Early-stage cloned human embryos, but not stem cells.

Scientists at Stemagen, a small biotechnology company in La Jolla, CA, reported yesterday that they have for the first time generated cloned human blastocysts--early-stage embryos--from adult skin cells. This is the first step in generating stem cell lines matched to individuals, which are crucial for creating new cellular models of disease and potentially important for future tissue replacement therapies. (See "Next Steps for Stem Cells" and "The Real Stem Cell Hope".) The new findings also confirm that access to fresh eggs from healthy young donors is a key part of successful cloning. Lack of access to human eggs has been the major barrier in the field. (See "Human Therapeutic Cloning at a Standstill".)

Cloned blastocysts have been generated before, but from embryonic stem cells rather than from adult cells. Scientists theorize that embryonic stem cells are easier to turn into blastocysts because of their earlier developmental stage.

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