Scientists Create Human Sperm from Stem Cells
By Alice Park Tuesday, Jul. 07, 2009 
A colony of human embryonic stem cells is seen on a computer monitor at the University Wisconsin-Madison Darren Hauck / Getty Researchers at Newcastle University in England report they have coaxed the first human sperm cells from embryonic stem cells, in a remarkable demonstration of how quickly the field of stem cell science is moving.
The achievement, described in the journal Stem Cells and Development, comes just 11 years after the first human embryonic stem cell line was created — an eye-blink in scientific terms — in the lab of James Thomson at the University of Wisconsin.
Although the development once again raises the specter of creating humans in a Petri dish or custom-designing egg and sperm cells for reproduction, lead author Karim Nayernia says that was not his team's intention. Rather, the experiment was a proof of concept that stem cells can generate any cell in the body — not only the dozens of tissues that make up the human body, but also those egg and sperm cells that may give rise to new bodies altogether. "Other cell types don't generate the next generation," says Nayernia, a professor of stem cell biology at Newcastle University. "This makes a very big difference between our study and the study of other cell types from embryonic stem cells."
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