O'Keeffe Francis J, Mendz George L
School of Medicine, The University of Notre Dame Australia, Sydney, NSW 2010, Australia.
Biology (Basel). 2025 Jan 21;14(2):104. doi: 10.3390/biology14020104.
Discourses on human embryo experimentation often refer to monozygotic twinning and individuation. A criterion to establish regulations that guide human embryo research proposes that individuation is achieved once the embryo ceases to have the potential for dividing into two or more viable entities at about 15 days of gestational age. This standard is based on an updated version of a developmental model initially proposed by George Corner. A fundamental problem with this approach is the model's lack of sufficient evidence to explain adequately human embryo twinning and, consequently, to serve as a basis to establish appropriate ethical guidelines for embryo experimentation. In addition, subsequent formulations of Corner's model added an extension of blastomere totipotency to different moments of gestation, without a proper scientific basis. The model is also challenged by monozygotic twinnings that result in placental and amniotic arrangements incompatible with Corner's framework. Investigations into the physiology of fertilisation and of the zygote suggest that individuation may occur at a very early stage. An alternative description of monozygotic twinning may explain better sesquizygotic twinning events and serve to re-evaluate the individuation criterion. The study aims to investigate deficiencies in the embryology of this model and assess their ethical implications.
关于人类胚胎实验的论述常常提及单卵孪生和个体化。一项用以制定指导人类胚胎研究法规的标准提出，在妊娠约15天时，一旦胚胎不再具备分裂为两个或更多可存活个体的潜能，个体化便得以实现。这一标准基于乔治·科纳最初提出的发育模型的更新版本。该方法的一个根本问题在于，该模型缺乏足够的证据来充分解释人类胚胎孪生现象，因而无法作为为胚胎实验制定适当伦理准则的依据。此外，科纳模型的后续版本将卵裂球全能性的延伸扩展至妊娠的不同阶段，但却缺乏适当的科学依据。该模型还受到单卵孪生所导致的胎盘和羊膜排列与科纳框架不相容情况的挑战。对受精生理学和受精卵的研究表明，个体化可能在非常早期的阶段就已发生。对单卵孪生的另一种描述或许能更好地解释半同卵孪生事件，并有助于重新评估个体化标准。本研究旨在探究该模型胚胎学方面的缺陷，并评估其伦理意义。
