Mouse stem-cell-based embryo models mimic natural blastocysts

Mouse stem cells have been used to create an embryo model that mimics the stage where an embryo implants into the uterus.

A new method for making blastoids, a type of stem-cell-based embryo model (SCBEM), has been developed by researchers from the California Institute of Technology (Caltech), Pasadena, California. These blastoids resemble the embryo at the blastocyst stage, where it would typically implant into the uterus. The study, published in Developmental Cell, showed that the blastoids responded to environmental factors, including nicotine, alcohol, caffeine and protein intake, in a similar way to a natural mouse embryo at the same developmental stage.

'These live models allow us to watch, in a dish, how early embryos organise themselves, and to test how common environmental exposures – like caffeine, alcohol, nicotine, and even high or low protein diets – affect that process,' said Professor Magdalena Zernicka-Goetz, Bren professor of biology and biological engineering at Caltech and research group lead.

The researchers were interested in modelling embryos at the blastocyst stage as implantation into the uterus is a point where many pregnancies fail, but the reasons why are not fully understood. Starting from a combination of three types of mouse stem cells to ensure all the required cell types were generated, the researchers developed a blastoid model which had a similar structure and dimensions to a mouse blastocyst. The 80 percent efficiency rate means that the blastoids can be produced reliably enough for screening the impacts of numerous environmental factors at different concentrations and timings.

'When applied to humans, it could help us understand why some embryos thrive while others fail, and how to optimise conditions for conception – whether natural or assisted,' said Dr Sergi Junyent, a Caltech postdoctoral scholar and co-first author of the paper.

SCBEMs are cell aggregates that aim to mimic the structure and function of embryos, allowing for research into the early stages of pregnancy. Research involving SCBEMs can complement research involving natural embryos.

This blastoid model could be used to understand environmental factors, including diet, that may cause pregnancies to fail at this crucial implantation stage. However, the group has only achieved a low efficiency in progressing the blastoids past the implantation stage, limiting the information they could gain about further development and effects on implantation itself.

As this model used mouse cells, further research would be required to establish if the same response is observed using a human blastoid model.