Understanding the very early stages of embryo development is of interest because this knowledge may help explain why a significant number of human pregnancies fail at this time.
Combining genetically-modified mouse ESCs and TSCs, together with a 3D scaffold known as an extracellular matrix, scientists were able to grow a structure capable of assembling itself and whose development and architecture very closely resembled the natural embryo.
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.
There was a remarkable degree of communication between the two types of stem cell: in a sense, the cells are telling each other where in the embryo to place themselves.
Interactions between the different types of stem cell are important for development, but the striking thing that new work illustrates is that this is a real partnership - these cells truly guide each other.
Comparing their artificial ‘embryo’ to a normally-developing embryo, the team was able to show that its development followed the same pattern of development.
The stem cells organise themselves, with ESCs at one end and TSCs at the other.
A cavity opens then up within each cluster before joining together, eventually to become the large, so-called pro-amniotic cavity in which the embryo will develop.
This is a technique that allows blastocysts to develop in vitro beyond the implantation stage, enabling researchers to analyse for the first time key stages of human embryo development up to 13 days after fertilisation.
This could overcome a shortage of embryos. Currently, embryos are developed from eggs donated through IVF clinics.
How Are Embryos Formed?- Once a mammalian egg has been fertilised by a sperm, it divides multiple times to generate a small, free-floating ball of stem cells.
- The particular stem cells that will eventually make the future body, the embryonic stem cells (ESCs) cluster together inside the embryo towards one end: this stage of development is known as the blastocyst.
- The other two types of stem cell in the blastocyst are the extra-embryonic trophoblast stem cells (TSCs), which will form the placenta, and primitive endoderm stem cells that will form the so-called yolk sac, ensuring that the foetus’s organs develop properly and providing essential nutrients.
- Previous attempts to grow embryo-like structures using only ESCs have had limited success. This is because early embryo development requires the different types of cell to coordinate closely with each other.
