Pioneering Code of Practice released for use of stem cell-based embryo models in research

4 July 2024
stem research webstory image

1. A growing human gastruloid after embryonic stem cell aggregation. Credit Naomi Moris/University of Cambridge

Hull York Medical School and the University of Hull have been part of a major new project led by the University of Cambridge and Progress Educational Trust, to create the first ever UK guidelines for the generation and use of stem cell-based embryo models in research.  

These models can be created in the lab and mimic aspects of early human embryo development, which raises various ethical considerations.  

The use of stem cell-based embryo models is not regulated explicitly by existing UK law, which has created uncertainty for scientists and held back research.  

The new SCBEM Code of Practice proposes clear guidance and oversight processes, to bring greater transparency and openness to the research and reassurance to the public.  

Research using embryo models can advance understanding of early human development and possible causes of infertility.  

Stem cell-based embryo models (SCBEMs) are three-dimensional biological structures that mimic aspects of early human embryo development. They can be created in the lab from stem cells, and can provide new insights into critical stages of early human development that are normally inaccessible to researchers. 

Embryo model work is expected to lead to new interventions for a range of conditions, including revolutionising treatments for recurrent miscarriage, understanding developmental disorders and improving the success rate of IVF. 

Although embryo models are not the same as human embryos, they mimic aspects of early human development – and this has raised ethical concerns.  

The previous lack of a regulatory framework for the use of SCBEMs in research has left scientists and research organisations uncertain about the acceptable boundaries of their work, both legally and ethically, and unsupported in their decision-making. Signing up to the SCBEM Code of Practice will remove these obstacles.  

The guidelines, released today, provide the first code of practice for the use of stem cell-based embryo models in the UK. 

Professor Roger Sturmey, Professor of Reproductive Medicine at Hull York Medical School and Chair of the SCBEM Code of Practice Working Group, said: "We are confident that the Code will enable the UK to continue to lead the world in research into early human development, while ensuring that this research is ethically robust. 

"Stem cell-based embryo models offer great opportunities for advancing our understanding of early development and studying possible causes of infertility. However, at present these models are not addressed directly in UK law or regulation. We are therefore delighted to have published the Code of Practice for the Generation and Use of Human Stem Cell-Based Embryo Models, which will provide much-needed guidance to researchers, and provide wider reassurance that research in this area is being pursued in a responsible manner."  

Led by the University of Cambridge, the SCBEM Code of Practice Working Group included researchers and practitioners from Hull York Medical School, Babraham Institute, Biolawgy, Brighton and Sussex Medical School, the Francis Crick Institute, the Medical Research Council, Newcastle University, University College London, the the University of Edinburgh, the University of Exeter and the University of Manchester. 

Professor Kathy Niakan, Chair of Cambridge Reproduction and Professor of Reproductive Physiology at the University of Cambridge, and member of the SCBEM Code of Practice Working Group, said: "The new Code of Practice provides processes for decision-making in research using stem cell-based embryo models so that scientists can proceed confidently, while maintaining public trust in this vital area of research." 

Key points of the Code 

The new SCBEM Code of Practice sets out standards to make sure that research using SCBEMs is rigorous, upholds ethical principles and maximises the potential benefits. Key to this will be a dedicated oversight committee that will review each proposed research project.  

The Code recognises that there must be a limit to how long embryo models can be grown in the lab. However, many different types of embryo model are being developed, representing distinct developmental stages and developing at different rates, making it impossible to impose a single fixed limit. Instead, researchers will be required to provide clear justification of the length of their experiments on a case-by-case basis. 

The Code prohibits any human SCBEM from being transferred into the womb of a human or animal, or being allowed to develop into a viable organism in the lab. 

Professor Niakan said: "Embryo models have huge potential and we want to realise this, while also limiting the risks. The new Code of Practice will allow stem cell-based embryo models to be grown in the lab long enough to gain meaningful biological understanding, but researchers will have to fully justify what they’re doing in scientific and ethical terms." 

How are embryo models useful to research? 

Research using embryo models can improve knowledge of human development, including early pregnancy loss and pregnancy disorders, congenital defects and the precursor events that affect adult human health and disease. 

The models could also be used for some investigations that are not permitted using human embryos. For example, there are currently significant limitations to clinical trials and the use of many medicines during pregnancy. Models of early development could be helpful to improve options for drug treatments during pregnancy in the future.  

Stem cell-based embryo models open new research avenues that can complement, but not replace, the limited studies possible with actual human embryos. The SCBEM Code of Practice states that neither of these areas of research can or should replace the other for the foreseeable future. 

How was the Code produced? 

The SCBEM Code of Practice Working Group was made up of researchers and practitioners at institutions across the UK, including experts in science, law, ethics and regulation. In drawing up the Code, the team consulted widely with researchers, practitioners, and major funders and regulators of embryo model research.   

The work was also informed by a public dialogue, held earlier this year, to explore public attitudes towards research involving embryo models.   

Christina Rozeik, Programme Manager of Cambridge Reproduction and member of the SCBEM Code of Practice Project Team, said: "Throughout the process of developing the Code of Practice, we’ve  been keen to engage with as wide a range of stakeholders as possible, including researchers, experts in law and bioethics, regulators and funders." 

She added: "A public dialogue enabled us to include public voices during the development of the Code, taking account of their hopes, concerns and sensitivities around research involving stem cell-based embryo models. Participants were excited by the potential of embryo model research, but also strongly supportive of oversight." 

Sandy Starr, Deputy Director of the Progress Educational Trust (PET) and member of the SCBEM Code of Practice Project Team, said: "Research involving stem cell-based embryo models has enormous potential to improve human knowledge and health, but clearer governance is needed to help researchers work responsibly and maintain public trust. Our Code of Practice addresses this need. It takes into account an extensive range of expert and lay perspectives we’ve gathered over the past year."  

How will the Code be enforced? 

The Code is not legislative, but the team proposes that it should be adopted by UK researchers, funders, research organisations, professional societies and publishers. 

Widespread use is expected to deter the funding and publication of research that fails to meet the standards set out in the Code. As a result, adherence to the Code will become an essential part of credible science, providing increased transparency and accountability for embryo model research. 

Given the rapid pace of research using embryo models, the Code will be reviewed regularly.   

Professor Niakan said: "Research using stem cell-based embryo models is very new, and our understanding of the science is rapidly evolving. We’ve taken the opportunity to respond to the current situation, and we’ll continue to update the Code of Practice as the science continues to develop."  

Dr Peter Rugg-Gunn, Group Leader and Head of Public Engagement at the Babraham Institute, and member of the SCBEM Code of Practice Working Group, said: "Establishing this guidance takes stem cell-based embryo models out of the grey zone and onto more stable footing so we can fully explore their usefulness, while providing the essential reassurance that this research is being conducted carefully and with appropriate scrutiny."  

Creation of the SCBEM Code of Practice (fully titled: Code of Practice for the Generation and Use of Human Stem Cell-Based Embryo Models) was led by Cambridge Reproduction – an interdisciplinary research centre at the University of Cambridge - in partnership with the Progress Educational Trust (PET)  –  a charity that improves choices for people affected by infertility and genetic conditions. 

The work was funded by the BBSRC, the University of Cambridge Impact and Knowledge Exchange fund, and UKRI Sciencewise.

View the SCBEM Code of Practice.

For media enquiries contact: University of Hull Press Office, telephone: +44 (0)1482 465268 or email