The Weizmann Institute scientists have created a model that has a close resemblance to an early human embryo. The embryo model offers insights into the enigmatic early stages of human development without the ethical dilemmas associated with traditional embryo research.

The embryo model is created using stem cells, without sperm, eggs, or a womb. It resembles a 14-day-old human embryo.

The research, published in the journal Nature, represents the first “complete” embryo model, encompassing all the crucial structures found in a human day-14 embryo. This was considered impossible previously.

The utilisation of naive stem cells is central to the research. It was reprogrammed to possess the capability to develop into any type of tissue within the human body. The embryo model can also produce hormones, leading to positive results on a pregnancy test in a laboratory setting. This functionality demonstrates the accuracy of the model.

The embryo model’s primary objective is to gain ethical insights into the critical but poorly understood initial weeks post-fertilisation. These early stages are marked by significant changes that have remained elusive to scientists, posing risks of miscarriage and birth defects. Professor Jacob Hanna, a key figure in the research, points out the limited knowledge surrounding this crucial period in human development and maintains how this work aims to fill that gap.

Embryo research has long been subject to legal, ethical, and technical challenges. However, with the Weizmann Institute’s embryo model, scientists can explore this intricate period without the ethical controversies associated with traditional embryo research methods.

Four distinct cells will be cultivated. Epiblast cells serve as the precursors to the embryo itself or the future foetus. Trophoblast cells, the progenitors of the placenta, are a vital organ for sustaining the developing embryo. Hypoblast cells are responsible for forming the supportive yolk sac. Extraembryonic mesoderm cells are critical for various developmental processes.

About 120 of these cells are combined, and scientists observe the transformation process. Approximately 1% of this cell mixture exhibited an extraordinary capability to spontaneously self-organise into a structure bearing resemblance to a human embryo. Though not identical to a human embryo, this biological engineering will make it easy to understand the earliest stages of human development.

Professor Jacob Hanna notes the significance of the meticulous interplay of providing the correct mix of cells and creating the appropriate environment for this process to occur.

The nurtured embryo models are allowed to develop until they reach a stage analogous to that of a 14-day-old embryo following fertilisation. This developmental stage is critical as it serves as the legal boundary for normal embryo research.