Nuclear Transfer, Altered

THE FIRST STEM cells were discovered in the early 1900s. Since then, stem cell research has mainly relied on three different sources for obtaining stem cells: embryonic cells, umbilical cord cells, and adult stem cells. For many years, murine embryonic stem cells have played a large part in helping us advance our understanding of many disease processes, including cancers. The abundance and ease of obtaining umbilical cord cells has also aided researchers.

Adult stem cells were used for the first time to produce a cloned mammal in 1995, when Dolly the sheep was born. However, it was not until 1998 that researchers took cells from human embryos and developed the first human embryonic stem cell lines. One of the first people to accomplish this feat was James Thomson at the University of Wisconsin.

After much consideration and discussion with ethicists regarding the morality of this matter, and taking into account that he would be using embryos that would otherwise have been discarded from fertility clinics, Thomson decided that the benefits of embryonic stem cell research outweighed the ethical issues that may be related to this type of research. He proceeded and was the first researcher to isolate cells from the inner cell mass of early embryos.

However, Thomson did not anticipate the intense surge in public debate regarding the controversial destruction of potential human life when embryonic stem cells are used. Similarly, in 1998, John Gearhart from Johns Hopkins University obtained stem cells from human fetal gonadal cells. In contrast to Thomson's procedure, which used in vitro human embryos, resulting in a great deal of controversy, Gearhart's method did not face as much antagonism, as the potential loss of human embryonic life apparently was not involved.

Many outspoken groups among the American public did not agree with embryonic stem cell research. Main concerns with regard to these issues included the destruction of human life (in the embryonic state) and the possibility of human cloning. Following these scientific breakthroughs, the major influencing factor in American stem cell research afterward remained the political leadership. A 1973 moratorium on federal funding for human embryo research was extended in 1998 by the U.S. Department of Health and Human Services.

Two years later, in 2000, President Bill Clinton allowed research funding for cells from aborted fetuses but not from human embryonic cells. Following Clinton's departure from presidential office, President George W Bush, who held firm beliefs regarding the preservation of embryonic human life, was concerned about more human embryos being produced for the sole purpose of their destruction for research use. Thus, in 2001, a substantial delay was placed on U.S. embryonic [Page 400]stem cell research when federal funding became limited only to the use of human embryonic stem cell lines derived before August 9, 2001, and disallowed taxpayer dollars from being used toward the destruction of human embryos.

Altered nuclear transfer holds promise for developing pluripotent cells without using functional human embryos.