More than 100 of the hybrids, made by fusing human skin cells with rabbit eggs, were allowed to develop in laboratory dishes for several days before the scientists destroyed them to retrieve so- called embryonic stem cells from their interiors. Although scientists in Massachusetts had previously mixed human cells and cow eggs in a similar attempt to make hybrid embryos as a source of stem cells, those experiments were not successful.
The team said it retrieved foreskin tissue from two 5-year-old boys and two men, and facial tissue from a 60-year-old woman, as a source of skin cells. They fused those cells with New Zealand rabbit eggs from which the vast majority of rabbit DNA had been removed. More than 400 of those new, fused entities grew into early embryos, and more than 100 survived to the blastocyst stage -- the point at which coveted stem cells begin to form.
The approach could help scientists wishing to mass-produce human embryos as sources of human embryonic stem cells. Stem cells can morph into all kinds of tissues and may be able to reverse the effects of various degenerative diseases. But to make cloned embryos, scientists need both normal body cells -- such as skin cells -- and egg cells, which have the unique capacity to "reprogram" the genes in body cells and make them behave as though they were embryo cells.
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