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 firstname.lastname@example.org 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.
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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