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Virgin process can produce stem cells, study says

WASHINGTON (Reuters) - Mouse embryos created through a "virgin birth" process called parthenogenesis show that egg cells can be a source of valued embryonic stem cells, researchers said on Thursday.
The cells can be closely matched to the immune system of the recipient, making them a potential source for transplants, the researchers report in Friday's issue of the journal Science.

There are fewer obstacles to developing these stem cells than by using cloning technology, also called somatic cell nuclear transfer, researchers said.

"I think it is a much more real-world possibility than nuclear transfer," said Dr. George Daley of Children's Hospital and Harvard Medical School in Boston, who led the study.

If the experiment could be reproduced in humans, such cells might provide an alternative way to produce tailored tissues for transplanting, or for studying disease, Daley said in a telephone interview.

"We are aggressively trying to produce human parthenogenetic embryonic stem cells," Daley said.

Stem cells are the master cells of the body, and while they occur throughout all tissues and organs, they are difficult to find and grow.

Those found in the earliest embryos are powerful because they can form any kind of cell and are virtually immortal in the laboratory. Scientists want to study them to understand disease and find ways to better help the body repair itself.

The use of human embryonic stem cells - which can be made either from embryos left over from fertility clinics or by using cloning technology - is controversial because of concerns about the sanctity of human life, and is restricted in some countries.

President Bush has allowed very limited use of federal funds for embryonic stem cell research, although privately funded labs can do what they like.

VIRGIN BIRTH

Daley's work, and the work of a few other labs, offers a third way - parthenogenesis. The word comes from Latin and Greek roots meaning virgin beginning, and the process occurs when an egg cell starts dividing to produce an embryo without the use of sperm to fertilize it.

Scientists have done this before with mice. In mammals, parthenotes -- embryos made using this process -- stop developing very early because they need genes from a father to complete development.

"What is really new is the realization that you can genetically select the parthenote cells that are a complete match for histocompatibility for the donor," Daley said.

That means a good immune match - an easy match for any tissue transplant. In theory, researchers could create batches of immune-matched tissue or even organs to use for transplant.

Even cells that were only a half-match to the donor took well as transplants in the mice, Daley's team reported.

But producing such stem cells still would require a large number of eggs donated by women, not an easy obstacle to overcome. Also, some groups object to the ethics of using a woman's body in this way.

Daley said the cell lines could also be studied for a better understanding of the basic biology of disease.

"For instance, a woman with a genetic condition - some kind of early-onset Parkinson's, bone marrow failure - you could use them as an in-vitro (lab dish) model of the disease," he said.

Maggie Fox
www.reuters.com

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