Embryos From Monkey Eggs Could Avert Debate Over Stem Cells
Monkey eggs that are chemically stimulated to grow into embryo-like organisms without the use of sperm can develop and yield embryonic stem cells capable of becoming other forms of tissue, a development that may alter the debate over cloning and embryonic stem cell research, the Boston Globe reports. Researchers from the Worcester, Mass.-based biotechnology firm Advanced Cell Technology and Wake Forest University report in today's issue of the journal Science that, using a process known as parthenogenesis, they were able to coax unfertilized monkey eggs into forming embryo-like organisms. Scientists were then able to cull embryonic stem cells from some of those parthenotes and use those cells to form functioning neural, muscle, fat and heart cells (Mishra, Boston Globe, 2/1). The cell line derived from those embryonic cells has "grown continuously" for 10 months, according to researchers at Wake Forest University (Fox, Reuters/Contra Costa Times, 1/31). Dr. Jose Cibelli, an ACT cloning expert, said that his group has begun experiments with human eggs and has achieved "encouraging results" so far, adding that "the bottom line is that we are very confident of repeating the process in humans" (Wade, New York Times, 2/1). Dr. John Gearhart, a stem cell researcher at Johns Hopkins University, noted that stem cells have also been produced through parthenogenesis using eggs from mice. However, he said that the cells derived through the process would have "very limited medical use" in humans because they could only be used for transplant tissue or therapies in the women who donated the eggs, thereby automatically limiting the use of the technology to women of reproductive age (Recer, AP/Nando Times, 1/31). Gearhart said that it is "theoretically possible" to make parthenotes from sperm, but it has not yet been successfully attempted. However, the biotech firm Stemron has theorized that because cells derived from parthenotes have only maternal DNA, they could "greatly reduce the complexity of tissue-transplant matching" for recipients other than the egg donor, and the company has proposed creating a tissue bank that would hold cells produced from about 200 to 300 parthenotes (Regalado, Wall Street Journal, 2/1).
Previous mammal experiments have demonstrated that parthenotes cannot develop to term if placed in a womb; therefore, a parthenogenically derived "embryo" cannot be said to be "deprived of future life when its stem cells are removed," the New York Times reports. Many people have objected to embryonic stem cell research and therapeutic cloning because they require the destruction of human embryos, which opponents see as potential human life. However, the process of parthenogenesis may allow researchers to circumvent those objections. Roman Catholic ethicists have not yet issued an opinion on whether organisms created through parthenogenesis can be considered life or whether embryonic stem cells derived from parthenotes are "morally acceptable," but there are indications that the Catholic church "might accept the procedure" as ethical, the Times reports. Dr. Kevin Fitzgerald, a Jesuit priest and geneticist at Georgetown University, said that parthenotes could be considered analogous to a hydatiform mole -- an embryo that, due to a pregnancy complication, "loses" its chromosomes from the eggs and instead retains two sets of chromosomes from the sperm, the "exact opposite" genetic makeup of a parthenote. Fitzgerald said that he does not consider hydatiform moles to be human beings, "not because [they] could not develop into a baby, but because [their] imprinting was wrong," adding that the same reasoning could be applied to a parthenote. However, Richard Doerflinger, a spokesperson for the National Conference of Catholic Bishops, said that the church "favor[s] equal protection for all embryos, damaged as well as healthy." If the parthenotes "develop as organized embryos for the first few days and then stop, they might be just very short-lived human beings," he explained. However, "if someone can establish this is not a human being the moral problem is much reduced," he acknowledged (New York Times, 2/1). Doerflinger added that "if we don't know whether or not these entities are embryos, we shouldn't be destroying them" (Wall Street Journal, 2/1). However, researchers want to keep as many avenues of scientific inquiry open as possible. Parthenogenesis just "adds one more tool to the tool box," Kent Vrana, a Wake Forest researcher on the project, said, adding that he thinks "we'll end up needing all of them" (Powell, Boston Herald, 2/1). NPR's "Science Friday" today will feature a stem cell discussion with ACT President and CEO Michael West and stem cell researcher Catherine Verfaillie, whose team at the University of Minnesota recently announced it had created human tissue from adult stem cells. Check local listings for stations and times (NPR Web site, 2/1).This is part of the California Healthline Daily Edition, a summary of health policy coverage from major news organizations. Sign up for an email subscription.