Researchers at the Children's Hospital Boston, have developed a technique in mice to derive stem cells from a single egg coaxed to divide. The technique of forcing an egg cell to begin division without fertilisation by a sperm cell - known as parthenogenesis - has been achieved before, but the group in Boston has advanced the procedure to derive stem cells that can become many different tissue types for the first time. The team, led by Dr George Daley, first persuaded the mouse eggs to divide, they then used chemicals to force out one set of chromosomes, usually lost during fertilisation. Stem cells were then derived from the dividing eggs which were screened to ensure they shared the same major histocompatability complex (MHC) genes as the donating mother, this ensured that they would not be rejected if transplanted back into the same mouse.
The report, published in the journal Science, shows that the new technique can produce stem cells seventy per cent of the time. This is much more efficient than the standard SCNT (somatic cell nuclear transfer) technique that scientists used to clone Dolly the sheep, and have been trying, unsuccessfully, to develop in humans. There are various potential problems with the new procedure, one being that so far, genetically matched tissue can only be produced for the female that donated the egg. Even if the technique could be shown to work in humans, only women of child bearing age could, at this stage, benefit. There are also problems associated with cells derived through parthenogenesis as they have different expression of certain genes as there is no male 'counter' to the maternal copy. Parthenogenetically derived cells have previously been associated with malignancies or abnormal tissue growth.
Daley, commenting on the research noted that, 'Right now this technique is useful for basic research, but we are hopeful that parthenogenetic cells might prove useful for therapies...we'll have to demonstrate the safety and durability of cells derived from parthenogenetic embryonic stem cells before we could imagine any clinical use'.