Scientists Clone Mice from Adult Skin Stem Cells
Pastor Dale Morgan
Scientists Clone Mice from Adult Skin Stem Cells*
Using a technique called nuclear transfer, mice were cloned using adult
skin stem cells (right) and a more differentiated type of skin cell
(left). The mouse on the right is almost two years old and the mouse on
the right is one and a half.
New York NY (SPX) Feb 14, 2007
For cells that hold so much promise, stem cells' potential has so far
gone largely untapped. But new research from Rockefeller University and
Howard Hughes Medical Institute scientists now shows that adult stem
cells taken from skin can be used to clone mice using a procedure called
nuclear transfer. The findings are reported in the Feb. 12 online
edition of the Proceedings of the National Academy of Sciences.
Embryonic stem cells have received the most press for their potential to
generate healthy cells and tissues that could replace damaged or
diseased organs.
"Scientists are well-aware that tissue derived from someone else's
embryonic stem cells would be recognized as foreign and rejected by the
patient," says senior co-author Elaine Fuchs, the Rebecca Lancefield
Professor at Rockefeller and a Howard Hughes Medical Institute
investigator. "This is one of the reasons why scientists have focused so
much attention toward using nuclear transfer, which would allow us to
use adult stem cells from the same patient rather than those harvested
from an unrelated embryo."
Fuchs and her colleagues tested the method in adult stem cells taken
from the skin of mice.
Using purification methods developed in Fuchs' Laboratory of Mammalian
Cell Biology and Development, postdocs Valentina Greco and Geraldine
Guasch isolated stem cells from the mice's hair follicles. They gave
these stem cells to Jinsong Li, a postdoc in Rockefeller's Laboratory of
Developmental Biology and Neurogenetics, headed by senior co-author
Peter Mombaerts. To execute the nuclear transfer procedure, Li took
unfertilized mouse oocytes and replaced the nucleus of each oocyte with
a nucleus from these adult skin stem cells.
A main hurdle in nuclear transfer with adult cells has been its
efficiency -- out of a hundred attempts, only a handful may succeed --
with reported success rates never reaching into double digits. "The
efficiency of nuclear transfer is very low," says Li. "Using purified
adult skin stem cells as our source of nuclei, we have found that higher
nuclear transfer efficiencies can be achieved."
Greco, Guasch and Li compared the cloning efficiency of adult skin stem
cells with that of more differentiated skin cells and also with cumulus
cells -- the cells that surround a developing oocyte and have
traditionally been the preferred cell type for nuclear transfer. The
stem cells gave the best efficiency, yielding 19 pups, nine of which
grew up into normal, healthy, breeding adult mice.
This is not the first time scientists have tried to use adult stem cells
to clone mice. Experiments using adult hematopoetic stem cells -- the
cells in the bone marrow that all blood cells are derived from -- were
reported last year. But their conclusions were confusing, says
Mombaerts, and there are no reports on using adult stem cells for
reproducible cloning of mice that survive until adulthood. By using
cells from the same mouse and performing the experiments on the two
successive days, the Rockefeller scientists could directly compare adult
stem cells with other cell types.
Nuclear transfer can also be used to make embryonic stem cell lines, a
process which can be done in a tissue culture dish and which is simpler
and more efficient than generating a cloned mouse. Although this
procedure has not yet successfully generated human embryonic stem cell
lines, once technological hurdles are overcome, it may be possible in
the future to use a patient's skin stem cells to tailor make embryonic
stem cell lines, circumventing the problem of immune rejection.
Such stem cells might also be used to study a variety of different
diseases, for which patient tissue is often hard to come by.
"There are many diseases, such as liver, pancreatic and
neurodegenerative disorders where researchers are only able to obtain
affected tissue from autopsies," says Fuchs.
If on the other hand, scientists are able to generate embryonic stem
cells from the skin of a patient, for example an Alzheimer's patient,
these embryonic stem cells might be used in the laboratory to enable
scientists to generate neurons and study the neurodegenerative process.