Scientists have revealed some extraordinary mice: they were born from two male parents (photo).

At first glance, the idea of producing healthy offspring from two animals of the same sex seems unrealistic. However, scientists have once again demonstrated that the impossible is indeed possible.

A new study has been published in the journal Cell Stem Cell. Although the first successful experiments in this area were conducted several years ago, researchers have now managed to overcome the main challenges related to the survival of the offspring.

Scientists utilized genome editing and stem cell cloning techniques to eliminate the barriers that hinder the development of mouse embryos into healthy pups.

The issue arises from internal regulatory mechanisms (imprinting), where certain genes are only active in individuals of one sex. Therefore, when attempting to create offspring from same-sex pairs, researchers encountered genetic anomalies that occurred due to improper activation and deactivation of genes, which quickly led to the demise of the offspring. Such anomalies included overly large lungs and tongues that prevented the pup from breathing, as well as skull deformities.

To address these problems, scientists began editing the stem cells of one of the prospective "fathers." In this study, they focused on "haploid embryonic stem cells" (ESCs) extracted from sperm, and then identified about twenty key genes that posed problems due to imprinting.

Next, they employed the CRISPR/Cas9 tool to edit the genes, resulting in modified cells.

To develop the embryo, the researchers also needed to obtain an egg cell from a healthy female and remove its nucleus along with all DNA, leaving only the shell. They then inserted the stem cells from the edited sperm and another sperm cell that had not been altered into this shell.

This means that at this stage, they already had an egg cell with two sets of chromosomes, which is necessary for embryo development under natural conditions. However, in this case, both sets were obtained from different males.

Another challenge arose because the pups did not develop a placenta, as it can only originate from female cells. To resolve this issue, they had to "borrow" one from a donor mouse.

Ultimately, 36.7% of the embryos were able to develop into healthy pups. While this may seem small, it's worth noting that in 2023, scientists were able to produce only 7 healthy pups from 600 embryos, which is about 1%.

Nonetheless, some pups still required artificial feeding due to skull anomalies.

This new technology marks an important milestone in the advancement of genetic engineering, as it provides a pathway to treatments for diseases related to imprinting disorders. Additionally, it could advance cloning technologies or regenerative medicine, such as organ creation for transplantation. Furthermore, deepening the theoretical understanding of reproductive mechanisms in mammals will also be beneficial.

And of course, we cannot overlook the "elephant in the room" — creating offspring from same-sex pairs could assist in various fields, from preserving endangered animal species to combating infertility.

As previously reported, a cloned black-footed ferret female recently gave birth to healthy offspring. This marks the first instance in history where a clone has produced offspring.