any
other tissue type. For this reason, scientists have hoped that these cells might
eventually be used to rebuild tissues damaged by disease, trauma or age. Now researchers
from New York and Yale Universities have discovered remarkably versatile stem
cells in the bone marrow of adult mice. They describe their findings in this month's
issue of Cell.
Until recently, scientists believed that the only truly
versatile stem cells were those derived from early-stages embryos. But the scarcity
of these cellsÑalong with numerous ethical issuesÑhas limited their use in humans.
Stem cells derived from adults, on the other hand, were always considered too
specialized, capable of giving rise to only a few tissue types.
Even adult
bone marrow stem cells, however, can form bones and muscles, as recent studies
have shown in human and mice. So to see just how versatile these cells could be,
the researchers purified stem cells from the bone marrow of male mice, selecting
those with the highest potential to multiply. Then they transplanted one of these
cells each to female mice whose bone marrow had been previously destroyed by radiation.
By using color dyes that make the Y chromosome (which only male cells possess)
visible under special light, the researchers could see which cells in the females
were then derived from the transplant and which were not.
Eleven months
after the transplant, cells bearing the Y chromosome not only appeared in the
bone marrow and blood of the females, but had also contributed to the regeneration
of several other tissues, including the lungs, stomach, intestines, liver and
skin. Surprisingly enough, bone marrow stem cells were able to form epithelial
tissues, such as those in the skin or lungs, which have very different developmental
origins. "It is astounding that there are cells in our bone marrow that can become
so many different cell types," Diane Krause of the Yale Cancer Center says. These
results could help researchers develop therapies for many different human diseases
and injuries, but she cautions that this field is very much in its infancy, and
much more work is needed on both embryonic and adult-derived stem cells to move
ahead. |
