A team of American scientists reported that they had widened
the scope of a Japanese breakthrough in stem cells that many experts
have hailed as the greatest medical achievement of 2007.
In November, Shinya Yamanaka of Kyoto University and colleagues
announced they had reprogrammed human skin cells to have the multiple
potency of stem cells culled from human embryos.
Stem cells are early cells that differentiate into one of the 220
different types of cells in the body.
Medical researchers hope that one day, these cells can be grown in a
lab dish to become specific replacement tissue to replenish organs
ravaged by disease or damaged in accidents or warfare.
Yamanaka's team used a retrovirus to deliver four genes into skin
cells taken from a mouse and an adult human.
Turning the clock back
In essence, this turned the clock back so that these cells lost
their differentiated profile and became so-called induced pluripotent
stem cells, or iPS.
Reporting in Nature, a team led by George Daley of the
Children's Hospital, in Boston, Massachusetts, say they have been able
to use the same four genes to derive iPS from foetal lung and skin
cells, from neo-natal skin cells as well as from skin samples taken
from a healthy human volunteer.
The research is important as it marks a step forward to
"patient-specific" stem cells - in other words, transplanted stem
cells that carry the same genetic code as the patient and thus cannot
be rejected as alien by the body's immune system, they say.
The researchers also found that they could generate iPS without a
cancer gene called c-Myc that has been implicated in tumours in many
lab mice in earlier experiments.
That replicates a similar finding by Yamanaka's own team, published
after the first breakthrough was reported.
The researchers stress, though, that many hurdles lie on the road
ahead before iPS is certified as safe and effective and can be used to
grow replenishment tissue.
"Clinical success with human iPS cells must await the development of
methods that avoid potentially harmful genetic modification," they
write, saying that "a worthy goal" would be to find biochemicals to
replace gene infiltration for inducing iPS. – (Sapa/AFP)
Stem cell research gives hope
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