Modelling human embryogenesis: embryo-like structures spark ethical and policy debate
Human Reproduction Update, vol. 26, pp. 779–798
Abstract
BACKGROUND: Studying the human peri-implantation period remains hindered by the limited accessibility of the in vivo environment and scarcity of research material. As such, continuing efforts have been directed towards developing embryo-like structures (ELS) from pluripotent stem cells (PSCs) that recapitulate aspects of embryogenesis in vitro. While the creation of such models offers immense potential for studying fundamental processes in both pre- and early post-implantation development, it also proves ethically contentious due to wide-ranging views on the moral and legal reverence due to human embryos. Lack of clarity on how to qualify and regulate research with ELS thus presents a challenge in that it may either limit this new field of research without valid grounds or allow it to develop without policies that reflect justified ethical concerns. OBJECTIVE AND RATIONALE: The aim of this article is to provide a comprehensive overview of the existing scientific approaches to generate ELS from mouse and human PSCs, as well as discuss future strategies towards innovation in the context of human development. Concurrently, we aim to set the agenda for the ethical and policy issues surrounding research on human ELS. SEARCH METHODS: The PubMed database was used to search peer-reviewed articles and reviews using the following terms: 'stem cells', 'pluripotency', 'implantation', 'preimplantation', 'post-implantation', 'blastocyst', 'embryoid bodies', 'synthetic embryos', 'embryo models', 'self-assembly', 'human embryo-like structures', 'artificial embryos' in combination with other keywords related to the subject area. The PubMed and Web of Science databases were also used to systematically search publications on the ethics of ELS and human embryo research by using the aforementioned keywords in combination with 'ethics', 'law', 'regulation' and equivalent terms. All relevant publications until December 2019 were critically evaluated and discussed. OUTCOMES: In vitro systems provide a promising way forward for uncovering early human development. Current platforms utilize PSCs in both two- and three-dimensional settings to mimic various early developmental stages, including epiblast, trophoblast and amniotic cavity formation, in addition to axis development and gastrulation. Nevertheless, much hinges on the term 'embryo-like'. Extension of traditional embryo frameworks to research with ELS reveals that (i) current embryo definitions require reconsideration, (ii) cellular convertibility challenges the attribution of moral standing on the basis of 'active potentiality' and (iii) meaningful application of embryo protective directives will require rethinking of the 14-day culture limit and moral weight attributed to (non-)viability. Many conceptual and normative (dis)similarities between ELS and embryos thus remain to be thoroughly elucidated. WIDER IMPLICATIONS: Modelling embryogenesis holds vast potential for both human developmental biology and understanding various etiologies associated with infertility. To date, ELS have been shown to recapitulate several aspects of peri-implantation development, but critically, cannot develop into a fetus. Yet, concurrent to scientific innovation, considering the extent to which the use of ELS may raise moral concerns typical of human embryo research remains paramount. This will be crucial for harnessing the potential of ELS as a valuable research tool, whilst remaining within a robust moral and legal framework of professionally acceptable practices.
Authors 10
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Utrecht University · University Medical Center Utrecht · Maastricht University
Affiliation as printed
Department of Health Ethics and Society, Maastricht University, Maastricht, The Netherlands
Department of Medical Humanities, Utrecht University Medical Center, Utrecht, The Netherlands
School for Oncology and Developmental Biology (GROW), Maastricht University, Maastricht, The Netherlands
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Affiliation as printed
Ghent-Fertility And Stem cell Team (G-FAST), Department for Reproductive Medicine, Ghent University Hospital, Ghent, Belgium
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Maastricht University · Care and Public Health Research Institute
Affiliation as printed
Department of Health Ethics and Society, Maastricht University, Maastricht, The Netherlands
School for Care and Public Health Research (CAPHRI), Maastricht University, Maastricht, The Netherlands
School for Oncology and Developmental Biology (GROW), Maastricht University, Maastricht, The Netherlands
Socrates chair Ethics of Reproductive Genetics endowed by the Dutch Humanist Association, Amsterdam, The Netherlands
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Royal Netherlands Academy of Arts and Sciences · Ghent University Hospital · University Medical Center Utrecht · Oncode Institute
Affiliation as printed
Ghent-Fertility And Stem cell Team (G-FAST), Department for Reproductive Medicine, Ghent University Hospital, Ghent, Belgium
Oncode Institute, Hubrecht Institute-KNAW (Royal Netherlands Academy of Arts and Sciences) and University Medical Center Utrecht, Utrecht, The Netherlands
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Utrecht University · University Medical Center Utrecht
Affiliation as printed
Department of Medical Humanities, Utrecht University Medical Center, Utrecht, The Netherlands
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Leiden University Medical Center · Ghent University Hospital
Affiliation as printed
Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, The Netherlands
Ghent-Fertility And Stem cell Team (G-FAST), Department for Reproductive Medicine, Ghent University Hospital, Ghent, Belgium
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Royal Netherlands Academy of Arts and Sciences · University Medical Center Utrecht · Oncode Institute
Affiliation as printed
Oncode Institute, Hubrecht Institute-KNAW (Royal Netherlands Academy of Arts and Sciences) and University Medical Center Utrecht, Utrecht, The Netherlands
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Affiliation as printed
Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
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Maastricht University · Care and Public Health Research Institute
Affiliation as printed
Department of Health Ethics and Society, Maastricht University, Maastricht, The Netherlands
School for Care and Public Health Research (CAPHRI), Maastricht University, Maastricht, The Netherlands
School for Oncology and Developmental Biology (GROW), Maastricht University, Maastricht, The Netherlands
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Björn Heindryckx corresponding
Affiliation as printed
Ghent-Fertility And Stem cell Team (G-FAST), Department for Reproductive Medicine, Ghent University Hospital, Ghent, Belgium
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