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.