(单词翻译:单击)
The human body is a marvellous thing.
人体是一种神奇的东西。
But like anything built by evolution, it has plenty of flaws.
但和所有进化而来的东西一样，它也有很多缺陷。
Consider teeth.
想一想牙齿。
Whereas sharks grow new teeth throughout their lives, adult humans get one set, which must last 60 years or more.
鲨鱼一生中都会长出新牙齿，而成年人只有一副，必须持续60年或更长时间。
That is tricky.
这很棘手。
A combination of poverty, sugar-rich diets and poor hygiene means 2.5bn people around the world suffer from tooth decay, in which acid produced by mouth-dwelling bacteria eats away at the hard enamel that coats the outside of a tooth.
贫困、高糖饮食和卫生条件差的结合，意味着全球有25亿人患有蛀牙。蛀牙是指口腔细菌产生的酸侵蚀覆盖在牙齿外部的硬牙釉质。
That can open the door to painful infections, which cause further damage.
这可能会导致令人痛苦的感染，从而进一步损害牙齿。
Once decay has set in, all a dentist can do is fill the gap with an artificial plug—a filling.
一旦蛀牙开始，牙医所能做的就是用人工填充物填充空隙。
But in a paper published in Cell, Hannele Ruohola-Baker, a stem-cell biologist at the University of Washington, and her colleagues offer a possible alternative.
但是在《细胞》杂志上发表的一篇论文中，华盛顿大学的干细胞生物学家汉内莱·罗霍拉-贝克和她的同事提供了一种可能的替代方法。
Stem cells are those that have the capacity to turn themselves into any other type of cell in the body.
干细胞是那些有能力将自己转化为体内任何其他类型细胞的特殊细胞。
It may soon be possible, the researchers argue, to use those protean cells to regrow a tooth’s enamel naturally.
研究人员认为，很快就可以利用这些蛋白质细胞自然地再生牙齿牙釉质了。
The first step was to work out exactly how enamel is produced.
第一步是弄清楚牙釉质如何产生。
That is tricky, because enamel-making cells, known as ameloblasts, disappear soon after a person’s adult teeth have finished growing.
这是一个棘手的问题，因为牙釉质生成细胞，即成釉细胞，在人的成年牙齿生长完成后很快就会消失。
To get round that problem, the researchers turned to samples of tissue from human foetuses that had been aborted, either medically or naturally.
为了解决这个问题，研究人员转向了从人工流产或自然流产的人类胎儿中提取的组织样本。
Such tissues contain plenty of functioning ameloblasts.
这些组织含有大量的功能性成釉细胞。
The researchers then checked to see which genes were especially active in the enamel-producing cells.
然后，研究人员核对了哪些基因在产生牙釉质的细胞中特别活跃。
Tooth enamel is made mostly of calcium phosphate, and genes that code for proteins designed to bind to calcium were particularly busy.
牙釉质主要是由磷酸钙构成的，因此编码与钙结合蛋白质的基因特别忙碌。
They also assessed another type of cell called odontoblasts.
他们还评估了另一种被称为成牙细胞的细胞。
These express genes that produce dentine, another type of hard tissue that lies beneath the outer enamel.
这些细胞表达产生牙本质的基因，牙本质是位于外牙釉质下面的另一种硬组织。
