By creating eggs from male cells, researchers have produced mice with two biological dads, opening up whole new possibilities for reproduction in humans as well.
The development might eventually lead to therapies for severe cases of infertility and raise the tantalizing possibility that same-sex couples would one day be able to conceive a biological kid together.
Leader of the research, Katsuhiko Hayashi, said that “This is the very first case of making robust mammal oocytes from male cells.”
Within ten years, according to Hayashi, it will be theoretically feasible to produce a viable human egg from male skin cells. At the same time, however, others claim that given the fact that scientists have yet to produce s healthy lab-grown human egg from female cells, this timescale is rather overly optimistic.
Previously, scientists used a complex process that included genetic engineering to produce mice that had biological dads. However, this is a huge advancement because it is the first time that viable eggs have been grown from male cells.
Hayashi’s team is currently working on repeating this success using human cells, but there would be several obstacles to using lab-grown eggs for therapeutic applications, including proving their safety.
The renowned scientist mentioned that “Purely in terms of technology, it’ll be possible [in humans] even in ten years. I do not know whether they’ll be available for reproduction. That isn’t a question just for the scientific program, but also for [society].”
The method might potentially be used to cure extreme cases of infertility, such as those in women with Turner’s disease, in which one or more X chromosome copies are absent.
According to Hayashi, this application was actually the main driving force for the study.
Others said that adapting the method to human cells could be difficult.
Human cells must be grown for significantly longer periods of time before they can mature into an egg, which raises the possibility that cells will undergo unintended genetic modifications.
The dean of Harvard Medical School, Prof George Daley, referred to the work as “fascinating.”
He went on to say, however, that “We still do not understand enough of the unique biology of human gametogenesis in order to reproduce Hayashi’s provocative work in mice.”
A complex process was used in the study to convert a skin cell with a male XY chromosomal combination into an egg with a feminine XX combination.
To produce induced pluripotent stem (iPS) cells, male skin cells were reprogrammed to resemble stem cells. In order to create iPS cells with identical X chromosomes, the Y-chromosome of these cells was then removed and replaced by an X chromosome “stolen” from another cell.
Hayashi noted that “The biggest trick, is the duplication of the X chromosome. We tried to establish a system to duplicate the X chromosome.”
The cells were then grown in an ovary organoid, created to mimic the environment seen in a mouse ovary. The scientists obtained roughly 600 embryos after fertilizing the eggs with regular sperm.
These embryos were then placed into surrogate mice, which led to the birth of 7 mouse pups.
The young mice had a normal lifespan, seemed to be in good health, and eventually gave birth to young of their own.
Currently, Hayashi and his team, are working to try and duplicate the production of lab-grown eggs utilizing human cells.