BioWorld International Correspondent

DUBLIN, Ireland - Scientists in the UK have induced unfertilized human eggs to form embryos, opening up a potential new source of embryonic stem cells.

To date, Paul De Souza and colleagues at the Roslin Institute in Scotland have succeeded in producing six such embryos, or parthenotes, from around 300 eggs, but are not yet able to derive any stem cells. That outcome is on a par with work in the U.S. on human parthenogenesis, and the two groups have reported similar outcomes.

Describing the parthenogenesis research at the BA Festival of Science meeting in Dublin, Ireland, last week, De Souza said: "We have had some initial success in getting embryos through parthenogenesis but very few form blastocysts. The failure [of most] to get to this point suggests the genetic information [in the egg] is not sufficiently matured."

De Souza noted that most approaches to producing embryonic stem cells involve using embryonic tissue - derived by in vitro fertilization procedures - that is unsuitable for implantation. However, he hopes to develop a new source: immature eggs donated by women having a laparoscopic sterilization. In the first year of the donation program, 225 suitable donors were identified among women wishing to be sterilized. Of those, 75 assented to receive information, and 27 gave informed consent for eggs to be removed during the procedure.

The eggs subsequently were matured in vitro and stimulated electrically to start dividing into an early embryo. The in vitro matured oocytes also are being used in the creation of cloned human embryos.

De Souza said 25 years of embryo biotechnology has "opened up a new paradigm of using early embryonic tissue for regenerative therapy as opposed to reproduction." His overall aim "is to be among the first in the world to create therapeutically suitable human embryonic stem cell lines."

The work described was carried out at the Roslin Institute, home of the former cloned sheep Dolly, but De Souza since has moved to the University of Edinburgh, at which a new £40 million (US$72.8 million) Scottish Centre for Regenerative Medicine is due to open in 2006.

While parthenotes have genes from one parent only, a day earlier the government gave the go-ahead to researchers to create embryos with genetic material from three parents. Scientists at the Centre for Life in Newcastle will attempt to insert the pronuclei from the fertilized eggs of women who are carriers of mitochrondrial dystrophies into fertilized but enucleated eggs of unaffected women.

The technique has been used to prevent mitochrondrial dystrophy in mice. The researchers, who are funded by the Muscular Dystrophy Campaign, stressed that would be only the first step in developing techniques to prevent the transmission of mitochondrial DNA diseases. There is no intention of implanting any embryos.

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