Men are unlikely to become unwanted or obsolete in the foreseeable future, despite this week's claim by British scientists that they are the first in the world to create human sperm in the laboratory from human embryonic stem cells. But rabbinical arbiters would probably have a positive view of the procedure, according to a leading Israeli medical ethicist. Prof. Karim Nayernia, who led a team at Newcastle University, said their research was aimed at assisting infertile men to father children, and not to replace men as the fertilizers of human ova. Nayernia and colleagues said that it could take five years or more to turn their "accomplishment" into practical knowledge to help infertile men. The British team had previously produced baby mice from sperm using the same technique used to create human sperm, according to reports in the UK, but they reportedly have no intention of creating human embryos with them now, as it is presently illegal in their country. Nayernia said: "This is an important development as it will allow researchers to study in detail how sperm forms." Their study was published in Stem Cells and Development, which is a peer-reviewed publication but not regarded by Israeli stem-cell researchers - who are among the best in the world - to be among the highest quality journals in the field. Embryonic stem cells have a nearly unlimited ability to create any type of cells found in the body, and they have already been used to produce human egg cells, as well as heart, brain, endothelial (they line blood vessels) and pancreatic cells that function like ordinary differentiated cells. The human embryonic stem cells were taken from unneeded embryos donated by couples who had undergone in-vitro fertilization. This process of "destroying" embryos upset some prominent Britons, but it is permitted by Jewish law (Halacha). Dr. Mordechai Halperin, a prominent Israeli medical ethicist and gynecologist who is also an Orthodox rabbi, told The Jerusalem Post on Thursday that actually producing human sperm from embryonic stem cells is not forbidden by Jewish law, as days-old embryos in a test tube are not considered living human beings, and their use for experimental research that could help people is permitted if the embryo has no real potential to become a human being. If a couple wants a child but the husband has no sperm, he continued, it would be permissible to produce sperm using stem cells taken from non-reproductive tissue in his own body. "It has not yet been proven that a resulting embryo and fetus would be healthy using this process," Halperin pointed out. "It is all very theoretical at this point. However, there may be a halachic argument if a child is produced from a man's genes but not from his sperm. Would he be the father? Based on other halachic discussions, I think that even if he is not the producer of the sperm but gave genes from other cells, he would be regarded by Halacha as the father. If stem cells are taken from another source, there could be some difficulty. But minor problems could be overcome, as Jewish law is strongly in favor of continuity of the generations, especially if the man wants to be a father." According to the BBC, The Associated Press and other sources, some scientists had doubts about Nayernia's research, claiming the sperm they had allegedly produced weren't normal or fully developed. "I am unconvinced from the data presented in this paper that the cells produced... can be accurately called spermatazoa," said Allan Pacey, an andrology lecturer at the University of Sheffield. Pacey claimed the sperm "did not have the specific shape, movement and function of real sperm." However, defending his work, Nayernia countered that the cells "showed all the characteristics of sperm," and added that he and his team had aimed to "open up new avenues of research" for fertility problems instead of using them now to fertilize human ova. For example, it could explain why young boys who undergo chemotherapy for cancer can lose their fertility for life or understand how chemicals can endanger fertility. But if the artificial sperm are eventually used for fertilization, it would relieve the shortage of donated human sperm around the world. The BMJ (British Medical Journal) carried a news story by Susan Mayor on its online edition on Thursday, stating that the Newcastle scientists claimed to have used human embryonic stem cells with male and female chromosomes (XY and XX) to develop male germline stem cells. "Only XY cells were then prompted to complete meiosis - cell division that halves the number of chromosomes). These cells then developed into fully mature, functional sperm, called in-vitro-derived (IVD) sperm. "They based their technique for human sperm cell production on understanding the mechanisms underlying cell lineage decisions during early embryogenesis. They tracked the profile of the cell markers expressed by cells that develop into germ cells and then grew embryonic stem cells in a cell medium that encouraged differentiation into these cell types. Cells expressing the required markers were separated out by staining key surface proteins with a fluorescent marker. This picked out cells producing proteins coded for by a gene (Stra8) required for spermatogenesis. The final sperm cells were haploid and motile, which are essential characteristics of male gametes. Some of the motile cells had tail-like structures, similar to the flagellae of human sperm cells," Mayor wrote. As it takes human males more than 15 years to produce sperm from primoridal germ cells to sperm cells, Nayernia said it was difficult to study the process. But the advance has created a technique "for producing sperm in two to three months. We can study different factors, including environmental and genetic factors, that affect sperm development."