November 1, 2009 (Vol. 29, No. 19)
Parthenogenesis Could Sidestep Some of the Moral and Immune Rejection Issues
Remember this term: Parthenogenesis. This six-syllable word could be the answer to controversy-free stem cell research. Though the general public is well aware of the medical potential and controversies surrounding embryonic stem cells and iPS cells (induced pluripotent stem cells), a third way forward—parthenogenesis—has been surprisingly sidelined from the stem cell research debate.
Using this procedure, an unfertilized human egg, or oocyte, can be chemically induced to form a tiny cluster of cells that cannot mature into a human being, but from which a stem cell line can be created that has all the potential of an embryonic line. Parthenogenetic stem cells are unique because they do not destroy embryos nor involve any genetic manipulation, while creating stem cell lines that have the same potential as embryonic cells to provide any cell that might be needed for therapy.
This technology uses voluntarily discarded oocytes from women who have already decided to undergo fertility treatment in the hope of having a child or of helping others to have children. This source provides a more than ample supply of human oocytes to develop all the stem cell lines we would ever need. Further, once a bank of parthenogenetic stem cell lines is created, the need to go back and create new lines is greatly reduced. This is because parthenogenetic stem cells can divide indefinitely and provide a renewable resource.
Studies have demonstrated that using parthenogenetic techniques, cells from a single donor could be matched to general genetic patterns, known as human leukocyte antigens, of hundreds of millions of patients. Since a single line of these cells may eliminate immune rejection issues in large segments of the population, parthenogenetic stem cells could be enormously valuable as a treatment for diabetes, heart disease, liver disease, and macular degeneration.
Based on this technology, the world’s first human stem cell bank—one that serves the need for stem cell-based treatments in the general population—could conceivably be created. Akin to human blood typing, theoretically this means that only 200–300 eggs would need to be used to create stem cell lines that immune-match the entire band of human immune responses.
Kenneth C. Aldrich
Debunking the Egg-Farming Myth
Apart from moral quandaries surrounding the use of viable fertilized human embryos as the source of embryonic stem cells, stem cell research has also been a magnet for controversy due to fear and misinformation surrounding the creation of a human egg-farming industry. A number of women’s rights organizations warn against the potential exploitation of poor, minority women, students, and/or women from developing countries, for the purpose of egg harvesting.
The worry is that in the quest for human eggs for stem cell research, women who would not otherwise run the risks of ovarian stimulation will be induced to undertake potentially dangerous procedures. The belief that the creation of embryonic stem cells requires the need for large numbers of human oocytes is largely attributable to a technology called SCNT (somatic cell nuclear transfer) that was unsuccessfully used in early attempts to create human embryonic stem cells in Korea.
The fear that viable human embryos are being created solely for research purposes or that women are being exploited for their eggs simply does not apply to parthenogenesis. First, parthenogenesis does not lead to the creation of viable human embryos. No potential human life is destroyed. Second, parthenogenetic stem cell lines are created from excess eggs donated by women with the primary intent of undergoing IVF, and donation does not pose any additional risk to the donors.
Further, parthenogenesis may actually reduce the number of donors required because it allows for the creation of single lines of pluripotent stem cells that can be immune-matched (similar to how bone marrow is matched between donors and recipients) to large population groups. In other words, once a stem cell bank of perhaps 50–100 parthenogenetic stem cell lines is established, the need to continuously seek more eggs to match a population group may be greatly reduced or eliminated. The resulting immune-matched stem cell bank could become a valuable medical resource for regenerative medicine.
In July, the NIH finalized its guidelines for the federal funding of stem cell research. While the revamped guidelines expanded the scope of research into human stem cells eligible for federal funding, parthenogenetic stem cell research is not yet eligible for such government support.
We hope that appropriate review and approval of this burgeoning branch of stem cell research will come soon enough so that American researchers are not deprived of the benefits.
Already international researchers are using parthenogenetic cell lines to study the ways in which they may be more useful than embryonic lines, and there is a risk that if foreign researchers get too much of a head start, the U.S. could suffer in the long run as jobs and revenue follow the funding.
Given that parthenogenic stem cell lines behave just like embryonic stem cells but with the added advantages of solving certain moral dilemmas and addressing patient immune rejection issues, we believe that patients, practitioners, and politicians alike might some day agree that this new stem cell research technique represents a revolutionary way forward.
Kenneth C. Aldrich ([email protected]) is chairman, CEO, and co-founder of International Stem Cell. Web: www.internationalstemcell.com.
