Scientists engineer viable sperm in mice, offering hope to infertile men

Medical scientists engineer viable sperm in mice
Image Credit: Ram, Creative Commons

A group of scientists in China have successfully grown sperm in a lab environment for the first time, offering hope to infertile couples.

Working with mice, the team took embryonic stem cells, taken from mouse embryos, and used these to stimulate sperm-like cells, known as spermatids. The cells were chemically induced to become germ cells, which have the ability to change into other types of cell. Exposed to testicular cells and sex hormones, they were transformed into sperm-like cells - complete with the correct DNA and chromosomes – and inserted into eggs, which were in turn implanted into female mice. The remarkable result was healthy mouse pups, which were later able to reproduce normally themselves.

“We think it holds tremendous promise for treating male infertility”, says Nanjing Medical University’s Dr Jiahao Sha, co-senior study author.

He adds: “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.

“Because currently available treatments do not work for many couples, we hope that our approach could substantially improve success rates for male infertility.”

Infertility problems

Around 15% of couples experience fertility problems, about one third of which can be traced back to male infertility. One of the primary causes of male infertility is associated with meiosis – or cell division within the testes. In some men, this process is impaired or doesn’t take place at all, and for those who fail to produce any sperm, the only option currently is to use a donor.

Image Credit: Bobjgalind, Creative Commons

Image Credit: Bobjgalind, Creative Commons

The Chinese researchers, publishing in the journal Cell Stem Cell, have now established that it is possible to recreate meiosis, albeit in mice. It is hoped that a similar technique may in future be used to produce human sperm. Trials using primates is likely to be the next step, with a view toward future human trials, however, this would be subject to numerous ethical considerations.

“Significant step”

Professor Darren Griffin, Professor of Genetics at the University of Kent, says: “The paper, using mice, represents some excellent science in understanding the basis of meiosis – the process that drives genetics – and the work is exciting and well performed. However, we need to exercise a note of caution when considering it as a possible treatment option for infertile men sometime in the future. While the work is undoubtedly a significant step towards that goal, there are issues of reproducibility and safety in a human system (which may be quite different and more complex than in mice) that need to be addressed.”

“Landmark study”

Professor Chris Barratt, Professor of Reproductive Medicine at the University of Dundee, says: “There have been numerous attempts (and false dawns) to developing a robust system for in vitro meiosis. A number of studies have been published that have subsequently been difficult to repeat. This has led to the scientific community establishing a series of sentinel markers that need to be established to determine the fidelity of meiosis in vitro. This is a landmark study in that it has satisfied these internationally agreed standards.”

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