Stem cell technologyThe research institute in Scotland that created Dolly the cloned sheep has begun making so called "virgin birth" embryos that contain genetic material from only one person.
Although the embryos produced at the Roslin Institute are all female, it should be possible to produce a male-only embryo, in effect producing a male "egg".
The advance of stem cell and transplantation technology was discussed yesterday at Trinity College on the final full day of the BA Festival of Science. The possibility of a virgin birth male embryo was raised as well as research into organ transplant material from pigs and how to protect therapeutic stem cells from the immune system at a session titled: "21st century transplantation".
Roslin's Dr Paul de Sousa said the centre had successfully produced six "parthenogenic human embryos", embryos produced using a single cell from a single individual. At least two companies in the US have also produced parthenogenic embryos.
The new embryos did not require the use of animal derived mediums to help the egg or embryo grow and so they represent the "most therapeutically safe of those isolated to date", Dr Sousa said.
Researchers want to produce embryos in order to harvest embryonic stem cells, a form of basic, undefined cell that can change into any of the many cell types found in the body. Researchers believe these can be used therapeutically to reverse disease processes and repair tissues after a heart attack or Parkinson's disease. Harvesting embryonic cells is ethically contentious, however, because it requires the destruction of the embryo.
The six embryos had been brought to the "blastocyst" stage, Dr Sousa said. This is the stage when it becomes possible to recover stem cells.
It is significant that the embryos were produced via parthenogenesis rather than the nuclear transfer technique used to produce Dolly. The latter requires a donor egg and a donor cell.
This new technique only requires a single egg that is allowed to begin division before being arrested and then shocked or treated to begin cell division as though it were fertilised. The resultant embryo will have chromosomes provided only by the woman donor and it is significant that Roslin is already producing these parthenogenic embryos.
The eggs came from a woman who had requested a sterilisation, Dr Sousa said. About five per cent of attempts produce blastocysts, he said, and one in 10 of these will produce self-perpetuating embryonic stem cell lines for research.
The technique could be used to produce "androgenotes", male embryos having chromosomes provided by the father only, he said. Roslin is not producing androgenotes and has no plans to do so, but the technique would be similar to that applied in producing the woman-only embryos.
Imperial College London's Dr Anthony Warrens described ongoing efforts to produce a supply of transplant organs provided by genetically engineered pigs. Researchers were at a stage now where they would probably overcome the remaining immunology and microbiological difficulties "within five years", he said.
Imperial's Prof Maggie Dallman explained how alternatives to immune suppression drugs were being sought for when patients began receiving therapeutic donor stem cells. One promising area related to using the body's powerful immune system itself to protect the stem cells. It involves employing cells that dampen down the immune response to keep the stem cells safe.