A team of scientists have used cloning methods to produce stem cells from the skin cells of adult patients. To do this, researchers extracted DNA from the cells of two adult males, aged 35 and 75. The DNA was then fused with human eggs donated by four adult women. The study, published in the scientific journal Cell, shows that it might be possible for scientists to grow patient-specific cells to treat illnesses such as heart disease or even blindness.

This marks only the second time human stem cells have been cloned, and the first time cells from an adult have been successfully copied. The first such procedure, performed last year, was completed using cells from infants, which are considered more malleable. The scientists involved in the new study, based in Los Angeles and South Korea, showed that the cells they harvested could develop into any of the major tissues found in a human embryo, giving them the "potential for applications in a range of therapeutic contexts." Therapeutic cloning describes the concept of using a subject's DNA to create stem cells tailored for their own body, cells that could then be used to cure diseases or repair tissues in the original donor.

The US government has banned the use of federal money for human cloning research

But therapeutic cloning raises ethical questions. In 2005, The United Nations General Assembly adopted a non-binding declaration that called for the ban of human cloning on the grounds of dignity. And the United States government has restricted the use of federal funds for research into therapeutic or reproductive cloning.

By fusing DNA from skin cells with human eggs, the scientists were effectively creating a human embryo. While they harvested the cells during the early stages of cell multiplication, the resultant embryo could theoretically have been implanted into a host and brought to term, making it an actual human clone. The authors of the study choose not to address this issue, discussing instead the cells' potential for helping humans produced in the traditional manner.