The natural replacement of damaged cells by stem cells occurs actively and often in adult tissues, especially rapidly dividing cells such as blood cells. An exciting case in Boston, however, posits a kind of natural stem cell therapy provided to a mother by her fetus—long after the fetus is born. Because there is a profound lack of medical intervention, this therapy seems natural enough and is unlikely to be morally suspect. Nevertheless, we feel morally uncertain when we consider giving this type of therapy to patients who would not naturally receive it. Much has been written about the ethics of stem cell research and therapy; this paper will focus on how recent advances in biotechnology and biological understandings of development narrow the debate. Here, the author briefly reviews current stem cell research practices, revisits the natural stem cell therapy case for moral evaluation, and ultimately demonstrates the importance of permissible stem cell research and therapy, even absent an agreement about the definition of when embryonic life begins.
Although one promising technology, blighted ovum utilisation, uses fertilised but developmentally bankrupt eggs, it is argued that utilisation of unfertilised eggs to derive totipotent stem cells obviates the moral debate over when life begins. There are two existing technologies that fulfil this criterion: somatic cell nuclear transfer and parthenogenic stem cell derivation. Although these technologies are far from therapeutic, concerns over the morality of embryonic stem cell derivation should not hinder their advancement.
- HSC, haematopoietic stem cell
- PAPC, pregnancy associated progenitor cell
- stem cell
- pregnancy associated progenitor cell
- somatic cell nuclear transfer
- blighted ovum
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↵i Presumably this effect occurs in women who give birth to daughters as well, but because Herzenberg et al were screening for a y chromosome, these daughters’ fetal cells could not be detected at the time.3,4
↵ii Whether this spontaneously aborted menstrual extrusion constitutes life is beyond the scope of this paper. Common arguments against this premise include the mysterious process of twinning, in which a single embryo asexually reproduces to become two separate monozygotic individuals. The embryo cannot be a single life until this process is complete, the argument goes, which may take up to fourteen days, long after the period when a stem cell would be harvested. Additionally, the evidence of tetragametic conception challenges the individual personhood of each early embryo, because two separately fertilised eggs may fuse after seven days of separated development to form a single individual. According to this argument, each fertilised egg cannot constitute an individual person because one such personhood would disappear in the process of fusion. For more on this nuance of personhood versus life, see Daley’s lecture.6
↵iii A report in Nature from October 2005 challenges this assumption. Collaborating researchers were able to derive a totipotent stem cell line in mice from a single cell taken from the blastomere stage of an embryo—without harming the embryo itself. This technique, removing a single cell from the 8 or 16 cells of a blastomere, is routinely done in human pregnancies for preimplantation genetic testing; it seems acceptable, then, to use this technique for stem cell derivation. Chung Y, Klimanskaya I, Becker S, et al. Embryonic and extraembryonic stem cell lines derived from single mouse blastomeres. Nature2005: in press. doi:10.1038/nature04277.