The ISSCR Statement on New Research with Embryo Models

The ISSCR supports research with embryo models derived from human pluripotent stem cells that is conducted with scientific and ethical rigor. ISSCR encourages researchers to continue to follow the ISSCR Guidelines for Stem Cell Research and Clinical Translation when considering research in this emerging area. Recent work presented at the ISSCR 2023 Annual Meeting in Boston, USA this month and additional research posted online as preprints shortly thereafter highlights the rapid pace of progress in the development of stem cell-based embryo models. To aid public understanding of this progress and assist the media in accurate reporting, the ISSCR provides the following information.

Embryo models are organized three-dimensional structures derived from pluripotent stem cells that mimic the developmental processes that occur in early human embryos. Recent advances involve the growth of integrated embryo models, which contain both embryonic and extra-embryonic structures, from embryonic stem cells or induced pluripotent stem cells in laboratory dishes. Use of these models allows experimental modeling of the early stages of embryonic development that occur in the first few weeks of pregnancy. They can facilitate understanding of early pregnancy loss and placental failure, and help researchers gain basic knowledge of the early developmental origins of congenital defects in the heart, nervous system, and other organs.

Unlike some recent media reports describing this research, the ISSCR advises against using the term "synthetic embryo" to describe embryo models, because it is inaccurate and can create confusion. Integrated embryo models are neither synthetic nor embryos. While these models can replicate aspects of the early-stage development of human embryos, they cannot and will not develop to the equivalent of postnatal stage humans. Further, the ISSCR Guidelines prohibit the transfer of any embryo model to the uterus of a human or an animal.

ISSCR’s guidelines recommend that research with integrated embryo models can only proceed with a compelling scientific rationale and after careful review and approval by a specialized scientific and ethical oversight process. Integrated embryo models should also be maintained in culture for the minimum time necessary to achieve the scientific objective. And researchers must also comply with local laws and policies. Adherence to these guidelines ensures that stem cell research is ethical, practical, and appropriate.

The continued development of embryo models represents a step toward better understanding the earliest stages of human development and the developmental defects that can occur at this stage. For more information, consider reviewing Toward Guidelines for Research on Human Embryo Models Formed from Stem Cells and the SnapShot: Embryo models, both published in Stem Cell Reports, as well as the ISSCR Guidelines.

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