©2021 by The International Society for Stem Cell Research. All rights reserved.

No part of this document may be produced in any form without written permission of The International Society for Stem Cell Research.

Culture of Human Embryos

This page assembles the sections of the Guidelines that specifically address research involving the culture of human embryos.  Other sections of the Guidelines may be relevant to such research (e.g., Section 2.1 Review Process, Section 2.3 Procurement and Informed Consent of Human Biological Materials, and Section 2.4 Derivation, Banking, and Distribution of Human Cell Lines). 

2.2.2 Category 2

2.2.2 Category 2. Forms of research with embryos, certain chimeras, and stem cell-based embryo models that are permissible only after review and approval through a specialized scientific and ethics review process. A comprehensive review should be coordinated with other relevant oversight, such as that provided by human subjects review committees, in vitro fertilization (IVF) clinic oversight bodies, and animal research review processes (see 2.2.1), and the research should comply with local law and policy. All such research should have a compelling scientific rationale and necessitate the use of these materials rather than employ alternative models. The research should use the minimum number of embryos necessary to achieve the scientific objective. Forms of research requiring comprehensive review by a specialized review process encompass the following activities:

  1. Procurement and use of IVF human embryos for research in vitro.
  2. Procurement of human gametes to create research embryos in vitro.
  3. Research that generates human gametes from any progenitor cell type in vitro, when this entails performing studies of fertilization that produce human zygotes and embryos. The gametes may be derived from human pluripotent stem cells, oogonia, or spermatogonial stem cells that have been maintained in vitro, and they may be genetically modified or not. Any human embryos obtained from such gametes must only be studied in vitro, or be used to derive stem cell lines, such as embryonic stem cells.
  4. Research involving the genetic alteration of human embryos or gametes used to make embryos in vitro.
  5. Derivation of new cell lines from human embryos (not confined to pluripotent cell lines).
  6. Research involving the in vitro culture of human embryos where embryos are maintained in culture until the formation of the primitive streak or 14 days from fertilization, whichever occurs first. 

Culture of Human Embryos Beyond formation of the primitive streak or 14 Days

It is currently not technically feasible to culture human embryos beyond formation of a primitive streak or 14 days post-fertilization. However, culture systems are evolving, making this a possibility in the near future. Understanding the primitive streak, early germ layer development and primordial germ cell formation in humans is crucial to improve our understanding of and interventions for infertility, in vitro fertilization, pregnancy loss, and developmental disorders that occur or originate soon after implantation. Research using embryos is also crucial to validate integrated stem cell-based embryo models, which in the future may provide a more practical alternative to understanding some aspects of early human development.

Recommendation Given advancements in human embryo culture, and the potential for such research to yield beneficial knowledge that promotes human health and well-being, the ISSCR calls for national academies of science, academic societies, funders, and regulators to lead public conversations touching on the scientific significance as well as the societal and ethical issues raised by allowing such research. Should broad public support be achieved within a jurisdiction, and if local policies and regulations permit, a specialized scientific and ethical oversight process could weigh whether the scientific objectives necessitate and justify the time in culture beyond 14 days, ensuring that only a minimal number of embryos are used to achieve the research objectives.