Human embryonic stem cells (hESC), those very young cells that are a biological blank slate, have the potential to become more specialized, contributing to the workings of a wide variety of organs and tissues. Their potential to treat diseases such as Parkinson's is slow to be realized because of the ongoing ethical debate over harvesting hESCs, a process called deriving hESC lines. Additionally, it's a politically charged issue in the U.S. because it involves federal funding for research.
A recently published paper by Dartmouth Professor Ronald M. Green examines the moral questions and the scientific feasibility of deriving hESC lines in ways that avoid destroying living human embryos. The paper, published in the June 2007 issue of Nature Reviews Genetics, considers six current approaches: altered nuclear transfer, parthenogenesis, single-blastomere biopsy, somatic-cell dedifferentiation, the use of "dead" embryos, and the use of abnormal embryos. Green's goal, as stated in the paper, is "to greatly accelerate hESC research that is closer to being universally acceptable."
"I think we can pursue hESC research and also respect the sensitivities of our fellow citizens. It's not impossible to do both," says Green, the Eunice and Julian Cohen Professor for the Study of Ethics and Human Values, and the faculty director of the Dartmouth Ethics Institute. In addition to resolving current debates, he argues, these alternatives can make possible hESC lines that are ethically universal. "These would be analogous to the universal O-type blood group: lines that could be used by anyone regardless of their ethical views on the moral status of the embryo."
Green, who is also an adjunct professor of community and family medicine at the Dartmouth Medical School, says, "The six approaches differ in technique, most directly in how the blastocyst is created." The blastocyst, where hESCs are found, is the three- to five-day-old embryo that has not yet been implanted in the uterus. "Since many people regard the normal human blastocyst as morally deserving of protection, the challenge is to find methods of deriving hESCs that either leave the blastocyst intact and unharmed or avoid the use of normal blastocysts in the first place."
The paper explains the science behind the six approaches and describes the hurdles that must be overcome in making them useful in future stem cell research. Even though none of these options is free from scientific challenges or ethical and political problems, Green feels that we should support research now to develop them as a supplement tobut not a replacement for existing methods of hESC derivation.