New legal definition of embryo proposed

An international group of researchers has suggested refining the legal definition of a human embryo, as part of a proposed ethical framework for embryology that takes account of the increasing sophistication of embryo models.

Ambiguity about what constitutes an embryo can make it challenging to establish clear ethical boundaries for research involving stem-cell-based embryo models (SCBEMs). The authors of a new paper propose that a human embryo should be defined as 'a group of human cells supported by elements fulfilling extra-embryonic and uterine functions that, combined, have the potential to form a fetus'. This definition would exclude all of the embryo-like structures that have been created to date using stem cells, without the need for eggs or sperm .

Lead author Dr Nicolas Rivron, a developmental biologist at the Institute of Molecular Biotechnology in Vienna, said: 'These new propositions are part of an effort to bring clarity to ongoing research – to better classify the types of structures formed in the laboratory, to refine the legal definition of human embryos, and to pinpoint what currently makes models and embryos different from the legal standpoint.'

Earlier definitions of embryos have tended to assume that their creation must involve either fertilisation or cloning. Given the pace and trajectory of research involving SCBEMs, this assumption may not always be justifiable in future.

Dr Rivron said that he and his fellow authors hoped SCBEM research would 'benefit society by supporting the development of medicines to combat infertility and early pregnancy loss and by leading to a better understanding of the origins of congenital malformations and diseases'.

Their paper suggests possible 'tipping points', beyond which it may be advisable to place SCBEMs on a similar legal and ethical footing to conventional embryos.

The paper, published in Cell, may help to inform discussions of UK regulation that are currently being held by the Human Fertilisation and Embryology Authority and by the Governance of Stem-Cell-Based Embryo Models (G-SCBEM) project.

'This is a thought-provoking contribution to ongoing discussions about stem-cell-based embryo models – in particular, thinking through how these models should be categorised, and how their use in research should be governed' said Sarah Norcross, director of PET.

'G-SCBEM is currently developing a recommended governance framework for UK research involving embryo models. Papers such as this one, and the Guidelines from the ISSCR, all add to the rich body of material that G-SCBEM is taking into consideration.'