Researchers have succeeded in creating human embryonic stem cells by injecting DNA from a skin cell into an unfertilized egg, according to a study.

The study is published in the journal Nature.

A team of scientists from the New York Stem Cell Foundation Laboratory created 13 early-stage human embryos that were partial genetic clones of diabetic patients.

At the same time there is an important hitch to the announcement. The copies were not identical since each embryo carried three sets of chromosomes. This meant they were abnormal and wouldn't have been viable if implanted in a womb and carried to term. The researchers would have to eliminate the extra set of chromosomes and effectively create an embryonic human clone for the technique to ever become a viable treatment.

Hope has been present for a long time among scientists to create fresh human tissue and use transplantation to treat a range of ailments, such as heart disease and Parkinson's.

Dolly the sheep, the first cloned mammal, announced in 1997 was cloned using an egg to do the reprogramming trick. Her mother's skin cell was put in another sheep's egg, which no longer had its own DNA-containing nucleus. Ever since, science has been trying to make human blastocysts, the embryonic stage at which stem cells can be harvested. So far the de-nucleated egg approach has not worked in humans. In this study, Dr. Dieter Egli of the New York Stem Cell Foundation Laboratory in New York City and his colleagues were partially able to achieve this by means of a simply not removing the egg's own nucleus.

In 2004, Hwang Woo-suk, a South Korean scientist claimed to have created the first human embryonic clone and derived a stem-cell line from it, but that work was shown to be fraudulent.

Stem cells are basic human cells that can develop into nearly any kind of tissue.