Scientists have used artificial sperm¹ to restore fertility in a breakthrough that could allow thousands of men to fulfill² their dream of fatherhood.

科学家近日突破性地培育出“人工精子”，可以使不育男性重获生育能力，帮助数千男性实现“父亲梦”。

In ‘hugely exciting’ experiments, they have made sperm from scratch（白手起家） , and, for the first time, succeeded in using it to produce healthy young.

Remarkably³, the baby mice in the experiments went on to have offspring themselves. The landmark⁴ research paves the way for new drugs for infertility⁵, the heartbreaking but little-understood condition that affects one in six couples.

But it also opens a Pandora’s box of ethical⁶ dilemmas⁷. Possibilities raised range from men being made ‘redundant’ from the process of creating life, to babies being created through entirely⁸ artificial means.

Critics also question whether it is right to meddle⁹ with（瞎弄，乱动） the building blocks of life just to allow couples to satisfy their desire to have children.

Scientists have been trying for years to coax¹⁰（哄骗） embryonic¹¹ stem cells – ‘master cells’ widely seen as a repair kit¹² for the body – into turning into sperm. They have had some success but any mice that became pregnant by such means gave birth to unhealthy offspring that quickly died.

Now, Japanese scientists have come up with a series of steps that appear to solve the problem.

They started with stem cells taken from mouse embryos¹³ in the first days of life and, using a cocktail¹⁴ of chemicals and vitamins, turned them into sperm in the earliest stages of development. These were then transplanted into the testicles（睾丸） of infertile¹⁵ mice, where they grew into fully-functional sperm.

The ‘artificial sperm’ were then used to fertilise eggs, leading to the birth of 60 ‘grossly healthy’ baby mice, who went on to have families of their own, the journal Cell reports.

The Kyoto University researchers hope to be able to repeat their success using slivers¹⁶ of skin as starting material, allowing men to father children that are genetically¹⁷ their own.

Josephine Quintavalle, of campaign group Comment on Reproductive Ethics¹⁸, said the work was ‘total narcissism¹⁹（自恋）' and raised the possibility of ‘male eggs’ from men’s skin and ‘female sperm’ from women’s skin.

She added: ‘Who needs men? Who needs women? All that is required now are artificial wombs and we will have completely rewritten human reproduction.’