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【科技新闻】[ScienceNOW]你的父亲是一个干细胞
By Gretchen Vogel
ScienceNOW Daily News
11 July 2006
Scientists have managed to turn mouse embryonic stem (ES) cells into sperm that can fertilize an oocyte and produce live offspring. The feat, which is published in this month's issue of Developmental Cell, gives researchers a potential new tool to study sperm development and could eventually help scientists understand and even treat some kinds of infertility. But the strategy is far from perfect: Only seven mice were produced from 210 fertilization attempts, and they all died at a young age.
Several teams around the world have reported that they could turn mouse ES cells into spermlike cells by adding various growth factors (ScienceNOW, 10 December 2003). But none of those sperm have proved able to fertilize an egg and produce a live pup. Karim Nayernia of the University of Göttingen in Germany and his colleagues have now managed to take that final step.
The scientists treated mouse ES cells with retinoic acid, a known factor in sperm and egg development, and then selected for cells that expressed genes typical of early sperm development. In a second step, they treated those cultures with another dose of retinoic acid. After 72 hours, they found that some of the cells started to grow tail-like structures. Additional tests suggested that many of the cells had undergone meiosis, the special cell division that produces sperm and eggs.
To test whether the lab-made sperm were truly potent, the researchers injected them into mouse oocytes and then transferred resulting embryos into surrogate mothers. In 210 attempts, the team produced 65 two-cell embryos, seven of which survived to birth. Nayernia credits their success to their two-step system, which he says is more controlled than other attempts to derive germ cells from ES cells. However, he says, the system has its flaws. All seven mice that survived to birth were either much larger or much smaller than normal pups, abnormalities typical of cloned animals. Some lived just a few days, and all died within 5 months of birth. (Normal mice live several years.)
At least some of the problems seem to be due to faults in the process of DNA imprinting, says Azim Surani of Cambridge University in the United Kingdom. Imprinting turns certain genes on or off during sperm and egg development, and defects can often lead to animals growing larger or smaller than normal. The work "is an important piece of research," Surani says, but he adds, it's clear that sperm development has yet to give up its key secrets.
你的父亲是一个干细胞
科学家已设法把小鼠的胚胎干细胞（ES）变成精子，使之授精于一个卵母细胞并产生一个有生命的幼仔。此项壮举发表在本月的《Developmental Cell》期刊中，它不仅提供给研究者研究精子发育的一个有潜力的新的工具，并且能够最终帮助科学家理解甚至治疗某些类型的不育症。但是这项研究离成熟尚远：210例受精尝试仅产生了7个小鼠，而且它们均在年幼时死亡。
世界上的几个研究小组已报道，他们能通过添加不同的生长因子使小鼠的胚胎干细胞变为精子样细胞(ScienceNOW, 10 December 2003)。但都没有证明这些精子能给卵母细胞授精并产生有生命的幼仔。德国Göttingen大学的Karim Nayernia和他的同仁现在已经完成了这最后一步。
科学家用维A酸处理小鼠的胚胎肝细胞，维A酸是精子和卵子发育中的一个已知因子，然后选择表达基因典型的早期精子发育的细胞。第二步，他们用另一种剂量的维A酸处理培养物。72h后，他们发现一些细胞长出了尾巴样结构。另外的试验表明许多细胞经历减数分裂，这种特殊的细胞分裂产生了精子和卵子。
为了证实这种实验室制造的精子是否真正具有生殖能力，研究人员把它们注入小鼠卵母细胞中，然后把生成的胚胎转移到代孕小鼠中。在210例尝试中，实验小组制造了65个两个细胞的胚胎，其中的7个存活至出生。Nayernia把他们的成功归于两个步骤的方式，从胚胎干细胞获得精子要比其它尝试的控制更为严格。然而，他说这种方法仍然具有瑕疵。存活下来的所有7个小鼠要比正常的小鼠大很多或者小很多，这是克隆动物的典型异常。有一些仅生存了几天，且均在出生后5个月内死亡。（正常小鼠生命约为几年）
英国剑桥大学的Azim Surani说，至少某些问题似乎出在DNA标记过程中。在精子和卵子的发育过程中，确定的基因进行标记或未被标记，基因缺损经常导致比正常动物长的大或小。Surani说：“这项工作是科学研究中的一个重要部分，显然精子发育已揭下了它神秘的面纱。” http://www.dxy.cn/bbs/post/view?bid=116&id=6591992&sty=1&tpg=1&age=0 这两篇文章并不一样呀，出处也不同。 [标签:content1][标签:content2]
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作者:admin@医学,生命科学 2011-04-06 17:15
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