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Embryonic stem cells could develop into eggs and sperm in the laboratory
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.
"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."
Speaking before the conference, Prof Moore said: "One of the reasons for doing this research is that it may allow us to
investigate the very earliest processes of how a human gamete and gonad (ovary and testis) develops. Many scientists believe
that environmental chemical pollutants that mimic the action of hormones (so called endocrine disrupting chemicals) might
interfere with human development at this stage and cause congenital abnormalities, infertility and possibly cancer (in
particular testicular cancer). By developing suitable tests with embryonic stem cells as they differentiate to germ cells we
can investigate the action of these chemicals in the laboratory.
"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. It would not be reproductive cloning as fertilisation would
involve only one set of gametes produced in this way and therefore a unique embryo would form.
"In addition, if we could produce eggs from HESCs they could also be used for therapeutic cloning (somatic nuclear
replacement) circumventing the need for eggs from patients who donate them, as this is a major limitation of this technique
at the moment. We would then have completed the circle of making HESCs from eggs that came from HESCs - what came first the
chicken or the egg?!"
Contact: Emma Mason
wordmason@mac.com
European Society for Human Reproduction and Embryology
http://www.eshre.com
Celule stem embrionare ar putea dezvolta în ouã ºi spermã în laborator - Embryonic stem cells could develop into eggs and sperm in the laboratory - articole medicale engleza - startsanatate