MOSCOW, January 22. /TASS/. American and British biologists have discovered that embryo cells at the early stages of development will be highly susceptible to the coronavirus attacks if its particles manage to enter the system of a pregnant woman. The results of their observations were published in an article in the bioRxiv electronic library.

"Our finding that pre-implantation embryos are permissive to SARSCoV-2 entry highlights a potential vulnerability of these embryos in vivo. Additionally, the data presented here should prompt careful review of procedures surrounding in vitro fertilization during the COVID-19 pandemic and its aftermath," the researchers wrote.

Last February, Chinese biologists detected signs that the SARS-COV-2 coronavirus that caused the pandemic of COVID-19, may infect placental cells of pregnant women. This made scientists suspect that the pathogen may spread intrauterinally, entering an embryo through a placenta.

On the other hand, subsequent observations demonstrated that such cases are rare. Additionally, the scientists couldn’t register visible consequences of the coronavirus infection penetrating tissues of an embryo. Such an uncertainty resulted in many arguments whether the SARS-CoV-2 virus is dangerous for unborn children.

Consequences of infection

A group of American and British molecular biologists led by researcher Mauricio Montano of the Gladstone Institutes in San Francisco, USA for the first time ever tried to obtain direct answers to this question by experimenting with surplus embryos from fertility treatment and in vitro fertilization, donated strictly for research, and analogues of the SARS-CoV-2 particles.

The biologists were interested in two things - whether the ACE2 receptors and the TMPRSS2 proteases, critically important for the spread of the coronavirus, are present on the surface of embryonal cells, and if so, whether fragments of the SARS-CoV-2 membrane can penetrate them.

As it turned out, the answer was in the affirmative for all embryos obtained from donors with very different ethnic backgrounds. Their cells indeed were developing a large amount of ACE2 and TMPRSS proteins, and models of the coronavirus particles were easily penetrating them, resulting in their mass death despite the models’ inability to reproduce.

Such experimental results, as the researchers noted, indicate that the embryos will be particularly susceptible to the coronavirus infection at the early stages of their development when they are not protected anymore by a special glycoprotein membrane which surrounds unfertilized ova while the placenta and the own immune system haven’t been formed yet.

For this reason the scientists propose to think about additional measures of precaution in the operations of fertility clinics as well as to study in detail the effect of the SARS-CoV-2 virus on embryos of various animal models.