In a breakthrough scientific experiment, researchers at the University of Cambridge have developed a structure that looks like a mouse embryo, by using two type of stem cells and growing them in a 3D mold.

Stem cells are a type of cells that are produced after the fertilization of the egg by the sperm, in a process called "mitosis". Mitosis is simply the biological name for cell division. There are three type of stem cells: the embryonic stem cells (ESC), the extra-embryonic trophoblast stem cells (TSCs), and the primitive endoderm stem cells. 

During this early period of embryonic development, embryonic stem cells (ESCs) clump together to form an inner cell mass that gives rise to the embryo. The extra-embryonic trophoblast stem cells (TSCs) form the placenta while the primitive endoderm stem cells generate the yolk sac. This phase of development is known as "blastocyst".

Growing artificial embryo-like formations in a lab turned out to be an onerous challenge as previous scientific attempts used only ESC cells and have thus attained little success. This was particularly due to the fact that creating a functional blastocyst requires all the different cell types to talk to each other in order to organize their formation.

By learning from these previous experiments, Cambridge researchers were able to create a structure which has the ability to arrange itself and behaves like a normal embryo. To achieve that, they used a combination of genetically-modified mouse ESCs and TSCs, which were cultivated on top of a 3D mold (i.e.,  an extracellular matrix).

“Both the embryonic and extra-embryonic cells start to talk to each other and become organised into a structure that looks like and behaves like an embryo,” said lead scientist Magdalena Zernicka-Goetz, professor of Mammalian Development and Stem Cell Biology in the Department of Physiology, Development and Neuroscience.

The researchers were able to observe the sophisticated degree of communication between the cells. Communication between stem cells at this stage is vital to the formation of a healthy embryo as it enables them to place themselves in the right place at the right time.

Even though the artificial embryo followed the same pattern seen in natural embryos, the researchers said that the probability that it will develop into a healthy fetus is very thin as it needs the third type of stem cells (i.e., primitive endoderm stem cells) to form the yolk sac, which would provide the necessary nutrients for the embryo. 

Dr Andrew Chisholm, Head of Cellular and Developmental Science at Wellcome, thinks that  Professor Zernicka-Goetz’s work is an important step toward understanding the factors that cause a significant number of human pregnancies to fail at this stage.

Photo courtesy of Berna Sozen, Zernicka-Goetz Lab, University of Cambridge

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