Scientists have used cloning technology to transform human skin cells into embryonic stem cells, an experiment that may revive the controversy over human cloning.科学家利用克隆技术将人体皮肤细胞转化成为胚胎干细胞。这一实验有可能再度引起有关克隆人的争辩。

The researchers stopped well short of creating a human clone. But they showed, for the first time, that it is possible to create cloned embryonic stem cells that are genetically identical to the person from whom they are derived.研究人员的成果距建构出有克隆人还很很远，但他们首次指出，建构出同人类基因完全相同的克隆胚胎干细胞是有可能的。这些胚胎干细胞就来自人类。These stem cells can go on to differentiate into heart, nerve, muscle, bone and all the other tissue types that make up a human body.这些干细胞可以分化成心脏、神经、肌肉、骨骼和其它所有构成人体的的组织型。

Since the birth of Dolly the sheep in 1996, researchers have cloned about 20 different species, including rabbits, goats, cows and cats. Yet they so far have been unable to create biologically identical copies of any monkey or primate, including humans, possibly because their reproductive biology is more complicated.自1996年克隆绵羊多莉(Dolly)问世以来，研究人员早已克隆出有约20个有所不同物种，还包括兔子、山羊、奶牛和猫。然而研究人员至今无法建构出有在生物性上完全相同的猴子或灵长类动物（还包括人类）的克隆体，原因有可能在于这些生物的生殖生物学更加简单。But the refinements described in the latest experiment suggest that its a matter of time before they produce a cloned monkey, said Jose Cibelli, a cloning expert at Michigan State University, who wasnt involved in the study. It also means, he added, that they are one step closer to where the efficiency is high enough that someone is willing to try to clone a person, though that remains a distant─and disturbing─prospect.但密歇根州立大学(Michigan State University)克隆专家奇贝利(Jose Cibelli)说道，上述近期实验所叙述的种种改良指出，研究人员建构出有一只克隆猴只是时间问题。奇贝利没参予这项实验。

他还说道，这同时意味著这些研究人员距离有人不愿尝试克隆人只有一步之遥，虽然克隆人还是一个很远且令人不安的前景。The experiment was published online Wednesday in the journal Cell. It was funded by Oregon Health and Science University and a grant from Leducq Foundation of France.实验过程周三公布在专业期刊《细胞》(Cell)杂志的网站上。这项研究由俄勒冈身体健康与科学大学(Oregon Health and Science University)资助，法国纳迪克基金会(Leducq Foundation)获取赠款。

The researchers werent simply trying to reach a cloning milestone. Instead, they were looking for a better way to make fresh human tissue for the treatment of severe injuries or disease.研究人员并不只是企图超过克隆科学的一座里程碑。忽略，他们正在找寻一种更佳的方法以培育新鲜的人体的组织，并将其用作化疗相当严重损害或疾病。Lab-grown tissue has the potential to transform medicine, though it is still a long way from routine clinical use. For example, fresh nerve cells could alleviate spinal cord injuries, or newly made heart cells could repair a site scarred by a heart attack.实验室培育的的组织有可能转变医学，但它距离临床常规用于还有很长的路要回头。

例如，新鲜的神经细胞可以减低脊髓受损，新的培育的心脏细胞可以修缮心脏病发作导致的后遗症区域。One way to harvest fresh tissue is from human embryos. That is controversial because the embryos get destroyed in the process. Another way is to reprogram mature cells into an embryonic-like state, which can then be turned into other tissues of the body. But this method is relatively new and has yet to yield consistent results.提供新鲜的组织的来源之一是人类胚胎。但这种作法不存在争议，因为胚胎在这个过程中会被毁坏。另一种方法是将成熟期细胞展开新的编码，继而改建成类似于胚胎的状态。

改建后的细胞随后可以变为身体其它的组织。但是这种方法比较较新的，目前仍未获得完全一致的结果。

A third approach is to use cloning, as described in the Cell paper. This technique can yield fresh tissue that is an exact genetic match for the patient for whom it is intended.第三种方法是利用克隆技术，就像上述《细胞》杂志刊登的论文所叙述的那样。这种技术可以产生在遗传上同病人几乎给定的新鲜的组织。培育出有的新鲜的组织就是能用在同一病人身上。

The scientists first removed the DNA from an unfertilized human egg, and then inserted a patients mature skin cell─containing the patients DNA─into that egg. Next, they prompted a chemical reaction, causing the cells to fuse and begin development.科学家首先从一个并未受精卵的卵子中放入DNA，然后在卵子中植入所含病人DNA的成熟期皮肤细胞。之后科学家启动时一个化学反应，引起细胞融合、发育。That led to a blastocyst, a hollow ball of 50 to 100 cells. For a fetus to form, the blastocyst must be implanted in a womb. An inner clump of cells in the blastocyst goes on to form the embryo, while an outer layer goes on to make the placenta.这造成胚泡的构成。胚泡是所含50个至100个细胞的中空球。

想构成胎儿，胚泡必需植入子宫。胚泡中的内层细胞随后构成胚胎，外层细胞则构成胎盘。

For the tissue-growing experiment, the researchers focused on the clump of cells containing embryonic stem cells.对于培育的组织的实验来说，研究人员注目的是所含胚胎干细胞的这群细胞。With the help of certain growth chemicals, they were able to transform the stem cells into various cell lines and tissues, including beating human heart cells, said Shoukhrat Mitalipov, a development biologist at Oregon Health and Science University, in Portland, Ore., and a lead author of the study.俄勒冈州波特兰市俄勒冈身体健康与科学大学的发育生物学家米塔利波夫(Shoukhrat Mitalipov)说道，在某些“快速增长”化学物质的协助下，他们需要将干细胞变为各种细胞系和的组织，还包括人类心脏细胞。米塔利波夫是该研究的主要作者之一。The achievement is a long way from creating a cloned human embryo.研究人员所获得的成就距离建构克隆人类胚胎还有很长的路。

Even if the entire blastocyst had been implanted into a womb, it wouldnt have yielded a human clone. The blastocyst was missing a few cell types that it would need to implant, as well as suffering other deficiencies, said Dr. Mitalipov.即使整个胚泡被植入子宫，它也会产生出有克隆人。米塔利波夫博士说道，胚泡还缺乏一些其必须植入的细胞类型，同时也不存在其它缺失。Never mind the prospect of cloned humans; despite years of experiments, scientists have failed to clone monkeys.就更加不必托克隆人的前景了──尽管经过多年实验，科学家还没能顺利克隆猴子。Dr. Mitalipov said his lab had tried transplanting entire blastocysts into a monkeys womb, but those experiments hadnt yielded a single successful pregnancy.米塔利波夫博士说道，他的实验室曾尝试将整个胚泡植入猴子的子宫，但这些实验仍未构成一次顺利的胎儿。

We dont know why this is, said Dr. Mitalipov. You can make embryonic stem cells but it doesnt mean the embryo will implant.米塔利波夫博士说道，我们不告诉这是为什么，你可以建构出有胚胎干细胞，但这并不意味著胚胎需要被植入。He speculates that one reason why it may be more difficult to clone monkeys and humans is because the egg cells are more fragile than those of other species.他推断克隆猴子和人类的可玩性更大的原因之一有可能是和其它物种比起，猴子和人类的卵细胞更加薄弱。Dr. Mitalipovs main goal is to use cloning to treat illnesses. He next plans to use lab-made tissue and see if he can successfully treat a degenerative, blindness-causing eye disease in monkeys.米塔利波夫博士的主要目标是用于克隆技术医治。他下一步计划用于实验室培育的的组织，并仔细观察他否能顺利地化疗一种再次发生在猴子身上的、可造成失聪的退行性疾病。

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