Source of stem cells: ‘Virgin’ territory for British researchers
Roger Highfiel and Nic Fleming
The Daily Telegraph
Saturday, September 10, 2005
DUBLIN – Human embryos have been created in Britain without using sperm for the first time.
The “virgin conception” embryos, which mark a new way to grow a woman’s cells and tissues for a vast range of treatments, were revealed by an Edinburgh team.
The development is the second time in as many days that U.K. scientists have pushed back the boundaries of reproductive science.
On Thursday, approval was given to experiments to create embryos from three people to develop a novel treatment for a class of genetic disease.
In the short term, the new work will shed fresh light on hereditary diseases, the problems caused by cloning and on what happens when the regulation of genes in development goes awry.
The human embryo in question results not from a fertilized egg but from an egg that has been tricked into dividing, the British Association meeting in Dublin was told by Dr. Paul De Sousa. He now works at Edinburgh University but did the work at the nearby Roslin Institute, where Dolly the sheep was cloned.
It took Dr. De Sousa around 300 human eggs to create half a dozen blastocysts — human embryos that consist of around 50 cells, which can be used as a source of stem cells that can be grown into all 200 or so types of cells in the body.
Although attempts to grow stem cells from the blastocysts have not yet succeeded, as they have in non-human primates, Dr. De Sousa was confident it was only a matter of time. The embryos were grown by a process called parthenogenesis, which means “virgin birth” in Greek.
Although some scientists had thought the use of “parthenotes” in this research would sidestep objections from pro-life groups, Dr. De Sousa said this was not the case. “Someone who has a pro-life outlook will regard any usage of eggs and embryos for non-reproductive purposes as objectionable.”
Most plants can multiply by parthenogenesis, and so do all fungi and many animals, such as corals. But humans, like other mammals, do not because of a gene regulation process called
imprinting. This ensures genes from the mother and father must contribute if development in the womb is to reach term.
Initially, scientists are interested in using cells from parthenotes to shed light on cloning, which disrupts imprinting, and on the links between faulty imprinting and disease.
Parthenogenesis also offers the opportunity to grow cells from a woman who is suffering from a genetic disease, so that a very detailed study can be made of the cellular effects of the disease.
To create the parthenotes, immature human eggs are taken, with consent, from women who have undergone sterilization, and then grown in the laboratory.
Around half can be successfully matured this way and then persuaded to divide with a shock of electricity. But only five in every hundred will grow to the blastocyst stage, and then with only half the usual number of cells.
There are no plans to implant the embryos to create a pregnancy, Dr. De Sousa stressed.
The parthenote retains the full set of DNA from the egg donor and can be used to make her stem cells. If imprinting errors do not interfere, “tissue we could derive from such an egg and embryo would be compatible for transplantation,” he said.
In theory, these stem cells could be used to grow replacement brain tissue for a woman who had developed Parkinson’s disease.
© National Post 2005