Scientists have achieved remarkable new advances in embryonic cloning but unsettling ethical questions remain, writes Dick Ahlstrom, Science Editor
Advances in stem cell technology continue to rush ahead of the ethical concerns surrounding them. Major announcements from teams in South Korea and Britain underline the fact that while we stand on the threshold of lifesaving treatments, the possibility of cloned humans is an increasing danger.
Both countries currently lead the world in the creation of embryonic clones. These are artificial embryos produced using more or less the same technology employed to produce Dolly the cloned sheep some years ago.
But while the cloned embryo used to make Dolly was produced specifically to generate a true clone, the human-related work has more to do with something that can be derived from embryos - embryonic stem cells.
Stem cells are universal cells that can change to form any of the 200 different tissue types in the body. Exposure to certain proteins expressed in the growing embryo cause stem cells to change or "differentiate" into bone and muscle, liver and brain.
Scientists want to experiment on embryos as a way to get more stem cells, given their great promise in the treatment of intractable diseases. The assumption, based on animal experiments, is that stem cells forced to differentiate into specific cell types could be given to a patient to treat a wide range of ailments.
Stem cells changed into pancreatic cells could replace the missing cells that cause diabetes. Differentiated brain cells might be useful against Parkinson's or Alzheimer's diseases.
Scientists are years away from providing these treatments, but initial work shows that stem cells hold much promise. However, the ethical dilemma arises from the fact that harvesting embryonic stem cells unavoidably causes the destruction of an embryo.
Researchers are also experimenting with stem cells taken from adults and from umbilical cord blood, but embryonic cells have delivered the best results so far.
This is why research groups in South Korea's Seoul National University and in Newcastle University are so strongly focused on the use of embryos to acquire stem cells.
Prof Alison Murdoch and Dr Miodrag Stojkovic of Newcastle University announced this week that their team had produced the first human embryonic clones in Britain or by a western nation. The distinction of producing the first human embryonic clones was claimed 15 months ago by Prof Woo Suk Hwang and Dr Shin Yong Moon at Seoul National University.
While Newcastle's achievement is highly significant, the more important cloning advance comes from South Korea. Early last year Hwang's team cloned embryos and then produced self-replicating stem cell lines from them.
Now Prof Hwang and Prof Gerald Schatten from the University of Pittsburgh have significantly increased the success rate for producing embryonic clones and can now genetically tailor stem cell lines to match the original donors.
Hwang's clone success rate in 2004 was about one in 200 tries. In his new study, they increased their efficiency to one in 20 tries.
They found that eggs donated by younger women were three times as likely to succeed than eggs donated by women aged over 30. They also discovered that freshly harvested eggs worked much better than stored egg cells left over from fertility treatments.
Treatments remain some distance in the future, the research team warned. However, the question remains whether people will embrace them when they come or shy away, given the ethical issues surrounding them.