Sperm And Eggs Could Be Made From Stem Cells

20 June 2005
Sperm And Eggs Could Be Made From Stem Cells
by George Atkinson

English scientists say they have proved that human embryonic stem cells can develop into the early forms of cells that eventually become eggs or sperm. This opens up the possibility that eggs and sperm could be grown from stem cells and used for assisted reproduction and improved treatments for a range of diseases. 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).

The research was unveiled at the annual conference of the European Society of Human Reproduction and Embryology. "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," said researcher Behrouz Aflatoonian. "But at present it is very difficult to obtain human samples of these cells as they only occur early in development." Aflatoonian, from the University of Sheffield, 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 as well as 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," explained Aflatoonian.

The researchers said that one of the reasons for doing the research was that it may allow the investigation of the very earliest processes of how a human gamete and gonad (ovary and testis) develops. But they 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. Producing functional gametes is much more difficult, because we have to recreate for the cultured cells the environment of the developing follicle for egg development or the tissue of the testis for sperm. We want to test whether HESCs can differentiate to cells that produce the hormones for sperm and egg development and isolate these as well. What is extraordinary is that the embryoid bodies seem to produce spontaneously the tissue and environment conducive for sperm and egg development in quite a short time in culture," said researcher Harry Moore.

"Ultimately it might be possible to produce sperm and eggs for use in assisted conception treatments. This is a long way off and we would have to prove it was safe because, for example, the culture process may cause genetic changes. For some men and women this would be the only route for producing sperm and eggs," concluded Moore.

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