An obscure California biotech company says it has cloned the first embryos from adult human DNA. It's a claim that has been made by frauds and crackpot cults in the past, but the news been greeted with a sceptical welcome by other scientists.

The new research by Stemagen appears in the second division peer-reviewed journal Stem Cells. The firm says it replaced the nuclear genetic material in unfertilised human eggs with DNA from adult skin cells.

Stemagen wasn't able to harvest stem cell lines from the embryos it created, which is the point of "therapeutic cloning". It says it has painstakingly verified that they are genetically identical to the two male test subjects, however.

Following the Korean stem cell fraud scandal, human cloning claims are now greeted with special caution by the scientific community. Hwang Woo-suk duped the peer review system with his fabricated results in 2005. As well as falsely claiming to have grown embryos cloned from adults, Hwang said he had isolated their stem cells.

If verified, Stemagen's work won't be the first time the cloning technique (somatic cell nuclear transfer) has been successful in humans. Other groups have implanted DNA from later stage embryos.

It would nevertheless mark a minor breakthrough. Using adult DNA holds the promise of a personal supply of genetically identical stem cells, that scientists believe could be used to treat a catalogue of illnesses.

But progress in applying cloning techniques to humans has been painfully slow. It's almost 12 years since the birth of Dolly the sheep.

George W Bush's moratorium on federal funding of new stem cell lines hasn't helped the field in the US. Part of the problem worldwide has been the low supply of human eggs for research. The UK's Human Fertility and Embryology Authority yesterday approved a brace of projects to implant adult DNA into animal eggs to help tackle the shortage.

Other research groups are focused on turning back the clock on normal adult cells. If cells can regain the potential to develop into any other cell type (pluripotency, the property that makes embryonic stem cells so powerful) there would be little need for embryos or therapeutic cloning in stem cell research. ®

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