Scientists in the UK have proved that human embryonic stem cells can develop in the laboratory into the early forms of cells that eventually become eggs or sperm. Their work opens up the possibility that eggs and sperm could be grown from stem cells and used for assisted reproduction, therapeutic cloning and the creation of more stem cells for further research and for the improved treatments for patients suffering from a range of diseases.
Behrouz Aflatoonian will tell the 21st annual conference of the European Society of Human Reproduction and Embryology today (Monday 20 June) that the research also solves the practical and ethical problems associated with obtaining human samples of primordial germ cells (PGCs), which are the ancestral cells that eventually form eggs and sperm (gametes). "Investigating the mechanisms of human primordial germ cell and gamete development is important for understanding the causes of infertility and the potential harmful effects of environmental chemicals on reproductive development," he will say. "But at present it is very difficult to obtain human samples of these cells as they only occur early in development."
Mr Aflatoonian, who is a PhD student in Professor Harry Moore's laboratory at the Centre for Stem Cell Biology, University of Sheffield, UK, said that studies with mice embryonic stem cells had shown that they were capable of differentiating into PGCs and subsequently eggs and sperm, so he set out to see if the same applied to human embryonic stem cells (HESCs).
"We derived six embryonic stem cell lines from embryos donated for research under HFEA regulations by couples undergoing IVF treatment. In addition, we utilised cell lines from the University of Wisconsin.
"The human embryonic stem cells were allowed to develop into collections of cells called embryoid bodies. The embryoid bodies were tested to see which genes were active, or 'expressed', in them and it was found that within two weeks a very tiny proportion of cells in the embryoid bodies began to express some of the genes that are found in human primordial germ cells. Some cells also expressed proteins only found in maturing sperm. This suggests that HESCs may have the ability to develop into PGCs and early gametes as has been shown previously for mouse embryonic stem cells."
However, Mr Aflatoonian stressed that there was still a lot of work to be done before the promise of these early results could be translated into reality. "Embryoid bodies can differentiate into all sorts of tissue types, so we need to choose the cells that are going to develop into PGCs and then work out how we can encourage them to grow into gametes.