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

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

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

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

Critics also question whether it is right to meddle with the building blocks of life just to allow couples to satisfy their desire to have children.

Scientists have been trying for years to coax embryonic stem cells – ‘master cells’ widely seen as a repair kit 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 embryos in the first days of life and, using a cocktail of chemicals and vitamins, turned them into sperm in the earliest stages of development. These were then transplanted into the testicles of infertile 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 slivers of skin as starting material, allowing men to father children that are genetically their own.

Josephine Quintavalle, of campaign group Comment on Reproductive Ethics, said the work was ‘total narcissism’ 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.’

(Read by Lee Hannon. Lee Hannon is a journalist at the China Daily Website.)