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????PROMETHEUS, a Titan bound to a rock by Zeus,endured the daily torture of an eagle feasting on his liver, only to have the organ regrow each night. Compared with this spectacle, a video on the?website of Nature this week seems decidedly dull. It shows a collection of pink dots consolidating into a darker central glob. ????Butsomething titanic is indeed happening. The pink dots are stem cells, and thevideo shows the development of a liver bud, something which can go on to lookand act like a liver. Takanori Takebe and Hideki Taniguchi of Yokohama CityUniversity, in Japan, who madethe video, have created working human-liver tissue. Researchershave long dreamed that stem cells might be used to repair or replace damaged tissue,?an aspiration known as regenerative medicine. Embryonic stem cells, in particular, are “pluripotent”, meaning they are able to become any other type of cell. And it is now possible to induce pluripotency in cells that have not come from embryos, thus circumventing the ethical minefield previously??????????? associated with obtaining them. Last year Shinya Yamanaka of? Kyoto University won a Nobel prize for the invention of induced? pluripotency. He had shown how four signal proteins can reprogram adult cells into a pluripotent state. Beside dealing with the ethical problems of embryonic cells, Dr Yamanaka’s induced??pluripotent?stem (iPS) cells allow—at least in theory—a treatment to be created from a patient’s own body. This would have his own genetic make up and would thus not attract the attention of his immune system.?Realizing such treatments has been fiendishly difficult. But Dr Takebe’s paper in Nature is one of?????? several signs that the Promethean dream is slowly coming to life. 词汇突破：PROMETHEUS?普罗米修斯 Titan?巨人 ??????????Zeus?宙斯 ??????????Torture?折磨 ??????????feasting on?贪婪的吞噬 ??????????spectacle?壮观的景象 ??????????decidedly dull=very dull ??????????dots?小点????????consolidating 合并 ??????????glob一团 ??????????stem cells?干细胞干细胞(stem ce