Artificial Sperm

A handful of healthy mice made from sperm cells created in the lab have been hailed as a milestone in research that could ultimately provide new treatments for male infertility.

Scientists in China created the mice by fertilising normal mouse eggs with early-stage sperm cells that were manufactured from embryonic stem cells taken from the animals. To make the sperm, the mouse stem cells went through a complex series of steps known as meiosis that must be performed with extreme care to ensure the sperm develop properly.


Despite years of work, scientists have never managed to replicate the process with human stem cells, but the latest study could provide fresh impetus to the effort, according to Jiahao Sha, director of the Laboratory of Reproductive Medicine at Nanjing Medical University in China.

The creation of sperm and eggs - known as germ cells - for use in IVF raises particular safety issues, because any faults in their genetic material could harm not only the children born from the treatment, but all their future descendants.

“If it works, human germ cells could possibly be produced. However, in the current stage, ethics should be concerned, and any possible risks ruled out,” said Sha, who led the team

The scientists believe that the cautious, stepwise production of the sperm cells was crucial for the mice to be born healthy and fertile. The mice went on to mate and have fertile offspring of their own.

Ethical Concerns
Scientists have welcomed the landmark achievement but cautioned that the creation of human sperm to treat infertile men was a distant prospect fraught with concerns over safety, ethics and legality.

Fertility clinics in Britain are banned from using artificial sperm or eggs to treat infertile couples. But if the procedure is ever perfected, MPs could come under pressure to change the law. Instead of using stem cells, another promising approach aims to make sperm and eggs from adult skin cells.

Infertility in Population

Infertility affects about 15% of couples and males are solely responsible for 20 to 30% of cases. One major cause of male infertility arises when the cells in the testes fail to divide to form proper, working sperm. While other groups have made sperm cells in the lab, Sha believes his is the first to make them according to agreed “gold standards” and fully assess their quality.

Writing in the journal Cell Stem Cell, Sha describes how he made early stage sperm cells - round, tailless cells known as spermatids - and injected them into mouse embryos - it is important to remember spermatids are not fully functioning sperm as we know them. The fertilised embryos were transferred to females who bore at least six healthy mice. When these mice were old enough, they mated and produced a second generation of healthy babies.

Gold Standard
Mary Ann Handel, a scientist at the Jackson Laboratory in Maine, said: “All this is of importance for basic science in reproductive biology. The implications for managing human infertility or onco-fertility are there, but I think they are considerably further off in the future. Of course, as for any exciting advance, the real ‘gold standard’ will be independent replication of this work by other groups.

Study Replication

Terry Hassold, at Washington State University’s Center for Reproductive Biology, said: “There’s no question that the technique needs to be improved further, but if we can build on this as a technique that is doable in the laboratory, it really is going to change the way we think about cases of infertility that are currently unable to be treated by IVF. “The crucial question is whether someone else going to be able to replicate the study, and if that is the case then it really will revolutionise assisted reproduction as we know it.

Ethical & Medical Concerns
The ethical and medical concerns of this potential treatment are clear. The sperm cells produced must be close, if not perfect to avoid genetic faults being created and potentially passed down through future generations. Another concern is what happens when any offspring created in the future by this method then go on to have children with other people. In the worst case scenario there is the potential for DNA defects to pass through into the wider gene pool.