Lab-grown brain organoids: time for international oversight

For several days in mid-September, neuroscientist and stem-cell biologist Sergiu Pașca became inseparable from his phone. As one of the principal authors on a study by researchers at Stanford University in California reporting the successful transplant of laboratory-grown human brain ‘organoids’ into mice, he was doing many interviews every day.

Read the paper: Developmental xenocortication using human-derived organoids in mice

The mice had been bred so that almost all of their cerebral cortex was missing from their brains. The transplanted lab-grown human tissue survived and developed working connections to the mice’s brains and spinal cords (K. Kaganovsky et al. Nature 658, 430–441; 2026).

It is without doubt a landmark achievement. Animal studies can reveal only so much about the human brain, and options to study live human brain tissue inside a person are limited. Around a decade ago, the creation of organoids — tiny 3D cellular structures grown in the lab that mimic some functions of real organs — changed this. The latest finding, which represents the most extensive integration of human brain cells into an animal so far, opens up further possibilities to understand conditions such as cerebral palsy and autism spectrum disorders in a nervous system, and to test possible interventions.

At the same time, lab-grown organoids are prompting ever deeper ethical questions. Researchers are asking whether the animals receiving implanted brain organoids might gain any human-like properties of consciousness or cognition. How should these characteristics be measured, and what extra oversight should there be for such studies?

Discussions over establishing an international oversight mechanism for brain organoid research are well under way. Such an instrument was recommended in a policy paper published last year (S. P. Pașca et al. Science 390, 574–577; 2025), preceding a conference in late 2025 that Pașca and his colleagues co-organized with Stanford bioethicist Henry Greely. The event was attended by scientists, ethicists, philosophers, policymakers, science communicators and the families of people affected by brain conditions. It was held at the Asilomar conference centre in California, well known for a 1975 meeting of scientists and research funders that discussed the need for safety measures and oversight at the dawn of genetic modification techniques.

Hybrid brains: the ethics of transplanting human neurons into animals

Much has changed in the intervening five decades. Today, life scientists’ research plans must go through various regulatory and ethics processes before any experiments start. These are designed to ensure that experiments involving biological specimens are conducted safely, that consent has been obtained from study participants, including those donating cells, and that animal welfare requirements are met. That said, some of the questions raised by the latest research into brain organoids are not routinely considered.

What form any further oversight should take, and its terms of reference, are still being worked out. A report from the 2025 Asilomar conference, published earlier this month (see go.nature.com/4dvagey), shows that scientists have a strong desire for any oversight mechanism to provide a service to the research community, such as regularly updated and actionable guidance for research groups.

A crucial question is whether an existing organization or research network should take responsibility for oversight or if a new body should be set up. This is important, because the identity of any eventual entity will help to determine whether it commands authority in the research community for its recommendations to be followed. Existing scientific academies and professional societies have such authority. However, most represent discrete disciplines such as stem-cell research or neuroscience, whereas the study of brain organoids includes researchers from these fields and others in the social sciences and humanities.

Independent advice

The ethical arrangements behind Pașca’s latest study also offer a way forward. In addition to various research-ethics and safety requirements, Stanford established an independent group of ethics advisers who reported to the institution. Members were drawn from disciplines in the sciences, social sciences and humanities, as well as from patient groups. These ethics advisers were involved throughout the project, reviewed plans and documentation for the design of experiments and, where necessary, proposed amendments. They were key partners in the research process. Having independent ethics advisers closely involved throughout the life of a research project is the right thing to do. Not every university will have Stanford’s level of resources, but this is where an oversight mechanism could play a valuable part in providing such a service.

Mini models of the human brain are revealing how this complex organ takes shape

During early research into the use of genetic modification in food and agriculture, the field became embroiled in huge public and media controversies in Europe, Africa and the United States. One reason was a perception that scientists were moving too quickly and not consulting enough, amid concerns that risks and harms needed to be better understood before large-scale deployment occurred. It is clear that lessons have been learnt from those times.

A lot is riding on research using brain organoids. For all those who have been diagnosed with brain disorders, and for their families, this work opens up hope for better understanding and, one day, for treatments. It is thus essential that this research is done to the highest standards of safety, minimizing harms and involving a necessarily wide range of stakeholders from science, social science and patient groups.