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The year is 1998. A group of US scientists has announced it is the first to isolate human embryonic stem cells - the starting point of all cells before they transform into specialised entities that drive our heart, lung or brain. As with many scientific achievements the team understates its work's significance. The last line of its abstract in the eminent journal Science reads: ''These cell lines should be useful in human developmental biology, drug discovery, and transplantation medicine.'' CSIRO stem cell researcher Andrew Laslett describes this moment as the ''twitching point''. It was the first time scientists seriously considered it might be possible to manufacture large amounts of these primitive cells and coax them into other tissue cells with the ultimate goal of regrowing tissues and organs to treat diseases. ''This is when things started to become interesting,'' Laslett says. Scientists quickly realised stem cells extracted from IVF embryos - the process used by the US group - would never be an exact genetic match to a patient, a stumbling block in their ultimate goal to personalise tissue transplants. But if stem cells could be obtained from early embryos created with an individual's own cells - a technique known as somatic nuclear cell transfer, or therapeutic cloning - the problem would be solved. An international race to obtain cloned embryonic stem cells kicked off. On Thursday, a team led by Professor Shoukhrat Mitalipov from Oregon Health & Science University announced it had finally achieved the feat. The team took the nuclei from the skin cell of an eight-month-old baby and inserted it into a donor egg where the nucleus had been removed. The resulting embryos, and the stem cells that were extracted, are genetically identical to the baby. ''This study is a breakthrough development that overcomes a major scientific hurdle with significant implications for potentially treating a range of disease,'' Bryce Vissel, the head of the neuroscience research program at the Garvan Institute of Medical Research, says. Many scientists, including Australians, have tried to grow cloned embryonic stem cells, considered the holy grail of stem cells because they can be genetically matched to patients and don't require risky gene modifications. While the technique has succeeded in animals such as mice and monkeys, many believed it was impossible in humans, until this week. ''This has been long sought after by so many groups,'' says University of Melbourne stem cell scientist Martin Pera, whose team was the second in the world to isolate embryonic stem cells from IVF embryos and the first to coax them into brain cells in the lab. ''This has been the goal ever since the first human embryonic stem cells were described 15 years ago,'' he says. But stem cell research has moved on since 1998. Researchers have figured out how to transform adult cells to a very similar state as embryonic stem cells, known as induced pluripotent stem cells, or iPS, without embryos. Andrew Laslett says it is too early to predict what the new stem cell technique will mean for medical treatments. Clinical trials of cell therapies to treat disorders such as macular degeneration and spinal cord injuries are already under way. These therapies use stem cells extracted from IVF embryos so it is unlikely the new technique will influence their outcome. The new method has already sparked ethical discussions, some old, others new, especially from those who oppose the creation of embryos to later be destroyed. Deriving stem cells from cloned embryos will require a constant supply of eggs from women willing to donate them. But perhaps the most controversial aspect of the new technique, which develops an embryo in an almost identical process to that used to clone Dolly the sheep, is that it places scientists a step closer to being able to clone a human baby. ''I am a bit jealous of them,'' Sydney stem cell scientist Tomas Stojanov says of his American colleagues' success. As the CEO of Genea, formally Sydney IVF, Stojanov has led a group attempting the same breakthrough since 2008. ''We've spent a lot of time, money and good researchers on this goal,'' he says. There are two main reasons, Stojanov says, why the Oregon team succeeded where he, and many others, failed. It used high-quality eggs and incubated them in a special ingredient that stabilised the cells during development, he says. Their miracle elixir - caffeine. In Australia, Stojanov's is the only group with a licence to attempt stem cell extraction from cloned human embryos. But the team is only allowed to clone its embryos using low-grade IVF eggs that can't be used in fertility treatments. Stojanov says this limitation may be why his group failed to achieve the cloning milestone. Regardless of how stem cells are derived, the main motivation of the research has always been to create therapeutic treatments for people with crippling diseases such as Parkinson's, cerebral palsy, Duchenne muscular dystrophy, or spinal cord and brain injuries. ''It's really only now that these predictions are starting to come through,'' Laslett says. Most cell therapy clinical trials are based on stem cells derived using surplus IVF embryos, the same technique first described in 1998. Groups such as US company Viacyte, which is working on a diabetes therapy to replace insulin injections, have spent years perfecting experiments to produce the specific cell type they desire. ''A lot of people made the mistake of thinking stem cells are a black box and all you need is to throw a few growth factors at them and you'll get the cells you want,'' Viacyte's vice-president of science and technology, Australian Allan Robins, says. ''But you have to taken them through a lot of very defined steps, and you have to instruct them that you want pancreatic cells not something else like lung cells,'' he says. Robins suspects that given the years groups like his have taken to homogenise their cell lines, the new method of obtaining stem cells from cloned embryos will not be used for medical treatments any time soon. The main disadvantage of stem cells obtained from spare IVF embryos is they will almost never be an exact genetic match to a patient. A group of Japanese researchers overcame this problem in 2007 when it created embryonic-like stem cells without using embryos. Induced pluripotent stem cells are coaxed back to their embryonic state from adult cells. To do this, scientists introduce viruses into the cell that switch on specific reprogramming factors that reverse the cells' development. As well as being an exact genetic match to the patient, iPS cells are quicker and cheaper to produce. They won their inventor, Shinya Yamanaka, the 2012 Nobel prize. Induced pluripotent cells also sidestep the thorny ethical issue of creating embryos, only to destroy them, for research. But Stojanov says iPS cells are inferior to cloned embryonic stem cells in a similar way a plastic watch cannot compare with a Swiss-made timepiece. ''Both do a good job telling the time,'' he says. iPS cells can be genetically matched to a patient so they will be a good tool to screen drugs, he says. ''But if you are thinking about using stem cells for therapeutic applications then you need to have the gold standard.'' The long-term safety and stability of iPS cells is untested, he says. ''There's always a risk when you genetically modify any cells.'' Cloned embryos overcome this problem. Martin Pera says one important application for these stem cells will be to treat mitochondrial diseases, a group of mostly devastating diseases that are passed from mother to child. Therapeutic cloning can replace the faulty genes in the mother's egg with donor DNA while retaining the nuclear DNA that makes individual's unique. Since Dolly the sheep was born in mid-1996, cloning and stem-cell research has weathered many ethical debates, the most persistent being the destruction of embryos. Nicholas Tonti-Filippini, head of bioethics at the John Paul II Institute for Marriage and Family, says it is too early to conclude whether cloned embryonic stem cells will lead to therapies, but the invention of induced pluripotent stem cells makes the technique unnecessary. ''I don't support the destruction of human embryos and I think it is a very sad way for us to go in Australia,'' he says. The ban on human embryo research in Australia was lifted by Federal Parliament in 2006. The decision followed the 2005 Lockhart review of human cloning and human embryo research legislation, chaired by the late Federal Court judge John Lockhart. Loane Skene, a law professor at the University of Melbourne and member of the Lockhart committee, says the group considered whether it was prudent to create and destroy embryos for research. It concluded that these early embryos, known as blastocysts, were not like those formed during fertilisation, but biological constructs containing only one set of nuclear DNA. ''We saw it as being like a skin graft,'' she says. ''You take one part of yourself and put it on another part of yourself for treatment.'' Skene says the more pertinent ethical issue with the new stem cell technique is that it will require a constant supply of eggs from women willing to donate them. ''This technique is so new that a lot of eggs are going to be needed to test it,'' she says. ''And eggs are very precious.'' Eggs can be donated by two groups of women; those already undergoing IVF treatment or women prepared to have their ovaries overstimulated and their eggs removed via an operation. There is an argument for compensating women for the procedure, she says, but paying women for eggs is banned in Australia. The most divisive ethical issue sparked by the breakthrough technique surrounds the potential to clone humans, which is illegal in most countries, including Australia. Cloned embryos use the same somatic nuclear cell transfer procedure that created Dolly. The Oregon team is the first to grow cloned human embryos that survived long enough to extract stem cells. ''It is at a very similar stage where you could implant it back into a surrogate and theoretically get a human,'' CSIRO's Andrew Laslett says. Although this feat is still far from technically feasible, the Australian community vehemently opposes such research, as suggested by the 15-year jail sentence that would await any scientist who succeeded.

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