Scientists get stem cells from cloned human embryos

Scientists have finally recovered stem cells from cloned human embryos, a long-standing goal that could lead to new treatments for such illnesses as Parkinson's disease and diabetes.

A prominent expert called the work a landmark, but noted that a different, simpler technique under development may prove more useful.

Stem cells can turn into any cell of the body, so scientists are interested in using them to create tissue for treating disease. Transplanting brain tissue might treat Parkinson's, for example.

But transplants run the risk of rejection, so more than a decade ago, researchers proposed a way around that: Create tissue from stem cells that bear the patient's own DNA, obtained with "therapeutic cloning."

If DNA is put into a human egg, which is then grown into an early embryo, the stem cells from that embryo would provide a virtual genetic match. So in theory, tissues created from them would not be rejected.

That idea was met with some ethical objections because harvesting the stem cells involved destroying human embryos.

In yesterday's edition of the journal Cell, scientists at Oregon Health & Science University report harvesting stem cells from six embryos created from donated eggs.

Dr. George Daley, a stem cell expert at Children's Hospital Boston who didn't participate in the work, called the new results "one landmark step in a very long journey" toward creating DNA-matched transplant tissue.

Now, Daley said, scientists must compare the cloning approach with another technology that reprograms blood or skin cells directly into substitutes for embryonic stem cells. This approach is technically simpler and doesn't involve embryos.

But these substitute cells show some molecular differences compared with embryonic ones, which has led to questions about whether they can safely be used for treating patients.