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The Clk Man · #1 09-26-2010, 09:47 AM

Men have a source of potentially life-saving stem cells between their legs.

A team of American researchers has found a way to easily identify stem cells in the testicles of adult mice that can be coaxed to turn into brain cells, muscle cells, heart cells, blood cells and even blood vessels.

One day, they say, male patients may be able to turn to their own testicles as a source of stem cells to repair an ailing heart or kidney or to fix the brain damage caused by Alzheimer's or Parkinson's disease.

The procedure would involve removing a small piece of testicle - about the same amount used for a biopsy.

"We don't need a lot of material," says Marco Seandel, the lead author of a paper to be published today in the journal Nature and a stem cell researcher at the Howard Hughes Medical Institute in Maryland.

His team's work - and that of a German team also experimenting with stem cells extracted from testicles - is part of a growing international effort to look beyond the embryo for cells that can give rise to all human body parts and systems.

Embryonic stem cells have an endless capacity for self-renewal and can produce more than 250 kinds of specialized cells. Scientists are hoping to harness their regenerative powers to repair damaged tissue or organs, but harvesting these cells is controversial because embryos are destroyed in the process.

Adults have small numbers of stem cells, too - in bone marrow, muscle and other tissues and organs. But these don't seem to have the same superhero-like powers as embryonic cells. Stem cells in muscle, for example, give rise only to new muscle cells.

But a number of teams have been trying to coax adult stem cells back to an embryonic state.

In June, researchers in the United States and Japan announced they had done just that by inserting four genes into skin cells from adult mice.

Dr. Seandel and his colleagues didn't reprogram the testicular stem cells with new genes. They put them in a special growth medium, and the cells returned to a state in which they could turn into many different cell types - not just the precursors to sperm cells. In live mice, the stem cells became part of a functioning blood vessel. In the lab, the scientists transformed them into brain cells, cardiac cells and muscle cells.

The team has been hunting for stem cells in testicles for more than a decade. Dr. Seandel says it seemed like an obvious place to look, because testes produce sperm, which give rise to an entire human being if they fertilize an egg. Stem cells in the testicles are hard-working: The average male produces 40,000 sperm a second, the researchers say.

There was another, somewhat gruesome sign that testicular stem cells might turn into other types of cells quite easily. Testicular tumours, Dr. Seandel says, are sometimes found with hair, teeth or other tissue in them. The same is true for ovarian tumours, he says. But women don't have the equivalent of sperm-producing stem cells.

It wasn't easy finding the stem cells in men. They make up only 0.01 per cent of all cells in the testicles, says Shahin Rafii, also at Howard Hughes Medical Institute and a co-author of the paper.

The American team, which included researchers from Harvard University and the Weill Cornell Medical College in New York, discovered a protein that is unique to the small population of stem cells in the mouse testes. It is a marker they can use to easily identify the stem cells.

The U.S. researchers are trying to figure out why their experiment worked. They aren't sure why the adult stem cells reverted to a more embryonic state in the growth medium. If they can understand the process, the scientists say, they may be able to replicate it in other adult stem cells.