New Embryo Models Mimic Structures Found in Real Ones, Perfect Replica Is Not Desirable, Unlikely Possible

Lab engineers have been working on replicating human embryos to study them. They are close to making one that works like the real one, but they also know that creating a perfect replica will not be desirable.

Human Embryo Models

Jacob Hanna of the Weizmann Institute of Science in Rehovot, Israel, developed a new embryo model that closely resembles the real thing. Scientists and ethicists recently spoke with Science News about the different issues surrounding human embryo models.

A human embryo is the result of the fertilization of an egg and sperm, according to Amander Clark, president of the International Society for Stem Cell Research.

On the other hand, embryo models self-assemble from pluripotent stem cells, which can't create almost any type of cell in the body. According to Clark, a UCLA stem cell researcher, developmental biologist, and geneticist, embryo models do not arise from the product of fertilization by two gametes and do not, therefore, fit the clinical, medical, or scientific definition of an embryo.

Researchers have long studied the first week or so of human development using donated human embryos or model embryos. Scientists discovered how a blastocyst, a ball of cells, develops from those. Blastocysts have an inner cluster of cells that will develop into the body and an outside layer of cells that will form the placenta and other support structures for the developing fetus.

According to stem cell researcher and embryologist Jacob Hanna of the Weizmann Institute of Science in Rehovot, Israel, the actual action occurs in the first few weeks of life. After fertilization, the embryo begins to develop all its organs between day seven and day 35.

He added that the remaining eight months are just the embryo's growth. Once it transforms from a ball of cells to a structure, anyone on the street can identify it as an embryo.

Researchers have assembled embryo models with some, but not all, cell types required for typical development. The recently discovered embryo models imitate the components present in an embryo implanted in a uterus, despite lacking a uterus. According to Clark, the models are modeling a very narrow window of embryo development, including the activities that occur as an embryo implants and how the embryo self-assembles. However, they essentially collapse after that. She added that no model accurately replicates the real one.

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Human Embryo Models Ethical Concerns

The thought of replicating human embryos raised eyebrows, with many wondering if they can result in babies. Embryo models can help experts study pregnancy failures and could lead to better fertility treatments, according to stem cell biologist Magdalena Żernicka-Goetz of the University of Cambridge and Caltech. However, per the report, embryo models don't result in babies.

Hanna said that it's illegal to use embryo models in the uterus. He added that even if he wanted to, those structures could never be implanted as implantation only occurs when embryos have one to 64 cells.

Hanna noted that the post-implantation models have gone beyond that stage, so the embryo models will never succeed biologically.

Alfonso Martinez Arias, a developmental biologist at Pompeu Fabra University in Barcelona, who previously made gastruloids that could model development up to day 19 after fertilization, said that the goal of scientists is to understand the process of cell assembly and how it creates the organs and tissues of the body. He added that making babies from embryo models is not something they should do or is on the horizon.

The outlet added that it's neither desirable nor possible to create a perfect replica of an embryo. Martinez Arias hoped they could develop it for research, and people would stop speculating how far they could go with it without considering how they would return.