for National Geographic News
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.")
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.
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