Is therapeutic cloning on the skids?

Is the juggernaut of therapeutic cloning grinding slowly to a halt? Recently (Tuesday, May 6) a bill authorising it in Western Australia failed on a conscience vote in the upper house by a vote of 18 to 15. WA Premier Alan Carpenter may use it a trigger for an early poll. For local supporters of the controversial technique, it was a bitter blow. Similar acts were preceded by impassioned debate in Canberra and in Victoria, Tasmania, New South Wales, Queensland and the ACT - but in the end therapeutic cloning always cruised through.

The decisive factor seems to have been a brilliant new technique in stem cell science that matches the promise of therapeutic cloning without its heavy ethical baggage. The creation of “induced pluripotent stem cells” (iPS cells) was announced by Japanese researcher Shinya Yamanaka last November - and overnight both the medical and political landscape changed dramatically.

The WA vote marked the first time that cloning has been put to the vote since this discovery. It will hearten opponents in the UK, where the issue is threatening to tear Gordon Brown’s government apart.

Therapeutic cloning involves creating a human embryo by injecting a patient’s DNA into a woman’s egg, allowing it to develop, killing it, and extracting “pluripotent” embryonic stem cells. These can develop, at least theoretically, into any cell in the body. By contrast, Yamanaka’s technique begins with a patient’s skin cell. By introducing a clever combination of precisely targeted retroviruses, he alters key genes which “reprogram” the skin cell to a pluripotent state. No need to beg or pay women for their eggs. No destruction of embryos. No ugly battles with politicians. It is a development so simple, so clever and so momentous that Yamanaka is being mentioned as a candidate for a Nobel Prize.

The political consequences are obvious. Some politicians care nothing for the dignity of embryos; some care passionately. But most feel that creating and sacrificing embryos for the sake of cures for dread diseases is a necessary evil. Yamanaka’s breakthrough gives these fence-sitters a way out - cures without ethical controversy.

Significantly, induced pluripotent stem cells featured in the speeches of at least three Western Australian MLCs. The new development might persuade South Australian MPs to balk at endorsing cloning, too, when they debate their own bill.

Yamanaka’s achievement is not the sort of good news that withers under the glare of peer review from hostile colleagues. On the contrary, according to the authoritative journal Nature Reports Stem Cells, "The enthusiasm with which the highest-tier ES cell [embryonic stem cell] scientists have turned to reprogramming speaks volumes".

The scientist who first isolated human embryonic stem cells, James Thomson, of the University of Wisconsin, calls it the end of an era. “If you can’t tell the difference between iPS cells and embryonic stem cells [ESC], the embryonic stem cells will turn out to be an historical anomaly,” he says. Ian Wilmut, the Scot who cloned Dolly the sheep, has also jumped ship.

The switch in Thomson and Wilmut’s allegiance has little to do with ethics. They see only one thing wrong with embryonic stem cells: they don’t work too well. Much like a new computer operating system which displaces a clunkier rival, iPS cells are rapidly making cloned stem cells obsolete.

One important advantage is that iPS cells are a 100 per cent match for the patient. Cloned cells, on the other hand, contain mitochondrial DNA from a woman's egg. This makes quality control very difficult and will lead to problems with rejection. Therapeutic cloning also requires an abundant supply of eggs. This could eventually entail exploiting poor women, a possibility which cast another shadow over the bill for WA MLCs.

Of course, iPS cells have problems. Japanese researcher Shinya Yamanaka developed them by using retroviruses and gene factors which could cause cancers. But scientists are very confident that the cancer hurdle will disappear.

"It’s going to happen sooner than people think," says Richard Young, of the Whitehead Institute, one of America’s leading stem cell research centres. And Nature Reports Stem Cells is optimistic: "A cadre of talented young investigators trained on ES cells and ready to surpass their mentors is chafing at the bit. As a result of this ferment, the convergent view of numerous leaders in the field is that the retroviral delivery problem will be solved within a year or so."

Despite the bubbling interest in iPS cells, most stem cell scientists still insist that research on embryos must not be stopped. As a recent editorial in New Scientist puts it, "ESCs remain the gold standard for pluripotent class, and cloning remains the gold standard for developmental reprogramming." So the debate in the professional journals is bound to continue.

But now that the purpose of creating and destroying cloned embryos has shrunk from cures for dread diseases to blue sky research and drug testing for multinational pharmaceutical companies, politicians everywhere will be having second thoughts about the wisdom of casting a vote for cloning.