'Egg sharing' and 'hybrid embryos' offer hope for stem cell research

Two announcements made last week have important implications for the future progress of human stem cell research in the UK. Both were related to research involving 'therapeutic cloning' - the creation of stem cell lines from patients with incurable diseases (such as Alzheimer's and cardiomyopathy) in order to study the genetic mechanisms behind, and the development of, these diseases, and to test new drugs.

Therapeutic cloning requires a technique called SCNT, where the nuclear DNA from an adult cell is placed into an empty egg and the resulting embryo is used as a source of cloned stem cells. A limiting factor in the progress of this research has always been the low number of human eggs available for experimental use. Last year, the Newcastle NHS Fertility Centre and the North-East England Stem Cell Institute (Nesci) launched a controversial 'egg sharing' initiative that offered women half-price IVF in return for them donating half their harvested eggs to research. This week it was announced that seven of the 12 women that were selected for the scheme are pregnant, including one who is expecting twins.

Professor Alison Murdoch, who is leading the project, said: 'We're delighted that this scheme has enabled so many couples to have a family from IVF treatment. Their choice to take part in the egg-sharing scheme means that important research is able to progress and we hope these successes will encourage other people to come forward'. Critics of the scheme are concerned about the ethics of trading human gametes for financial reward - selling human eggs or sperm is illegal in the UK - and whether participation reduces a woman's chance of pregnancy.

Meanwhile, the HFEA (Human Fertilisation and Embryology Authority) announced that it has granted a third UK research centre a licence to create 'human-animal hybrid' embryos. The 12-month licence was granted to the Clinical Sciences Research Institute at the University of Warwick for the use of pig eggs in therapeutic cloning. It allows the researchers, led by Professor Justin St John, to transfer human nuclear DNA from individuals affected by cardiomyopathy into pig eggs which contain no nuclear DNA but retain their mitochondrial DNA. This results in embryos that have 99.9 per cent human DNA and 0.1 per cent pig DNA. The research team then plan to use chemicals to remove all traces of pig DNA from the resulting stem cells and replace it with human mitochondrial DNA. If they succeed, it will be the first time animal eggs have been used to create human stem cell lines that are completely free from animal DNA.

The resulting stem cells will also be used to study the genetic mechanisms behind cardiomyopathy. Professor St John explains: 'We will effectively be creating and studying these diseases in a dish. But it's important to say that we're at the very early stages of this research and it will take a considerable amount of time'.