Gastruloids

How can a scientist study the early stages of mammalian and human life without the need for a full embryo due to practical and ethical concerns? The solution is gastruloids. Gastruloids are aggregates of embryonic stem cells that are used to mimic the stages of life when an embryo is still developing. They can be made from stem cells that come from embryos or pluripotent stem cells (stem cells that have the ability to give rise to other types of stem cells). These stem cells come together, and in certain conditions, resemble an embryo. However, they cannot fully form into an organism as they are missing several key traits. 

Gastruloids are very convenient for scientists to use: Although they use stem cells, which can be difficult to derive, they only need the correct environment to form embryo-like structures and stimulate the events an embryo would go through. These events include germ layer formation (also known as gastrulation), body axis formation, and symmetry breaking. Gastrulation is the process by which an embryo develops layers for the body and stops acting as a blob of tissue. There are three main layers: the ectoderm, mesoderm and endoderm. The ectoderm is the outermost layer and consists of skin and the nervous system. The mesoderm is the middle layer and houses the less complex parts of the body, such as muscles, bones and blood. The endoderm contains complex organs like the gut and lungs. Body axis formation refers to the process by which an embryo differentiates the anterior and posterior of a body. This helps determine where organs and features go. Symmetry breaking refers to, of course, the breaking of the symmetry of an embryo. This sets up the body plan and is closely tied to body axis formation. 

After these initial events, gastruloids can’t mimic embryos further as a number of traits and features are unable to be made. These features include many parts of the brain – like the forebrain, midbrain and hindbrain – and the heart, unless the gastruloids were specifically engineered. In addition, they lack extraembryonic tissues like the placenta, yolk sac, and amnion. Nevertheless, scientists can still use gastruloids to study congenital and genetic disorders, test drugs, and study how embryos and organisms form.

Reference:

Arias, A. M., Marikawa, Y., & Moris, N. (2022a). Gastruloids: Pluripotent stem cell models of mammalian gastrulation and embryo engineering. Retrieved from Gastruloids: Pluripotent stem cell models of mammalian gastrulation and embryo engineering - PMC 

Communicatie, A. (2024). Review: Gastruloids as model system for embryonic development. Retrieved from Review: gastruloids as model system for embryonic development 

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