Word: nayernia
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...outside, however, IVD sperm are not identical to normal sperm. "We think, for normal structure development, sperm needs the testes environment," says Nayernia. It takes 15 to 16 years in the testes before the primordial germ cells that morph into spermatogonia, or a primitive precursor of the germ cells, are able to mature into sperm cells that can successfully fertilize an egg. (See the top 10 medical breakthroughs...
...sperm are not ready for transplantation into human patients - in any case, British law prohibits their transplantation into people - but they may provide valuable clues to the causes of male infertility. Nayernia's group is now working on creating sperm from the skin cells of infertile men (the sperm cells in the current study were generated from embryos discarded by fertility clinics), and by studying the way those sperm develop, researchers may gain insight into the origins of infertility and potential new treatments. Theoretically, for example, if sperm could be created from the cells of a cancer patient...
...cells allow researchers to witness the normal development of sperm for the first time. "In the human, sperm development is a very long process," Nayernia says. "It takes more than 15 years and is not an accessible system. With this system, we can now watch that development in three months...
That's how long it took Nayernia's team to nurture sperm from embryonic stem cells, using a special cocktail of growth factors, nutrients and retinoic acid, a derivative of vitamin A. It is worth noting that researchers could generate IVD sperm only from male embryos; when they tried using stem cells from a female embryo, they were unable to get sperm to mature past the spermatogonial stage. That suggests that genes located on the Y chromosome, which female cells do not contain, may be essential for triggering the maturation of the primitive sperm cell...
...unclear whether IVD sperm may eventually be able to fertilize an egg successfully - the ultimate measure of similarity between IVD sperm and normal sperm. (Nayernia is currently testing whether mouse eggs fertilized with IVD sperm can lead to a healthy animal.) If the researcher can generate human IVD sperm that look like normally developed sperm and can get the artificially created germ cells to fertilize an egg, then he can allow the resulting embryo to develop for 14 days - according to U.K. law, embryos created for research purposes must be destroyed at that point. "We would need to study that...