A method for persuading human eggs to start dividing as though they have been fertilised could provide a less controversial source of embryonic stem cell (ES cells), say UK researchers. The scientists, based at the University of Wales in Cardiff, also say that the technique might help improve the success rate for couples undergoing ICSI (intracytoplasmic sperm injection) treatment.
The researchers, who published their findings in the journal Reproduction, have discovered that human eggs injected with a substance called phospholipase C-zeta (PLC-zeta) will start dividing. PLC-zeta is a protein produced by sperm, discovered by the Cardiff team two years ago, New Scientist magazine reports. The injected eggs will grow for about 4-5 days, until they reach the 50-100 cell blastocyst stage of development. Because they only contain genes from the mother, such 'parthenogenetic embryos' could never develop further, but they could still be used as a potential source of ES cells.
Many scientists believe that ES cells hold great promise in the treatment of a wide range of diseases, since they can grow into any type of body tissue. However, human ES cell research is controversial, since it involves the destruction of embryos. Several groups are trying to find ways of growing ES cells without using embryos, either by creating parthenogenetic 'embryos', or using other approaches.
Last week, US scientist William Hurlbut, who opposes embryo research, said it should be possible to create cloned human embryos that are incapable of growing a placenta. Since 'embryos' created using this 'altered nuclear transfer' technique would not be able to develop into a fetus, Hurlbut believes it could provide a way for American scientists to create new human ES cells with government funding. The use of federal funds for stem cell research involving the destruction of embryos has been prohibited by Bush since 9 August 2001.
The leader of the latest study, Karl Swann, hopes that his team will be the first to obtain ES cells from human parthenogenetic blastocysts. However, some pro-life groups might still object to this research. 'I'd be happier if it was beyond all reasonable doubt that it could not become a human life', said Josephine Quintavalle of Comment on Reproductive Ethics (Core). She added that women must not be exploited to provide eggs for this purpose.
PLC-zeta could also help couples undergoing ICSI, a fertility treatment in which a single sperm is injected into an egg in the laboratory. Embryos produced in this way do not always start dividing and growing, possibly because the sperm has defective PLC-zeta. Adding some of this substance could overcome this problem, say the scientists.