Scientists’ first attempt at creating structures resembling human embryos in the laboratory using stem cells has led to calls for stricter regulation in the rapidly developing field of stem cell research.

In the last seven days, numerous laboratories from around the globe have published pre-print studies summarising their work. As the research has not yet undergone peer review, experts advise treating these studies with caution.

A structure resembling an embryo was created in the labs without the use of sperm, eggs, or fertilisation using human embryonic stem cells, which can differentiate into any type of cell.

The goal is to provide scientists with a model to study human embryos in ways that were previously impractical due to ethical considerations in the hopes of learning new information about the causes of birth defects, genetic disorders, infertility, and other issues during pregnancy, Al Jazeera reported.

The first announcement was made last Wednesday at the annual meeting of the International Society for Stem Cell Research in Boston by Magdalena Zernicka-Goetz of Cambridge University and the California Institute of Technology.

A preliminary study describing the work done by the Jacob Hanna team at the Weizmann Institute of Science in Israel on stem cell-based human embryo models was published on Thursday.

The Zernicka-Goetz team then quickly released a preprint of their own that provided additional details. Other labs with bases in China and the US also published pre-prints late last week.

Researchers have disputed media reports that the cell clusters were “synthetic embryos,” arguing that because they were created from stem cells, they were not strictly synthetic and should not be categorised as such.

The highly competitive nature of research in embryo-like structures has been highlighted by the papers published by the Zernicka-Goetz and Hanna teams in August last year.

Both teams claimed to have accepted their studies and presented their work at conferences. Hanna, however, rejected the idea of being the first, claiming his models had more advanced features.

“The similarity of Hanna’s model to the natural embryo is remarkable, almost uncanny,” said Jesse Veenvliet, a researcher at Germany’s Max Planck Institute of Molecular Cell Biology and Genetics.

Expert Darius Widera advises waiting for peer review before comparing stem cell biology research, stating the immense impact and avoiding unhealthy hype, as new guidelines are needed.

According to Al-Jazeera, both labs developed embryo models for 14 days, the legal limit for growing human embryos in many countries. After 14 days, embryos form organs, including the brain, a “black box” period.

Most research regulations apply to fertilised embryos, allowing new embryo-like models.

Cambridge University has launched a UK project to develop the first governance framework for stem cell-based human embryo models. Scientists have emphasised that they do not intend to implant the models into a human womb, as previous research in a female macaque failed.

James Briscoe of Britain’s Francis Crick Institute called for researchers to proceed cautiously, carefully, and transparently, saying: “The danger is that missteps or unjustified claims will have a chilling effect on the public and policymakers, this would be a major setback for the field.”