US team takes Japanese stemcell breakthrough a step further

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http://ca.news./s/afp/071223/health/health_stemcells

Sun Dec 23, 2:52 PM

PARIS (AFP) - A team of American scientists reported Sunday 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.

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 on Sunday in Nature, a team led by 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.