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科學家首次成功以成人細胞克隆胚胎
　　新華網4月21日電 據科技博客網站Gizmodo報道，自從克隆羊多莉18年前誕生以來，科學家以同樣技術使用成人細胞克隆胚胎的探索就從未止息。現在，他們終於成功了，在器官移植及其他使用乾細胞的治療技術方面向前邁進了一大步。
　　去年，一個科學家團隊取得重大突破，成功克隆出首例人類胚胎。他們是用胎兒跟八個月大的嬰兒提取細胞的。最新的結果發表在《乾細胞》雜誌上，是從兩個分別為35歲和37歲的成人那裡提取的皮膚細胞。
　　以成人細胞克隆出胚胎意味著有一天，我們可以颳去一小塊皮，培植出胚胎，生長出來的乾細胞就有自己的DNA。這些乾細胞可以培育成特定的組織，包括可供移植的器官。
　　基本的流程跟克隆多莉羊差不多。從成人細胞里提取的包含DNA的細胞核植入捐贈的卵子中，卵子捐贈者的細胞核則被移除。科學家將這一方法運用到20種生物上，但涉及到人類就比較棘手。
　　當然，這一結果並不意味著克隆寶寶即將誕生。胚胎還缺少一些細胞，不能移植到子宮。這也是為什麼科學家一直在拿猴子做實驗的原因。
　　人類克隆技術最大的用處在於，將胚胎作為個人乾細胞的來源。目前，我們以體外受精殘留或成人細胞作為乾細胞的來源，但兩種技術都有缺陷。體外受精的乾細胞不能完美匹配病患，而基因重組很難完全在成人細胞里完成。
　　任何以克隆技術進行的治療都還很遙遠，即使有了基礎的研究，還存在許多倫理問題。多莉羊誕生已經18年了，克隆技術的道德困境仍未得到絲毫改善。
　　譯者：王俊景
　　百度新聞與新華網國際頻道合作稿件，轉載請註明出處。
　　Scientists Have Cloned Embryos From Adult Cells For the First Time Ever
　　Ever since Dolly the sheep was cloned eighteen years ago， scientists have been trying and failing to use that same technique to create cloned human embryos from adult cells. Now， they've finally succeeded， in what could a major step toward personalized organ transplants and other therapies that rely on a pool of stem cells。
　　Last year， a different team of scientists reported a breakthrough in creating the first cloned human embryos ever. That team used cells taken from a fetus and an eight-month-old infant. This new result， published in the journal Cell Stem Cell， tweaks the procedure to make it also work with skin cells from two adult men， ages 35 and 75.
　　Confirming that human clone embryos can indeed be made with adult cells means we could potentially someday scrape off a bit of your skin， put it in a cloned embryo， and extract stem cells personalized with your DNA. Those stem cells can then theoretically be programmed grow into any type of tissue—including an organ for transplant。
　　The basic process is the same as the one used to clone Dolly. The nucleus， which contains DNA， is sucked out of the adult cell and carefully placed in a donor egg， whose own nucleus has been removed. Scientists have gotten this process to work in over 20 different species， but humans， until recently， have proven tricky。
　　This result does not mean that cloned babies will be born anytime soon， however. The resulting embryo was missing some types of cells and would not have been able to implant in the womb. The difficulty of getting embryos to grow in the womb is， in fact， why partly scientists still haven't been able to clone monkeys。
　　The most promising use of this human cloning technique is in creating embryos as a source of personalized stem cells. Currently， we get stem cells from embryos leftover from in vitro fertilization (IVF)—or we reprogram them from adult cells. Both techniques have their drawbacks， however， as IVF stem cells do not perfectly match the patient's， and the reprogramming may not ever be entirely complete in adult cells， according to some studies。
　　Any therapies that may result from cloning adult cells is still far， far off on the horizon. Even with this basic lab research， plenty of questions about the moral implications of human cloning remain. It's been 18 years since Dolly—but the ethical dilemmas haven't changed a bit。
（編輯：SN098）