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In cases of couples struggling to conceive, the cause can sometimes be the fact that the male partner has been born with an extra sex chromosome, known as X and Y chromosomes. This additional chromosome can cause problems in that it interferes with the creation of healthy mature sperm.

This condition is known as sex chromosome trisomy (SCT) and is estimated to affect around 0.1 percent of males. In the UK, this equates to around one in every 500 males being born with SCT, which will affect their ability to have children in the future. Depending on whether the man possesses an extra X or Y chromosome, the conditions are known as Double Y Syndrome and Klinefelter’s Syndrome, respectively.



Scientists from the UK and Japan have released details of a novel new technique aimed to help sufferers of SCT. The team used stem cells to create sperm from the connective tissues of infertile mice.

Creating sperm from stem cells

The study, titled ‘Fertile offspring from sterile sex chromosome trisomic mice’ was published on August 17 in the journal Science. The study was carried out as a collaboration between scientists at the Francis Crick Institute in London, and at Kyoto University in Japan.

The first stage of the research was to extract fibroblast connective tissue cells, taken from the ears of the mice. These were then transformed into stem cells and during this process, the additional sex chromosome was lost. The team then used chemical signals to encourage the stem cells to develop into immature sperm cells, before injecting these sperm cells into the testes of the mice. Once injected, the immature sperm cells matured into healthy and fully functioning sperm which was used to produce fertile offspring.

Much more work to be done

Whilst it might be quite a while before we see a treatment like this become widely available, the team of scientists involved in this study have already begun to conduct preliminary trials on three men who have the condition known as Klinefelter syndrome, where they are born with an extra X chromosome. The scientists have so far managed to produce healthy stem cells, without the extra sex chromosome, using fibroblast cells taken from the men.

Microscope diagnosis

Microscope diagnosis (maxpixel)

Whilst this sounds very exciting, there are more hurdles to overcome. One of them is the risk of tumours forming as a result of injecting the immature sperm cells back into the mice. As explained by Dr James Turner from the Francis Crick Institute: “In our mouse experiments we have to inject cells that have the potential to become sperm back into the testes to help them finish developing. But we found that this caused tumours in some of the mouse recipients. So reducing the risk of tumour formation or discovering a way to produce mature sperm in a test tube will have to be developed before we can even consider this in humans.”

Another hurdle is the fact that before any treatment such as this could be made available in the UK, the law banning the use of artificially produced sperm would have to be changed. Despite these issues, the study is certainly an exciting step forward for the possible application of methods such these in the future.

Top image: First sperm winner. (maxpixel)

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Emma Stenhouse, MSc

Emma qualified with a BSc (Hons) in Equine Science in 2003 and has had a passion for horses since a young age. She continued her academic career with an MSc in Applied Marine Science, gained in 2004. Emma’s main scientific focus was the navigational techniques of sea turtles and whether they use the acoustics of the surf-zone as a cue for nesting. She then worked for a sea turtle conservation project on the Pacific coast of Costa Rica before travelling to New Zealand where she worked as a Mari...Read More

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