Zack Wise/The New York Times

In August 2022, NIH researchers from the University of Cambridge successfully created a synthetic mouse embryo model using cultured mice stem cells. This project aimed at using stem cells to express specific genes that would lead to the development of these mouse stem cells into embryos.

Stem cells are undifferentiated cells that developed into specialized cells with specific functions.

Prof. John Schimenti, biomedical sciences, explained the processes involved in this project as well as its implications for the future of scientific research.

There are many different types of stem cells and the relevant type for these experiments are called embryonic stem cells. These are totally undifferentiated and in the right context, could make all cells in the body by giving rise to more differentiated cells, Schimenti said.

The stem cells are placed in a culture medium, which optimizes their growth by stimulating cell-to-cell communication. This communication is necessary because cells use signaling during embryonic development.

This system of cell communication as a means of embryonic development is similar to the process of natural embryonic development in mammalian pregnancies such as humans.

During fertilization, the fertilized eggs cells divide into an embryo as it implants into the uterus.

Scientists had applied this knowledge by taking embryonic stem cells extracted in the lab and combining them with these early embryos. They were then placed in the uterus of a mouse subject and the resulting fetus contained cells that were partly, if not entirely, from the stem cells.

While the fetus develops, the mother starts to grow a new organ called the placenta, which supplies the fetus with the necessary nutrients as well as oxygen and glucose. The placenta guides the development of organs, acts as an immunological barrier to protect the fetus against infections, and synthesizes fatty acids and cholesterol, among other critical functions.

However, scientists found it challenging to mimic this natural environment in a petri dish because there was no placenta, which would have normally supplied the right balance of nutrients to the developing embryo.

To direct the development of the synthetic embryo, the researchers in this project started with embryonic stem cells that were completely undifferentiated. They then differentiated some of them into two different cell types by adding the corresponding developed cells.

The first group of differentiated cells would ultimately form the placenta and the other would become the yolk sac, a membranous structure attached to an embryo where the embryos first blood cells are made.

There are three different types of cells present: the unadulterated embryonic stem cells and the two partially differentiated helper tissues. They are mixed together after doing experiments to figure out the right ratios of factors like gas and nutrient levels, Schimenti said.

The project, starting in 2012, culminated in a synthetic embryo with a semi-functioning brain and heart. The organs were semi functioning because while they did work, they were not enough to independently sustain life.

This outcome significantly adds to the understanding of not only stem cells but the science of embryonic development because it allows scientists to experiment with embryonic development in real time. The University provides a unique opportunity to engage more with these concepts through its initiatives for stem cell research such as the Ansary Center for Stem Cell Therapeutics and the later established Cornell Stem Cell Program.

Moving forward with this breakthrough, researchers at the University continue to refine the different aspects of stem cell research by pushing development further and improving the efficiency of the organs being developed.

Despite this scientific breakthrough, there is still more to contribute in the study of the relationship between stem cells and regenerative medicine.

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Cornell Prof Explains Relevance of Creating Mouse Embryos from Stem Cells - Cornell University The Cornell Daily Sun