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Scientists have succeeded in growing the special stem cells that direct the sperm production process outside of the body. The method has only been proven in mice, but researchers hope it may apply to humans. The ability to culture these cells is an initial step that could lead in multiple directions, including correcting the sperm of infertile men, genetic engineering in humans (if ethically acceptable), and generating embryonic stem cells without the controversial step of creating an embryo. This ability would make it possible to swap mutated genes in cells for normal or improved ones. In the case of infertile men, for example, the sperm production cells would be removed, genetically treated, and put back in the testis, where they should produce normal sperm.
Researchers also hope to learn how to make the cells produce sperm outside the body. The genetically altered sperm could then be used directly for in vitro fertilization. This technique would be useful in animal breeding; however, the ethics of human usage is still a matter of debate.
This technique might also be used to solve the controversial issue of embryonic stem cells. The sperm production cells have many of the same characteristics as embryonic stem cells and are only a couple of developmental steps away from them. Researchers hope to be able to "walk them backward" to become embryonic stem cells. These could then be converted into the specialized cell types needed to repair damaged organs.