Could fertility breakthrough lead to babies with no mothers?
"Fertility breakthrough means babies could be conceived from skin cells – so men can have babies with each other," is the excitable headline in the Daily Mirror.
But the research in the news is at an early stage – and was in mice. Despite reporting to the contrary, the study involved female eggs, not skin cells.
This experimental UK research involved mice whose eggs were tricked into starting to develop and divide as if they had been fertilised.
These "fake" embryos were then injected with sperm and implanted into female mice. There was an up to 24% success rate producing healthy offspring.
However, this is very early-stage research and it is important that we do not speculate about its potential implications at this point.
Mice are not human and this may not be an appropriate model on which to base predictions of how the process happens in humans.
As the authors acknowledge, their work only demonstrates a principle – there are major barriers to overcome before reproduction in humans without egg cells would be a technical possibility, not to mention the ethical questions.
Just because you can do something doesn't necessarily mean you should.
Where did the story come from?
The study was carried out by researchers from the University of Bath in the UK, and the Institute for Toxicology and Experimental Medicine ITEM and the University of Regensburg in Germany.
It was funded by the UK Medical Research Council. The authors declared no conflicts of interest.
The study was published in the peer-reviewed journal, Nature Communications. It is open access, so you can read it for free online.
For the most part, the media coverage around the topic was accurate, stressing that the work is in its early stages.
But headline writers decided to pick up the hype ball and run with it. Many headlines talked about "motherless babies", which did not acknowledge that the study still relied on eggs taken from a female.
The Daily Mirror speculated about men having babies with each other, while the Daily Mail imagined a world without mothers. All of these concepts are pretty far removed from a small study involving mice.
What kind of research was this?
This mouse study aimed to look at the possibility of tricking sperm into believing they were fertilising normal eggs.
Embryologists first observed fertilisation in the late 19th century, and it has long since been assumed that only an egg cell fertilised with a sperm cell can result in a live mammalian birth.
The exact mechanisms of fertilisation – what happens when a sperm fuses with an egg – are not well known, and researchers aim to understand these processes more.
Animal studies are often used in the early stages of research to see how biological processes may happen in humans.
But we are not identical to animals, and the mechanisms in humans may differ and need to be tested in other ways.
What did the research involve?
This complex laboratory study used mice to observe if healthy offspring could be produced using a technique that bypasses the usual processes of fertilising an egg cell with a sperm.
Scientists used chemicals to trick mouse eggs into developing as though they had been fertilised.
These unusual embryos, known as parthenogenotes, were in the stage of cell division and contained a half set of chromosomes. These embryos usually die after a few days, as they do not have the correct programming.
Sperm was then injected into the embryos and they were transferred into female mice. The success of the process was determined by the ability of the mice to produce healthy offspring.
What were the basic results?
After injecting the sperm into the embryos, some were observed to develop normally and on transfer into female mice grew into apparently healthy mice pups.
In total, 30 pups were produced with a success rate of up to 24%, depending on the stage when the embryo cell cycle was injected with sperm.
Some pups went on to have offspring of their own, and some of these also had pups.
The researchers further describe in detail the cellular processes that took place when the embryo cells were injected with sperm.
How did the researchers interpret the results?
The authors say the ability of embryos to reprogramme sperm in the process of cell division (mitosis) blurs functional distinctions between the different cell lines: sex cells, body cells and early-stage embryonic cells.
They further suggest that their work "calls into question the argument that parthenogenotes do not have the potential for full-term development and are accordingly a more acceptable source of human embryonic stem cells".
Conclusion
This experimental study in mice shows that normal egg fertilisation is not the only way of maturing a sperm into a form needed to create all the tissues in the body.
The researchers suggest that if it is possible to produce healthy mice babies by injecting sperm into pseudo-embryos, it might one day be possible to repeat the process in humans using cells that are not from eggs.
They hope to extend the research to study the potential for skin cells to replace eggs in the future.
However, as the authors acknowledge, this early work only demonstrates a principle – there are major barriers to overcome before reproduction in humans without egg cells would be a technical possibility, aside from ethical questions.
Mice are not human – this means this may not be an appropriate model on which to base predictions of how the process happens in humans.
There are many more research stages to undergo to further understand these findings and their possible implications.
One final point is that if you ever see a news article with a question mark in the headline – like this one: "Could fertility breakthrough lead to babies with no mothers?" – the answer is almost always "We don't know".
