Stem cells formed from skin
2007-12-24 10:15
Washington - A third team of
researchers has found a way to convert an ordinary skin cell
into valued embryonic-like stem cells, with the potential to
grow batches of cells that can be directed to form any kind of
tissue.
Their study, published on Sunday in the journal Nature,
shows the approach is not a rare fluke but in fact something
that might make its way into everyday use.
Scientists hope they are starting an age of regenerative
medicine, in which people can get tailor-made treatments for
injuries, diseases such as Parkinson's and diabetes, and in
which scientists can study disease far better than before.
Dr George Daley of Harvard Medical School and Children's
Hospital Boston and colleagues got their skin cells from a
volunteer, whereas the other two teams of researchers who have
accomplished the feat got theirs from commercially available
cells grown in labs - a seemingly small difference, but one
Daley says shows it is feasible to get cells from any
volunteer.
"Ours is the only group to go from skin biopsy to cell
line," Daley said in a statement.
They said they are now working to generate the so-called
induced pluripotent stem cell or iPS cells to match a variety
of diseases.
Daley cautioned the approach is not ready to test in
people. The researchers use viruses called retroviruses to
carry in four genes that transform the skin calls back into
their primitive and malleable state.
And when injected into mice, the human iPS cells often
formed tumours. Daley's team is afraid this method might cause
cancer or other unforeseen problems in human beings.
They also reprogrammed mesenchymal stem cells, a distinct
adult stem cell type isolated from bone marrow that is the
precursor of fat, bone and cartilage.
Work continues
Daley said his team would also continue to work with true
embryonic stem cells, taken from days-old embryos. While their
use is controversial because it involves the destruction of the
embryo, most stem cell experts say it is essential to continue
to study them.
"Understanding how to derive stem cells from embryos may
teach us how to make the reprogramming process that much more
efficient," Daley said.
It was by studying embryonic stem cells that researchers
learned which genes are needed to make ordinary cells act in
the same way. Daley's lab used four genes and discovered that
two were essential for turning back the clock and making the
skin cells act like embryo cells, and two others helped them
grow efficiently.
His team also converted foetal and embryonic cells into
various cell types, and found these were far easier to work
with.
"The fact that embryonic and foetal cells convert more
efficiently than adult cells was suggested in mouse studies but
the pattern is quite apparent with human cells," Daley said.
"This suggests that there are many aspects of the biology of
reprogramming we still need to understand to make the process
more efficient."