Human sperm from stem cells?

LONDON - British scientists claimed yesterday to have created human sperm from embryonic stem cells for the first time, an accomplishment they say may someday help infertile men father children.

The technique could allow researchers 10 years from now to use the basic knowledge of how sperm develop to design treatments to enable infertile men the chance to have biological children, said lead researcher Karim Nayernia, of Newcastle University, whose team earlier produced baby mice from sperm derived in a similar way.

Nayernia emphasized, however, that the early findings, published in the journal Stem Cells and Development, were intended to further research, not create babies.

Stem cells can become any cell in the body, and scientists have previously turned them into a variety of new entities, including cells from the brain, pancreas and heart.

Some experts said they weren't convinced that Nayernia's team had actually produced sperm cells. Several critics also said the sperm cells that were created were clearly abnormal.

"I am unconvinced from the data presented in this paper that the cells produced by Professor Nayernia's group from embryonic stem cells can be accurately called 'spermatazoa,' " said Allan Pacey, a senior lecturer in andrology at the University of Sheffield.

Pacey said in a statement that the sperm created by Nayernia did not have the specific shape, movement, and function of real sperm.

Azim Surani, a professor of physiology and reproduction at the University of Cambridge, said the sperm produced by the Newcastle team were "a long way from being authentic sperm cells."

Nayernia said that the cells "showed all the characteristics of sperm," but that his group's intention was simply to "open up new avenues of research" into infertility with their early findings - not use the sperm to fertilize eggs.

Creating embryos from lab-manufactured sperm is banned in Britain, he said.