Mouse Fetuses Generated Without Eggs Or Sperm

The artificial mouse embryos were created using special stem cells called extended pluripotent stem cells which have the ability to generate all 3 cell types found in early embryos; the stem cells were coaxed into turning into the 3 embryo cell types and to self assemble into embryo like structures by soaking them in nutrients and growth stimulants. 

“They essentially did the job on their own – you could see the cells that would become the placental tissue moving to the outside while others that would form the fetus moved to the inside,” says Jun Wu of the University of Texas Southwestern Medical Center.

7% of the artificial embryos were successfully implanted in the uteruses of female mice, which were surgically removed a week later by caesarean section and the following microscopic examination showed they had started to form early fetal structures that had major malformations. “The tissue structure and organisation were not as good as in normal embryos,” says Wu.

This is the first known experiment wherein artificial embryos have been found to have started to develop into fetal tissue in a uterus. Previously artificial mouse embryos have been made from stem cells but they were not successfully implanted or only formed placental cells but not the other types once implanted. 

Now the question is how to fine tune the artificial embryos to develop into perfectly formed fetuses. According to Wu the reason for doing this isn’t to generate offspring, rather to test the ability of the artificial embryos to grow in the womb to see how realistic they are; once they are realistic enough they will be able to use them as substitutes for real embryos that normally would have been harvested from mice. These embryo models could be studied in dishes to examine early development, potential causes of birth defects, and to optimise IVF conditions and screen drugs. “Our goal is to have a scalable system for producing hundreds or even thousands of these embryo-like structures,” says Wu.

Findings suggest that one day it may be possible to generate offspring from artificial embryos. Some of the extended pluripotent stem cells used were originally made by reprogramming ear cells from adult mice, if the same could be done with human ear, skin, or other non-reproductive cells we could generate viable human embryo like structures without eggs or sperm. “But this remains science fiction,” says Wu. 

According to Nicolas Rivron at the Institute of Molecular Biotechnology there are no good scientific or medical reasons to make human babies from artificial embryos without sperm or eggs. But, artificial embryos could potentially be used to study fertility issues in the future, such as taking skin cells from an infertile person to form artificial embryos to study their growth and identify genetic causes of infertility, he says going on to add, “Along with the possibility to test drugs, this could help to prevent or fix pregnancy-related problems.”