Engineered living systems (ELS) are rapidly achieving a level of sophistication beyond organoid structures; soon, researchers may be faced with blurred lines of what constitutes a synthetic embryo. The 14-day rule, developed by bioethicists almost forty years ago, sets a clear demarcation of developmental stage at which research on intact human embryos must cease. This ethics module will focus when ELS should be considered equivalent to embryos and whether existing standards should be revisited in light of modern day technologies that can bypass naturally occurring phases of development.


You have recently started a collaboration with a colleague that has developed an advanced in vitro model of the nervous system from human induced pluripotent stem cells (hiPSCs) using new synthetic biology tools. When you see the most recent data, and based on your knowledge of embryogenesis, you realize that this new in vitro model reassembles and recapitulates the brain structure of a well-developed embryo beyond any recent reports in organoids formation. You immediately think of the incredible opportunity to study questions related to human brain development that could not be studied before, and the impact it can have on your field.

1. Would you consider applying the 14-day rule to this scenario? Why? Why not?

2. How is this discussion different for brain organoids as compared to other organoids such as liver, heart, kidney, etc.? Why?

3. We can easily identify the “primitive streak” due to its well-defined structure, but how about other higher-level characteristics such as identification of pain, consciousness, etc.?

4. Should you considerer developing any new ethics rules for such organoids and organoid structures?

Further resources:

Addressing the ethical issues raised by synthetic human entities with embryo-like features

Assembly of embryonic and extra-embryonic stem cells to mimic embryogenesis in vitro

A New Form of Stem-Cell Engineering Raises Ethical Questions