Scientists clone embryos from adult monkey

Scientists have for the first time cloned embryos from an adult monkey, paving the way for major advances in human therapeutic cloning and stem cell research.

Before now, no one has provably succeeded in cloning viable primate embryos using the "Dolly the Sheep" method of transferring DNA from an adult cell.

The American team not only created surviving embryos, but generated two culture lines of embryonic stem cells (ESCs) from them.

ESCs extracted from early-stage embryos have the potential to develop into virtually any kind of body tissue.

Scientists believe they could be used in future to treat degenerative diseases such as Parkinson's and Type 1 diabetes, without any risk of a graft being rejected by the patient's immune system. Human ESCs would also be invaluable to scientists investigating the causes of disease.

The US scientists led by Dr Shoukhrat Mitalipov, from Oregon Health and Science University in Beaverton, produced the embryos and stem cells from skin cells donated by 14 rhesus macaque monkeys.

Twenty "blastocysts" - early embryos consisting of a ball of cells - were created, from which the researchers derived two separate lines of embryonic stem cells.

The technique used was an adaptation of that employed by scientists at the Roslin Institute in Edinburgh to produce Dolly the Sheep, the first mammal ever cloned from an adult cell, in 1996.

Nuclear DNA from the adult skin cells was inserted into monkey eggs whose own genetic material had been removed. The eggs were then chemically stimulated to trigger cell division.

Although many animals have been cloned in this fashion since the birth of Dolly, the technique has never before been shown to work for primates.

In 2004, South Korean cloning pioneer Dr Hwang Woo-suk claimed to have cloned human embryos and used them to obtain stem cells. It later emerged that Dr Hwang had fabricated his work and he was dismissed in disgrace from his professorship at Seoul University.

A year later, British scientists at Newcastle University announced that they had cloned embryos from human eggs. Unfortunately none of the four clones lived longer than five days, and it proved impossible to derive stem cells from any of the embryos.

The US breakthrough was due to be published in a forthcoming edition of the journal Nature. But amid growing excitement and speculation, the journal decided to release the details today.