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成年人细胞首次克隆出早期胚胎

更新时间:2014-4-18 21:40:15 来源:华尔街日报中文网 作者:佚名

Scientists Make First Embryo Clones From Adults
成年人细胞首次克隆出早期胚胎

Scientists for the first time have cloned cells from two adults to create early-stage embryos, and then derived tissue from those embryos that perfectly matched the DNA of the donors.

The experiment represents another advance in the quest to make tissue in the laboratory that could treat a range of maladies, from heart attacks to Alzheimer's. The study, involving a 35-year-old man and one age 75, was published Thursday in the journal Cell Stem Cell.

The creation of the first early-stage human clones, using infant and fetal cells rather than those from adults, was reported last year. The new experiment, with a few tweaks, confirms that striking and controversial breakthrough and also shows the technique works on mature cells.

'The proportion of diseases you can treat with [lab-made tissue] increases with age. So if you can't do this with adult cells, it is of limited value,' said Robert Lanza, co-author of the study and chief scientific officer at Advanced Cell Technology Inc. of Marlborough, Mass. The study was funded in part by the government of Korea and done at a lab in California.

Such experiments are controversial because when cells are extracted from an early-stage human embryo, it destroys the embryo, which some people believe is equivalent to taking a life.

And while the embryos created in these recent experiments may have certain limitations that would prevent them from giving rise to a human clone even if implanted in a womb, that prospect is now scientifically closer.

As with the 2013 experiment, done by researchers at the Oregon Health and Science University, Dr. Lanza and his colleagues first extracted the DNA from an unfertilized human egg and replaced it with the DNA from one of the older donors. The egg automatically 'reprogrammed' its DNA until it reached a stage of the embryo known as a blastocyst--a hollow ball of 50 to 100 cells.

Cells from the blastocyst then were cultured in a lab dish and yielded stem cells that were an exact match to the donor's DNA. Those stem cells subsequently were turned into other tissue types, such as heart cells, which potentially could be transplanted into the patient without triggering an immune rejection.

'I'm happy to hear that our experiment was verified and shown to be genuine,' said Shoukhrat Mitalipov, a development biologist at Oregon Health and Science University, in Portland, Ore., who led the 2013 study that Dr. Lanza and his colleagues have now replicated.

Despite this advance, experts say it wouldn't be easy to create a full-fledged human clone. Scientists have been trying for years to clone monkeys and have yet to succeed. Even the cloning of less-complicated creatures--from sheep to rabbits and dogs--required years of tweaking, and lots of wasted eggs and deformed fetuses, before it worked.

The recent experiments, nonetheless, have some observers worried. Dozens of countries have laws explicitly banning human reproductive cloning, though there is no equivalent federal law in the U.S. Most U.S. states don't have such laws either, though a few, such as California, do.

'If we're closer to some rogue scientist or fertility doctor using published techniques to create cloned humans, it certainly ups the stakes and means we should be moving to put a federal law in place,' said Marcy Darnovsky, executive director of the Center for Genetics and Society, a nonprofit public interest group in Berkeley, Calif.

科学家成功克隆了两名成年捐献者的成熟细胞并培养出早期胚胎,然后从这些胚胎中衍生出了人体组织,与捐献者的DNA完全吻合。这还是科学史上的第一次。

这项成果周四发表在科学期刊《干细胞》(Cell Stem Cell)上,意味着实验室培育人体组织的研究又向前迈进了一步。制造出的人体组织可以用来治疗心脏病、阿兹海默症等多种疾病。两名捐献者均为男性,年龄是35岁和75岁。

去年,科学家第一次克隆出人类早期胚胎,不过使用的是婴儿和胎儿的细胞而非成人细胞。而最新的研究证实了这项惊人并且备受争议的重大突破,也证明了克隆技术对成熟细胞同样适用。

研究报告的撰写人之一、马萨诸塞州马尔堡Advanced Cell Technology Inc.首席科学长兰扎(Robert Lanza)说,年龄越大的人体细胞克隆后可治疗的疾病就越多,如果不能用成人细胞培育组织,这项技术的实用价值就有限。这项研究的经费一部分来自韩国政府,是在加利福尼亚州一个研究所完成的。

人造胚胎实验一直备受争议,因为从一个早期胚胎中提取干细胞后,胚胎就会被摧毁,一些人认为这等同于扼杀生命。

虽然近期实验中培育出来的胚胎可能存在一定的局限性,即便植入子宫也无法成长为克隆人。但从科学角度看,这个可能性正变得越来越大。

和去年由俄勒冈健康科学大学(Oregon Health and Science University)完成的胚胎实验一样,兰扎和他的同事首先从一枚未受精的人类卵细胞中摘除原有DNA,然后植入从一名捐献者的成熟细胞中提取出的DNA。合成后的新细胞自动按照植入DNA序列“重新编程”,直到胚胎进入囊胚期,即由50至100个细胞组成的一个中空的球形幼胚。

之后科学家从囊胚中提取出细胞,并在培养皿里培育成干细胞,干细胞的DNA与那名成熟细胞捐献者的DNA完全一致。这些干细胞最终衍生出了其他组织形态,例如心肌细胞等等,形成的组织有望被移植入患者体内而不至引发排异反应。

俄勒冈健康科学大学发育生物学家米塔利波夫(Shoukhrat Mitalipov)说,“我很高兴有人验证了我们的实验并且证明了它的真实性。”米塔利波夫主持了2013年的研究项目,兰扎和他的同事又在今年把它重现了一遍。

尽管已经取得了这样的进步,但专家们指出,创造完全成熟的克隆人绝非易事。多年来,科学家们孜孜不倦地尝试克隆猴子,但至今未能成功。即使是克隆不那么高等的动物(例如绵羊、兔子和狗),科学家们也投入了好多年的心血,而且在成果出来前耗费了无数的卵细胞和无数的畸形胚胎。

近期的研究成果让一些观察者十分担忧。现在,世界上有几十个国家明令禁止人类生殖性克隆。美国政府没有类似的联邦法律,多数州也没有这种禁令法规,但加利福尼亚等一些州例外。

遗传学与社会中心(Center for Genetics and Society)是设在加州伯克利的一个非营利性公益组织,该组织执行理事Marcy Darnovsky说,如果放任疯子科学家或不孕不育症医生利用公开的技术培育克隆人,无疑会加大风险,所以应当出台一部合适的联邦法律。

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