However, he said that embryonic stem cells remained the most obvious source of cells for such transplants, as foetal tissue - used in some experiments - was scarce, and so-called "adult stem cells" had never been converted into the right type of brain cells, despite 15 years of research.

BBC: NEWS | Health | Mouse cloned to cure Parkinson's

Thus far, iPS cells have been a less controversial and more acceptable source of stem cells for conservative politicians to promote.

FORBES: The Line Between Embryonic And Pluripotent Stem Cell Research Is Blurring

The issue of cloning and embryonic stem cell research intersect when it comes to possible uses of cloned tissue as a source of stem cells.

CNN: House poised to consider human cloning

Now that the technique appears to work with human cells, the process could be another source of generating stem cells that may ultimately treat patients, says Mitalipov.

CNN: SHARE THIS

But the achievement could establish another important source of stem cells that patients can generate to ultimately treat themselves.

CNN: SHARE THIS

Some researchers have testified before Congress that clones might provide a source of stem cells and compatible DNA for patients in need of stem cell treatment.

CNN: House votes to ban human cloning

Dr Frisen reckons that they may offer several advantages over human embryonic stem cells which, although easier to manipulate, are a controversial source of new tissue because they are still mainly obtained from aborted fetuses.

ECONOMIST: Stem cells

But for others, the promise of stem cell research is outweighed by the moral cost of the source of the cells.

CNN: Looking for middle ground in a minefield