Written by Isobel Young, Science Writer
Until recently, synthetic embryos only existed in sci-fi novels. Now, researchers from the Weizmann Institute of Science in Israel have transformed science fiction into science fact. A new study, published in Cell, outlines how the team of researchers utilized an ex utero platform that they had previously developed to induce post-gastrulation development of naïve pluripotent stem cells from mice, resulting in the formation of the world’s first synthetic embryo.
Unlike human embryos, synthetic embryos (also known as sEmbryos or SWEMs) are generated without an egg, sperm or fertilisation. Instead, the synthetic embryos in this study were produced via cell-aggregation of pluripotent stem cells. While previous embryo-like models have been developed using embryo derived TSC lines, this is the first time that embryonic cells have undergone gastrulation and resulted in an embryo. Gastrulation is the process by which the blastula undergoes cell differentiation, resulting in the formation of different cell lineages and thus develops into a gastrula.
Formation of organs
The team were successful in growing post-gastrulation SWEMs. They found that the SWEMs had structures that resembled early formation of neural tubes, gut tubes and beating hearts. They identified these structures using whole-mount immunofluorescence to identify structure specific markers. Detection of Sox2 expression and Brachyury+ cells indicated the formation of the neural tube. Heart cells were detected by positive expression of MHC-II and Gata4, and the structure resembling the gut tube was identified by Sox17 expression. The team also performed transversal cross-plane sectioning, which further supported their findings from the whole-mount immunofluorescence.
The author says the study “underscores the dormant self-organization capability of naïve pluripotent stem cells into advanced organized whole embryo like entities.” Not only does this provide scientists with a clearer understanding of embryonic development, but also provides a useful tool to researchers in the biotechnology field.
As with any other piece of research, this study does have some weaknesses. Firstly, only a very small number of SWEMs were successful. 95% of the cells that underwent cell-aggregation did not develop into post-gastrulation embryos. This indicates that this is not a reliable method of synthetic cell production. However, this study is just the beginning. It provides a springboard for future research to occur, where more reliable methods of SWEM production can be established.
With the increasingly tense political atmosphere surrounding the ethics of stem cell research, synthetic embryos could be the solution for easing such concerns. This is because the researchers found that the SWEMs were not capable of developing into living animals- transplantation of SWEMs into the wombs of mice did not result in a successful pregnancy. This is helpful in eliminating the concern that using embryos in scientific research is preventing a possible life from occurring. While this study demonstrates a huge leap of knowledge and potential future applications of pluripotent stem cells, it is important to recognize that due to the novelty of this research, an ethical grey area remains.
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