Scientists have grown a synthetic embryo for the first time without fertilized eggs, and it could open the door to growing organs and tissues.
Key Points:
- Researchers at the Weizmann Institute of Science have grown synthetic mouse embryo models outside the womb starting solely with stem cells grown in a dish.
- The method opens up new horizons for studying how stem cells form various organs in the developing embryo
- It could make it possible to grow tissues and organs for transplant using synthetic embryo models
Researchers at the Weizmann Institute of Science have grown synthetic mouse embryo models outside the womb starting solely with stem cells grown in a Petri dish.
The study, published this week in the journal Cell, has opened up horizons for studying how stem cells form different organs in the developing embryo.
This method could one day make it possible to grow tissues and organs for transplantation using synthetic embryo models.
“The embryo is the best machine for making organs and the best 3D bioprinter; we tried to emulate what it does,” said Jacob Hanna, a senior scientist in Weizmann’s department of molecular genetics.
Dr Hanna, who led the research team, said scientists already knew how to restore mature cells to the ‘stem’ or self-renewal.
A diagram showing the innovative method for growing synthetic mouse embryo models from stem cells (without eggs, sperm, or matrix) developed in the lab of Dr. Hanna. (Provided: Weizmann Institute of Science)
However, going in the opposite direction, and getting stem cells to differentiate into specialized cells or form whole organs, had proven much more problematic.
“Until now, in most studies, specialized cells were often difficult to produce or aberrant, and tended to form a mixture rather than well-structured tissue suitable for transplantation,” Dr Hanna said.
“We managed to overcome these obstacles by unleashing the self-organizing potential encoded in stem cells.”
Dr. Hanna’s team built on two previous advances in his lab.
One was an efficient method to reprogram stem cells back to a naïve state, that is, to their earliest stage, when they have the greatest potential to specialize into different cell types.
The other, described in a scientific paper in Nature in March 2021, was the electronically controlled device the team had developed over seven years of trial and error to grow natural mouse embryos outside the womb.
This device keeps embryos bathed in a nutrient solution in continuously moving beakers, simulating the way nutrients are delivered by maternal blood flow to the placenta, and closely monitors oxygen exchange and atmospheric pressure.
In previous research, the team had successfully used this device to grow natural mouse embryos from day five to day 11.
In the new study, the team set out to grow a synthetic embryo model solely from naïve mouse stem cells that had been grown for years in a Petri dish, bypassing the need to start with a fertilized egg
This approach is extremely valuable because it could largely avoid the technical and ethical problems involved in the use of natural embryos in research and biotechnology.
Compared to natural mouse embryos, the synthetic models showed 95% similarity in both the shape of the internal structures and the gene expression patterns of different cell types.
The organs seen in the models gave every indication of being functional.
For Dr. Hanna and other embryonic development and stem cell researchers, the study opens up a new field.
“Our next challenge is to understand how stem cells know what to do – how they assemble themselves into organs and find their way to their assigned places within an embryo,” Dr Hanna said.
“And because our system, unlike a uterus, is transparent, it may prove useful for modeling birth defects and implantation of human embryos.”
In addition to helping to reduce the use of animals in research, synthetic embryo models could in the future become a reliable source of cells, tissues and organs for transplantation.