Editorial: Questions about synthetic embryos

The importance of research cannot be overestimated, but ethical and legal issues must be prioritized

The scientific community is excited about using stem cells to create the world’s first synthetic human embryo, a breakthrough that could help researchers study the earliest stages of human development. From an ethical point of view, it is fascinating but also disturbing that embryos are not formed from the union of sperm and eggs, but are developed by using stem cells in the laboratory. Two teams of scientists at the University of Cambridge in the United Kingdom and the California Institute of Technology in the United States have announced that they have grown embryo-like structures made entirely of human stem cells, more advanced than any previous effort. About 14 days after fertilization, the synthetic embryos developed to a stage comparable to natural embryos. While this is good news for medical researchers, as it spurs further research into genetic diseases, it also raises ethical and legal questions. Ethical issues are associated with the manufacture of human embryos, especially embryos older than 14 days. Last year, the Weizmann Institute in Israel implanted embryo-like models made from mouse stem cells into the wombs of female mice; similar experiments on monkeys in China failed. However, their synthetic model has features such as a gut, the initial stages of brain cell development, and a beating heart. Synthetic embryos promise to reveal the so-called “black box” periods of fetal development – the periods before pregnancy progress can be detected by scans.

Stem cell-based models could provide a window into miscarriage cases and facilitate the study of genetic diseases without the use of early embryos. The primordial embryo did not have a heart or underdeveloped brain, but included cells that went on to form the placenta, yolk sac, and the embryo itself. The latest breakthrough raises the possibility of further research on the topic, which could one day lead to the development of living things from synthetic embryos. This makes a strong case for strict legislation to curb misconduct. The breakthrough underscores how quickly science in this field outpaces the law. The importance of research progress cannot be overestimated, but relevant ethical and legal issues should be addressed as a priority. Another important open question is whether it is theoretically possible for these structures to grow into living things. Synthetic embryos grown from mouse cells are nearly identical to natural ones, according to reports. But when they were implanted in the wombs of female mice, they did not develop into living animals. Over the past few years, scientists have learned more about how to coax stem cells to develop into increasingly complex structures. Artificial kidneys, hearts and more are being made in labs, though they’re still too crude for medical use.