A team of Japanese scientists has produced viable sperm from the stem cells of mice. The experiment could be a breakthrough toward treating infertile humans.

The Kyoto University researchers say they managed to induce mice stem cells into creating sperm precursors that were transplanted into infertile male mice. The mice then produced sperm that was successfully used to fertilize eggs in vitro.

A paper published last week in the Cell academic journal said the offspring were healthy and fertile.

Team leader Mitinori Saitou said the scientists believe their success may help develop infertility treatments in humans.

Experts outside the group say it's a first step toward infertility treatment although specific applications are still a long way off.