Infertility breakthrough as scientists successfully create viable sperm from monkey stem cells

Sperm have been made from monkey stem cells and used to fertilise a macaque egg in a scientific breakthrough that could lead to human infertility treatments. 

Researchers took some stem cells, converted them into primitive sperm and showed this was capable of fertlising an egg from a rhesus macaque.

The monkeys share similar reproductive mechanisms to humans, making them an ‘ideal and necessary model for exploring stem cell-based therapies for male infertility,’ experts at the University of Georgia (UGA) said.

It comes fives years after scientists were able to create sperm in a laboratory and use it to father healthy baby mice in another pioneering move.

The hope is that the research could one day pave the way to help men with defects that leave them unable to produce sperm, as well as those whose fertility has been damaged by cancer treatment or infections such as mumps.  

Breakthrough: Sperm have been made from monkey stem cells and used to fertilise a macaque egg in a scientific breakthrough that could lead to human infertility treatments (stock image)

Making sperm in the testes, which takes more than a month from start to finish in most mammals, is one of the longest and most complicated processes in the body. 

The UGA-led study is the first to show that functional sperm cells can be made in a dish using primate embryonic stem cells.

These cells can morph into any other type of tissue but are made into immature sperm cells with the help of chemicals, hormones and testicular tissue.

They must also go through a careful rearrangement of their DNA during a process called meiosis, where the sperm cells lose half of their chromosomes so a fertilised egg has a normal amount. 

‘This is a major breakthrough towards producing stem cell-based therapies to treat male infertility in cases where the men do not produce any viable sperm cells,’ said lead researcher Charles Easley, an associate professor at UGA’s College of Public Health.

Researchers used embryonic stem cells from rhesus macaque monkeys to generate immature sperm cells known as round spermatids, which do not have a head and a tail for swimming because they’re at an earlier stage in their development.

These spermatids were shown to be capable of fertilising a rhesus macaque egg. 

Although scientists had previously been able to produce sperm-like cells using mouse stem cells, rodent sperm production is distinctly different to that of humans.

Until now, the researchers said, it wasn’t clear the technology could ever work to help male infertility. 

‘This is the first step that shows this technology is potentially translatable. We’re using a species that’s more relevant to us, and we’re having success in making healthy embryos,’ said Easley.   

Researchers used embryonic stem cells from rhesus macaque monkeys to generate immature sperm cells known as round spermatids, which do not have a head and a tail for swimming because they’re at an earlier stage in their development. These spermatids were shown to be capable of fertilising a rhesus macaque egg (pictured)

This autumn, the researchers plan to take the next step of implanting these embryos into a surrogate rhesus macaque to examine whether they can produce a healthy baby. 

If that step is successful, the team will carry out the same process using spermatid-like cells derived from macaque skin cells. 

That’s because another challenge the field needs to overcome is that no human adult has embryonic stem cells.

Scientists think that converting skin cells into a stem-cell state, which can be done reliably, is the solution.

In 2016, Chinese research converted stem cells into immature sperm and fertilised an egg to produce baby mice.

The study showed they were all healthy and grew up to have offspring of their own.  

The latest research has been published in the journal Fertility and Sterility Science. 

HOW DO SPERM MOVE?

Sperm are vital in human reproduction and the motility of the male cells is crucial. 

In order to help the sperm cells move, they evolved a ‘tail’ which is called  a flagellum.

Sperms’ tails play a critical role in their ability to swim and consequently fertilise an egg.

 Sperm are vital in human reproduction and the motility of the male cells is crucial. Sperms’ tails play a critical role in their ability to swim and consequently fertilise an egg

Sperm tails consist of around 1,000 building blocks, including structures known as tubulins, which form long tubes.

Attached to these tubes are moving molecules called motorproteins.

These pull and bend sperm tails, enabling them to swim. 

The movement of the tail is powered by a mitochondria, the powerhouse of a cell, which produces energy.