What qualifies as a live embryo?
What qualifies as a live embryo?
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什么才算是活胚胎？
DOI：
10.1080/15265160500318795
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Wasserman,David
中科院分区：
文献类型：
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作者：
Wasserman,David
S.Matthew Liao(2005)认为，胚泡移植方法对于干细胞研究的保守派反对者来说不会像它的几个竞争对手那样令人反感，这些竞争对手包括：使用孤雌生殖将卵母细胞制成不能完全怀孕的胚胎，从“死”胚胎中获取干细胞，以及创造一个没有形成胎盘或妊娠能力的“伪胚胎”。廖添丁认为，这些替代方案未能向“胚胎学家”--那些相信胚胎人格的人--提供足够的保证，即活胚胎在获得干细胞的过程中不会被破坏。在第一种情况下，“通过孤雌生殖创造出正常发育的人类似乎只是个时间问题。也许目前的技术导致这些胚胎不能发育成完全的人类“(11)。在“死亡”胚胎的情况下，可能有方法启动阻止细胞分裂的胚胎，就像除颤器可以用来启动心脏骤停的个体一样。如果是这样，细胞分裂受阻并不一定意味着胚胎死亡“(11)。也有可能打开假胚胎中不活跃的发育基因，使它们变成真正的胚胎(11)。然而，似乎也可以对廖添丁提出的从5-7天大的胚胎中获取多能细胞做出类似的断言：尽管这些细胞目前还不能发育成人类，但可能很快就会有方法恢复几天前失去的这种潜力。如果提取的干细胞可以成为全能的，那么这些细胞，就像那些经历了“改进”的孤雌生殖过程的实体，复活的“死”胚胎，以及开启了妊娠基因的假胚胎，都将被称为活胚胎，对于胚胎学家来说，它们将是人。虽然通过胚泡移植方法提取干细胞可能在道德上不会有问题，因为它将保存胚胎，同时确定提取细胞的单独身份，但一旦使该细胞具有全能，就不能像提取它的胚胎一样受到实验的影响。然而，正如廖添丁所代表的那样，胚胎论者的反对似乎更加强烈。拟议中的干细胞来源应该被视为活胚胎，因为它们可以通过未来的技术变得全能，这样即使没有转化，它们也不应该被销毁以获取干细胞。但这难道不也意味着，任何干细胞，无论如何提取，都不会受到危险的实验，因为干细胞也可以成为全能的？此外，由于克隆技术可能很快就能使任何体细胞完全分化，难道这些细胞现在不应该被视为活胚胎，排除卫生和美容，更不用说医疗干预了吗？廖，或者他预计会反对的胚胎学家，可能会回应说，使细胞具有活胚胎地位的不仅仅是技术上的全能可能性。至少还有另外两个相关的条件，胚胎学家可能会强加给他们，以区分“未改良的”孤雌生殖的卵母细胞(我称之为“孤雌细胞”)、假胚胎和“死”胚胎与正常的干细胞和体细胞。首先，前者而不是后者可以在不失去特性的情况下成为全能细胞-它们可以成为全能细胞，而不是
S. Matthew Liao (2005) argues that the Blastocyst Transfer Method will be less objectionable to conservative opponents of stem-cell research than several of its rivals: using parthenogenesis to make oocytes into embryos that are not capable of complete gestation, harvesting stem cells from “dead” embryos, and creating a “pseudo-embryo” without the capacity to form a placenta or gestate. Liao sees these alternatives as failing to provide adequate assurance to “embryoists”—those who believe in the personhood of embryos—that a live embryo is not being destroyed in obtaining stem cells. In the first case,“it seems likely that it is only a matter of time before normal-developing human beings can be created via parthenogenesis. Perhaps the present technique is causing these embryos not to be able to develop into full term human beings”(11). In the case of “dead” embryos, there may be ways to jump-start embryos that have arrested cell division, much like a defibrillator can be used to jump start an individual with cardiac arrest. If so, an arrest in cell division does not necessarily mean the embryo is dead”(11). And it may be possible to turn on the inactive development genes in pseudo-embryos, making them into the real thing (11). It seems, however, that a similar claim could be made about the pluripotent cells Liao proposes harvesting from 5–7 day-old embryos: although these cells cannot at present develop into human beings, there may soon be ways of restoring that potential, lost just days earlier. If extracted stems cells could be made totipotent, those cells, like the entities subjected to an “improved” process of parthenogenesis, revived “dead” embryos, and pseudo-embryos that had their gestational genes turned on, would all qualify as live embryos and would be, for the embryoist, persons. While the extraction of stem cells by the blastocyst transfer method might not be morally problematic, since it would preserve the embryo while establishing the separate identity of the extracted cell, that cell, once made totipotent, could not be subject to experimentation any more than the embryo from which it was extracted. The embryoist’s objection, though, as Liao represents it, appears to be even stronger. The proposed stem-cell sources should be regarded as live embryos just because they could be made totipotent by a future technology, so that, even untransformed, they should not be destroyed to harvest stem cells. But wouldn’t this also mean that no stem cell, however extracted, could be subject to dangerous experimentation, because stem cells could also be made totipotent? Moreover, since cloning techniques may soon be able to make any somatic cell totipotient, shouldn’t each of those cells now be regarded as a live embryo, precluding hygiene and grooming, let alone medical intervention? Liao, or the embryoists whose objections he anticipates, might respond that it is not the mere technological possibility of making a cell totipotent that gives it the status of a live embryo. There are at least two other related conditions the embryoist could impose that might distinguish oocyctes subject to “unimproved” partheogensis (which I will call “parthoocytes”), pseudo-embryos, and “dead” embryos from normal stem and somatic cells. First, the former but not the latter could be made totipotent without losing identity—they could become totipotent cells, rather