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Human pluripotent stem cells have been used to generate models of the human embryo (stem cell-based embryo models; SCBEMs). Pluripotent stem cells are unspecialised cells that posses the ability to develop into other cell types. SCBEM is an umbrella term used to refer to a range of models that vary in complexity and completeness of modelling an embryo.  

Scientists propose that human SCBEMs can be used to better understand early embryo development and this knowledge could have the potential to explore factors contributing to pregnancy loss, miscarriages and to improve IVF outcomes. SCBEMs have also been proposed to be useful in drug testing and discovery.   

With increasing sophistication and completeness of human SCBEMs in modelling the embryo, the focus of the current debate includes how existing legislation relates to technological progress in this area, and whether the same laws governing embryo research should apply to SCBEMs as well.  

In the UK, as of February 2024, human SCBEMs are not explicitly defined or regulated by existing legislation governing embryo research. 

Opportunities in introducing regulation of human SCBEMs include the requirement for an assessment of the extent to which SCBEMs resemble or differ from an embryo, clarity on restrictions surrounding their maintenancein vitroand understanding public concerns and perceptions around them.  

In November 2023, the Human Fertilisation and Embryology Authority proposed reformation of the Human Fertilisation and Embryology Act 2008. The report recognised human SCBEMs as pressing scientific issues and included proposals for greater discretion to approve new developments under flexible trial mechanisms with the aim of “future proofing” scientific developments.  


Key Points 

  • Human SCBEMs are created from pluripotent stem cells. 
  • Human SCBEMs could allow novel forms of investigation into embryonic processes that would not be possible or practical with human embryos. 
  • The terminology describing SCBEMs can vary; they have been referred to as artificial embryos, synthetic embryos, stembryos, synthetic human entities with embryo-like features (SHEEFs), embryo-like structures (ELS), embryo models and embryoids. 
  • Internationally, legal definitions and regulations around human SCBEMs varies from no explicit regulation to different limits on its research. 
  • The International Society for Stem Cell Research have created guidelines to address the international diversity of cultural, political, legal and ethical issues around the emerging technology and its application in research and treatment. 
  • Stakeholder suggestions towards effective oversight of SCBEMs include (i) identifying similarities and differences between SCBEMs and human embryos, (ii) an independent oversight process involving experts and lay members (iii) conducting public engagement to increase public understanding and identifying concerns surrounding the technology. 


POST is grateful to Jahnavi Bhaskaran for researching this briefing, to the Nuffield Foundation for funding her fellowship, and to all contributors and reviewers. For further information on this subject, please contact the co-author, Natasha Mutebi. 

POSTnotes are based on literature reviews and interviews with a range of stakeholders and are externally peer reviewed. POST would like to thank interviewees and peer reviewers for kindly giving up their time during the preparation of this briefing, including: 

Members of the POST Board* 

Steve Pugh, Department of Health & Social Care (DHSC)* 

Department of Science, Innovation & Technology (DSIT)  

Professor David Albert Jones, Anscombe Bioethics Centre* 

Professor Paula Amato, American Society for Reproductive Medicine (ASRM) 

Victoria Askew, Human Fertility and Embryology Authority UK (HFEA) 

Dr Zoe Bolton, Lancaster University* 

Dr Chris Burns, Medicines and Healthcare products Regulatory Agency (MHRA)* 

Dr Lee Carpenter, UK Stem Cell Bank (UKSCB), Medicines and Healthcare products Regulatory Agency (MHRA)* 

Professor Sara Fovargue, University of Sheffield* 

Professor Sarah Franklin, University of Cambridge 

Dina Halai, Human Fertility and Embryology Authority UK (HFEA) * 

Professor Soren Holm, University of Manchester* 

Dr Hafez Ismaili M’hamdi, Maastricht University  

Professor Emily Jackson, London School of Economics and Political Science (LSE)* 

Professor Susan Kimber, University of Manchester 

Dr Jonathan Lewis, University of Manchester* 

Professor Robin Lovell-Badge, The Francis Crick Institute* 

Dr Calum MacKellar, Scottish Council on Human Bioethics* 

Professor Saitou Mitinori, Kyoto University  

Dr Naomi Moris, The Francis Crick Institute* 

Professor Megan Munsie, University of Melbourne* 

Dr Laura O’Donovan, Lancaster University* 

Dr Greg Pike, Society for the Protection of Unborn Children (SPUC)* 

Dr Peter Rugg-Gunn, Babraham Institute* 

Dr Nicolas Rivron, Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA)* 

Dr Peter Ruane, University of Manchester 

Sandy Starr, Progress Educational Trust (PET)* 

Professor Roger Sturmey, University of Manchester* 

Ranveig Svenning Berg, Nuffield Council on Bioethics* 

Dr Robert Watson, Human Tissue Authority (HTA)*  

Professor Stephen Wilkinson, Lancaster University* 

Dr Nicola Williams, Lancaster University* 

Right to Life UK  

* denotes people and organisations who acted as external reviewers of the briefing. 

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