Researchers in China have successfully created functioning sperm in the lab, using embryonic stem cells from mice. The sperm-like cells were used to produce healthy mouse offspring which gave birth to the next generation.
"Reproducing germ cell development in vitro has remained a central goal in both reproductive biology and reproductive medicine," says co-senior study author Jiahao Sha of Nanjing Medical University. "We established a robust, stepwise approach that recapitulates the formation of functional sperm-like cells in a dish.”
Germ cells are the type of cell that gives rise to sperm and egg cells in males and females respectively - this process is called meiosis, and takes place in the ovaries or testes.
For over a decade researchers have been working on re-creating meiosis in the lab, but it wasn’t until 2014 that a group of biologists described a “gold standard” in the journal Cell for the rigorous steps scientists need to take to establish that meiosis truly has occurred.
Now the team from China has met this gold standard for the first time, and claims this will lead the way to infertility treatments in humans. The cells they coaxed out of mouse embryonic stem cells resembled spermatids, a round cell that can mature into tailed sperm. The research was published today in Cell.
Dr Orly Lacham-Kaplan from Mary MacKillop Institute for Health Research has brought major breakthroughs in this field in the past decade, and she believes this new study is “not that different” from previous achievements.
Already in 2006 a team lead by researchers from the University of Newcastle, UK managed to achieve a similar result, and authors of the 2014 gold standard claim this study came “very close”. However, the few mouse pups produced all died prematurely.
This time Chinese researchers were able to fertilise egg cells in an IVF-type procedure and breed healthy mice, although Dr Lacham-Kaplan cautions the success rate was still low, with only 14 pups born out of 148 embryos.
"When you look at the outcome of this study, everything looks normal, but the proportion of live pups born out of this procedure is very small,” she says.
“So if you do want to translate this back to a human situation - would it be feasible to use? I'm really not sure,” she adds. As with most stem cell research, there would be many ethical challenges to overcome before such work could be done on human offspring.
"From a research point of view it's a great study in developmental biology, but in terms of practising it in a clinical environment, I'm not sure that would be the right thing to do," says Lacham-Kaplan, citing the low birth rate of the mice.
Still far from human clinical use
Professor Gareth Jones from the University of Otago believes that another major ethical consideration for using this procedure in humans is the fact that embryonic stem cell use always involves the destruction of embryos.
“We will have to see whether this would prove as revolutionary as it sounds,” says Jones. “But there is little doubt it will be seen as contentious.”
Currently the researchers are planning to use their work for researching the molecular mechanisms involved in meiosis, and possibly move on to do similar experiments with primates.
However, they are optimistic the results of this study could indeed lead to human fertility treatments.
"If proven to be safe and effective in humans, our platform could potentially generate fully functional sperm for artificial insemination or in vitro fertilization techniques," says Sha.