Scientists claim to have created artificially human sperm in the laboratory for the first time, a major breakthrough which could pave the way for development of treatments for male infertility.

A team at the University of Newcastle has treated male embryonic stem cells (ESCs) with a range of substances, which converted them first into germline stem cells and subsequently into spermatogonial stem cells.

These divided to produce "haploid" spermatocytes with just 23 chromosomes, which went on to mature into sperm, the 'New Scientist' reported.

According to the scientists, if further tests can demonstrate that the lab-grown sperm are indeed identical to the natural kind, they might be helpful in understanding male infertility.

And, a more distant possibility is the creation of sperm from a woman's cells, allowing a lesbian couple to have a child, they said.

In fact, all seven mouse pups produced by the team in

2006 after fusing normal eggs with mouse sperm created in the

lab died within five months. This was because chemical caps called methyl groups had blocked vital genes in the sperm.

But, in this current experiment, published in the 'Stem Cells and Development' journal, the scientists have solved the problem in mice first by putting spermatogonial cells into mouse testes before they mature.

"The sperm then have a normal shape and normal methylation patterns," Nayernia said.

And, in the same experiment, the scientists are carrying out tests to see if the same thing happened with the human sperm. In fact, for humans, they claim to have developed "artificial testes" to do the same job.

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