Real-time visualization of chick embryo development from egg to chick

Efforts to observe chicken embryonic development date back to Aristotle date back to 300 BC. However, because the chicken's eggshell is opaque, it has been necessary to break the shell to observe the embryonic development occurring inside the egg. As a result, attempts have been made to develop transparent artificial culture vessels. A previously reported method involves removing embryos from their shells after being incubating them for 3 days and then hatching them in a transparent artificial culture vessel. However, when fertilized chick embryos immediately after laying (0-day-old embryos) were cultured using this method, they did not develop normally.

The researchers investigated the cause of this issue and discovered that the yolk membrane covering the surface of the blastoderm (the area where local cell division occurs during egg development) became dry by the third day of culture (3-day-old embryos). To prevent the yolk membrane from drying out, the researchers utilized a rotary shaker with the top plate rotating at an angle of 7°. This innovation prevented the membrane covering the blastoderm from drying out, which subsequently improved the survival rate of the 3-day-old embryos. Furthermore, as these embryos continued to be cultured using the conventional shell-less method, embryonic development progressed, leading to the successful hatching of several normal chicks on the 21st day after the start of incubation.

The results of this research are expected to provide a foundation for various applications, including chick embryo development, toxicity assessments, and regenerative medicine.