Final Report (all chapters)

4.5.3 Making Eggs
After twenty years of research on mouse embryonic stem cells (ESCs), scientists have been
able to coax these cells into just about any kind of cell. Since a group of researchers at the
University of Pennsylvania announced in 2003 that they had succeeded in transforming mouse
ESCs into eggs, it has now been demonstrated that mouse ESCs can indeed be converted into
any kind of mouse cell – i.e., that they are totipotent. 78 Coaxing mouse stem cells into becoming
oocytes did not require a sophisticated cocktail of growth factors, a fact prompting optimism in
the scientific community about replicating these results in higher mammals, primates, and
humans. The eggs were produced through a process similar to ovulation. The oocytes underwent
meiosis, the process by which eggs and sperm give up half of their genetic material, and
produced embryo-like structures through a process known as “parthenogenesis.” Interestingly,
eggs were produced by both female and male ESCs.
What is the scientific rationale for this experiment? According to the University of
Pennsylvania scientists, the experiment could defuse many concerns surrounding research
cloning. Somatic cell nuclear transfer is notoriously very inefficient and requires a large number
of oocytes to succeed. Retrieving human oocytes in large numbers is an ethically questionable
undertaking at best and an unacceptable proposition at worst. The researchers hope that
dramatically increasing the availability of oocytes will change the terms of the debate about
research cloning: If embryos could entirely be produced in vitro, many opponents of research
cloning might find this line of research far less objectionable. A large supply of artificial eggs
would also prevent a market for natural oocytes from emerging; the scientists also indicated that
their research could advance our understanding of infertility and of menopause.
The rationale offered by these scientists for attempting to produce artificial oocytes is
laudable and hopefully not entirely unrealistic. But as pointed out earlier, important scientific
experiments often have applications not anticipated by the researchers. In the present case, it is
not too difficult to identify some of these unanticipated consequences. As noted above, scientists
have made eggs not only from female, but also from male embryonic stem cells. Conceivably,
then, a gay couple may be able to produce their own genetically related children through IVF and
surrogacy. In this scenario, one man would contribute the sperm and the other the eggs. While
some in the gay community may salute this development as an important step toward equal
access to parenthood, others may point to possible deleterious consequences for the well-being
and the personal identity of children. In allowing men to become mothers, this procedure would
also undermine the principle that each child should have a genetic father and mother.
78
Claire Ainsworth, "Artificial Human Eggs Created," New Scientist, July 2, 2001; Rachel Nowak, "Mice Born
from Rat-Matured Eggs," New Scientist, September 28, 2002; Sylvia Pagàn Westphal, "Embryonic Stem Cells
Turned into Eggs," New Scientist, May 1, 2003; Azim Surani, "Stem Cells: How to Make Eggs and Sperm,"
Nature 427 (2004); Nicholas Wade, "Pennsylvania Researchers Turn Stem Cells to Egg Cells," New York Times,
May 2, 2003; Rick Weiss, "In Laboratory, Ordinary Stem Cells Are Turned into Eggs," Washington Post, May 2,
2002.
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