Researchers grow mouse embryos outside the uterus to reveal hidden growth stages

Scientists at the Weizmann Institute of Science have announced they're growing advanced mouse embryos outside the uterus. The method would allow the researchers to view the hidden first stages of embryonic development as the mouse embryo grows from a very tiny ball of cells through organ growth. Researchers want to observe how the small ball of identical cells grows to an embryo from first attaching to the uterine wall and then developing into body systems and organs.Researchers say this has been a "highly-sought grail" in the field of studying embryonic development for a century. The method the researchers created for growing mouse embryos outside the womb during the initial stages after embryo implantation through more advanced stages will allow the researchers a new tool for understanding the development of an embryo that is encoded in the genes inside it.

They hope to gain detailed insight into birth and development effects and those involved in embryo implantation. Researchers on the project say that most of the knowledge known today about mammalian embryonic development was learned from observing processes in non-mammal species like frogs and fish that lay transparent eggs. It has also been gathered in the past from dissecting mouse embryos and capturing static images.

Researchers have had the idea of growing embryos outside the uterus through advanced stages since the 1930s. Early experiments had limited success, and embryos developed via this method tended to be abnormal. In the new process, the researchers renewed that effort focusing on the way development happens with embryonic stem cells. During seven years of trial and error, the team came up with a two-step process that allowed them to grow normally developing mouse embryos outside the uterus for six days, about one-third of their 20-day gestation period.

During that time, embryos had a well-defined body plan with visible organs. The process starts with mouse embryos that are several days old, which was right after they would've implanted in the uterus. They consisted of about 250 identical stem cells and were placed in a special growth medium in the laboratory where they attached to the medium as they would to the uterine wall. The team can also inject genes or other elements in the cells and get results consistent with development inside a mouse uterus. The team also plans to attempt to create artificial embryos made from stem cells in the future.