Ethical Stem Cells?
In a process that could offer a strategy for overcoming many of the ethical concerns over the use of embryonic stem cells, researchers at Advanced Cell Technology have created a line of such cells from a single human embryonic cell. Unlike existing methods, the procedure leaves the embryo viable, raising the possibility it could be widely used to create embryonic cells without destroying embryos. The work is described in this week’s Nature journal.
Robert Lanza and his team at Advanced Cell Technology (ACT), a biotech company based in Alameda, CA, adapted a technique used by in vitro fertilization (IVF) clinics to perform genetic screening. The technique enabled the ACT team to extract a single cell from an embryo and to preserve its viability. The experiments resulted in the creation of two new lines of embryonic stem cells.
Embryonic stem cells, which can develop into any type of cell in the human body – and thus have vast research and medical potential – are usually grown from a mass of cells harvested from the embryo; the procedure destroys the embryo. In 2001, President Bush limited federal funding, including from the National Institutes of Health, to research on a small set of embryonic stem cell lines that already existed. As a result, the number of cell lines available to researchers who receive federal funding are few and of limited robustness.
Last December, Lanza and his coworkers published results reporting on mouse embryonic stem cells grown from a single cell. The new work applies the technique to grow human embryonic stem cells, Lanza says, and should end the ethical dilemma of needing to destroy embryos to create stem cells.
“There is now no rational ethical argument against stem cell research, now that we can preserve the embryo,” he says. “The existing cell lines are weak, they’re old, there are too few of them, and they are difficult to maintain. What we wanted to do with this process was to ensure that there are enough lines available. This should give the entire field a boost.”
Lanza says the new method for growing embryonic stem cells is consistent with current practices used in IVF clinics, which often extract a cell from an pre-implanted embryo in order to perform pre-implantation genetic diagnosis (PGD). “Normally the cell is taken in the IVF clinic and used immediately for testing,” Lanza explains. “What we’re saying is, let it grow overnight, there is still time to do the test and implant the embryo, and then use the rest of the biopsy for stem cell generation. It doesn’t change the outcome of the test, it doesn’t present any other risk to the embryo, and it ensures that there is a cell line out there that matches the child and his or her siblings.”
That scenario could be limited, however, because only a small percentage of embryos used in IVF clinics actually undergo PGD. “We would certainly not recommend that IVF with PGD should become routine in order to generate a stem cell line for each individual,” says Zev Rosenwaks, director of The Center for Reproductive Medicine and Infertility in New York City. “Other than that, the procedure seems like a perfectly reasonable proposition for cases when PGD is already being performed.”
According to Rosenwaks, only 5 to 10 percent of all IVF subjects undergo PGD for specific genetic and chromosomal disorders. There is no evidence that children born from PGD embryos are harmed by the procedure.
Lanza’s work could advance the field by removing the ethical barrier of embryo destruction. “This would be a serious and profound breakthrough for those involved in the science of stem cell research,” says Laurie Zoloft, director of bioethics at Northwestern University’s Center for Genetic Medicine. Those opposing stem cell work because it requires the destruction of embryos “now will be able to support this research.”
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