Mouse Testicles Yield Promising Stem Cells

John Roach
for National Geographic News
March 24, 2006
German researchers announced today that they have isolated stem cells in adult mouse testicles that have properties similar to those of embryonic stem cells.

When injected into early mouse embryos, the cells contributed to the growth of various mouse organs, including heart, brain, and lungs.

If the method works in humans, it could provide an alternative source for stem cells, avoiding the ethical controversy of generating stem cells from human embryos, said the researchers from the Georg-August University of Göttingen.

"We can turn these into all kinds of tissue, from beating cardiac and vascular cells to neurons, skin cells, and liver cells," Gerd Hassenfuss, a member of the research team, told New Scientist magazine.

The discovery opens the possibility, at least for men, of a limitless supply of fresh stem cells tailored to their individual genetic makeup, according to the researchers.

"It definitely needs to be looked at in more detail, but it's exciting, totally exciting," said Renee Reijo Pera, codirector of the University of California, San Francisco ,Human Stem Cell Biology program.

Embryonic stem cells are unspecialized cells. They can grow into any type of cell found in the body.

Scientists hope embryonic stem cells can eventually be used to grow new tissue and replacement organs, and to cure a range of ailments from spinal cord injuries to Parkinson's disease.

To study human embryonic stem cells, researchers develop cell lines from stem cells, which are initially harvested from fertilized human eggs, such as those left over from in vitro fertilization.

Because harvesting destroys the embryo, the practice is controversial among some religious conservatives who regard it as a form of murder. (Read National Geographic magazine's "Stem Cells: The Great Divide.")

Testicle Tissue

In the study, to be reported next week in the journal Nature, researchers isolated sperm-producing stem cells from adult mouse testicles and showed that under certain conditions, some cells grew into colonies much as embryonic stem cells do.

The researchers had a success rate of 27 percent.

"These isolated [stem cells] respond to culture conditions and acquire embryonic stem cell properties," the team writes in Nature.

The researchers dubbed these cells multipotent adult germline stem cells (maGSCs).

Like embryonic stem cells, these testicle-derived cells can contribute to the development of multiple organs when injected into embryos, the researchers said.

Chris Higgins, director of the Medical Research Council's Clinical Science Center at Imperial College London told that the cells have been shown to have some, but not all, of the characteristics of embryonic stem cells.

"There needs to be further research before we really get excited about it," he said.

Prior to this research, Takashi Shinohara of Kyoto University in Japan found embryonic stem cell-like cells in mouse testicles but only in animals up to two days old.

The new research shows this is also possible with adult mice, Hassenfuss and colleagues write.

Human Trial

The German team believes these cells can also be established from tissue taken from adult human testicles.

Hassenfuss has already begun taking testicle-tissue samples with consent from patients undergoing operations for other conditions, New Scientist reports.

The cells must be taken from the testicle, as they are not available from a sperm or semen sample, he added.

If the technique works with humans, this "may allow individual cell-based therapy without the ethical and immunological problems associated with human embryonic stem cells," Hassenfuss and colleagues write in Nature.

"Furthermore, these cells may provide new opportunities to study genetic diseases in various cell lineages," the team added.

The University of California's Reijo Pera cautioned that the current study is only applicable to half the population.

"There's still women," she said. However, she added, the discovery should "spark incredible interest in identification of cells" that have similar properties.

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