Scientists Make Human Sperm From Embryonic Stem Cells

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Main Category: Stem Cell Research
Also Included In: Fertility
Article Date: 08 Jul 2009 - 2:00 PDT

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UK scientists have announced this week that they have found a way to make human sperm from embryonic stem cells in a laboratory, a breakthrough that they hope will help us better understand the causes of infertility.

The research is published on 8 July as an online paper, ahead of print, in the journal Stem Cells and Development and is the work of Professor Karim Nayernia at Newcastle University and the NorthEast England Stem Cell Institute (NESCI) and colleagues.

The authors wrote that research has already revealed that human embryonic stem cells can be coaxed to develop into a range of specific cell types using methods that mimic what goes on during the early development of the embryo.

In humans and other animals, sperm cells in grown up males originate from "a founder population of germline stem cells", a type of primordial germ cell that is set aside during early development of the individual as an embryo.

By the time the individual is born, the primordial germ cells have formed gonocytes which then differentiate into adult male sperm stem cells which can self-renew and make sperm cells. Sperm stem cells are unique, wrote the authors, because they are "solely dedicated to transmit genetic information from generation to generation".

Nayernia said in a press statement that the more we know about this process, of going from germ cell to differentiated sperm cell, the better we will be able to understand the causes of male infertility:

"This understanding could help us develop new ways to help couples suffering infertility so they can have a child which is genetically their own," said Nayernia.

"It will also allow scientists to study how cells involved in reproduction are affected by toxins, for example, why young boys with leukaemia who undergo chemotherapy can become infertile for life -- and possibly lead us to a solution," he added.

Nayernia and colleagues took male embryonic stem cells (carrying XY chromosomes) and using a new medium containing vitamin A derivative (retinoic acid), turned them into germline stem cells that were then coaxed to complete meiosis, or cell division, with characteristic halving of the chromosome set.

The new germline stem cells displayed all the markers indicative of fully mature sperm.

When they tried to apply the method to female embryonic stem cells (carrying XX chromosomes), they only produced early stage sperm that did not progress any further.

This showed that the genes on the Y chromosome are essential for cell division and for ensuring fully mature sperm is produced, said the authors.

The authors concluded that their new method of:

"In vitro modeling of human gametogenesis provides a new approach for studying biology of human germ cells and establishment of therapeutic approaches in reproductive medicine."

Sperm produced in this way, called In Vitro Derived sperm (IVD sperm), cannot be used in fertility treatment. Not only is it against the law in the UK, but the researchers said this is not what they are interested in anyway: they want to use the method for research. As Nayernia explained:

"While we can understand that some people may have concerns, this does not mean that humans can be produced 'in a dish' and we have no intention of doing this."

"This work is a way of investigating why some people are infertile and the reasons behind it. If we have a better understanding of what's going on it could lead to new ways of treating infertility," he added.

The announcement has been received with some scepticism.

Dr Allan Pacey, a sperm biologist at the University of Sheffield, told the BBC that was not convinced the sperm were fully developed. He said the images that the team have released aren't of sufficiently high resolution and he would need to see more data.

"They are early sperm, but functional tests would be needed to know exactly what has been achieved," said Pacey.

The North East England Stem Cell Institute (NESCI) is a collaboration between Newcastle and Durham Universities, Newcastle NHS Foundation Trust and other partners.

"In Vitro Derivation of Human Sperm from Embryonic Stem Cells."
Karim Nayernia, Jae Ho Lee, Majlinda Lako, Lyle Armstrong, Mary Herbert, Manyu Li, Wolfgang Engel, David Elliott, Miodrag Stojkovic, John Parrington, Alison Murdoch, Tom Strachan, Xin Zhang.
Stem Cells and Development. Jul 2009, ahead of print.
doi:10.1089/scd.2009.0063

Additional sources: North East England Stem Cell Institute, BBC News.

Written by: Catharine Paddock, PhD
Copyright: Medical News Today
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