Why regulating stem cell–based embryo model research is important (yet controversial)

The stem cell-based embryo model (SCBEM) takes advantage of the flexibility of pluripotent stem cells (non-reproductive cells that can give rise to many different types of cells) to resemble that of embryos. While this model has helped to advance research in diseases and develop therapies or treatments, it has also sparked international debate on what regulations should be placed on this type of experimentation. Researchers reviewed what countries are doing to regulate SCBEM and proposed what regulation should look like for this field of stem cell research to move forward in a manner that everyone can agree is ethically sound.

The researchers published their results in EMBO Reports in March 2025.

Stem cell-based embryo models (SCBEMs) are a major improvement for studying human development and diseases or issues that can arise with it, which can then lead to research regarding treatments and therapies for those diseases. These cells are human in origin, but the embryos involved were generated from pluripotent stem cells. While most studies use embryonic stem cells, SCBEMs can also be created using induced pluripotent stem cells (iPS cells), which are reprogrammed from somatic cells such as skin or blood. These cells are distinctly different from germ cells, which are egg and sperm cells.

Currently, only a few countries are participating in governing SCBEM research. Australia has deemed that blastocyst-like structures (cluster of cells resulting from a fertilized egg) are to be treated the same as an embryo (early stages of growth for an animal resulting from a fertilized egg). The UK similarly set out “codes of conduct” for this research, though they also brought in public opinion to inform the policymakers’ decision. Japan has been involved in exploring regulation of this type of research and is aiming to take the lead in developing ethical and innovative guidelines to foster a positive outlook on the field of regenerative medicine and developmental biology using SCBEMs.

“Against this backdrop, our paper reviews international trends in the regulation of SCBEM research, examines the national-level debates that have taken place in Japan, and surveys what regulatory strategies have been adopted,” said Tsutomu Sawai, corresponding author of the study and a professor (special recognition) at the Graduate School of Humanities and Social Sciences, Hiroshima University.

What was uncovered during the research were three key areas for improvement: the limited citizen participation in establishing policies, difficulty in coordinating multiple regulatory frameworks and the uncertainties that can arise regarding informed consent when working with human-based stem cells resembling an embryo. These three areas are enough to provide a network of hurdles to cross, especially when the current regulations vary so widely on how they were established. Some regulations are put in place with reliance on researcher-led guides, others rely on the existing government policies to put SCBEM regulations into place.

The suggestions put forth in this review are that fertilized embryos should be treated and classified as distinctly different from SCBEMs and therefore should not have the limits imposed upon them some might believe is necessary. Each project will have its ethical suitability determined by committees working under the International Society for Stem Cell Research (ISSCR) to ensure their work meets the guidelines set forth. This will help to alleviate some of the complexities of working with multiple frameworks for policy-making and give researchers a solid definition of what can be expected.

“Ultimately, our goal is to contribute to the formation of a robust, ethically sound, and internationally aligned regulatory system for SCBEM research,” said co-author Tomonori Nakamura, an associate professor at Kyoto University’s Institute of Advanced Study of Human Biology.  

To reach this goal, multinational cooperation is needed to adhere to international standards set forth. This will involve each country developing regulations that are in line not only with international standards but also with its own existing regulatory framework and its citizens’ perspectives. Japan’s eagerness to develop this type of framework and keep it adaptable will ideally help usher other countries into this area of ethical, innovative and dynamic research.

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Tsutomu Sawai of the Graduate School of Humanities and Social Sciences at Hiroshima University, Shu Ishida, Chie Kobayashi, Gyo Nakao and Tsutomu Sawai of the Uehiro Division for Applied Ethics at Hiroshima University, Tomonori Nakamura and Tsutomu Sawai of the Institute for the Advanced Study of Human Biology at Kyoto University, Tsutomu Sawai and Julian Savulescu of the Yong Loo Lin School of Medicine at National University of Singapore, Yasuna Murase of the Graduate School of Arts and Sciences at The University of Tokyo, Tomonori Nakamura of the Department of Anatomy and Cell Biology at Kyoto University and of the Hakubi Center for Advanced Research at Kyoto University and Julian Savulescu of the Oxford Uehiro Center for Practical Ethics at University of Oxford, Biomedical Ethics Research Group at Murdoch Children’s Research Institute and Melbourne Law School at The University of Melbourne contributed to this research.

The Japan Society for the Promotion of Science, JST Research Institute of Science and Technology for Society, the Uehiro Foundation on Ethics and Education and the Singapore Ministry of Health under Enablers and Infrastructure Support for Clinical Trials-related Activities Funding Initiative made this research possible. 

About Hiroshima University

Since its foundation in 1949, Hiroshima University has striven to become one of the most prominent and comprehensive universities in Japan for the promotion and development of scholarship and education. Consisting of 12 schools for undergraduate level and 5 graduate schools, ranging from natural sciences to humanities and social sciences, the university has grown into one of the most distinguished comprehensive research universities in Japan. English website: https://www.hiroshima-u.ac.jp/en