Researchers in Israel have reported a new system, which includes rotating bottles filled with nutrients, that is able to keep mouse embryos alive enabling them to form hind limbs and all their major organs.
Understanding the processes that lead to the formation of tissues and organs is important to answer fundamental questions about our development. In mammals, this occurs after the embryo is implanted into the uterus. This makes it relatively inaccessible for observation and manipulation. As a result, our understanding of the events occurring from pre-gastrulation to organogenesis remains limited. In addition, establishing these conditions outside the uterine environment remains challenging. While researchers have proposed a number of culture techniques since the 1930s, these platforms remain highly inefficient for normal embryo survival. Protocols for extended culturing are unfortunately still lacking.
Mouse embryos grown ex utero
In this study, published in Nature, researchers devised a method for growing mouse embryos outside a uterus for longer than ever before.
The team’s process began by growing the embryos on culture plates that enabled development of embryos before gastrulation until the hind limb formation stage. The researchers transferred late gastrulating embryos to a set of rotating jars, keeping them alive for an additional four days of development.
Moreover, the team introduced molecular tags into certain cells in the embryos to follow the fate of those cells as development progressed. The system was also manipulated to add labelled primitive microglia progenitors into the embryo, which partly integrated, proliferated and migrated into the developing host brain.
This study for the first time showcases that the processes of gastrulation and organogenesis can be recapitulated in petri dishes in a mammalian species. The techniques used have opened doors for making embryos more accessible for detailed study of many aspects of development. The team hope to next grow mouse embryos created by in vitro fertilisation, rather than ones from natural pregnancies, to observe the process from day zero.
Image credit: By Science Photo Library – canva.com